• The reaction between compounds having –C=O group and HCN proceeds faster or is more reactive when the groups associated with the carbonyl carbon tend to be less bulkier or the steric hindrance provided to the carbonyl carbon is lesser.
• Presence of more electron pushing groups (like –CH3) with the carbonyl carbon, decreases the delta positive charge on the carbon atom.
• Due to less positive charge on the carbon atom, the association with the CN- ion (of HCN) is slower, so the nucleophilic addition reaction happens slowly.
• In CH3CHO, only one –CH3 group is present (electron pushing group), whereas in CH3COCH3, two –CH3 groups are present, and in this way due to lesser steric hindrance and less number of electron pushing groups, the reaction of CH3CHO happens faster with HCN.
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