Organic Lab Reactions 113

Organic Lab Reactions 113 - 83 a-thiophenealdehyde, 84 and...

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108 THE CANNIZZARO REACTION Hydrohydrastinine does not arise by ring closure of the corresponding alcohol during the reaction, since the alcohol is stable to alkali under the conditions of the reaction. Further examples of the Cannizzaro reaction for polysubstituted benzaldehydes are given in Table V. TABLE V POLYSUBSTITUTED BENZALDEHYDES Substituents 2,4-diBr-5-OCH 3 2-Cl-3-OH-5-Br 2-Cl-3-OCHs-5-Br 2-Br-3-OH-4-OCH 3 2-Br-3,4-diOCH 3 2-Br-3,5-diOCH 3 2-Cl-3,5-diOCH 3 Yield of Acid 90% 80% 90% 86% 92% ' 85% 87% Alcohol 95% 85% 90% 80% 73% 90% 90% Conditions 50% KOH; 60-70°; 4-5 hr. 50% KOH; 60-70°; 4-5 hr. 50% KOH; 100°; 5 hr. 50% KOH; 100°; 30 hr. 50% KOH; 100°; 15 hr. 50% KOH; 100°; 8 hr. 50% KOH; 100°; 3 hr. Reference 75 75 75 82 82 82 73 Aldehydes which are cleaved under the conditions of the reaction have been omitted, but pertinent references may be found in the literature cited. Heterocyclic Aldehydes The Cannizzaro reaction of heterocyclic aldehydes has been examined in a few cases only. Furfural,
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Unformatted text preview: 83 a-thiophenealdehyde, 84 and a-pyridylal-dehyde 86 undergo the reaction normally to give the expected products. 3-Formyl-l,2,5,6-tetrahydro-l-ethylpyridine resinifies upon treatment with potassium hydroxide, 86 a behavior consistent with the observation that it is structurally similar to an a,/3-unsaturated alicyclic aldehyde. 3,4-Dibromothiophene-2,5-dialdehyde undergoes a complex series of reactions, involving both cleavage (loss of —CHO) and dismutation, when treated with alkali. 87 Of particular interest in this connection is the fact that under certain conditions the ester composed of the usual 82 Lock, Monatsh., 64, 341 (1934). 88 Org. Syntheses, Coll. Vol. I, 2nd ed., 276 (1941). 84 Biedermann, Ber., 19, 636 (1886). 86 Harries and Lenart, Ann., 410, 107 (1915). 86 Wohl and Losamtsch, Ber., 38, 4170 (1906). 87 Steinkopf and Eger, Ann., 533, 270 (1938)....
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This note was uploaded on 11/20/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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