OCHEM Exam 1

when drawing 3D molecules, a dash suggest that the ____

molecule is going into the page (like a GASH)

when drawing 3D molecules, a wedge suggest that the ____

molecules is coming out of the page (like a hedge)

Alkyl Halide

This is an alkane + halide (Cl, Br, I) (single bonds)

Alkene

this is when there is a double bond

Alkyne

this is when there is a triple bond

Alcohol

Ketone

Aldehyde

Carboxylic Acid

Acyl Halide

Ether

Thiol

Sulfide

Aromatic Ring

Anhydride

Ester

Amide

Resonance structures are in an

equilibrium

resonance structures are drawn with ____

brackets and a double sided arrow

Curved arrows are used to show ____

electron movement

the curved arrows starts where ____

electrons are currently located

the curved arrow ends where ___

electrons will end up

If we can draw resonance structures, it means that the electrons are _____

delocalized

When electrons are spread out, it increases _____

stability

don’t draw a curved arrow from a single bond____

single bonds break, no resonance

Amine

Induction

when electrons shift around and create a dipole moment

London dispersion forces

almost every molecule has these

Dipole-Dipole Force

when molecules line up their opposite charges (partial negative and partial positive attracted to each other)

Dipole-Dipole force on boiling point

= higher boiling points

More polar = higher _____

boiling point

Hydrogen Bonding

when lone pair of NOF is bonded to a hydrogen (these are electronegative elements attracting H)

more hydrogen bonding =

more dipole-dipole, gives us higher boiling points

branching decreasing ________

boiling point (they can’t stack on top of each other and easily exert connective forces)

Like dissolves ____

like (non polar dissolves non polar) (polar dissolves polar)

To be delocalized, a lone pair of electrons must be adjacent to an atom with

an unhybridized p-orbital

molecules with the same molecular formula can have different structures. these are called ____

constitutional isomers

atoms commonly bonded to Carbon include

C, N, O, H, Cl, Br, I , F

carbon forms ___ bonds

4

nitrogen forms _____ bonds

3

Oxygen forms _____ bonds

2

hydrogen forms _____ bonds

1

as internuclear distance increases (they get farther apart), the ____ increases

energy (and stability decreases)

the attractive forces between positive ___ and negative _____ keep bonds at optimal length

nuclei, electrons

Orbitals are clouds of _____

electron density

P orbitals have ____ and ___ sides

postive and negative (happy and sad)

A bond occurs when orbitals ______

overlap

When positive (happy) orbitals/waves overlap with each other, it creates _____

constructive interference (waves reinforce each other)

When a positive (happy) and a negative (sad) orbital overlap with each other, it creates _____

deconstructive interference (waves cancel each other and create a node)

Molecular orbital theory:

have blobs that can overlap and can create

constructive interference, we get a _____

bond

degenerate orbitals mean they are _____

equal in energy

think of ethylene hybridization:

• how many bonds does the carbon make? 3

• This means it is sp2

• this means that its s orbital and 2 of its p orbitals will be combined to make lower energy orbitals

• this means that one s orbital remains up at the top, unhybridized and still higher energy

• 
  

s orbital makes bonds _______

shorter (the more s character it has, the shorter it is) and vice versa

Sigma Bonds

head on over lap

what do the unhybridized p orbitals do?

they create side to side pi bonds

Pi Bond

side to side overlap

Which is weaker, pi or sigma bond?

Pi bonds are weaker because there is less surface overlap, farther apart.

when a molecule has a triple bond and is sp:

they make two pi bonds, because there are 2 unhybridized p-oritals that are overlapping

when there is a double bond (sp2), there is one ____ and one _______ bond

sigma and pi (because there is one unhybridized p orbital

When there is a triple bond (sp), there is one ______ and two ____ bonds

sigma and two pi bonds. this is because there is two unhyrbidized p orbitals that can overlap to create these side to side pi bonds

to flashcards on molecular geometry

do it bro

when drawing skeletal structures, if there is no charge on oxygen, it means that there are ____

two lone pairs and 2 bonds (cancels with the 6 valence electrons)

when drawing skeletal structures, if there is a negative charge on oxygen, it means that there are ____

