Optical Isomerism And Reaction Mechanisms

Question 1

Which halogenoalkanes can do Sn2

Answer 1

Primary

Question 2

Process of Sn2 mechanism

Answer 2

-Nucleophile approaches from opposite side of molecule to halogen as like charges repel
-forms transition state with overall negative charge with nucleophile and halogen both bonded
-halogen leaves

Question 3

What is produced by Sn2

Answer 3

Optically active product if optically active halogenoalkane

Question 4

How many steps in Sn2

Answer 4

One as nucleophile attacks and leaving group depart simultaneously

Question 5

Which halogenoalkanes do Sn1 and why

Answer 5

Secondary and tertiary as presence of methyl groups prevents the nucleophile from attacking from the other side of the halogen

Question 6

Why is it possible for carbocation to be produced by secondary/tertiary

Answer 6

Due to positive inductive effect of the surrounding alkyl groups which stabilise positive charge

Question 7

What is process of Sn1 mechanism

Answer 7

Halogen leaves forming carbocation
-forms planar intermediate which can be attacked from above or below with equal probability by nucleophile
-forms two forms of chiral alcohol in racemic mixture so in equal proportions (optically inactive)

Question 8

Which step slow and which fast in Sn1

Answer 8

First step slow (forming carbocation) second fast (attack by nucleophile)

Question 9

Which is faster Sn1/2

Answer 9

Sn2