ochem week 2 part 1
General Chemistry Review Topics
Previous Topics:
Electronic Activity: Understanding how electrons engage in chemical interactions.
Bond Formation: The processes and theories surrounding how atoms bond to form molecules.
Electromagnetic Forces: Discussion of the forces that govern atomic and molecular behavior.
Hybridization: Learning about the mixing of atomic orbitals to form new hybrid orbitals.
Current Focus:
Resonance Structures: Emphasis on how resonance allows for multiple Lewis structures to signify the same molecule, illustrating the delocalization of electrons.
Introduction to Reaction Mechanisms: An overview of the step-by-step processes that describe how reactions occur at the molecular level.
Structural Representations of Molecules
Lewis Structures: Clearly delineates all atoms, bonds, and lone pairs to represent the connectivity and electron distribution within a molecule.
Condensed Structures: Offers a simpler overview of molecular structure by summarizing the arrangement without detailing every single bond.
Bottom Line Form: Provides a minimalistic representation for easier visualization of complex molecular structures.
Resonance Structures
Concept of Resonance: Illustrates that molecules can be represented in various forms based on electron distribution; each form, or resonance structure, contributes to the hybrid that represents the actual molecule.
Importance of Resonance: Vital for understanding a molecule's stability, reactivity patterns, and electron movement during reactions.
Formal Charge: Mastering the calculation and application of formal charges is crucial for constructing accurate resonance forms and predicting molecular behavior.
Charge Stability and Structure
Electron Distribution: Explores how electrons can redistribute during chemical reactions, which is pivotal for understanding reaction mechanisms.
Comparative Stability: Highlights the tendency of more electronegative atoms (like oxygen) to preferentially bear negative charges, whereas less electronegative elements (like carbon) are more stable with positive charges.
Common Resonance Examples
Acetate: Serves as a key illustration of resonance, demonstrating the shifting of electrons between bonds and charges, highlighting the concept of delocalization.
Amines and Amides: Examination of how resonance plays a role in the structural stability of both positively charged amines and neutral amides, stressing the role of delocalized electrons in reducing charge density.
Free Radicals
Definition & Significance: Free radicals are highly reactive species with unpaired electrons; they play crucial roles in many organic reactions and are often a focus in studying reaction mechanisms due to their instability.
Functional Groups in Organic Compounds
Classification of Functional Groups: A systematic approach to understanding various functional groups and their significance in organic chemistry, which is fundamental for classification and reactivity prediction.
Examples include:
Hydrocarbons: Varieties such as alkanes, alkenes, alkynes, and arenes are the foundational building blocks of organic molecules.
Heteroatoms in Compounds: Such as alcohols, amines, and ethers, which add diversity to organic structures and reactions.
Carbonyl-Containing Compounds: Including aldehydes, ketones, and carboxylic acids, which are pivotal in understanding organic synthesis and reactivity.
Systematic Naming of Compounds
Alkane Classification: Detailed exploration of different classes of hydrocarbons based on the number of carbon atoms, with specific examples such as methane, ethane, propane, butane, etc.
Importance of Common Prefixes: Knowledge of prefixes for carbon numbers (C1 to C12) is critical for correctly naming and classifying organic compounds, aiding in clear communication of molecular structure.
Lab Resources
Recorded Lab Videos: Availability of recorded instructional videos aids students in grasping complex experimental procedures, particularly beneficial during remote learning, enhancing their understanding and preparation for actual lab participation.
ochem week 2 part 1
when will weekly quizzes start? A: this week!
review from l ast week
if we draw a line to a letter, that's whats attatched
resonance (formal charge)
resonance will be about moving charges around in our molecule
we essentially have more or less electrons in the valence shell than we started with with formal charge
EX: methanol has a shared set of electrons with h and carbon then 2 lone pairs vs mothoxide, its 3 lone paits and 1 bond of carbon, but the hydrogen that left brought another electron, making it turn into a negative molecule
nitroge with a positive charge is more common
hydroxide o-, hydroite o+
RESONANCE
what resonance means is that we have a more positive and neg charge on a molecule, but something more complex goes on where they share more ---
acetate (C=O-OH) turns to C-O-O(-) on the molecule, but we can switch with the other o because they'll both be the same atom
mostly happens with highway esque p orbital
if you have to put a negative on one or the other atom, its more likely to be kept on the more electronegative atom
delocalized is when the negativity can spread across different atoms, localized is when they stay in one place
-easy way to identify a resonance structure could be when a charge/loen pair is on a atom which is bonded to an atom with a double bond
amides have a resonance structure even when they're completely neutral
these are stronger bonds (easy to break, we would be brittle!)\
an arrow indicates a charge or lone pairs is moving from one atom to the next or moving around
radicals are single unpaired electrons, where another resonance structure can occur, but they're highly unstable, exothermic, and therefore easily exploseive
peroxide's oxygen is the most common occurrence of free radicals
anti-oxidants help clear up free radical oxidants
chapter 5
the most common thing to look for to find resonance strong is a double bond near a charge or lone pair (good indicator of a p orbital, pi bond)
charge on double bond is NOT accessible , too far AWAY not accessible (roadblock)
resonance structure direction name= amyl(?)
major resonance contributer= putting the charge/lone pair on the most stable atom (often the most electroegative)
when its neutral its most stable- no need for a resonance structure
reaction mechanisms
we have everything in a setup, and in the end, there will be a idfferent setup. reaction mechanisms expllain the order of what was formed to what was bond to get from point a to point b
nuclei did not move, h was taken by o instead of hopping to it
CHAPTER 2:
FUNCTIONAL GROUPS
functional groups are how we divide ochem to make everythig consistent. most of this would be how we take one functional groups (common atom group for molecules) and tur it into another
most o fthe molecules are naturally present in body, some are made in natural proceses, may be observe catysts, mabe help with pharmceutics
hydrocarbonsn- compounds made of ONLY c and h
alkane, alkene, alkyne, arene, alkyl halide* (loosely, c ad h and a halogen, but the halogen makes one bond)
every kind of sugar has a bunch of alcohol gorups
thiols act similarly to alcohols, and amines act similarly to -__
carboxylic vs aminoa acid
carbonyl= including a bunch of functional gorups depepdnging on what its attatched to
memorize the shape and name of alkane, alkyl halide, alkene, alkyne, arene, alcohol, ether, epoxide, thiol, thioether, amine (with 2 and 3 degree), aldehyde, ketoe, carboxylic acid, ester, acyl halide, anydride, armide, nitrile
alkane is the most simple hydrocarbon, ex: gas -depending on the size it can be liquid or gas, fairly unreactive
sometimes alkanes undergo radical reactions
CH4= methane___. natural gas, like on a stove burner
reall really big alkanes turn greasy and solid
6-10 carbons=car 15-25= plane
naming organic molecules
NUMBER OF CARBONS 1-meth 2-eth3- prop/pup
4- but 5-pent 6-hex 7=Hept 8- oct 9-non 10-dec 11-undec 12-dode
ochem week 2 part 1
Transcript
Basically going to be the same notes with the exception of I take the question.
