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Organic Lab Reactions 105

Organic Lab Reactions 105 - R RR'CHCHO H,C0 OH CHO C R CH 2...

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iOo THE CANNIZZARO REACTION TABLE I R CH 3 CH« CH 3 CH 3 CH 3 GH 8 R' CH, CH 3 CH 3 CH 3 CH, C 2 H S Base Aq. K 2 CO 8 Aq. KOH NaOAc Ca(OH) 2 Ca(OH) a 1 AT KOH Conditions Room temp. Room temp. 100° 150" , 0-100° Products (yields) Aldol only Aldol, glycol, acid Glycol-i-butyrate Aldol (40%), Glycol (10%), glycol isobutyrate (20%), acid (16%) Isobutyl alcohol (8%), glycol (18%), acid Glycol (40%), acid (21%) Refer- ence 41 41 41 39 39 29 This reaction appears to be of limited usefulness as a preparative method. The fact that the ester is sometimes isolated 39> 41 is of interest in connection with the mechanism of the Cannizzaro reaction (p. 97). Aldehydes with One a-Hydrogen Atom, in the Presence of Formalde- hyde. Aldehydes of the type RR' CHCHO may condense with formalde- hyde according to the following equation. R' RR'CHCHO + H,C0
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Unformatted text preview: R' RR'CHCHO + H,C0 OH-\ CHO C R \ CH 2 0H The /J-hydroxyaldehyde so formed may then undergo a crossed Cannia-zaro reaction with formaldehyde to yield a /3,/3-disubstituted trimethyl-ene glycol. R' CHO R' CH 2 OH \ R \ + H 2 C0 OH" \ CH 8 0H R C \ C HC0 2 H CH 2 0H This reaction has been found to be a useful method of preparing jS,0-disubstituted trimethylene glycols. Examples are given in Table II. Aldehydes with Two a-Hydrogen Atoms, in the Presence of Formalde-hyde. Aldehydes of the general type RC(CH 2 OH) 2 CHO are formed by the condensation of formaldehyde with aldehydes having two a-hydrogen atoms. ATT _ RCH 2 CHO + 2H 2 CO >• RC(CH 2 OH) 2 CHO...
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