Which of the following alkenes has the largest molar heat of hydrogenation (ie, releases the most heat upon hydrogenation) ?

A) 2,3-dimethyl-2-butene
B) 2-methyl-2-butene
C) trans-2-butene
D) cis-2-butene
E) 1-hexene

1-hexene has the largest molar heat of hydrogenation because it is a longer chain alkene compared to the others listed. Longer chain alkenes generally have higher heats of hydrogenation due to the greater number of interactions and bonds that can be formed during the hydrogenation process.