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Nucleophilic substitution

According to the Edexcel Chemistry Unit 4 Paper Jan 2011, one enantiomer of 2-chlorobutane reacts with hydroxide ions to form a mixture of enantiomers of butan-2-ol because 2-chlorobutane forms a carbocation intermediate. The past paper assumes that 2-chlorobutane reacts by SN1.

However, according to the Edexcel AS Student Book and my teachers, primary and secondary halogenoalkanes react with nucleophiles by SN2, forming a five-bonded transition state. Therefore you should expect for inversion to happen and only one enantiomer of butan-2-ol to form. Only tertiary halogenoalkanes react by SN1, forming a carbocation intermediate.

Is it possible for the past paper to be right?