Question 12 of 26beginner🔧 ApplyShort Answer3 marks

Write the equations for the preparation of 1-iodobutane from

(i)

1-butanol

Answer

CH₃CH₂CH₂CH₂OH + HI → CH₃CH₂CH₂CH₂I + H₂O (1-butanol reacts with hydroiodic acid to form 1-iodobutane)

(ii)

1-chlorobutane

Answer

CH₃CH₂CH₂CH₂Cl + NaI → CH₃CH₂CH₂CH₂I + NaCl (1-chlorobutane reacts with sodium iodide in dry acetone - Finkelstein reaction)

(iii)

but-1-ene

Answer

CH₃CH₂CH=CH₂ + HI → CH₃CH₂CH₂CH₂I (but-1-ene undergoes addition reaction with HI following Markovnikov's rule)

Explanation

The question asks for three different methods to prepare 1-iodobutane. Part (i) involves nucleophilic substitution of alcohol with HI. Part (ii) is explicitly covered in the context under Halogen Exchange (Finkelstein reaction), where alkyl iodides are prepared by reaction of alkyl chlorides/bromides with NaI in dry acetone. NaCl formed precipitates in dry acetone, facilitating the forward reaction by Le Chatelier's Principle. Part (iii) involves electrophilic addition of HI to but-1-ene, where iodine adds to the less substituted carbon following Markovnikov's rule.

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