Benzyl alcohol, from Cannizzaro reaction

CANNIZZARO S REACTION. BENZOIC ACID AND BENZYL ALCOHOL FROM BENZALDEHYDE 1... 

Prior to the commercial development of this process benzyl alcohol was obtained from benzaldehyde [100-52-7] which undergoes the Cannizzaro reaction (2) upon treatment with potassium hydroxide. High yields of benzyl alcohol and potassium benzoate are obtained by this route which cannot compete with the present day process because of the high cost of benzaldehyde (qv). 

Radical intermediates were proposed at an early stage in the history of the Cannizzaro reaction, and this possibility has been resurrected to account for the detection of some 20% of a-D-benzyl alcohol in the products of the Cannizzaro reaction of a-D-benzaldehyde in aqueous alkaline dioxan. This has been rationalized in terms of formation of the benzaldehyde radical anion, which abstracts a H-atom from the solvent (Chung, 1982). Epr spectroscopy of reacting solutions of p-Cl-,/ -NO 2 and / -CF3-benzaldehyde as well as benzaldehyde itself in THF HMPA (9 1) yielded spectra of the aldehyde radical anions identical to those produced by the action of metallic... 

In F, benzyl alcohol is the hydrogen-rich product from hydride transfer to benzaldehyde in the Cannizzaro reaction the hydrogen-deficient species is benzoic acid. Hydride transfer to the carbonium ion derived from benzyl alcohol also results in the formation of toluene, an even more reduced species. As shov n in Equations 11 and 12, these Cannizzaro-like transformations are essentially redox type, at least in respect to hydrogen balance. 

Derivation (a) By a Cannizzaro reaction from benzaldehyde, (b) by esterifying benzyl alcohol with benzoic acid, (c) by treating sodium benzoate with benzyl chloride. 

This reaction could also afford the heptaldehyde self-condensation product, some benzyl alcohol and benzoic acid (from the Cannizzaro reaction) as byproducts authors reported that a higher temperature favours the jasminaldehyde formation. By slowly adding heptaldehyde, to keep its concentration low, a 99%... 

Benzyl alcohol is the second most important product from benzyl chloride. Stanislao Cannizzaro deduced its structure in 1853 from the reaction of benzaldehyde with potassium hydroxide. 

Scheme 9.4. The Caimizzaro reaction. The oxidation-reduction of benzenecarbaldehyde (benzaldehyde) to benzenecarboxylic acid (benzoic acid) and phenylmethanol (benzyl alcohol). Note the transfer of a hydride (H ) ion from one carbon to another, accounts for the oxidation (hydrogen, H, loss), and reduction (hydrogen, H , gain). (See Cannizzaro, S. Liebigs Ann. Chem., 1853,88, 129.)...

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