So you have to be in the room to get the question. I'm going to be asking you this at least three more times.
When is Yalls recitation? Is it Tuesday or Thursday? Tuesday. Tuesday. Great. You don't have restation will start next week for you.
Right? It starts on Thursday. So our recitation week starts on Thursday. Your recitation zero will be due this Thursday at 9am Right.
So make sure you turn in your recitation zero by then.
Right. So Thursday is the first day of recitation week. Right. So your virtual state will be next. Okay, everybody at this point should have received an email from gradescope and an email from Square.
So if you have not got either of those, please let me know.
Send me an email telling me I've got it. Make sure you check your spam folder first. But to me, you know the current issue there is I'll be using Square cap today, so if you haven't been able to get onto squarecap yet, also a square pack should be $5.
If it's more than $5. Also let me know because it's another problem that we need to get fixed.
But if it's not working today, just write your answers down on like a piece of paper or something and hand it to me.
We'll figure it out and fix it by there. Okay. Any other housekeeping questions before we get into actual stuff?
Yes, not next week, but the week after. And I believe an announcement on that should be posted in your lab.
Else. Yes, this is another lab question, but on the syllabus they said they would link like a lab manual for us to buy or something and I can't find that anywhere.
Should have asked. I believe all of the lab manual stuff is basically just going to be posted on dlc.
So rather than getting the hard copy, you'll get like a PDF of the lab review.
That's how we used to just give you a lab manual and then everybody got sent online for like six months and that just messed everything up.
And we moved a bunch of stuff online and I don't know where we are in that process.
I know everything exists online. Have you guys know about the videos? So during the pandemic if you haven't heard about them, you probably will.
But this is for lab. During the pandemic, Dr. Cupboard recorded videos of him doing the experiments and uploaded them essentially just because you had to do something.
But a lot of students find them super useful because you basically watch the experiment before you Go do it.
So you have a much better enablers. So just a heads up, those exist. I think we link them to them on elc, but they're maybe for things that's mostly depend on the most helpful kind of what those resources.
So they exist. They're just an extra resource, period. Okay. Yeah. Livestock start for another two weeks because we're still figuring out TA issues.
Yay, budget. Any other questions? Okay. All right, so we're going to finish up this kind of general chemistry review, right?
So we've talked about electronegativity, molar bonds, how those play into interlecting forces.
We talked about orbitals and hybridization, right.
How those two things go together. Those are all connected to our fester theory. That's just our three dimensional atomic atoms exist in 3D space, not 2D on our favorites.
And then we started to talk about skeletal and line bond structure.
So we went through that. We just kind of do it again, just get a little bit practice model.
That's where we will have that square cut question to give us.
And then we'll finish up this chapter talking about the resonance structures.
And then we'll do kind of a brief introduction to what a reaction mechanism is.
You'll see a bunch of those you have technically already seen.
Should have already seen one. But there'll be a whole lot for us. But that is where we're heading. And then we'll start with chapter two. Chapter. All right, so we've got our bond line form for our molecules.
That's what we're going to be using for the vast majority of stuff this semester.
However, there are technically other ways that these things can get drawn.
The one you've been seeing probably are Lewis structures, right?
That's where we are going to write out explicitly every single atom and generally every single lone pair and bond and everything.
Right. With some of these bigger molecules that could be incredibly time consuming, obnoxious and get really cluttered.
Right. Get hard to see actually what's happening because you just have so much stuff that you've written out.
For example, this vitamin A molecule has a bunch of carbons, right?
If we were to write out every single hydrogen in there, that would take a long time and also kind of start to obscure what we're even actually seeing in that term.
All right. So drawing out these bottom line forms is going to be one way more.
It's going to save you a lot of time. It's also going to give you more straight flow in terms of what we're actually looking at.
So the Other form that you will see is the condensed form.
So that's where we're going to essentially draw our structure, but like write it out as a line, kind of the inverse.
Right, Our bond line. We're only drawing out bonds. We're leaving the carbons and hydrogens off our condensed structure.
We're not drawing any bonds. The only thing we're drawing out is the atoms that we've got.
So again, this is the preferred way that we will be using and seeing stuff.
These condensed ones, you'll just also go and count.
All right, so if you will log onto square cap, you can do it on your computer or your tablet or your phone.
The way square cap works, if you haven't, if you're not familiar with it, there's either multiple choice or fill in the blank type answers.
If got both of the display, they're all fill in the mic, but they're just unnumbered.
So you can log in your phone. You're not going to be drawing anything in there.
There are four separate questions. You should need the code here to get into the class.
Waqj95. If my handwriting is bad, which is. I tried. And then there's those four questions. So take a minute, work on that. We got your answers. Work question. When will weekly quizzes start? Me too, Me too. Yeah, cuz wherever. It's like I know each of the ends. Like the chicken, like ends. Yeah. That's one. And in the center of that where they connect is on.
Yeah. So that's four. It's just five, six, seven at that. It'll indicate what's actually on there. If it's not a carbon, that's. That's why it's a no. So it'll be seven instead of eight. All right, so for our expression up here, we've got that carbon indicator there.
We'll call it carbon 4. How many bonds are attached to carbon? 4. How many bonds have we drawn out on the screen? Four. Four. We've drawn out four bonds. How many bonds does carbon make? Four. Four. Right. So we've drawn out all four. Do we draw out bonds to hydrogens? No. So if we draw out four bonds, none of them are two hydrogen.
Can we have a fifth bond that's to a hydrogen? No. No. So are there any hydrogens? No. No. So the answer here is zero. Right. There's no hydrogen set in that carbon. If we're looking at the second question up here. Right. So that's our carbon. We'll call it 2. So we're just going to go 1, 2, 3, 4, 5. And then we can call the other 26 instead of. All right, so we're looking at carbon 2. Now, how many bonds have we drawn to carbon? 2, 3, 3. Right, so we've drawn two single bonds and a PI bond.
