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?
a. (CH₃CH₂)₂NH
b. (CH₃CH₂)₃N
c. CH₃CH₂CH₂OH
d. (CH₃CH₂CH₂)₂OH

Which has

a. the higher boiling point: 1-bromopentane or 1-bromohexane?

b. the higher boiling point: pentyl chloride or isopentyl chloride?

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?

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

c. N,N-Dimethylformamide has a boiling point of 150 °C, and N-methylacetamide has a boiling point of 206 °C, for a difference of 56 °C. Explain why these two nitrogen-containing isomers have a much larger boiling point difference than the two amine isomers. Also explain why these two amides have higher boiling points than any of the other four compounds shown (two amines, an ether, and an alcohol).

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

(d) HOCH₂—(CH₂)₄—CH₂OH or (CH₃)₃CCH(OH)CH₃

(e) (CH₃CH₂CH₂)₂NH or (CH₃CH₂)₃N

(f)

Contrary to expectation, the addition of more fluorines to ethane lowers the boiling point. Explain this phenomenon.

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

(b)

Which of these phenomena result from hydrogen bonding?

What type of intermolecular force is likely to occur between two water molecules ($H_{2}O$) or strands of DNA ($\mathrm{DNA}$)?