Organic Lab Reactions 111

Organic Lab Reactions 111 - _ XYCeHs-CHO + O H - -...

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106 THE CANNIZZARO REACTION least one ortho position is open, except 2,4-dinitrobenzaldehyde and those compounds in which one of the substituents is a hydroxyl group ortho or para to the formyl group (seep. 104). When both ortho positions are filled with halogen or nitro groups the reaction of the aldehyde with alkali takes a different course; the, formyl group is removed as formic acid and is replaced by a hydrogen atom. CHO OH-- HCO 2 - (X=Br, Cl, I, NO 2 ) 2,4-Dinitrobenzaldehyde undergoes the same kind of change, but 2- nitro-4-halo- and 2-halo-4-nitrobenzaldehydes undergo normal dis- mutation. A free hydroxyl group ortho or para to the formyl group interferes with both the cleavage and the dismutation reactions. The effect of two ortho alkyl groups is not recorded. Examples of the cleavage TABLE IV
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Unformatted text preview: _ XYCeHs-CHO + O H - - XYC6H3CH2OH + X Y C 6 H 3 e O O -X 2-C1 3-C1 3-OMe 2-1 2-C1 2-Br 3-OH 2-NO2 3-OH 2-C1 3-OH 3,4-BenzoG8-naphthal-dehyde) Y 5-C1 5-C1 5-OMe 3-OH 3-OMe 5-OH 4-OMe 5-OH 4-OH 3-OH 4-NOa ' Yield of Alcohol 90% 90% 88% 80% 80% 70% 86% 70% 0* 87% 39% ^80% Acid 84% 90% 88% 80% 80% 80% 80% 0* 96% 97% 82% Reference 70 73 73 74 75 67 67 67 67 76 67 77 * After treatment with 50% potassium hydroxide for twenty-four hours, 95% of the aldehyde was recovered. 78 Lock and Nottes, Monatsh., 68, 51 (1936). 74 Lock and Nottes, Monatsh., 67, 320 (1936). 76 Lock and Hoseaus, Monatsh., 62, 178 (1933). 78 Lock and Hoseaus, Monatsh., 55, 307 (1930), 77 Sah, Rec. trav. Qhim., 69, 461 (1940),...
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