Stabilities of alkanes can be compared by converting thesecompounds to a common product and comparing the amount of the heat given off. One possibility would be to measure the heat of combustion from converting alkenes to CO 2 and H 2 O. The heats of combustion are of large values and measuring small difference in these large numbers is difficult. Alkene of the lowest heat of combustion among isomeric alkenes is of the lowest energy and is most stable The stability of alkenes is often compared by measuring the heat of hydrogenation (heat given off, Δ H° h ) during catalytic hydrogenation. The heat of hydrogenation is in small number, which provides more accurate energy difference For a compound containing more than one double bond, Δ H h ° is the sum of heat of hydrogentation of individual double bonds. For non-conjugated dienes, this additive relationship is found to hold. For conjugated dienes, however, the measured value is slightly lower than expected. Cumulated dienes, which are even less stable than non-conjugated dienes. The more stable is the alkene, lower is the heat of combustion and heat of hydrogenation. More highly substituted double bonds are usually more stable. In case of cyclokanes, compounds having higher angle strain are less stable In which of the following is, Δ H° h the maximum?

Question

Stabilities of alkanes can be compared by converting thesecompounds to a common product and comparing the amount of the heat given off. One possibility would be to measure the heat of combustion from converting alkenes to CO 2 and H 2 O. The heats of combustion are of large values and measuring small difference in these large numbers is difficult. Alkene of the lowest heat of combustion among isomeric alkenes is of the lowest energy and is most stable The stability of alkenes is often compared by measuring the heat of hydrogenation (heat given off, Δ H° h ) during catalytic hydrogenation. The heat of hydrogenation is in small number, which provides more accurate energy difference For a compound containing more than one double bond, Δ H h ° is the sum of heat of hydrogentation of individual double bonds. For non-conjugated dienes, this additive relationship is found to hold. For conjugated dienes, however, the measured value is slightly lower than expected. Cumulated dienes, which are even less stable than non-conjugated dienes. The more stable is the alkene, lower is the heat of combustion and heat of hydrogenation. More highly substituted double bonds are usually more stable. In case of cyclokanes, compounds having higher angle strain are less stable In which of the following is, Δ H° h the maximum? (A) H2C = CH2 (B) H2C = C = CH2 (C)  (D)

Tardigrade Admin · Accepted Answer

Cumulative diene is less stable and, hence, more Δ H° h and more Δ H° c

$H_{2} C = C H_{2}$

$H_{2} C = C = C H_{2}$

Cumulative diene is less stable and, hence, more $Δ H^{\circ}_{h}$ and more $Δ H^{\circ}_{c}$

H2​C=CH2​

H2​C=C=CH2​

Cumulative diene is less stable and, hence, more ΔH∘h​ and more ΔH∘c​

$H_{2} C = C H_{2}$

$H_{2} C = C = C H_{2}$

Cumulative diene is less stable and, hence, more $Δ H^{\circ}_{h}$ and more $Δ H^{\circ}_{c}$