Starting with Propanol (CHCHCHOH), show how would you synthesize the following substances

2. (a) Starting with Propanol (CH
   CH
   CH
   OH), show how would you synthesize the following substances? Use equations only, showing structures of reactants, reagents and all intermediate products. (i) 3-Hexanol {CH
   CH
   CH
   (OH)CHCH
   CH
   } (ii) Propanoic acid (CH
   CH
   COOH) (iii) 2-Pentene (CH
   CH
   CH=CHCH
   ) (iv) Ethyl propyl ether (CH
   CH
   CH
   OCH
   CH
   ) (b) Give the structure the major product(s) formed when 2-Butanol (CH
   CH
   CH
   CH
   OH) reacts with the following reagents: (i) KMnO
   /H
   O
   (ii) SOCl
   (iii) Conc. H
   SO
   /heat (iv) PCC/CH
   Cl

The Correct Answer and Explanation is:

(a) Synthesis from Propanol

(i) 3-Hexanol

1. Convert propanol to propyl bromide using PBr₃: CH₃CH₂CH₂OH + PBr₃ → CH₃CH₂CH₂Br
2. Perform a Grignard reaction with ethylene oxide to obtain 3-pentanol: CH₃CH₂CH₂MgBr + C₂H₄O → CH₃CH₂CH₂CH(OH)CH₃
3. Extend the carbon chain using another Grignard reagent to yield 3-hexanol: CH₃CH₂CH₂CH(OH)CH₃ + CH₃CH₂MgBr → CH₃CH₂CH₂CH(OH)CH₂CH₃

(ii) Propanoic Acid

1. Oxidize propanol using a strong oxidizing agent like KMnO₄ or CrO₃: CH₃CH₂CH₂OH → CH₃CH₂COOH

(iii) 2-Pentene

1. Convert propanol to propyl bromide using PBr₃: CH₃CH₂CH₂OH + PBr₃ → CH₃CH₂CH₂Br
2. React with sodium ethoxide to form 2-pentene via elimination: CH₃CH₂CH₂Br + C₂H₅ONa → CH₃CH₂CH=CHCH₃

(iv) Ethyl Propyl Ether

1. Convert propanol to propyl bromide using PBr₃: CH₃CH₂CH₂OH + PBr₃ → CH₃CH₂CH₂Br
2. Perform Williamson ether synthesis using sodium ethoxide: CH₃CH₂CH₂Br + C₂H₅ONa → CH₃CH₂CH₂OCH₂CH₃

(b) Reactions of 2-Butanol

(i) KMnO₄ / H₃O⁺

Strong oxidation forms butanone and eventually butanoic acid: CH₃CH₂CH(OH)CH₃ → CH₃CH₂COCH₃ → CH₃CH₂COOH

(ii) SOCl₂

Forms 2-chlorobutane via substitution: CH₃CH₂CH(OH)CH₃ + SOCl₂ → CH₃CH₂CHClCH₃

(iii) Concentrated H₂SO₄ / Heat

Under acidic dehydration, 2-butene is formed: CH₃CH₂CH(OH)CH₃ → CH₃CH=CHCH₃

(iv) PCC / CH₂Cl₂

Mild oxidation leads to butanone: CH₃CH₂CH(OH)CH₃ → CH₃CH₂COCH₃

Explanation

Each transformation is guided by standard organic chemistry principles. The oxidation of propanol yields propanoic acid, whereas conversion to a Grignard reagent allows chain extension to 3-hexanol. Williamson ether synthesis efficiently forms ethyl propyl ether. For 2-butanol, oxidation and dehydration reactions play key roles in obtaining ketones, carboxylic acids, and alkenes. Understanding these fundamental reactions provides insight into broader organic synthesis strategies.