Organic Chem

Question 1

Stability of carbocations

Answer 1

more substitutied are more stable, less substituted are less stable

Question 2

stability of carbanions

Answer 2

less substituted are more stable, more stubstituted are less stable

Question 3

constitutional isomers

Answer 3

same molecular formula, different configuration

Question 4

conformational isomers

Answer 4

same molecule but differ in their rotation around a sigma bond

Question 5

anti-gauche-syn conformation

Answer 5

anti is most stable, gauche is in middle, syn is least stable

Question 6

stereoisomers

Answer 6

molecules that have the same atoms and connectivity but different spatial arrangements

Question 7

assigning priority in steroisomers

Answer 7

1. highest atomic number gets highest priority
2. isomers with highest weight get higher priority
3. In case of a tie, follow to next closest atom
4. multiple bond is counted as two single bonds

Question 8

right hand rule of assigning priority

Answer 8

face lowest priority group into the paper, clockwise rotation means it is R, counterclockwise is S

Question 9

Fischer projection

Answer 9

spine faces into page, arms face out

Question 10

enantiomomers

Answer 10

non-superimposable mirror images

Question 11

diastereomers

Answer 11

non-superimposable, non-mirror images

Question 12

how to tell the difference between diasteromers and enantiomers

Answer 12

enantiomers have both chiral centers switched, diastereomers only have 1 switched

Question 13

racemic

Answer 13

only enantiomers are racemic

Question 14

epimers

Answer 14

subset of diastereomers that differ at one chiral center, OH on the right is a D sugar, OH on th lefts is an L sugar

Question 15

anomers

Answer 15

epimers that form as a result of ring closure, alpha is down, beta is up on the anomeric carbon

Question 16

meso compounds

Answer 16

when one side of a molecule is a mirror image of the other side, are not optically active

Question 17

determining Z and E conformation

Answer 17

highest priority on same side = Z

highest priority on opposite side = E

Question 18

extraction of organic amines

Answer 18

use a weak acid, protonates the amine, giving a positive charge, making it soluble in aqueous layer

Question 19

extraction of carboxylic acids

Answer 19

use a weak base to deprotonate the acid, giving it a negative charge, making is soluble in aqueous layer

Question 20

extraction of phenols

Answer 20

use dilute NaOH to deprotonate, making it soluble in aqueous layer

Question 21

TLC separation is by…

Answer 21

polarity, stationary phase is polar, so less polar molecules travel further

Question 22

Rf

Answer 22

the distance a sample travelled in TLC divided by the solvent front, it is always positive and less than 1, higher = travelled further, less polar

Question 23

reverse phase HPLC

Answer 23

usually has a non-polar stationary phase so more polar compound elute first

Question 24

size exclusion chromatography

Answer 24

counter-intuitive, larger molecules travel faster through the gel, and smaller molecules get caught

Question 25

gas chromatography

Answer 25

mobile gas phase and liquid stationary phase, occurings from different volatilities, the more volatile components spend less time in the liquid phase and elute first

Question 26

branching effect on BP

Answer 26

more branches = lower BP, easier to separate molecules

Question 27

IR C=0

Answer 27

1735-1680, strong

Question 28

IR C=C

Answer 28

1680-1620

Question 29

IR C triple bond

Answer 29

2260-2100

Question 30

IR C triple bond N

Answer 30

2260-2220

Question 31

IR C-H

Answer 31

3300-2700

Question 32

IR N-H

Answer 32

3150-2500

Question 33

IR O-H

Answer 33

3650-3200, broad

Question 34

How to read NMR

Answer 34

1. number of unique hydrogens correspond to number of signals 2.

Question 35

formula for degree of unsaturation

Answer 35

(2*Carbons+2-H)/2

Question 36

splitting

Answer 36

determine the number of neighboring hydrogens and then add 1