Question

Compounds X and Y are both C5H11Cl products formed in the radical chlorination of pentane. Base-promoted E2 elimination of X and Y gives, in each case, a single C5H10 alkene. Both X and Y react in SN2 fashion with sodium iodide in acetone; Y reacts faster than X. What is the structure of Y?

Answer 1

For X, if the product were 3-chloro-2-methylhexane, it could give two elimination products, therefore it isn’t X. 2-Chloro-2-methylhexane isn’t chiral. Therefore X is 1-chloro-2-methylhexane.

For problem two, X and Y cannot be 2-chloropentane as it would give two different alkenes. The reaction of Y is faster than X therefore X is 3-chloropentane and Y is 1-chloropentane as primary chlorides react faster in SN2 reactions.

So the structure is

1-Chloropentane