Pinenes are unsaturated compounds. The structures of two pinenes are shown.
A mixture of these two pinenes reacts with hot concentrated acidified \(\mathrm{KMnO_4}\).
What are the molecular formulae of the organic products?
Correct Answer: \( \boxed{\mathrm{A}} \)
Hot, concentrated acidified \(\mathrm{KMnO_4}\) cleaves carbon-carbon double bonds.
Therefore, the correct answer is (A).
What is the major product when 2-methylpent-2-ene reacts with hydrogen bromide?
Correct Answer: \( \boxed{\mathrm{B}} \)
Hydrogen bromide adds across the double bond by electrophilic addition following Markovnikov’s rule.
Protonation forms the more stable tertiary carbocation at carbon-2.
The bromide ion then attacks this carbocation to form:
\(\mathrm{2\text{-}bromo\text{-}2\text{-}methylpentane}\)
Therefore, the correct answer is (B).
Pent-2-ene is reacted with cold, dilute, acidified manganate(VII) ions.
What is the major product?
Correct Answer: \( \boxed{\mathrm{A}} \)
Cold, dilute, acidified manganate(VII) ions oxidise an alkene by adding two hydroxyl groups across the carbon-carbon double bond.
Pent-2-ene therefore forms the vicinal diol:
\(\mathrm{CH_3CH_2CH(OH)CH(OH)CH_3}\)
Oxidative cleavage to carboxylic acids occurs only under hot, concentrated oxidising conditions.
Therefore, the correct answer is (A).
