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Where does the OH - ion attack in crossed cannizaro reaction? more electophilic carbonyl carbon (Then the H - reacts on the less electrophylic carbonyl carbon in the next RDS) or the less electrophilic one (Then the H - reacts on the more electrophylic carbonyl carbon in the next RDS) ??? plz help.

Where does the OH- ion attack in crossed cannizaro reaction?
  • more electophilic carbonyl carbon (Then the H- reacts on the less electrophylic carbonyl carbon in the next RDS)     or
  • the less electrophilic one (Then the H- reacts on the more electrophylic carbonyl carbon in the next RDS)  ??? 
plz help.

Grade:12

2 Answers

Sunil Kumar FP
askIITians Faculty 183 Points
9 years ago
Cannizzaro involves two moles of the same aldehyde.being converted to one alcohol and one carboxylic acid.

Cross cannizzaro involves using a ketone and a special aldehyde, usually formaldehyde, being converted into formic acid and an alcohol.
hydroxdide ion attack the formaldehyde hcho is the chief hydride donor
thanks and regards
sunil kr
askIITian faculty
Sumit Majumdar IIT Delhi
askIITians Faculty 137 Points
9 years ago
Dear student, OH- attacks the electron-deficient carbon in the initial stage. This is followed by a hydride shift and ultimate proton exchange to form the final stable species. Of almost all aldehyde's compatible for the Cannizzaro rxn formaldehyde is perhaps most e-deficient. So OH0- always attacks it first. The compound that OH- attacks initially gives the acid ultimately.
Regards
Sumit

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