Dolbier HW Solutions 352

Dolbier HW Solutions 352 - 446 ALDEHYDES AND KETONES:...

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stabilization of the carbocation intermediate; the more stable carbocation (R 5 CH 3 ) is formed faster than the less stable one (R 5 H). 17.25 ( a ) The reaction as written is the reverse of cyanohydrin formation, and the principles that govern equilibria in nucleophilic addition to carbonyl groups apply in reverse order to the dissocia- tion of cyanohydrins to aldehydes and ketones. Cyanohydrins of ketones dissociate more at equilibrium than do cyanohydrins of aldehydes. More strain due to crowding is relieved when a ketone cyanohydrin dissociates and a more stabilized carbonyl group is formed. The equi- librium constant K diss is larger for than it is for ( b ) Cyanohydrins of ketones have a more favorable equilibrium constant for dissociation than do cyanohydrins of aldehydes. Crowding is relieved to a greater extent when a ketone cyanohydrin dissociates and a more stable carbonyl group is formed.The measured dissociation constants are
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This note was uploaded on 09/28/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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