Question

Draw a structural formula for the alcohol formed by treating each alkene with borane in tetrahydrofuran (THF) followed by hydrogen peroxide in aqueous sodium hydroxide and specify stereochemistry where appropriate. (a) C=C1CCCCC1 (b) CC1=CCCCC1 (c) CCC=C(C)C (d) C=CCCCCCC (e) C=CC(C)(C)C

Short answer

Answer: The products of hydroboration-oxidation reactions are as follows: (a) cyclohexanol, (b) 1-methylcyclohexanol, (c) 2-methyl-2-butanol, (d) 1-octanol, and (e) 2,2-dimethyl-2-butanol.

Step-by-step solution

(a) Reaction with C=C1CCCCC1 (cyclohexene)

Cyclohexene reacts with borane to form a cyclic intermediate where boron is attached to the less substituted carbon. After treatment with hydrogen peroxide and sodium hydroxide, the boron will be replaced with a hydroxyl group. The resulting product is cyclohexanol. Product: OC1CCCCC1

(b) Reaction with CC1=CCCCC1 (1-methylcyclohexene)

1-methylcyclohexene reacts with borane to form a cyclic intermediate where boron is attached to the less substituted carbon (the one without the methyl group). After treatment with hydrogen peroxide and sodium hydroxide, the boron will be replaced with a hydroxyl group. The resulting product is 1-methylcyclohexanol. Product: CC1(O)CCCCC1

(c) Reaction with CCC=C(C)C (3-methyl-1-butene)

3-methyl-1-butene reacts with borane to form an alkylborane intermediate where boron is attached to the less substituted carbon (terminal carbon). After treatment with hydrogen peroxide and sodium hydroxide, the boron will be replaced with a hydroxyl group. The resulting product is 2-methyl-2-butanol. Product: CC(C)(C)CO

(d) Reaction with C=CCCCCCC (1-octene)

1-octene reacts with borane to form an alkylborane intermediate where boron is attached to the less substituted carbon (terminal carbon). After treatment with hydrogen peroxide and sodium hydroxide, the boron will be replaced with a hydroxyl group. The resulting product is 1-octanol. Product: CCCCCCCCO

(e) Reaction with C=CC(C)(C)C (3,3-dimethyl-1-butene)

3,3-dimethyl-1-butene reacts with borane to form an alkylborane intermediate, where boron is attached to the less substituted carbon (terminal carbon). After treatment with hydrogen peroxide and sodium hydroxide, the boron will be replaced with a hydroxyl group. The resulting product is 2,2-dimethyl-2-butanol. Product: CC(C)(C)C(C)O