Some physico-chemical themes / by Alfred W. Stewart with five plates and thirty-seven diagrams in the text.

  • Alfred Walter Stewart
Date:
1922
Catalogue details

Licence: In copyright

Credit: Some physico-chemical themes / by Alfred W. Stewart with five plates and thirty-seven diagrams in the text. Source: Wellcome Collection.

    42/450 (page 26)
    powers of a series of menthyl esters and brucine salts derived from the higher normal fatty acids, he arrived at a mean value which he designates as the “ normal ” value for the menthyl ester or the brucine salt. On comparing the deviations from this normal value in the cases of compounds containing conju¬ gated double bonds and others in which the conjugation was destroyed by partial saturation, he found that the conjugated substances showed very much greater deviations. For example, pyruvic acid (I.) contains a system of conjugated double bonds whilst in lsevulinic acid (II.) this conjugation is destroyed by the interposition of two methylene radicles :— CH3—C—C—OH I! II O O (i.) CH3—C—CH2—CH2—C—OH II II o o (II.) The deviations from the normal value found by Hilditch in the case of the menthyl esters and brucine salts of these acids are given below :— Menthyl ester. Brucine salt. Pyruvic acid +28° + 162'2° Lasvulinic acid +11*8° 4- 71 *9° A similar result is found in the case of the camphor mole¬ cule ; for the substitution of a carbonyl radicle for a methylene group leads to a very great increase in rotatory power:— csh14 Camphor. /CH2 =0 [a]20° = 55'2C L JDi Camphorquinone. c8h14 c=o c=o [a]20° = 113-2° L JD Even space-conjugation may make its influence felt upon optical rotatory power. On examining the rotations of the menthyl esters of a series of dibasic acids, Hilditch 1 found the following values for the molecular rotation :— 1 Hilditch, Trans., 1909, 95, 1578.