Question

Which of the following alkenes will have the highest heat of combustion?

• A. $1$
• B. $2$
• C. $3$
• D. All have equal value of heat of combustion.

Answer 1

The correct option is A $1$


Alkene 1 has one alpha hydrogen.
Alkene 2 has four alpha hydrogens.
Alkene 3 has five alpha hydrogens.
More the number of alpha hydrogens, more are the hyperconjugative structures and more is the stability of the alkene.
More the stability of alkene , lesser is the heat of combustion.
So, the least stable alkene , i.e. 1 will have the highest value of heat of combustion.