Describe the structures of the functional groups in alcohols, phenols and ethers, giving bond angles and bond lengths with reasons.

1. 1 · State the common feature. In all three, oxygen forms two σ bonds and carries two lone pairs.
2. 2 · Alcohol. C-O-H 108.9°, less than 109°28′, because of lone pair repulsion.
3. 3 · Phenol. C-O 136 pm (methanol 142 pm): partial double bond by conjugation, and an sp² carbon.
4. 4 · Ether. C-O-C 111.7°, more than tetrahedral, because the bulky alkyl groups repel.
5. 5 · Draw the three structures. Draw methanol, phenol and methoxymethane with the angles and bond lengths marked.
6. 6 · Close in one line. So lone pairs shrink the angle, bulky groups widen it, and conjugation shortens the C-O bond.

Scoring tip: Write the numbers (108.9°, 111.7°, 136 pm, 142 pm); each one scores.