Which of the two stereoisomers of 4-t-butylcyclohexyl iodide `(""^(127) I^(-))` will undergo `S_(N)^(2)` substitution with `""^(128)I^(-)` faster, and why?

Options

A. A will react faster because it is the more stable of the two isomers
B. A will react faster because it will yield a more stable product, and the transition state for both reactions is of the same energy
C. A will react faster because the approach of `""^(128) I^(-)` can depart unhindered.
D. B will react faster because it is less stable than A, and the transition state for both reactions is of the same energy

Answer

D

Explanation

- due to 1,3 repulsion I.G. tendeny increase so rate of reaction