Orgo: Organic Chemist's Toolbox

Question 1

Formula for units of unsaturation

Answer 1

(2C+2+N-H-X)/2

Question 2

Carbocations are most stable when… vs Carbanions are most stable when (opposites)

Answer 2

Carbocations (most to least stable) - 3º, 2º, 1º, methyl

Carbanions - methyl, 1º, 2º, 3º

Question 3

Are alkyl groups, nitro groups, methoxy groups, NH2 e- donating or e- withdrawing groups?

Answer 3

Alkyl - e- donating
Nitro - e- withdrawing groups (increases acidity when attached to a phenol)
Methoxy - e- donating (decreases acidity of phenol ring bc adds charge in and neg charges go on carbons)
NH2 - e-donating group

Online: Electron donating groups generally have a lone pair on the atom directly bonded to the aromatic ring.

Question 4

If have nucleophile and electrophile, who gets attacked?

Answer 4

Electrophile attacked by nucleophile (lewis base)

Question 5

What increases Nucleophilicity?

Answer 5

Nucleophilicity increases with:

a) more neg charge
b) going down periodic table (FOR THE SAME GROUP), increasing size so increase polarizability
c) going left across periodic table (FOR THE SAME ROW), increasing EN bc better able to support the neg charge but we want something that is super unstable with their neg charge and wants to give it away
d) increasing basicity (after all it is a lewis base)

Question 6

Good LGs are:

Answer 6

Resonance stabilize, weak bases (LG ability increases with size), Neutral LG (H2O, ROH - a whole ass alcohol)
If you protonate strong base (bad LG such as HO-, RO-, NH2-, etc) then it becomes a good LG (H2O)

Question 7

We love anti periplanar except for when…

Answer 7

there are two groups that are not too large that can have hydrogen bonding within the molecule - then gauche is preferred

Question 8

MCAT’s fav nucleophile:

Answer 8

H2O (MCAT’s fav nucleophile!)

Cl-/Br-, NH3 (ammonia), CH3- (carbanion)

Question 9

Periodic trend for nucleophilicity, basicity, and acidity

Answer 9

Nuc -> increase left and down
Basicity -> increase left and up (makes sense bc think about how uncomfy the molecule is now and how much more stable it would be with added H)

Question 10

Examples of common electrophiles - can read to refresh

Answer 10

Carbocation, carbonyl compounds, alkyl halides (bc for last two that O or X is really pulling e- density away from that carbon

Question 11

Molecule is chiral if…
____ compounds are achiral
A chiral center has….

Answer 11

It is not superimposable over mirror image
meso achiral
four different groups attached

Question 12

Periodic trend for nucleophilicity, basicity, and acidity

Acidity neumonic and trends

Answer 12

Nuc -> increase left and down
Basicity -> increase left and up (makes sense bc think about how uncomfy the molecule is now and how much more stable it would be with added H)
Acidity neumonic = RAI a.k.a. really angry idiots
Resonance, atom (increase across row, increase down column), Inductive

Question 13

Molecule is chiral if…
____ compounds are achiral
A chiral center has….
If a molecule is achiral, we cannot assign a absolute configuration

Answer 13

It is not superimposable over mirror image or conformer of mirror image
meso achiral
four different groups attached

Question 14

*Optical activity - clockwise represented by ____, counter clockwise represented by ______
Optical activity value of racemic mixture/pair of enantiomers?
Do they tell you about R or S?

Answer 14

+ clockwise, dextrorotary (d)
- counterclockwise, levorotary (l)

racemic mixture/pair of enantiomers -> optical activity value is 0
Tells you nothing about R and S and you can’t determine optical activity without experiment

Question 15

*Optical activity - clockwise represented by ____, counter clockwise represented by ______
Optical activity value of racemic mixture/pair of enantiomers?
Do they tell you about R or S?
Is there a connection b/w diastereomers and optical activity?

Answer 15

+ clockwise, dextrorotary (d)
- counterclockwise, levorotary (l)
Must have a chiral center
racemic mixture/pair of enantiomers -> optical activity value is 0
Tells you nothing about R and S and you can’t determine optical activity without experiment
No connection b/w diastereomers and optical activity

Question 16

*Geometric isomers

Answer 16

Do not require chiral centers
cis/trans alkenes
5 membered rings

Question 17

*Geometric isomers

Answer 17

Diastereomers that differ in orientation of substituents around ring or a double bond.
Do not require chiral centers bc can’t rotate around double bond or ring
cis/trans alkenes
rings

Question 18

*Resolution

Answer 18

separate racemic mixture

Question 19

*Resolution

Answer 19

separate racemic mixture by adding a probe and resulting products will be diastereomers, capable of separation due to different physical properties

Question 20

Anomers

Answer 20

Epimers that form as a result of ring closure

Remember anomeric carbon after sugar closes it can have substituent face up or down

Question 21

Meso compounds:

characteristics, optically active?

Answer 21

Must contains chiral centers, internal plane of symmetry, symmetrical chiral centers must have opposite configurations
NOT optically active (achiral) - the optical activity of one side of the molecule cancels out the other side

Question 22

*For optical activity you need…

Answer 22

CANNOT BE MESO

Must have a chiral center (4 different groups attached)

Question 23

Isomers

Stereoisomers and examples of two types

Answer 23

General term for same molecular formula Stereoisomers - same bond connectivity, different spatial arrangement of atoms ex. enantiomers and diastereomers