But there's a total of three bonds. Right, so we've drawn out three. How many are we missing? One. We need that fourth bond. We need four. So how many hydrogens are we going to have? One. Alright, and then lastly over here we've got carbon five.
How many bonds are we are drawn to carbon? Five? One. So how many are we missing? Three. Three. So how many hydrogens do we have? Three. All right, so I've numbered out our carbons here.
One, two, three, four, five. And then we also have up here six and seven. Right. So how many telocarbons do we have? Seven. Seven. Right, so the end of a line is a carbon and a bend in the line is a carbon.
Otherwise it's going to be explicitly linked. Right, so there, that O. Right there, this here O bound to like end a carbonate or something.
Right. If we've drawn a line to a letter S, what's attached?
So any questions on any of this? Yeah, so there's a carbon. So this is our carbon right there. And then it has three hydrogens coming off of it at the end of this chicken.
So if we drew it out right, we would have. And then that's where we would have three H's. And then we'd also have that right there. Like I'm now tendenced I out. Any other questions? All right, so we're going to talk about resonance.
Resonance is going to be quite important. But before we can talk about resonance, we have to talk about charges.
Resonance is going to be about moving charges around in our molly.
So this is a reminder for what our charges are. Formal charge. Formal charge is going to pound forth. There's a lot of words on this. Let me write them all down. Formal charge is essentially coming from. We have more or less electrons in that valence shell than we started with.
Right. So if we think about something like oxygen, oxygen starts with six electrons in this valence shell.
Right. If generally it's going to have four of those electrons in the form of two lone pairs.
Those are all oxygens. The other two electrons are going to be shared up in the form of bonds.
Right. So normally we have something like this methanol structure down here where we've got a shared set of electrons with that H.
A shared set of electrons with that carbon, and then two sets of electrons that are all oxygen presented, right?
So our total of six. But we also match the octane, right? So our octagon rule is satisfied, but we got those shared electrons in the bond.
If instead we have this methoxide over here, where now we have three lone pairs in one bond, what we've essentially done is taken the electron, right?
So if we think about like, one electron for oxygen, one electron for hydrogen, we now have just put them both on oxygen, right?
So now oxygen has one more electron than it brought to this situation to begin with.
It brought six to start with, and now it effectively has seven.
So if it has an extra electron, what should that charge be?
What charge does an electron have? Negative. Negative. So if it has an extra one of those, it should be negative, right?
So if we get an extra electron, we get a negative charge.
Generally, what we're going to see when we do that is we turn a bond into a lone pair, right?
So we've only net gained one electron because one of those was there to begin with, right?
So we go from this bond to a lone pair. We now have two electrons in that lone pair, but one of those was there to start with and form that bond, usually.
So something like an acid base reaction is generally going to do something like this, right?
We pull off H plus, so we're left behind with a minus.
Talk a lot more about that space. But that's another kind of easy example. The option we get is if we essentially have enough electrons and then we kind of lose one, right?
So if we're going from a bond to a lone pair, that's why you get our anion.
Going from a lone pair to a bond would give us a cation similar idea.
We're just going in reverse. So for our nitrogen, we usually have three bonds and one lone pair.
If we have a lone pair and we figure out we find something that is, say, missing an electron, and so we share that lone pair to make a bond.
What we're going to end up with is one less electron we started with.
So it started with five, now it has four that fully belong to that nitrogen, because one of those that initially was its sole electron, it's now sharing with hydrogen, right?
So that's how we're getting our charges. This is a chart, basically summarizes the ones that you will need to even bother.
So essentially, if our carbon is going to have too many electrons, it's either going to have the missing sum, be positively charged, have an extra electron, be negatively charged, Is carbon more or less electronegative than nitrogen?
Less. What about oxygen? Also less. Right. So if our options were were to give oxygen a negative charge or to give carbon a negative charge, which one would be better?
Oxygen. Which is more electronegative? Oxygen. Oxygen. So if it's more electronegative, it wants that negative charge, it's more happy with it.
So it's better to have O minus than carbon. Right. Let's take that idea and flip it. Which of those would prefer a positive charge? Carbon. Because it's less electronegative. Right. Or more electropositive. Right. It's a scale. So generally speaking, if our options are to give extra electrons to one of our atoms, more likely things like oxygen are better.
If we're going to move electrons, things like carbon are better, giving us a positive.
We will see both in this class. One of them tends to be mildly annoying, the other one tends to blow up.
The blowing up one is the one where we the negative charges on carbon.
So otherwise nitrogen, generally nitrogen with a positive charge is common.
Nitrogen with a negative charge less so we will encounter it in this class, but it's much less common.
And oxygen with a minus or a positive. Both of those are common. Right. Hydroxide is O minus. Hydronium is O plus. You'd use both of those when of times already. They're not going away. Basically the entirety of sn that will come back up more later, but you'll see quite a lot of it.
So now on to the more relevant bit. This, this is going to. These positive charges are going to play into our resonance structures.
We're talking about a structure having resonance.
What that means is that what we have is some sort of positive or negative charge somewhere on our molecule that is not fully centered in that spot.
So if we were looking at that methoxide from earlier, right.
That negative charge that's on this oxygen here is just on the oxygen.
Right. It has that extra electron. The oxygen is more electronegative. It's hogging the electrons in the bond between the O and the carbon anyway.
Right. There's nowhere else for it to go. The oxygen just has the negative charge. That's the end of the story. There's nothing more complicated going on. Right. When we have a resonance, that's not the case anymore, something more complex is going to go on.
Because what we're going to have, instead of just like an O and a carbon and that's it, is we're going to have other atoms present that might be more electronegative or might be able to kind of share in that electron distribution.
Right. Electrons are always moving around. So if they have a path to move to a different atom that may want it, then they can take that and that will make it more stable.
Right. So the common example is acetate, just kind of any carboxylic acid that has been deprogated.
Right. So any of our carboxylic acids that look like that, once we pluck that H off and make that minus charge right there, that's going to be our carboxylate.
The carboxylate is the generic term for that. So that is going to have a resonance. Right. We could look move these electrons from that charge, that lone pair into that bond and from this bond to make that charge right there.
