The same alkane is obtained from the catalytic hydrogenation of both alkene A and alkene B. The heat of hydrogenation of alkene A is 29.8 kcal/mol, and the heat of hydrogenation of alkene B is 31.4 kcal/mol. Which alkene is more stable?

Rank each group of compounds in order of increasing heat of hydrogenation.

(b)

Rank each group of compounds in order of increasing heat of hydrogenation.

(a) hexa-1,2-diene; hexa-1,3,5-triene; hexa-1,3-diene; hexa-1,4-diene; hexa-1,5-diene; hexa-2,4-diene

Consider the Cope rearrangement, a reaction we describe in Chapter 20.

(a) Using the knowledge we have gained here in Chapter 9, suggest a one-step, concerted mechanism that explains the formation of B from A.

(b) Which side of the reaction would you expect to be favored? Justify your answer.

(c) Which product, A or B, would you expect to be hydrogenated with the more exothermic heat of hydrogenation?

Rank the following alkenes in order of stability (1 = most stable; 5 = least stable). Explain your order.                                                                                                                                                                                   

a. Which is the most stable: 3,4-dimethyl-2-hexene, 2,3-dimethyl-2-hexene, or 4,5-dimethyl-2-hexene?

b. Which compound has the largest heat of hydrogenation?

c. Which compound has the smallest heat of hydrogenation?

Of the compounds you named in Problem 45:

a. Which is the most stable?

a.

b.

c.

d.

e.

f.

Of the compounds you named in Problem 45:

b. Which is the least stable?

a.

b.

c.

d.

e.

f.