2. Molecular Representations

Predict which compound in each pair has the higher boiling point. Explain your prediction.

(a) CH₃CH₂OCH₃ or CH₃CH(OH)CH₃

(b) CH₃CH₂CH₂CH₃ or CH₃CH₂CH₂CH₂CH₃

Which of the following pure compounds can form hydrogen bonds? Which can form hydrogen bonds with water? Which ones do you expect to be soluble in water?

e. CH₃(CH₂)₃CH₃

f. CH₂=CH—CH₂CH₃

g. CH₃COCH₃

h. CH₃CH₂COOH

Draw the hydrogen bonding that takes place between

a. two molecules of ethanol.

b. two molecules of propylamine.

For each pair of compounds, circle the compound you expect to have the higher boiling point. Explain your reasoning.

a. (CH3)3C—C(CH₃)₃ or (CH₃)₂CH—CH₂CH₂—CH(CH₃)₂

b. CH₃(CH₂)₆CH₃ or CH₃(CH₂)₅CH₂OH

c. CH₃CH₂OCH₂CH₃ or CH₃CH₂CH₂CH₂OH

Predict which compound in each pair has the higher boiling point. Explain your prediction.

(e)

(f)

Draw the hydrogen bonding that takes place between

c. a molecule of dimethyl ether and two molecules of water.

d. two molecules of trimethylamine and a molecule of water.

Diethyl ether and butan-1-ol are isomers, and they have similar solubilities in water. Their boiling points are very different, however. Explain why these two compounds have similar solubility properties but dramatically different boiling points.

N-Methylpyrrolidine has a boiling point of 81 °C, and piperidine has a boiling point of 106 °C.

b. Tetrahydropyran has a boiling point of 88 °C, and cyclopentanol has a boiling point of 141 °C. These two isomers have a boiling point difference of 53 °C. Explain why the two oxygen-containing isomers have a much larger boiling point difference than the two amine isomers.

List each set of compounds in order of increasing boiling point.

a. hexane, octane, and decane

Rank the following compounds from highest boiling to lowest boiling:

Explain the following:

a. 1-Hexanol has a higher boiling point than 3-hexanol.

Explain why

c. H₂O (100 °C) has a higher boiling point than HF 120 °C2.

d. HF 120 °C2 has a higher boiling point than NH₃ (-33 °C).

Which of the following compounds forms hydrogen bonds between its molecules?

1. CH₃CH₂OCH₂CH₂OH

2. CH₃CH₂N(CH₃)₂

3. CH₃CH₂CH₂CH₂Br

In each pair of compounds, which compound has the higher boiling point? Explain your reasoning.

c. 2,2,5-trimethylhexane or nonane

In each pair of compounds, which compound has the higher boiling point? Explain your reasoning.

b. nonane or 2-methylheptane