Structural Effects on Heats of Hydrogenation

The energy differences as measured by heats of hydrogenation are within the range of experimental error of those obtained from heats of combustion (Section 5.8). 

The positions of three isomeric butenes show their relative heats of formation. 

Explain why the stability of 2-methyl4-propene can be compared to the stabihty of the isomeric butenes using heat of combustion data, but these stabilities cannot be direcdy compared using heat of hydrogenation data. 

The heats of hydrogenation of 3-methyl-1-butene and 2-methyl-2-butene are 127 and 113 kj mole respectively. Assuming that the following equilibrium reaction can be established, predict the 

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