Major Product

Correct Answer: C. 3.

The reagents used are indicative of a hydroboration/oxidation reaction, which results in the net addition of water across a double bond. The boron adds to the less substituted carbon of the alkene, which then places the hydrogen on the more substituted carbon (anti-Markovnikov addition); this eliminates answer (A). Both, the boron and the hydrogen add simultaneously on the same face of the double bond (syn addition)−therefore the methyl group must be trans to the newly introduced borane (eliminate B, D). Answer E is an intermediate in the reaction; note that base and hydrogen peroxide are used to oxidize the borane into the hydroxyl final product (answer C).

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