Arrange the following alkanes in decreasing order of their heats of combustion.
(i) `underset(("Neo-pentane")(i))(CH_(3) - underset(CH_(3))underset(|)overset(CH_(3))overset(|)(C) - CH_(3))`
(ii) `underset("(Iso- pentane)" (ii))(CH_(3) - underset(CH_(3))underset(|)(CH) - CH_(2) - CH_(3))`
(iii) `underset(("n-pentane"))(CH_(3) - CH_(2) - CH_(2) - CH_(2) - CH_(3))`

Options

A. `(i) gt (ii) gt (iii)`
B. `(iii) gt (i) gt (ii)`
C. `(iii) gt (ii) gt (i)`
D. `(i) gt (iii) gt (ii)`

Answer

C

Explanation

(iii) is most stable because of less steric repulsion `therefore` least heat of combustion.