Right. So we can either draw it one way where we have the electrons of oxygen 1, or we could move those electrons with 1 oxygen.
Right. What we're essentially going to do here is we're taking the electrons that are in and essentially extra electrons that are sitting in a P orbital and we're shuffling them along a series of P orbitals to another P orbital.
I could accept those electrons, right. What we're allowed to do, we're allowed to do this because everything has those P orbitals.
They make kind of like a highway for the electrons to travel along.
So we're usually only going to see resonance if we have some sort of double or triple bond.
We don't usually see resonance for SP3 hybridized things.
So we need that spdris, that key orbital highway for the electrons to travel along for something like acetate.
These both of these oxygens are basically the same.
They're both oxygens. One of them isn't better than the other. And so we're going to end up with is essentially a 50, 50 slit between sometimes it looks like that and sometimes it looks like that.
Right now it's not moving back and forth. This is not an equilibrium. It's not like we could freeze it or take a picture of it and it looks like one of these and not the other.
In reality, what's happening is at any given point it looks like both.
Right? So what we generally. That isn't helpful for us if we're trying to draw a structure out, right.
We're trying to put this complicated, you know, super microscopic thing on a piece of paper, right?
So we just put this structure down and we call it good enough and we move.
Sometimes it's not good enough, in which case we may draw what's referred to as the hybrid form.
So that's where the bonds that we're kind of making and breaking as we move the electrons around, we draw them as dashes, right?
So that's our hybrid form right here, where we have these kind of high bonds are dashed.
And then we put that partial negative charge to show that we have that charge distribution there.
So we have basically two half negative charges instead of one whole negative charge.
And that's going to be more stable than one whole negative charge on.
So generally, these resonance forms are going to indicate that something is more stable in that with that charge than we have or than something that doesn't have resonance.
We also can have compounds where they're not evenly distributed.
So, for example, this amide compound here, we have this same deal, but now instead of an O minus, we have an N minus.
So we've swapped out that oh for NH2. So we remove one of those H's and we get N minus, which is more electronegative, O or N O.
Right. Closer to fluorine. Fluorine's the most electronic. So we're going to go up and go. Right. So O is more electronegative. So if we have to put a negative charge on one of those two atoms, which is best?
Oh, right. So of these two, one of them is that. Right. That guy is the better one. That's not to say that it only looks like that. It still looks like both. It just looks more like that one. Whereas this one basically looks the exact same.
Right. Since both these are the same, if we took a picture of it, it would look like we had blended them together.
Right. If we took a picture of this, it would also look like we had blended them together, but we had like 90% of that and 10% of this.
So we still see both present. It's just that our distribution kind of shifts from like 50, 50 to 70, 30 or 90, something like that.
So our resonance is always describing what actually something looks like because these electrons are always moving around in every single one place.
The term we use to describe that when these electrons aren't stuck on one atom is delocalized, as opposed to localized.
Localized, where they're stuck on the block. So. So delocalized is going to be when they can spread across a couple of different.
Any questions so far? I have a few words. Great. Okay, so few more examples. Right. We can do this with cations as well. It's just instead of our electrons moving around to essentially have too many electrons that are all trying to, like, figure out the space where they can exist and be stable, we have not enough electrons.
So the ones that are there are trying to fill in the empty space.
So what we have for something like this cation up here, which next to the double bond is the electrons of the double bond are kind of constantly jumping back and forth trying to make each of these carbons happy.
And they can't do it, right, because there's not enough of them.
But they're going to keep moving back and forth trying to do so.
Right. So we're going to end up with something that looks like that.
We still have that partial double bond on one side and on the other side, it's just that now our partial charge is positive as anything.
We can also see this with compounds that have a resonance structure that is completely neutral.
So we can start off with a completely a neutral structure and have resonance forms that are relevant.
They may not be like the major contributor, right?
So we may have the most stable version that has no charges, but we have a version that has charges that is still stable enough that it matters.
Right? So one of those examples is amides a little bit. But amids are this double bond to an O and then a single bond to an.
Right. So you've seen carboxylic acids, they're very close to them in.
Oh, they have nh. They have this resonance structure when they're purely neutral, right?
So even if we don't have a charge to begin with, we do still have.
We do still have a lone pair here, right? And so we can pull those electrons in, make this N plus this O minus.
Right. And again, N is not as electronegative as. So putting a positive charge on that nitrogen isn't terrible.
Putting a negative charge on oxygen also isn't terrible.
So when we do this, we actually have a pretty decent compound in terms of the stability.
Obviously, it's not as good as no charges whatsoever.
But the fact that it's kind of the charges are where they should be, means that this resonance contributor isn't nothing, right?
It does still matter. So one of the things that that translates is, remember, single bonds can spin, right?
And double bonds can't. So if our single bonds can spin, but our double bonds can't, when we have that nitrogen in that amide, even though normally we would draw it like this, that is the major contributor.
That is a single bond between nitrogen and carbon, you would expect it to spin around.
It does not spin. It's pretty locked into place. That also makes that nitrogen carbon bond really strong.
It's actually very hard to break that bond, which is good because that's what our proteins are made of.
So your proteins are made up of a bunch of amino acids.
Those amino acids connect to each other by making these amide bonds.
If they were easy to break, we would fall apart. There's your biochementide, right? We've got our. These ambide structures. They're very stable and very strong in part because of this resonance.
Again, the charged version isn't the stable, but it still matters.
And then our last example is I have phenoxide. But any of these benzene compounds, right? So there are hexagons that look like that. Those double bonds all are connected to each other, right?
We can essentially the kind of easiest example is we just move them all over, right?
So we essentially move the double bonds between carbon 1 and 2 to between carbon 2 and 3 and 1 and 5.
Right. If we move all of them at the same time, we've basically been done.
Right. But we've also moved the bond. So we, we call it a resonance structure. In reality, these are the same thing, right? Essentially it's just all of electrons are moving around.
When it comes to benzene, it's actually particularly special.
There's a whole chapter in the textbook on. But you'll get to that number two. But we can draw a bunch of resonance structures and if we put stuff on the benzenes, those can also play in.
So that's what we're seeing here with this. As a result of this. Sometimes you'll see benzene rings run like that.
Which is essentially to say we don't have necessarily like alternating double and single bonds.
We just. They are all like a half double bond. Every single bond in that thing is the exact same.
