Organic Chemistry - Rules/Basics

Draw: Neutral Fully Bonded Boron (2 ways)

Key - 3 Bonds

Draw: Neutral Fully Bonded Carbon (3 ways)

Key - 4 Bonds

Draw: Neutral Fully Bonded Nitrogen (2 ways)

Key - 3 Bonds + 1 Lone Pair

Draw: Neutral Fully Bonded Oxygen (2 ways)

Key - 2 Bonds + 2 Lone Pairs

Draw: Neutral Fully Bonded Fluorine (1 way)

Key - 1 Bond + 3 Lone Pairs

Identify: The Charged Atom In This Molecule

Nitrogen - Has four bonds, no lone pair, results in + charge

Identify: The Charged Atoms In This Molecule

Rightmost Oxygen - 3 lone pairs, one bond, results in - charge
3rd Right Carbon - 3 bonds, results in + charge

Which atom(s) have an oxidation state of -1 (bonded with Carbon)?

Hydrogen (H) and Boron (B)

Which atom(s) have an oxidation state of +1 (bonded with Carbon)?

Nitrogen (N), Oxygen (O), Sulfur (S), Halogens: Fluorine (F), Chlorine (Cl), Bromine (Br), Iodine (I)

Which atom(s) have an oxidation state of 0 (bonded with Carbon)?

Carbon

Assign oxidation states to each molecule:

Left to right: 0, +1, +2, +3, +4

True or False: Molecules Rapidly Switch Between Resonance Structures

False, in truth the molecule exits in between the resonance structures

True or False: Curly arrows showing the making/breaking of sigma bonds are found in both reaction and resonance diagrams

False, curly arrows that make or break sigma bonds are found ONLY in reaction diagrams

Draw: The Trend of Electronegativity on the Periodic Table

Draw: The Trend of Atomic Radii on the Periodic Table

Rank from Most to Least Electronegative: N, B, C, F

F,N,C,B

Rank from Largest to Smallest: F, C, B, O

B,C,O, F

Rank from Smallest to Largest Difference in Electronegativity: Ionic Bonds, Polar Covalent Bonds, Covalent Bonds

Covalent, Polar Covalent, Ionic

True or False: Bond Length is Directly Proportional to Bond Strength. Explain your answer.

False between different elements since ionic/covalent components come into play (most ionic = strongest). True between the same elements

Rank from Shortest to Longest: Single Bonds, Double Bonds, Triple Bonds (between the same elements)

Triple Bonds, Double Bonds, Single Bonds

True or False: Triple Bonds are Stronger than Single Bonds, explain.

True, triple bonds are shorter and therefore stronger than the longer, weaker, single bonds.

Describe: Ionic Interactions

Interactions between ions, full +/- charges on atoms

Describe: Hydrogen Bonding Interactions

Bonds between Hydrogen and a more electronegative atom (O,N,S,Cl,F)

Describe: Dipole Interactions

A single molecule experiences charge (polarity) without the presence of another molecule (affects the orientation of molecules near each other)

Describe: van der Waals Interactions

Interactions between two non-polar molecules resulting in an induced dipole (the dipole is not present in individual molecules)

True or False: Intermolecular Forces that are More Sensitive to Distance are Stronger

False, the more sensitive a force is to distance the weaker the force is. For example, the weakest intermolecular force (van der Waals) is very sensitive to distance.

Which Molecule Would Have a Higher Boiling Point, CH3CH2(OH)CH3 or C9H20

Despite the presence of hydrogen bonding, and a dipole in CH3CH2(OH)CH3, the abundance of weak van der Waals forces in C9H20 result in greater overall strength in the molecule, thus resulting in a higher boiling point.

Would CH3F or CH3I have a higher boiling point?

While CH3F contains the most electronegative molecule (strong dipole moment), Iodine has 53 electrons, each of which acts as a van der Waals force. Strength in numbers, CH3I has a much higher boiling point

True or False: The Structure (Physical Shape) of a Molecule has No Effect on Boiling Point

False, molecules that are flatter (easier to stack) have higher boiling points than molecules that are "rounder" in shape, even if the number and type of molecules are the same.

What important features do we need to consider when determining the best resonance structure? Rank them in descending order of importance.

1. Full octets on all atoms (over is worse than under)
2. Minimum amount of charge (total number of +/- charges)
3. Charges match electronegativity
4. Minimized distance between charges

What is a rule for determining the hybridization of an atom?

Number of bonding domains (bonds + lone pairs) minus 1.

Are sp, sp2, or sp3 bonds shorter, why?

sp. S orbitals are held closer to the nucleus of the atom, so hybrid orbitals with more s character make shorter bonds. (stronger bonds)

What do hybrid orbitals make, what do p orbitals make?

Hybrid orbitals make sigma bonds or hold lone pairs
P orbitals make pi bonds or hold lone pairs

True or False: Every atom must have the same hybridization in every resonance structure

True

If the initial energy gap is large, how will orbital energy levels change upon mixing? What if the gap was small?

A large initial energy gap results in a small change in orbital energy levels
A small initial energy gap results in a large change in orbital energy levels

How does orbital overlap change orbital energy levels?

A greater overlap results in a large change in orbital energy levels
Less overlap results in a small change in orbital energy levels

Define: Nucleophile

Nucleus loving, hence electron rich, electron donor, Lewis base

Define: Nucleophilicity

How nucleophilic a nucleophile is

Define: Electrophile

Electron loving, hence electron poor, electron acceptor, Lewis acid.

Define: Electrophilicity

How electrophilic and electrophile is

Draw an oxonium ion

A (+) oxygen with three bonds

What is a carbocation

A positively charged carbon with three bonds.

What is the difference between an enol and an enolate?

Enol - OH bond
Enolate - O(-)

What factors affect acidity?

