Volume 1

Recent advances in organic chemistry / by Alfred W. Stewart.

  • Stewart, Alfred W. (Alfred Walter), 1880-1947.
Date:
1927
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Recent advances in organic chemistry / by Alfred W. Stewart. Source: Wellcome Collection.

    78/412 (page 58)
    is not in accordance with the results of experiment. Too much stress should not be laid on these exceptions, but one or two of them may be mentioned here. Harries 1 showed that unsaturated aldoximes or ketoximes may be reduced to unsaturated amines. Thiele himself men¬ tioned a case observed by Bredt and Kallen 2 in which hydro¬ cyanic acid adds on to cinnamylidene-malonic acid by simple addition to the double bond next the carboxyl radicle. Hin- richsen and Lohse observed that when cinnamenyl-cyanacrylic ester (I.) is allowed to react with bromine it yields a bromide of the formula (II.) shown below— /C=N (I.) C6H5 . CH : CH . CH : (/ ,OEt c=o /C=N (II.) C6H5 . CHBr . CHBr . CH : OEt 0=0 Inspection of the formula (I.) will reveal the fact that in it the conjugation is not a simple one wherein the conjugated linkages follow each other in a straight chain ; for the right- hand ethylenic linkage is obviously conjugated with the double bond of the carbonyl group and also with the triple bond of the nitrile radicle. This is what is termed crossed conjugation,3 of which the simplest type is found in compounds of the following structure :— (6) R'—CH=CH—C—CH—CH—R (1) (2) (3) (4) (5) A glance at this system will show that it might be regarded as containing two different chains of conjugation. The atoms 1, 2, 3, and 6 are included in one chain ; the atoms 6, 3, 4, and 5 are included in the second system. Now the manner in which such a system will react with an external reagent will naturally be governed to a large extent by the nature of the reagent and 1 Harries, Annalen, 1903, 330, 185. 2 Bredt and Kallen, Annalen, 1896, 293, 338. 3 Thiele, Annalen, 1899, 306, 87.