They're all kind of half. Way. So we'll see. You see a drawn. That's another way to think about it is double bonds are shorter than single bonds, right?
There's a length. We could measure how long they are and those double bonds should be shorter.
So in theory, if we draw out this benzene, we should see long, short, long, short, long, short.
We don't. They are all the exact same length, which is in between along one and short, right?
So we would expect to see like 1 and 2 and 1 and 2 and instead everything is 1.1.
So another way that we just kind of actually observe these resonance structures with le.
There's the arrows for you guys. That isn't whatever I was going to do. The arrows just show us how the electrons move around.
So we'll talk more specifically about this with resonance rules.
But Our arrows are going to show that the essentially a set of electrons is moving from one place to another.
Generally it's going to go from a bond to an atom, although sometimes it may go from like a bond to a bond, depending on what we're specifically drawing.
It does always have to start at the electron itself.
Any questions? So we're going to be using resonance structures a fair amount.
They're going to come up a lot more kind of in the second half of the semester, but it'll still come up throughout this kind of first step that we're discussing.
One more note on resonance structures. Everything we've done so far has been involved full charges, essentially a lone pair turning into a bond.
So we have a net charge change. There are also compounds that exist in chemistry that we generally refer to as free radicals.
They're exceptions to those octet rules where what we have is a single unpaired electron on one of our atoms.
Generally these compounds are non stable. They are not good if you form them. They like to react and unmake themselves very quickly, generally.
Also very exothermically. Whenever you have a reaction that is very rapid and exothermic, that is an explosion.
So peroxides, these or peroxides are kind of the main source of these radicals.
They are explosive for this reason. But we do occasionally run into them in organs. We avoid them mostly because of the exploding thing and then also because they're hard to control.
Right. Like if you make a radical, it will just react with literally anything nearby to get rid of itself.
Right. It does not want to exist. It's very unstable and it will react to the next closest thing to which occasionally can be what you want and usually is not.
But these radicals can exist in resonance forms which will make them a little bit more stable.
So we may be able to hang on to them for an extra few seconds, which might be helpful enough for the reaction to proceed the way that we want it to.
So you can see the exact same. They're going to follow the exact same rules as cations.
Generally speaking, we just have one electron. It's not charged because it's not an extra electron.
It's unpaired. Right. So our carbon started with four. This has not changed how many it started with or ended with.
Right. The total number of electrons around the carbon compared to how many it started with is the same.
It's just that now one of them is alone and that's that peroxide.
So because peroxide's oxygen is kind of one of the most Common sources of these radicals in the real world.
And we are made up of quite a bit of oxygen. These free radicals can be made of biological systems.
Sometimes that is not good for us the same way that it is not good for, you know, using in the lab.
But our bodies have generally adapted to take care of most of those issues.
So if you've ever seen foods that are advertising having antioxidants, Antioxidants are specifically to clear up the free radicals.
Right. So the radicals that get generated in your system, those are going to be.
The antioxidants are going to help clear that up.
So they where those kind of like good foods, superfoods and stuff like that.
It's worth it. What they're specifically fixing are these free radicals that are going to otherwise go in and destroy stuff.
We'll talk more about using these mechanism errors for radicals in chapter five when we get to mass effect.
Mass effect uses radicals because it kind of blows up small scale.
All right, any questions on resonance? All right, so I got one more square cat question for you guys.
It'll be the same code S.A. good. All right, so we're looking for if something is going to have a resonance structure.
The most common thing that you want to look for is if you have a double bond that is nearby at charge.
Right? Those are kind of, or it's. Or nearby a lone pair. None of these guys have lone pairs. But a double bond that's near to a lone pair or a charge is going to allow.
That's a good indication that we're going to have those P orbitals that can make that highway where they can talk to each other.
Right. Because that's what we're going to end up needing this to work.
So if we have a double bond specifically, that nearby is going to be one atom.
Oh, right. So we have a double bond. That is the atom that we are looking for. Right. In terms of being nearby, if it is on the double bond, the double bond actually can't like go, go help it out.
Right? You can't help out the thing if it's attached to you.
The way that the electrons are flowing, that charge on the double bond is not excessive for those P orbitals.
If, if you think about those molecular orbital shapes, Another way to think about it is the P orbital kind of that highway is perpendicular to the s P orbital.
And so if we have the electrons in that P orbital, the idea is we want to move them over there.
The problem is this charge is not going to be completely perpendicular to the hierarchy.
So It'd be like driving down the road and then trying to turn 90 degrees brighter on the side of the bridge.
Right. We can't do that. Please don't try. So we can't do that with the. If it's directly attached to the double bond and if it's too far away from the double bond, then we have other stuff getting in the way.
Right. It's a roadblock in our boat. Right. So there's a giant hole in the ground. We cannot get to the other side. So even if the charge was over here, it's just going to be stuck there.
It'll be localized over there and our electrons can't get to it because there is a block in that road.
Or SP3 hybridized carbons in the way. So in light of that, our answer here will be. So that position next to our double bond, it has a term.
We'll get more into naming and terms later. But that term is allylic. So it's gonna be a little. If you had like two directions that you could go, I guess there was like large, like if there's like another carbon attached to the right side or.
Yeah, like maybe. I'm just saying, like if you had like two double bonds, like you could go either direction.
Like which one would you choose? We can have one. We can have multiple residual structures. Okay, great. So we could have like something like this. Yeah, we can do this. Would have a random structure in both directions.
Yes, we would have one. It would be incredibly unstable. Two positive approaches. But in theory we would draw out. We could draw out this guy. Or both of those are R. We'd have all we can have. So things will have. Can have multiple resonance structures. We saw in the. This benzene based compound there's a bunch because we're kind of moving around.
All of those are just the process of moving those double bonds around.
Because we have three double bonds and they're all in a ring and then we have a lone pair.
So the more electrons that we have and the more sp2 hybridized atoms all connected to each other, we can just get residents with all those things.
Any other questions? Yeah. Would the major resonance structure be the original for D or for the double.
Yes. So the major resonance contributor is going to happen essentially.
It's going to be where we can. When we put the charge on the most stable. So putting a negative charge on the most electronegative atom.
Putting a positive charge on the least electronegative atom.
So when we have that distribution idealized, that's usually the major four Phase of version with no charges, we will talk a lot more.
So if our options are like positive charge on a carbon.
Positive charge on a carbon. For right now, we'll get into carbon charges and the specifics of those.
