Question

Identify the alkene obtained on dehydration of each of the following alcohols:

(a) 3-Ethyl-3-pentanol

(b) 1-Propanol

(c) 2-Propanol

(d) 2,3,3-Trimethyl-2-butanol

Answer 1

Answer:

Dehydration is B-elimination reaction which result in alkene formation. Geometrical isomers may form in but Zetsev product is major. CH3 CH3 HOC HC - H2C-Ć-OH H₃C HAC HC- H₃C H₂C- HC Несня - H₃C H2 CH3 3-ethylpent-2-ene 3-Ethyl-3-pentanol All ethyls are equivalent hence only one product results on dehydration. H2 H2C—C—OH 1-Propanol is terminal alcohol and hence only one and terminal alkene results on dehydration + H2C-CH CH2 prop-1-ene H2C propan-1-ol c) CH CH2 "fa- 2-Propanol is terminal alcohol and hence only one alkene results on dehydration HC-OH + CH CH3 CH3 CH3 d) CH3 CH3 Only B-protons fro-CH 3 are available for CH2 H3C— C —C—OH + H3C- -- dehydration. CH3 CH3 CH3 CH3 2,3,3-trimethylbut-1-ene 2,3,3-Trimethyl-2-butanol

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