Question

Out of the following compounds,
I.Pent-1-ene,
II.Pent-2-ene,
III.2-Methyl but-1-ene,
IV.2-Methyl but-2-ene,
Which pair has the lowest and the highest heats of combustion, respectively?

• A. (IV) and (I),respectively
• B. (I) and(IV), respectively
• C. (II) and (III), respectively
• D. (III) and (II), respectively

Answer 1

Answer: (A)

More-stable or more-substituted alkene has the lowest (more negative) $\Delta H^{\circ}_C, \Delta H_{\text {formation }}$, and $\Delta H^{\circ}{ }_{ h }$. The order of stability of alkene
:IV $>$ III $>$ II $>$ I.So the lowest $\Delta H^{\circ}_C$ is of (IV) and the highest is of (I)