That's like. Any other questions? Yeah, can you explain D? Yeah. So generally if we don't have a charge, then our resonance structure would just be taking something that's stable forcing charges.
Right. So in theory we could try and draw a structure that looks like that, right.
Where we just shove the electrons on the one carbon.
But that's way worse than what we started with. So in reality that's not actually doing anything.
And we could draw the exact same thing but backwards right away from the negative on the other side.
And that is equally just as unhelpful and just as unstable and in the opposite direction.
So we don't even have like, like for ammon for our amine over here because our charge distribution works out.
One of those is better. We could say that we have a little bit more positive charge here and a little bit more negative there, even on the neutral version.
Whereas here they would even cancel out. So we wouldn't even be able to say that. And then we have two double bonds separated by that sp3 carbon.
So even there the double bonds can't talk to each other is the issue.
Any other questions? All right, so the last thing I'm going to mention in this chapter is I'm just going to show you how we're going to draw reaction mechanism.
We're going to start to do that. We're going to. The first half of this class is really going to be about structure of organic compounds.
And then kind of the second half is where the reactions will really come in.
So we'll revisit this. We'll do a whole lot more practice a bit later. But I'll throw some arrows up there every now and then.
So you just. At least we're going to start here so you can see what we're doing.
So the weight reaction mechanism arrows are going to work in theory.
You have all seen at least one, which is the acid based reaction mechanisms that are.
We'll use good old acetic acid and ammonia. All right. Those are our compounds there. So when we are drawing a reaction happening and we're drawing those arrows, what we're doing is we're saying we have electrons in a current setup and then we're going to do a chemical reaction.
At the end of that we will have the electrons in a different setup.
Right. Things that were Lone pairs will be bonds. Things that were bonded to one molecule may not be.
Stuff is going to change. And what we're going to try and do is show how that change has occurred.
Right. So generally what we're going to describe is bonds that were broken and bonds that were formed.
If those happen in an order. Right. Let's say we break this bond and then we make that bond two different steps.
We would describe it that way, too. Our asset base is always going to be one step, and that's going to be first making the bond between our base and our H.
And at the same time, what we need to do. What we need to do is make H. Right. So in this case, our acetic acid is going to generate H by essentially kicking off the H and leaving its electrons behind.
So we're going to show that the electrons that H used to have, that it was shared with the electron that H is at, but it's sharing with that O it leaves behind in the process of this reaction.
Right. So that O gets the electrons. Right. It went from having two lone pairs and two bonds to three lone pairs and one.
So that's a negative charge. And then our nitrogen, that had that lone pair, it used to have two electrons, all to nitrogen.
It now has essentially an extra proton for all of the electrons it serves because it's picked up the H plus H left the electron behind, did not bring any to the party.
So now nitrogen has to make up for that. So now we have. We'll just draw. We can draw it out this way. Right. NH4 plus. I'm just showing the bond we've now made to that nature.
So the arrows here are describing how we have gotten from the starting material to the product.
Right. What has changed? We have broken a bond. We have made a bond between what? Right. With what sets of electrons? Right. We only have the one pair on the nitrogen, the one lone pair.
And now it's gone. Right. So that lone pair must have done. That's why we draw our arrows starting from here.
The general rule of thumb is we always draw our arrows with starting at electrons and ending at where the electrons go.
Electrons are the things that move. So what we need to do when we draw the arrow is describe how they are moving.
Right. Our nuclei are not moving around. The H did not pop off of the O. The H was taken from the O by the electron. Lonely. Any questions? Again, there will be a lot more of this later. We're just dipping our toe in for right now. Any questions on anything we've talked about general chemistry review wise and or some of the stuff that may be a bit new.
This is the end of chapter one. So here's your chapter one. Just for the record, if I ever don't call on you, it's a giant room in some of you's department.
I'm just not seeing you. I'm not ignoring you. Okay, now let's start talking about chapter two.
So great. Chapter two. The first thing in chapter two is not actually obvious, kind of.
So the first thing we're really going to talk about in chapter two is functional groups.
Functional groups are how we essentially divide up organic chemistry to talk about it in things where everything is relatively instant.
The idea is essentially a lot of our chemical compounds that we are dealing with are going to contain repeat patterns of atoms bound to each other.
Right? So I mentioned before, we have amides where we have that carbon double bonded to an O, single bonded to an N.
Those are very similar to carboxylic acids where we have a C double bond to an O, single bond to an.
Oh, right. So those are both going to be related to each other, these guys down here, but different.
But also they're very common. They repeat, right? Amino acids contain carboxylic acid form. When they react via your enzymatic processes to make proteins, they get linked together, then they turn into anodes.
So we have a functional groupid conversion that happens for all of these chemical processes for turning our amino acids into proteins.
Right. So a lot of organic chemistry we're going to talk about like turning functional groups from one thing to another, right?
Or making bonds using alkenes or something like that.
Right. So a lot of the chemistry here focuses on these functional groups because they're the repeating patterns that are all going to behave very similarly and that we are like made up.
Right? So of all of these guys, which one of these is not? Generally, Generally some of these are not necessarily going to occur naturally in your body except in very specific circumstances, But a lot of them actually will.
Right? So alcohols, alkenes, arenes, alkanes, thiols, amines, all three kinds, aldehydes, ketones, carboxylic acids, esters, amines and nitriles are all relatively common, actually occurring, Right?
They are attached to molecules that are in your body right now that's doing things.
So the rest of them are. Can be made in processes, Right? So they may be. Or any substitute acid cycle or something like that.
They may be either similar to how enzymes are doing reaction processes, maybe recently that they may be used to manufacture and synthesize things like drugs or plastics that we use in real life.
So these functional groups generally are common kind of repeating things.
They're broadly. We can break them down into kind of three categories.
This is how I'm going to do it. Yeah. So like for the ones right, there's a lot up there, but for like say ether and it's.
There's the bond going up and it's not going to anything.
Is that representing a carbon? It could be anything. Yes, it could be a carbon, it could be another oxygen, it could be a hydrogen, it could be whatever.
Whenever there's a bond and there's nothing on the end of it.
That's generally these functions are part of the molecule, not the whole.
So we could have a molecule that has a bunch of these things.
Right. So for example, acetaminophen. Right. So this is Tylenol. Looks like this. Right. So we have in here an Arene, an alcohol and an anil.
Right. All three of those are in that molecule and part of Alphabet.
