9. Alkenes and Alkynes

Rank the following compounds from most stable to least stable:

trans-3-hexene, cis-3-hexene, cis-2,5-dimethyl-3-hexene, (Z)-3,4-dimethyl-3-hexene

The energy difference between cis- and trans-but-2-ene is about 4 kJ/mol; however, the trans isomer of 4,4-dimethylpent-2-ene is nearly 16 kJ/mol more stable than the cis isomer. Explain this large difference.

For each set of isomers, choose the isomer that you expect to be most stable and the isomer you expect to be least stable.

(a)

Explain why each of the following alkenes is stable or unstable.

(a) 1,2-dimethylcyclopentene

(b) trans-1,2-dimethylcyclopentene

(c) trans-3,4-dimethylcyclopentene

(d) trans-1,2-dimethylcyclodecene

When the alkyne ${\mathrm{CH}}_3-C\equiv C-{\mathrm{CH}}_3$ is treated with ozone followed by water, how many carboxylic acid products are formed?

Which of the following is the correct structure for $3-\mathrm{hex}\mathrm{yne}$?

Which of the following alkenes is the most stable?

Which of the following alkenes is the most stable?