3 lone pairs and one bond

if there is a positive charge on oxygen, it means that there is

3 bonds and one lone pair

if there is a no charge on nitrogen, it means that there is

3 bonds and 1 lone pair

if there is a - charge on nitrogen, it means that there is

there will be 2 bonds and 2 lone pair

if there is a + charge on nitrogen, it means that there is

4 bonds and no LP

when it comes to delocalized p-orbitals and resonance, these electrons are flowing between

the unhybridized p orbitals in sp and sp2 structures. The lone pairs of adjacent atoms are located in their own p orbitals, which can interact with these unhybridized orbitals. (motion of electrons going back and forth keep it strong and stable)

when drawing resonance structures, push the electrons that are in a double bond up onto an atom to make ____

a lone pair

when drawing resonance structures and shifting around double bonds, you can’t just shift a double bond to the left on a carbon on the edge because that is saying it is double bonded to an oxygen, which can’t happen. INSTEAD you make something called ____

an anionic carbon, which means it has a lone pair

What are the five bonding patterns when making resonance structures?

• allylic lone pair

• allylic carbocation

• a lone pair adjacent to C+

• a pi bond between two atoms of differing electronegativity

• conjugated pi bonds in a ring

vinyllic atoms are positioned ____ a double bond

IN

allylic atoms are positioned ______ to a double bond

next to, adjacent to

Pattern #1: when drawing the delocalization of allylic lone pairs, the LP travels towards ____

the double bond (the double bond and lone pair essentially swap place)

Pattern #1: carrying charges

when you move a lone pair in a negative atom, the lone pair follows the negative atom

when you move a lone pair in a neutral atom, where the lp one was is now positive and where the lone pair is now is now negative

Pattern #2: Allylic carbocation

• we want to neutralize a plus charge because carbon DOES NOT like being positive

• essentially shifting positive charge

• if we see conjugation, more than two

Pattern #3: LP adjacent to carbocation

You move the lone pair to neutralize the positive charge on carbon

Pattern #4: a pi bond between two atoms of different electronegativity

you can make structures that don’t fulfill an octet, while they don’t exist often, they still do

• electrons in a pi bond (a double bond) are more attracted to an electronegative atom and will become a lone pair on that atom, getting rid of the double bond

Pattern #5: conjugated pi bonds enclosed in a ring

• because they are conjugated, the p orbitals are overlapping (double bond)

• pi bonds can be pushed over one position, clock wise

Assessing most significant resonance structure form

1. have the most number of filled octets

2. have fewer formal charges (neutral is more stable)

3. a structure with a negative charge on the more electronegative (more stable/happy)

4. equally good lewis structures are equally good (equivalent contributors)

what does it mean to draw a resonance hybrid?

draw a dotted line to show the movement between the two forms

how to tell if skeletal structures have higher or lower boiling points?

long bent structures have more effective London dispersion forces and can stick together better = higher boiling point

Acid ____ a proton

donates

Base ____ a proton

accepts

conjugate base:

what forms when the acid gives away its proton

conjugate acid:

what happens when the base accepts the H

negative charge and lone pairs

probably a base

has a proton

probably an acid

Base ___ the proton and the electrons that are in the bond ___ with the acid

takes and stay

Base uses a lasso of ____ to take ____

electrons — the hydrogen from an Acid

A strong acid or base are more -____

REACTIVE:

Strong base: will take any hydrogen it sees

Acid: will lose hydrogens easily

Lower pKa means:

the STRONGER the acid

When an acid loses a proton, it forms a ______, which has a ____

conjugate base, lone pair of electrons

To determine the stability of the conjugate base, you have to look at the stability of the _____

lone pair

If a conjugate base is very stable, we have a ______

strong acid

Priority Scale: What factors affect the stability of negative charge? (ARIO)

• type of atom that carries the charge

• resonance

• inductive effects

• the type of orbital the charge resides in

Which is the stronger acid? #1: type of atom

1. First thing you do, is draw a conjugate base

• more electronegative atom is more stable because it is more electronegative and likes being negative emore

Which is the stronger acid? #2: resonance

1. if a compound has more resonance structures, it is more stable because it spreads out charge

   1. draw conjugate base, scribble out H, add negative charge

   2. more acidic = conjugate base more stable = more resonance

Which is the stronger acid? #3: induction (dipole-dipole)

1. electronegative groups decrease the pKa (stronger acid)

2. dipoles stabilize conjugate base, stabilizing charge across molecule even further

3. more induction = more stable = stronger acid