So that's the idea, which is not drawing out on the bonds.
They're probably going to have more than one. More than one. There are more functional groups than this. I'm just not making, you know. So for example, we might describe this Aryan attached to N O H as a phenol functional group instead of just saying Aryan.
Alright. It happens enough that it gets its own specialty.
There's more. You just don't need to worry about anything else.
And in reality you don't actually need to worry about the ones.
The ones in parentheses are here for convenience because you will see, right, epoxides are basically fancy ethers.
They will actually come up quite a bit and are pretty relevant.
So it's worth knowing what that name is as Pokemon group.
Even if it's like technically not in your desk. As a. As its own special. Yeah. Is there like. Is there going to be somewhere high level highlighted, like every functional group that we need to know for the test?
Yes, they are on the slide. They are also in table 2.1. It's just the first one. There's two tables in your textbook functional group.
The first one has the ones you need to know. The other one has the rest that were just already there that didn't feel like deleting.
Like I said, there's a bunch. The ones you specifically will need to know are those.
They are also unsight. Any other questions? Yeah. Yes. So we can broadly classify these in three groups.
The first of those is hydrocarbons. So that's just going to be anything that's made up of only carbon and hydrogen.
Very discrete. So alkenes. Alkenes and alkynes are the kind of classic ones.
Arenes also generally follow this hydrocarbon category, although they'll behave a little bit differently.
Basically, alkanes are just carbons singly bound to do other carbons with hydrogens in it.
That's technically the focus of this chapter. They tend to do nothing except explode. Not on their own. It's just things like gasoline generally are a whole bunch of hydrocarbons and primarily alkanes.
And really the only thing we did they're very good at doing is burning.
So they're just not the most interesting of things.
Alkenes and alkynes do more stuff. So we'll talk more about those in the second half of the semester when we're actually talking about reactions.
And then arenes again, are even a little more complicated than that.
Alkyl halides, I'm putting here sort. So they're made up of carbons and hydrogens and they halogen.
They are here sort of because for the purposes of this class, all of those halogens make one bond.
I know you have like chlorate, superchloride, whatever.
We're not building with that. Right. All of those fluorine, chlorine, bromine, iodine, make a single bond.
Which means that if you just kind of swap out a hydrogen for chlorine, your molecule looks incredibly similar to the way it did before and it will behave similarly to the wafer.
So we kind of can categorize them in this hydrocarbon family because they're not then possible making other bonds.
If it's not even bromine or I'm not even really polar.
So there's a lot of compounds that say sub H for F and otherwise the molecule behaves exactly the same.
But just now it's more soluble than polar solids.
So they're kind of halfway between hydrocarbons, depending on what we're using them for.
And our second group, which I'm just probably calling heteroatoms, which is just our compounds that are contain single bonds to atoms that are not hydrogen or carbon.
At least one, maybe one. So our alcohols. Right. Are carbon bound to. Oh, the reason that we call alcohol alcohol, but ethanol alcohol is.
It's kind of the basest and most easiest version of an alcohol functional group that we can get.
But there are a lot of things that contain alcohol functional groups.
Multiple amino acids contain alcohol functional groups.
Every kind of sugar has a Bunch of alcohol functional groups.
There are a bunch of alcohols that are not ethanol.
Isopropanol and methanol are the most common ones.
Drink those, they are bad for you. Methanol specifically will kill you, I think. Nitroprobal may not kill you, but it won't be a fun time.
But again, those are all discomforts. Ethers are generally an alcohol exhibit. Instead of a carbon bound to an O bound to an H, we've got carbon bound to an O bound to another carbon.
So it's sandwiched between two carbons. So generally this will take us from something that can hydrogen bond, it's going to have really strong intermolecular forces to something that can't because we don't have an oh, which means that we now have really weak London dispersion or really weak forces as opposed to really strong.
Right. So something like ethanol versus something like diethyl ether.
Ethanol boils at 78 degrees, diethyl ether boils at 35.
So dramatic change because now we don't have the.
Oh, and like I said, they're kind of ethers. Right. We still just have O single bounds of two carbons, but they are very good at a lot of reactions specifically.
And so we actually discuss them and use them kind of a little bit more.
Even though they aren't really their own functional thiols and amines are going to be similar.
Thiols behave increasing similar to alcohols because that S if you look at the periodic table is right below.
O actually can behave very similarly to what O does.
And then amines are singly bound to nitrogen. Because nitrogen can make multiple bonds. We can have a nitrogen with one carbon or with two separate single bonds to carbon or three separate single bonds.
We actually have four separate single bonds to carbons, kind of.
That's a quaternary salt. That's different. And generally these are all going to behave similarly.
We can't hydrogen bond anymore once we put three carbons on.
But the nitrogen, hydrogen, carbon bonds on their own tend not to be most strong anyway.
So it doesn't have that much of an impact by the time we're adding three carbons, something like that.
It's usually the line. The spurge, of course, is starting to get pretty strong anyway.
We don't see a ton of change. But amines are the other component of those amino acids, right?
So carboxylic acids are one side, amines are the other.
And then our last group are the carbonyl containing.
So a carbonyl is a term for a carbon double bonded to an oxygen.
It's just the broad term for that system. Right. C double bond O is a carbonyl that can then include a bunch of different functional groups depending on what that carbon is also attached to.
So if that carbon is only attached to other carbons or hydrogens, we get either aldehyde or a P.
So if there's one H, it's an aldehyde. If there's two Hs, these singular compounds form aldehyde.
And it can't do anything else. We have C, this guy right here that can't. There's no bonds that we can make. Right. So for our ketones, we could keep going. For our aldehydes, we could keep going. For formaldehyde. We're done. So it's just the single compound. We don't really call it a functional group because there's only just the one thing.
Right. It's the one compound. So all of these functional groups. The idea is there is a handle on that compound from which we could build and add more things and add other functional groups as well.
Right. Some of these compounds, by definition, we run into a wall.
So those don't count for functional groups. Right. Formaldehyde is not a functional group because we're done.
But ales and ketones are essentially like. You can think of them as hydrocarbon carbonyls as opposed to these other hetero carbonyls.
Argylic acids are carbonyl plus alkyl esters, carbonyl plus ether, acyl halides, carbonyl plus alkyl halide.
And high carbons are weird. They're essentially carboxylic acid plus carboxylic acid minus one.
But they're essentially two carbonyls connected by an O.
