A) geometrical isomerism
B) optical isomerism
C) neither optical nor geometrical isomerism
D) both optical and geometrical isomerism
Correct Answer: B
Solution :
When acetaldehyde is treated with aqueous sodium hydroxide solution, it undergoes aldol condensation (because of the presence of \[\alpha -H\] atom) as \[\text{C}{{\text{H}}_{\text{3}}}\text{CHO + HC}{{\text{H}}_{\text{2}}}\text{CHO}\xrightarrow[\text{NaOH}]{\text{Dil}\text{.aqueous}}\] \[\underset{\text{(showsopticalisomerism)}}{\mathop{\underset{\text{aldol}}{\mathop{\text{C}{{\text{H}}_{\text{3}}}\overset{\text{*}}{\mathop{\text{C}}}\,\text{H(OH)C}{{\text{H}}_{\text{2}}}\text{CHO}}}\,}}\,\] Since, the aldol formed contains one symmetric carbon atom, it will show optical isomerism. On heating, aldol loses water and gives an alkene. \[C{{H}_{3}}CH(OH)C{{H}_{2}}CHO\xrightarrow{\Delta }\] \[\underset{\text{(shows geometrical isomerism)}}{\mathop{\text{C}{{\text{H}}_{\text{3}}}\text{CH=CHCHO}}}\,\] The obtained alkene shows geometrical isomerism.You need to login to perform this action.
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