Q.60 - Organic Chemistry

Question

Draw the major product formed when (R)-1-chloro-3-methylpentane is treated with each reagent: (a) ${\mathbf{\text{NaOCH}}}_{\mathbf{\text{2}}}{\mathbf{\text{CH}}}_{\mathbf{\text{3}}}$ ; (b) KCN; (c) DBU.

Step-by-Step Solution

Answer

The major products formed from the given reagents are as follows:

Type of the base used

Weak bases favor E1 reactions, while strong and bulky bases favor E2 reactions only.

 

For reaction (c), DBU is used, which is a strong and bulky base. Hence the product formed is an E2 product.

Type of the nucleophiles used

Weak nucleophiles such as water and methanol promote a mixture of both ${\text{S}}_{\text{N}}\text{1}$ and E1 reactions. Strong nucleophiles such as hydroxides and ethoxides and promote a mixture of both ${\text{S}}_{\text{N}}\text{2}$ and E2 reactions.

 

Both ethoxides and potassium cyanides are powerful nucleophiles. Hence they promote ${\text{S}}_{\text{N}}\text{2}$  reactions. Hence,  ${\text{S}}_{\text{N}}\text{2}$ products are formed from reactions (a) and (b).

Explanation

Keeping into account all the key points, the products with their mode of reaction are shown below:

Representation of all possible substituted products from reagent a

Representation of all possible substituted products from reagent b

Representation of all possible eliminated products from reagent c