Fundamentals of Organic ChemistryChemistryAlcohols Phenols and Ethers
The conversion of ethanol to propanenitrile is best achieved by:
Options
- ACH ₃- CH ₂- OH + KCN TsCl / Pyridine,
- BCH ₃- CH ₂- OH + HCN
- CCH ₃- CH ₂- OH [ (ii) KCN ] (i) TsCl / Pyridine
- DCH ₃- CH ₂- OH + CH ₃ CN
Correct answer
C. CH ₃- CH ₂- OH [ (ii) KCN ] (i) TsCl / Pyridine
Step-by-step solution
Ethanol ( CH ₃ CH ₂ OH ) cannot undergo nucleophilic substitution directly with CN ⁻ because the hydroxide ion ( OH ⁻ ) is a poor leaving group. First, ethanol is reacted with p -toluenesulfonyl chloride (TsCl) in the presence of pyridine to convert the poor leaving group ( -OH ) into an excellent leaving group, tosylate ( -OTs ). CH ₃ CH ₂ OH TsCl / Pyridine CH ₃ CH ₂ OTs In the second step, the ethyl tosylate is treated with potassium cyanide ( KCN ). The cyanide ion ( CN ⁻ ) acts as a strong nucleophile and disp