2. Molecular Representations

Draw the hydrogen bonding that takes place between

a. two molecules of ethanol.

b. two molecules of propylamine.

PRACTICE:Which of the following pairs of molecules would have the highest boiling point?

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).

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.

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

(c) CH₃CH₂CH₂CH₂CH₃ or (CH₃)₂CH₂CH₂CH₃

(d) CH₃CH₂CH₂CH₂CH₃ or CH₃CH₂CH₂CH₂CH₂Cl

Which has

h. the higher boiling point: diethyl ether or butyl alcohol?

Identify the hydrogen bond donors and hydrogen bond acceptors in the following molecules.

(a)

In Table 7.2, what is the smallest alkane, the smallest terminal alkene, and the smallest terminal alkyne that are liquids at room temperature, which is generally taken to be 20 °C to 25 °C?

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

In each pair, choose the compound you would expect to have the highest boiling/melting point.

(b)

In each pair, choose the compound you would expect to have the highest boiling/melting point.

(c)

Identify the hydrogen bond donors and hydrogen bond acceptors in the following molecules.

(b)

In each pair, which would you expect to have the higher melting point?

(a)

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.