Five isomeric alkenes A-E each undergo catalytic hydrogenation to give 2-methylpentane. The IR spectra of these five alkenes have the following key absorptions (in cm-1):
Compound A: 912 (s), 994 (s), 1643 (s), 3077 (m)
Compound B: 833 (s), 1667 (w), 3050 (weak shoulder on C-H absorption)
Compound C: 714 (s), 1665 (w), 3010 (m)
Compound D: 885 (s), 1650 (m), 3086 (m)
Compound E; 967 (s), no absorption 1600-1700, 3040 (m)
Propose a structure for each alkene.