Daily answer writing · Tue, 10 Nov, 2026
Cannizzaro reaction: mechanism, proof of direct hydride transfer, and the crossed reaction with HCHO
Give the mechanism of the Cannizzaro reaction of benzaldehyde with concentrated NaOH. What experimental evidence shows that the hydride is transferred directly from one aldehyde molecule to the other and not taken from the solvent? Explain why (i) acetaldehyde does not undergo this reaction, and (ii) in the crossed Cannizzaro reaction of benzaldehyde with formaldehyde, benzyl alcohol and sodium formate are the main products.
Syllabus: Common to CSE Paper II, IFoS Paper II and Geo-Scientist Mains Paper III (organic): reaction mechanisms of aldehydes and ketones, Cannizzaro, aldol, kinetic and isotopic evidence for mechanisms.
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