Organic Lab Reactions 106

Organic Lab Reactions 106 - 46 in aqueous solution at...

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ALDEHYDES WITH TWO a-HYDROGEN ATOMS 101 TABLE II RR'CHCHO + HCHO — RR'C(CH 2 OH) 2 + HCOOH R CH 3 CH 3 CH 3 CH 3 CH 3 R' CH 3 CH 8 C2H6 C 3 H7 C 6 H 6 Amount of Alde- hyde 2* 1 * 48 g. 45 g. 100 g. HCHO 1* 2.08* 32.8 g.f 17.9g. f ' Base _ 12% ale. KOH KOH 23 g. KOH 16.8 g. Product (CH 3 ) 2 C(CH 2 OH) 2 (CH 3 )2C(CH 2 OH) 2 (CH3)(C 2 H 6 )C(CH 2 OH) il (CH 3 )(C 3 H7)C(CH 2 OH) 2 (CH 3 )(C 6 H 6 )C(CH 2 OH) 2 Yield 20*40% 70% 77% 84% 81% Refer- ence 42 43 44 44 44 * Parts by weight, t Weight of formalin. In the presence of excess formaldehyde a crossed Cannizzaro reaction ensues, leading to a trimethylol alkane. RC(CH 2 OH) 2 CHO H 2 CO -^-> RC(CH 2 OH) S HCO 2 - In the special case of acetaldehyde the reaction is that used in the well- known method of preparing pentaerythritol. 46 CH 3 CHO + 4H 2 CO + £Ca(OH) 2 -* C(CH 2 OH) 4 + (HCO 2 )Ca/2 Because of the technical importance of pentaerythritol, this reaction has been the subject of considerable investigation. The condensation is best effected by calcium hydroxide
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Unformatted text preview: 46 in aqueous solution at moderate temperatures (15-90), using an excess of formaldehyde over the ratio (4CH 2 O : ICH3CHO) required by theory. A ratio of 5 : 1 has been found to v give satisfactory yields (73.5%), a smaller proportion of formaldehyde causing the production of considerable amounts of the ether, [C(CH 2 OH) 3 CH2]2O. 47 In technical practice an excess of 40-60% 42 Meyersburg, Monatsh., 26, 41 (1905). "Fischer and Winter, Monatsh., 21, 301 (1900). "Franke, Monatsh., 34, 1904 (1913). 46 Org. Syntheses, Coll. Vol. I, 2nd ed., 425 (1941). 46 Corbellini and Langini, (Horn. chim. ind. applicata, 15, 53 (1933) [C. A., 27, 4526 (1933)]. 47 Friederich and Brtinn, Ber., 63B, 2681 (1930)....
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