Ch 7 & 8 Substitution & Elimination reactions

Question 1

Sn1 kinetics

Answer 1

1st order

K[R-X]

Question 2

Sn2 mechanism

Answer 2

1-step, concerted reaction

no intermediate

Question 3

Sn1 mechanism

Answer 3

2-step

1 intermediate = carbocation

Question 4

Sn2 stereochemistry

Answer 4

configuration inversion, stereospecific

always backside attack

Question 5

Sn1 stereochem

Answer 5

retention + inversion

non-stereospecific, racemic mixture (because does backside and frontside attacks)

Question 6

Sn2 R-group preference/identity

Answer 6

methyl>primary>2ndary>tertiary

because of steric effect
AKA fewer R groups if better

Question 7

Sn1 R group preference/identity

Answer 7

tertiary>2ndary>primary>methyl

because of electron effect
AKA more substituted (more R groups) is better bc is more stable carbocation

Question 8

Sn2 alykl halide

Answer 8

(most favored to not possible) H3C > RH2C >R2HCX >R3C

Question 9

Sn1 Alkyl Halide

Answer 9

(most favored to not possible)

R3C-X > R2HC-X > RH2C-X > H3

Question 10

Sn2 nucleophile

Answer 10

good nucleophile preferred (- charge, like OH-)

Question 11

Sn1 nucleophile

Answer 11

does not matter

usually uses weak Nucleophile (like HOH) to avoid competition with Sn2

Question 12

Sn2 leaving group preference

Answer 12

good leaving group

bc have to leave in rate-limiting step

Question 13

Sn1 leaving group

Answer 13

good leaving group

bc has to leave in rate-limiting step

Question 14

ex of order of pref of good leaving group

Answer 14

I > Br > Cl > F

increasing pref of halogens going down PT

Question 15

Sn2 solvent

Answer 15

polar, aprotic

ex: acetone

Question 16

Sn1 solvent

Answer 16

polar, aprotic

ex CH3CH3CH2-OH

Question 17

E2 Kinetics

Answer 17

2nd order

rate = K[R-X][Base]

Question 18

E1 Kinetics

Answer 18

1st order

rate = K[R-X]

Question 19

E2 mechanism

Answer 19

1-step, concerted

Question 20

E1 mechanism

Answer 20

2 steps

Question 21

E2 intermediate?

Answer 21

no intermediate

Question 22

E1 intermediate?

Answer 22

carbocation

Question 23

E2 alkyl halide

Answer 23

(most favored to possible)
R3C-X > R2HC-X > RH2C-X
bc of steric effect, favors more substituted R groups, more stable

Question 24

E1 alkyl Halide

Answer 24

(most favored to NOT possible)
R3C-X > R2HC-X > RH2C-X
bc of steric effect, favors more substituted R groups, more stable

Question 25

E2 base

Answer 25

favors good base

Question 26

E1 base

Answer 26

does not matter | but tries to use weak base to avoid competition with E2

Question 27

does follow E2 Zaitsev rule?

Answer 27

yes

Question 28

does E1 follow Zaitsev rule?

Answer 28

yes

Question 29

E2 stereochem

Answer 29

favors antiperiplanar = transition state | H and X on opposite sides

Question 30

E1 stereochem

Answer 30

no stereochem (carbocation is flat)

Question 31

what is the Zaitsev rule

Answer 31

the major product is labeled as the more stable (more substitued double bonded) elimination product the minor product is less stable/less substituted

Question 32

mechanism for RCH2X (primary) with a strong base and Nu?

Answer 32

Sn2 and E2

Question 33

mechanism with RCH2X (primary) with strong bulky base?

Answer 33

favors E2

Question 34

Mechanism for RCH2X (primary) with a strong Nu?

Answer 34

favors Sn2

Question 35

mechanism for (R3C-X) (tertiary) with a strong base?

Answer 35

E2 (NEVER SN2)

Question 36

Mechanism for tertiary (R3C-X) with weak base and Nu?

Answer 36

Sn1 and E1

Question 37

mechanism for 2ndary (R2CH-X) with strong base and Nu?

Answer 37

Sn2 and E2

Question 38

mechanism for 2ndary (R2CH-X) with strong and bulky base

Answer 38

E2

Question 39

mechanism for 2ndary (R2CH-X) with a weak base and Nu?

Answer 39

Sn1 and E1

Question 40

if the alkyl halide is primary, what is NOT possible and why?

Answer 40

SN1 and E1 because of carbocation stability

Question 41

if the alkyl halide is tertiary, what is not possibly and why?

Answer 41

Sn2 bc of steric hinderance

Question 42

if the electron pair donor is bulky, is it a Nu or a Base?

Answer 42

base

Question 43

if OH- a base, Nu, or both?

Answer 43

both

Question 44

is OCH3 a base, Nu, or both?

Answer 44

both

Question 45

is H- a base, Nu, or both?

Answer 45

base, bc too small to be a Nu

Question 46

is H2N a base, Nu, or both?

Answer 46

both

Question 47

is I- a base or Nu?

Answer 47

Nu

Question 48

if a electron donor has a neg charge, is it strong or weak?

Answer 48

STRONG

Question 49

what classifies a reaction as a heterolysis

Answer 49

one-step, no intermediate = concerted rx

Question 50

what classifies a reaction as a homolysis?

Answer 50

is a stepwise reaction = has a reactive intermediate

Question 51

what is activation Energy?

Answer 51

energy difference between transition state and reactant | energy barrier that must be overcome for a rx to occur

Question 52

what classifies the transition state

Answer 52

the species with the max value of energy

Question 53

what is the rate-limiting step

Answer 53

step with the highest activation energy | the slow step

Question 54

what is a catalyst

Answer 54

accelerates a reaction by lowering the activation energy, while itself is unchanged during the rx

Question 55

Sn2 Kinetics

Answer 55

2nd order | K[R-X][Nu]