2. Molecular Representations

Rank the boiling points of the following molecules. Explain your ranking ( 1 = highest bp; 3 = lowest bp ).

a. Which compound would you expect to have a greater dipole moment, methyl acetate or butanone?

b. Which would you expect to have a higher boiling point?

Imidazole boils at 257 °C, whereas N-methylimidazole boils at 199 °C. Explain the difference in boiling points.

Rank the following isomers in order of increasing boiling point, and explain the reasons for your order of ranking.

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

(a)

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

(d)

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

(b)

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)

Which of the preceding compounds forms hydrogen bonds with a solvent such as ethanol?

1. CH₃CH₂OCH₂CH₂OH

2. CH₃CH₂N(CH₃)₂

3. CH₃CH₂CH₂CH₂Br

What is the smallest straight-chain alkane that is a liquid at room temperature (which is about 25 °C)?

Which has

i. the greater density: heptane or octane?

j. the higher boiling point: isopentyl alcohol or isopentylamine?

k. the higher boiling point: hexylamine or dipropylamine?

Which of the preceding compounds forms hydrogen bonds with a solvent such as ethanol?

4. CH₃CH₂CH₂NHCH₃ 

5. CH₃CH₂CH₂COOH

6. CH₃CH₂CH₂CH₂F

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?