2. Molecular Representations

Ionic compounds like sodium acetate have a high melting point. Despite this, they are highly soluble in water. Why?

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?

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

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

1. CH₃CH₂OCH₂CH₂OH

2. CH₃CH₂N(CH₃)₂

3. CH₃CH₂CH₂CH₂Br

Which compound is the least polar compound in a mixture analyzed by thin-layer chromatography (TLC)?

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

Draw a picture of the hydrogen bonding in methanol.

For each pair of compounds, predict which one has the higher molecular dipole moment, and explain your reasoning.

c. cis-2,3-dibromobut-2-ene or trans-2,3-dibromobut-2-ene

d. cis-1,2-dichlorocyclobutane or trans-1,3-dichlorocyclobutane

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

b. Octane, (CH₃)₃C—C(CH₃)₃ and CH₃CH₂C(CH₃)₂CH₂CH₂CH₃

The structure of which of the following compounds suggests that it has the highest boiling point?

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

a. hexane, octane, and decane

Choose the molecule in each pair you'd expect to have the higher boiling point. Explain your reasoning.

(a) eicosane ( C₂₀H₄₂) vs pentadecane

Which has

g. the higher boiling point: 1-bromopentane or 1-chloropentane?

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

What types of molecular interactions are primarily responsible for the stability of base pairs in $DNA$?