Question

Consider the following statements in reference to S_N1, S_N2, E1 and E2 reactions of alkyl halides. To which mechanism(s), if any, does each statement apply?

a) Involves a carbocation intermediate

b) Is first-order in alkyl halide and first-order in nucleophile

c) Involves inversion of configuration at the site of substitution

d) Involves retention of configuration at the site of substitution

e) Substitution at a stereocenter gives predominantly a racemic product

f) Is first-order in alkyl halide and zero-order in base

g) Is first-order in alkyl halide and first order in base

h) Is greatly accelerated in protic solvents of increasing polarity

i) Rearrangements are common

j) Order of reactivity is 3°> 2° > 1° > methyl

k) Order of reactivity is methyl > 1°> 2° >3°

Answer 1

a) Involves a carbocation intermediate

E₁, S_N1

b) Is first-order in alkyl halide and first-order in nucleophile

S_N2

c) Involves inversion of configuration at the site of substitution

S_N2

d) Involves retention of configuration at the site of substitution

S_N1

e) Substitution at a stereocenter gives predominantly a racemic product

S_N1

f) Is first-order in alkyl halide and zero-order in base

E₁

g) Is first-order in alkyl halide and first order in base

E₂

h) Is greatly accelerated in protic solvents of increasing polarity

S_N1, E₁

i) Rearrangements are common

S_N1, E₁

j) Order of reactivity is 3°> 2° > 1° > methyl

S_N1, E₁

k) Order of reactivity is methyl > 1°> 2° >3°

S_N2