38. Secondary alcohols on catalytic dehydrogenation by Cu-Ni couple give;
a) Ketone
b) Aldehyde
c) Carboxylic acid
d) Amine
Secondary alcohols undergo catalytic dehydrogenation by Cu-Ni couple to yield ketones.
Reaction Overview
Vapors of secondary alcohols passed over Cu-Ni catalyst at elevated temperature lose two hydrogen atoms, forming a carbonyl group (C=O) in the ketone. The general reaction R₂CHOH → R₂C=O + H₂ proceeds via surface adsorption on Cu-Ni, followed by hydride and proton elimination. This distinguishes secondary alcohols, which lack alpha hydrogens on one side unlike primary alcohols yielding aldehydes over Cu at 573 K.
Option Analysis
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a) Ketone: Correct. Cu-Ni facilitates dehydrogenation of the -CH(OH)- group to >C=O, as confirmed in standard organic chemistry catalysis.
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b) Aldehyde: Incorrect. Aldehydes form from primary alcohols (RCH₂OH → RCHO); secondary alcohols lack the required -CH₂OH structure.
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c) Carboxylic acid: Wrong. Acids require further oxidation beyond dehydrogenation, typically with stronger agents like KMnO₄, not Cu-Ni catalysis.
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d) Amine: Incorrect. No nitrogen source exists; amines arise from reduction reactions like nitro group reduction, unrelated to alcohol dehydrogenation.
This CSIR NET-style question tests alcohol classification and catalytic specificity, where Cu-Ni ensures selective ketone formation ideal for exam preparation.
