organic reaction mechanism

Question 1

electrophiles

Answer 1

species that want electrons
- often positive charges

Question 2

nucleophiles

Answer 2

have excess of electrons

Question 3

SN1

Answer 3

unimolecular nucleophilic subsitution reaction
two step mechanism
carbocation intermediate

Question 4

nucleophilic substitution

Answer 4

nucleophile attacks electrophile
- nucleophile replaces the leaving group as a new substituent on the electrophile

Question 5

how to identify the nucleophile

Answer 5

has one or more lone pairs and excess electrons

Question 6

how to identify electrophile

Answer 6

partial or full positive charge that wants to accept elecrons

Question 7

leaving group

Answer 7

typically a weak base, that will break its bond with the electrophile after nucleophilic attack with nucleophile

Question 8

common leaving groups

Answer 8

Br- , cl- , I-, Oh-. R3N

Question 9

general mechanism of nucleophilic SN1 reaction

Answer 9

1. the nucleophilic attack
2. transfer of e- to LG
3. LG leaves

Question 10

two major types of nucleophilic substitutions SN1 and SN2

Answer 10

sn1 and sn2
1 and 2 are based on the rate laws of the reaction

Question 11

sn1 rate law is dependent on

Answer 11

the concentration of the substrate

Question 12

sn2 rate law dependent on

Answer 12

the concentration of substrate and nucleophile

Question 13

sn1 mechanism

Answer 13

1. leaving group leaves first
2. carbocation forms (unstable)
3. nu attack
4. nu deprotinated

Question 14

rate limiting step of sn1 rxn

Answer 14

the carbocation formation
- very slow

Question 15

how to enhance carbocation stability

Answer 15

1. make carbocation more substituted
   terciary carbocations> secondary> primary

Question 16

is sn1 racemic

Answer 16

yes, produces 50/50 mix

Question 17

sn2

Answer 17

backside attack and inversion of steriochemistry
tranition state includes nu bond forming and LG breaking

Question 18

favor sn2

Answer 18

strong nu (OH-)
not sterically hindered primary> secondary >tert

Question 19

polar protic solvents

Answer 19

hydrogen atoms attatched to polar molecule, water, etoh, meoh

Question 20

polar aprotic solvent

Answer 20

c=o but no hydrogen in polar molecule ex: acetone and dmso

Question 21

which nucleophilic reaction is favored by polar protic solvents, why

Answer 21

sn1 because it is able to hydrogen bond and stabilize the carbocation

Question 22

which nucleophilic reactionis facored by polar aprotic solvents

Answer 22

sn2

Question 23

what is the key to the sn2 mechanism

Answer 23

steric hindreance

Question 24

rate law of sn2

Answer 24

depends on concentration of substrate and nu

Question 25

strengh of nu in sn1

Answer 25

doesnt matter

Question 26

strength of nu in sn2

Answer 26

strong and nonbulky

Question 27

steriochemistry of sn2

Answer 27

inverted bc of backside attack

Question 28

nucleophilic elimination

Answer 28

lg is kicked out and replaced with a double bond can also be E1 and E2

Question 29

E1 mechanism

Answer 29

similar to SN1 mechanism - unimolecular rate law driven by carbocation formation - nu pulls off e- from adjacent c form double bond 1. LG leaves and C+ form 2. nu pulls hydrogen and form db

Question 30

E2 mechanism

Answer 30

bimolecular rate law strong base attacks electrophilic hydrogen and leaving group leave at same time

Question 31

Zaitsev rule

Answer 31

the double bond formed is more substituted

Question 32

fisher esterification

Answer 32

acid catalyzed conversion of COOH into an ester COOH +ROH in presence of acid

Question 33

fisher esterification mechanism

Answer 33

1. protination of carbonyl oxygen with acid 2. oxygen of alochol attack electrophilic carbonyl carbon 3. protinate OH group 4. then carnboyl carbon does electrophilic attack and removes h2o leaving group 5. water deprotinates carbonyl oxygen

Question 34

how is fischer esterification reversed

Answer 34

hydrolysis OR group is leaving group and OH attacks and reforms subsitutent to form COOH and ROH

Question 35

imine formation

Answer 35

nucleophilic substitution with NH3 group or NH2R or NHR2 c=n replaces c=o

Question 36

shiff base

Answer 36

imine with a carbon substitioent

Question 37

imine formation mechanism

Answer 37

1. protinate the cabronyl oxygen 2. amine group attacks carbonyl C 3. proton transfer from n to O to make h2o grup 4. N attacks cabtonul and h2o leaves 5. n group is deprotinated by wter

Question 38

what happens to a ketone if it undergoes nucleophilic addition

Answer 38

hemiketal formation

Question 39

tautomerization

Answer 39

two structures interconvert at equilibrium not resonance

Question 40

keto - enol tautomerization

Answer 40

keto and enol forms c=o and c=c acid and basic mechanisms

Question 41

requitement for enol tautomer

Answer 41

at least one hydrogen on the adjacent alpha carbon

Question 42

enolate

Answer 42

keto-enol intermediate with neg charge acts as a nuclephile

Question 43

enolate formation can be catalyzed

Answer 43

by acids and bases

Question 44

micheal addition

Answer 44

a, b unsaturated aldehydes or ketones generated aldehyde attacks double bond and forms an a, b unsaturated aldehyde

Question 45

robinson annulation

Answer 45

micheal addition followed by aldol condensation so it becomes ciclical and one of the aldehydes becaomes an oh

Question 46

aldol condensation

Answer 46

nucleophilic alpha carbon attack on electrophilic carbon to form new c-c bond

Question 47

retro aldol

Answer 47

reverse aldol condensation reaction