Question
Give plausible explanation :
Cyclohexanone forms cyanohydrin in good yield but 2, 2, 6-trimethyl cyclohexanone does not.
Cyclohexanone forms cyanohydrin in good yield but 2, 2, 6-trimethyl cyclohexanone does not.
✓
Answer
Carbonyl group of cyclohexanone is polar so on this nucleophilic addition of HCN occurs easily and forms cynaohydrin in good yield.
But in case of 2, 2, 6-tri-methyl cylohexanone presence of three methyl groups shows + I effect (electron repelling effect) so polarity of carbonyl group decreases and due to steric hinderance of these three methyl groups the attack of $\overline{ C } N$ (Nucleophilic) becomes difficult. So yield of cyanohydrin fromed by the addition of HCN on this is very Low.
But in case of 2, 2, 6-tri-methyl cylohexanone presence of three methyl groups shows + I effect (electron repelling effect) so polarity of carbonyl group decreases and due to steric hinderance of these three methyl groups the attack of $\overline{ C } N$ (Nucleophilic) becomes difficult. So yield of cyanohydrin fromed by the addition of HCN on this is very Low.
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