Resonance
Hybridization
Electronegativity
Polarizability
Inductive effects
Charge balance

How does electronegativity affect acidity?

More electronegative = more acidic

How does hybridization affect acidity?

sp is most acidic, sp2 is intermediate, sp3 is least acidic
From sp3 to sp2 pka changes by about 5, from sp2 to sp pka changes by about 20.

How do inductive effects affect acidity?

The presence of electronegative atom/atoms not attached to the H bond in question that influences the pka of the bond.

(The electronegativity of the atom/atoms, the number of atoms, and the proximity of the atom to the bond affect the strength of inductive effects)

Inductive effects make very minute changes

How does resonance affect acidity?

1. "Share the burden" if the conjugate base of an acid is capable of sharing negative charges via resonance (more stable) the acid has a lower pka (more acidic)
2. "Move charge to a new atom" if the charge can be moved to a new atom more suited to carry a charge the pka is reduced.
3. "Hybridization" resonance structures determine hybridization

How does polarizability affect acidity?

Atoms with more electrons (lower in the periodic table) are easier to remove a proton from (more polarizable). More polarizable = lower pka.

Which side of an equilibrium equation is favoured?

The side of the equilibrium that is favoured is the one with a higher pKa

What are the rules for predicting bond strength?

1. Bond order wins - lower bond order = stronger bons
2. Atomic radius impacts bond length/strength (larger radii result in longer, weaker bonds)
3. Lone pairs (in the second row) repel each other resulting in weaker bonds

How does hybridization affect C-H bond strength?

S orbitals are held closer to the nucleus of the atom, so hybrid orbitals with more s character make stronger bonds.

How does substitution affect C-H bond strength?

More surrounding bonds to carbon atoms result in weaker bond strength.

If a C radical is unstable, what do we know about the C-H bond it came from?

The C-H bond it came from was strong (it didn't want to break)

If a C radical is stable, what do we know about the C-H bond it came from?

The C-H bond it came from was weak (it was okay to break), there were more C-C bonds surrounding the C-H bond (substitution)

How does resonance affect bond strength?

Resonance involves delocalization of electrons over multiple bonds so they have both single and double bond character making them stronger than the single bond.

How do you determine the index of hydrogen deficiency?

(2x(# of carbon atoms) + 2) - (number of hydrogen atoms)
or the number of rings + the number of pi bonds

Rank the stability of radicals that came from primary, secondary, and tertiary C-H bonds.

1. Tertiary
2. Secondary
3. Primary

More surrounding C-C bonds make the C-H bond weaker and thus more stable as a radical

What are the three names for C-H bonds near C-C single bonds? What defines each?

Primary - 1 C-C bond surrounding the center C of the C-H bond
Secondary - 2 C-C bonds surrounding the center C of the C-H bond
Tertiary - 3 C-C bonds surrounding the center C of the C-H bond

What are the two names for C-H bonds near C-C double bonds? What defines each?

Vinylic (connected to a C=C bond)
Allylic (beside a C=C bond)

What are the two names for C-H bonds near C-C triple bonds? What defines each?

Acetylenic (connected to a C-C triple bond)
Propargylic (next to a C-C triple bond)

What are the two names for C-H bonds near benzene rings? What defines each?

Aryl (on the benzene ring(
Benzylic (next to benzene ring)

What does a + Hf value indicate? What about a - Hf value?

A +Hf is less stable, a -Hf is more stable

How do branches affect stability?

More branches (number not length) create more stable molecules (in Alkanes)

Explain what each of these statements mean:
Hf is more positive
Hf is less negative
Hc is more negative

ALL state the same thing: the molecule being described is less stable.

Are trans double bonds or cis double bonds more stable?

Trans bonds are more stable because they have fewer steric interactions (non-bonding regions in close proximity). Rings are the exception since you can't have a trans ring)

How is stability determined in Alkenes and Alkynes?

How substituted the pi bond is (more C around the bond makes a stronger bond)

What are the reactivity factors of Cl for primary, secondary, and tertiary bonds?

Primary - 1
Secondary - 3.9
Tertiary - 5.2

What are the reactivity factors of Br for primary, secondary, and tertiary bonds? (approx)

Primary - 1
Secondary - 80
Tertiary - 1600

What are the steps of chain reactions? What is the purpose of each?

1. Initiation (any steps that increase the number of unpaired electrons)
2. Propagation (sum together net reaction + # of radicals are conserved)
3. Termination (steps that consume unpaired electrons)

When using peroxides, what steps of a chain reaction change?

Only initiation

How to C-C bonds connected to a benzene ring differ from other C-C bonds?

These C-C bonds are very weak, so the C-H bonds of the C next to a benzene ring are most likely to be broken and replaced with a halogen

Are sp2/sp bonds involved in radical halogenation?

No, these bonds are too strong to be involved in radical halogenation. Weaker bonds are of most interest

When are the # of types of C greater than the # of types of H?

When one or more C atoms have no H attached

When are the # of types of H greater than the # of types of C?

When there are protic functional groups (OH, NH, SH etc), or when the structure of the molecules is such that hydrogens can be identified from any direction

What does the range below 1500 represent on an IR spectrum?

Single bonds to carbon

Where are double bonds to Carbon found on the IR spectrum?

~1500-~1800

Which kind of bonds fall between 2000-2500 on an IR spectrum?

Triple bonds to Carbon

Where are bonds to hydrogen (OH, NH, CH) on an IR spectrum?

Above 2500

Draw an OH group on an IR spectrum

Key: Deep, wide curve

Draw a standard NH2 group on an IR spectrum

Key: Two close bumps (NOT ALWAYS NH2)

Draw a standard NH group on an IR spectrum

Key: One bump (NOT ALWAYS NH! Two NH2 bumps could be very close together!)