Don't worry too much about those. You'll just talk about them more next semester. Anyway. Just showing you their thing that's there. Amines are criminal fluid amines. And then again, nitriles are also a little bit weird.
Essentially, that nitrile does not contain a carbon double bond O, but it will behave as though it does have one, which is also kind of a weird thing that it does.
So again, we'll talk more about that in LK2. Just we broadly put that in this category because it's going to behave like it's a carbonyl, even if it doesn't actually have one.
So, okay, any questions about functional groups?
So broadly speaking, you need to memorize these ones.
The ones in parentheses, I guess, technically don't need to.
Well, I will say you need to know what they are Epoxide is really the only one.
You don't need to like, make you make me memorize it, but we're gonna it a lot, so you might as well do it because you're going to need to know it.
But these are the ones that you will need to know. Okay, 12:25. Yep. Cool. All right, so we'll start talking about alkanes.
We're not going to get too deep into the naming of alkanes because it's a long and annoyingly kind complex system that nobody enjoys doing, including me, but we have to.
All right, so alkanes are our first functional group that we'll get to.
They are the simplest of hydrocarbons. So if we only have carbon and hydrogen and we don't have any PI bonds, there's no double bonds, there's no triple bonds.
Everything is singly bound to everything else. Everything is SP3 hybridized. These are our. They are, generally speaking, pretty boring in terms of the reactions that they can do and the things that we can use them for.
They are good for burning, and that's about it. So the gasoline you put in your car primarily made up of alkanes and other hydrocarbons.
Whenever you get gas, you know, you push the little button.
The was it 87, 90, 93, something like that. You just try and push the cheapest one or whatever your parents told you when you got a card.
If you look at it, it says octane rating that is measured based on the alkane, the type of alkane that you are burning, the types of alkanes that you are burning and how they burn, and when they are burning in the engine, essentially what's good for that.
We'll go on that tangent next time. So that's our alkanes. Most, mostly pretty boring. Depending on how big they are, they will be liquid or gas.
So our smallest hydrocarbon is methane. Carbon with four hydrogens. Right. That's methane. Methane is generally the source of natural gas. So if you have that, if you have like gas in your house, like a gas stove or something like that, methane is probably what's being buried, burned.
When you have that. If we added an extra couple of carbons and hydrogens, so we have C2H6, we're going to get.
Ethane also tends to be mixed in with that nitrogen gas, also gas from temperature.
We add another carbon. We have three carbons, C3H8. That's propane, as in the propane that may be attached to the grill outside of your apartment.
Add one more carbon we get butane, as in like the butane torches that you may use.
By the time we get to pentane, that is where we start to give a leak.
So the first four carbons, carbon groups are all going to be gases, are in temperature.
Pentane, we're going to get a liquid that boils at like 30 or 35 degrees.
And then hexane and bigger tend to be liquids at room temperature.
If we get really, really big, that's where you'll start to get things that are like greasy and oil tend to ever turn solid, but that liquid will get really, really thick.
So those also the kind of larger chains. So they're like making like 15, 20 carbon long chains.
Those tend to also be used as jet. So the things we put in our cars tend to be between like 6 and 10 carbons.
The things that go on planes tend to be between like 15 and 25.
Different engines, they just burn differently.
Combustion science is a whole other thing. But that's. All of these are alkanes, what we tend to use alkanes for.
Whenever you get crude oil out of the ground, it's generally just a mixture of a bunch of scrap, right?
Everything from painting, because that's the kind of smallest liquid all the way up to these like 10, 25, 35 carbon chain things.
And they're all just mixed together and so they separate it out, usually via distillation, and they sell it off to whoever actually wants that specific kind of carbon.
So a lot of times it will be sold by just here's a giant mixture of carbon that all boiled at 70 degrees.
Here's a barrel, and then that's just kind of what you burn, depending on what's in there.
So sometimes they're literally sold by boiling point.
Other times it's a little bit more specific. Okay, we're going to get into the system, the systematic naming of compounds.
People discovered and named things a very long time ago, for centuries.
And for a long time that was fine because we could just figure out something like vinegar and we would name it acetic acid and that would be that.
But we didn't really have anything else. The problem is eventually we figured out that there's a whole lot more possibilities that the more carbon that we stick on things, the more stuff that we attach, the more functional groups that we discover.
It turns out that just individually naming every single compound is not going to work out our.
So instead there's a system where if you follow the system, you will be able to name anything, because things can get Complicated quite fast.
The system has to include everything. The system can also get itself get quite complicated.
We're going to start small. I'll teach you the basics and anything that's way more complicated than that basically won't be a concern for you guys.
The other slight problem with this is anybody in here?
Has anybody taken like retaking this class? Did anybody take Ochem, any kind of organic chemistry?
Not last semester or not here. Okay. You may have learned different rules. I am sorry, Please try to. We're using the most recent rules and most recent is relative because Most recent is 2013.
So still 11 years ago. It's just that the ones that the other people tend to be using and stuck with are from 1993, which is before even I was born.
And they still haven't updated the textbooks. So we updated our textbook for these, you know, 11 year old rules.
But you may see in other different. A couple of different things, different answers or something like that.
For the rest of you, you haven't learned any of this.
So you're only going to learn the one which is this one.
So you're fine. Also science guys, if you use science guys, I'm not sure if they have fixed this or not.
They were mad at us last semester. Their naming rules, I believe were also the old ones, the new ones.
So if there's difference between the things that I tell you, the things that they tell you, I'm the one who writes your test.
So go with the best. Okay. It's very small changes for the most part. I'll mention them offhand as we get to them. They're also mentioned in your textbook, specifically what they are.
But it's generally not kind of like the rules. All this stuff here is the same amount, right? If you have one carbon, that's the name. That's it. And I'll leave with this just because we're kind of.
We'll get familiar with the media next time. But generally speaking, the compounds are going to be named based on how many carbons are contained in the have longest continuous chain of carbons.
These prefixes you will have to memorize up to 12 carbons.
If it has 1, it is meh. If it is 12, 2 it is F. If it has 3 Pro 4. But those are the weird ones. Then they kind of turn back into normal ones. Pent hex kept right. You've seen pentagons and hexagons and henagons.
So those ones, they start to get similar again. Ox, non, jack. Those are things you've seen the first four are the weird.
But you do have to memorize these. We will use them a little. All right. We'll pick up here on Thursday.
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