Ochem Mid 2

Front 1

Symmetry

Back 1

molecules possess an axis of rotation or mirror plane.

Front 2

Chiral

Back 2

Has a nonsuperimposable mirror image; has no elements of symmetry.

rotates plane polarized light and is optically active

Front 3

Achiral

Back 3

Has a superimposable mirror image; has elements of symmetry. Not optically active; does not rotate plane polarized light.

Front 4

Chiral Center/Stereocenter

Back 4

Any carbon with 4 different groups on it.

Front 5

Stereoisomers

Back 5

Two molecules with the same bonds but have different overall orientation/shape of substituents

Front 6

Diastereomers

Back 6

Not same, not mirror images. cis vs. trans. two or more chiral centers. different physical properties (*feet vs. hands). some centers the same, some opposite

Front 7

Enantiomers

Back 7

exact mirror images, not superimposable. Almost identical BP, MP, density and color. Different in chiral environments (*left hand vs. right hand)

Front 8

Alpha

Back 8

detects how much light rotates

Front 9

Levorotatory

Back 9

rotates light to the left/counterclockwise (L)

Front 10

Dextroratatory

Back 10

Rotates light right/clockwise (R)

Front 11

Racemic Mix

Back 11

50/50 blend of both enantiomers; no net rotation. One enantiomer will be (+), one will be (-), so they will have equal but opposite degrees of rotation

Front 12

# of Stereoisomers

Back 12

2^n where n = # of stereocenters

Front 13

Chiral Identical Molecules

Back 13

all stereocenters are the same

Front 14

Meso Molecules

Back 14

Have chiral centers but are not chiral because they have internal mirror plane. Will be R and S.

Front 15

Diastereoselectivity/Stereoselectivity

Back 15

Having a preference for a particular diastereomer when it comes to halogenation of alkanes (either having the radical come in from top or bottom can have different preference)

Front 16

Effect of K in Hooke's Law

Back 16

K= bond rigidity. the more rigid the bond, the faster it will vibrate. triple bond>double bonds>single bonds

Front 17

Hydrogen bonds

Back 17

3600 - 2700 cm-1

Front 18

OH

Back 18

broad, big, very noticeable band. 3200-3650 cm-1

Front 19

NH

Back 19

3250-3500 cm-1, not as broad. NH2 will have two peaks so we can differentiate

Front 20

C triple bond C-H

Back 20

sharp at 3300 cm-1 (terminal alkyne)

Front 21

C double bond C-H

Back 21

sharp at 3200-3250 cm-1

Front 22

C-C-H

Back 22

2800-3000 cm-1. not useful

Front 23

0=C-H

Back 23

sharp, very noticeable at 2650 -2700 cm-1

Front 24

C triple bond C

Back 24

2100-2200 cm-1. Sharp peak

Front 25

C triple bond N

Back 25

2200-2260 cm-1. sharp peak around this region

Front 26

C=O

Back 26

1690-1760 cm-1

Front 27

C=C

Back 27

1620-1680 cm-1

Front 28

SN2 (Bimolecular nucleophile substitution)

Back 28

1 step process, bonds made and broken at the same time. Use backside attack

Front 29

Backside attack

Back 29

reverses stereocenter from S to R; R to S

Front 30

Leaving group

Back 30

- willing to become negative and take electrons

- conj bases of strong acids.

-I>Br>Cl>F.

-Directly related to pKa of acid (more negative pka = better leaving group)

Front 31

Charge of Nucleophile

Back 31

The more negative the charge, the better the nucleophile

Front 32

Speed of Reaction depends on...

Back 32

1. Leaving group

2. Nucleophile

3. Substrate

Front 33

Bascisity

Back 33

More left on periodic table, more basic = more willing to share partial negative. Stronger bases are better nucleophiles

Front 34

Solvation of Ions

Back 34

-slows the reaction/weakens the nucleophile

-big ions are less affected by solvent shell

Front 35

Protic solvents

Back 35

Can H bond; good solvent shells for ions

(H20, R-OH, R-NH2)

In Protic solvents: F

Front 36

Aprotic Solvents

Back 36

no hydrogen bonds, poor solvent shells, don't trap good bases (acetone, DMF, DMSO)

In Aprotic Solvents: F>Cl>Br>I

Front 37

Polarizability

Back 37

larger atoms are more polarizable, e- can drift towards substrate; easier to give away e-

Down the periodic table we get better Nu-

Front 38

Steric Henderance

Back 38

bulky Nucleophiles have slower reactions.

Front 39

Substrate Effects on SN2 reactions

Back 39

1. methyl>primary>secondary>tertiary because steric hinderance blocks nucleophile in transition state

2. Branches next to reacting center also slow reaction, larger branches = slower

Front 40

Solvolysis

Back 40

solvent breaking

H20 as solvent= hydrolysis; we get an alcohol

Alcohol as solvent = alcoholysis; we get an ether

Front 41

SN1

Back 41

unimolecular substitution. 2 step mechanism, leaving group leaves, then nucleophile is added. get racemic mix

Front 42

To get a good SN1 reaction

Back 42

polar solvent (esp. protic) stabilizes cation by saturation.

substrate tertiary>secondary>primary>CH3

because hyperconjugation makes carbon more stable.

Front 43

YOU WILL GET SN1 WHEN

Back 43

tertiary > secondary

good LG

Nu- irrelevent

protic solvent

Front 44

YOU WILL GET SN2 WHEN

Back 44

CH3>primary>secondary

ok LG

good Nu-

aprotic solvent

Front 45

E2

Back 45

base removes H before LG leaves

occurs with strong base

secondary or tertiary

Front 46

antiperiplanar

Back 46

when leaving H and LG are 180 degrees apart in E2 reaction

Front 47

How to Alcohols act:

Back 47

sp3, polar, H-bond, water soluble, high BP

Water soluble because of H-bonds. Helps share H20 H-bonds especially <6C on alcohol.

Front 48

pka of Alcohols

Back 48

15-18

Front 49

Steric Hinderance affect on acidity

Back 49

Lowers acidity. There is less space for solvation which would stabilize the negative charge on the conjugate base of the acid.

Front 50

Induction

Back 50

Having EN neighbors pulls e- from several bonds away. Increases the acidity of the acid (lower pka)

4+ bonds away has functionally no affect

Front 51

Alkyloxonium ions

Back 51

strong acids

-2 -- -4 pka

Front 52

Oxidation

Back 52

-loss of electrons

-increase in ox. state

-Add O. More bonds to EN atoms

-loss of H

Front 53

Reduction

Back 53

-gain electrons

-decrease in ox. state

- less bonds to EN atoms

-loss of Oxygen/ Add H