Question

Among the given alkenes, the least value for heat of combustion is for :

• A.
• B.
• C.
• D. All have equal values of heat of combustion

Answer 1

The correct option is B


Alkene in option (a) has 2 alpha hydrogens.
Alkene in option (b) has 8 alpha hydrogens.
Alkene in option (c) has 6 alpha hydrogens.
More the number of alpha hydrogens more is the stability and lesser is the heat of combustion.
Order of stability:
$2>3>1$
Decreasing order of heat of combustion:
$1>3>2$
So, (b) is the correct option.