Photochemical reactions in monolayers I—Photochemical properties of the ketoimino linkage

Abstract

Abstract In a number of previous communications it has been shown that chemical reactions occurring in organic compounds spread in monolayers at the surface of aqueous substrates can be investigated by observation of the phase boundary potential and surface pressure. In this paper an application of the method to photochemical reactions in monolayers is described. This mode of approach makes possible photochemical investigation of organic compounds of high molecular weight and is particularly suitable for the exact study of the action of ultra-violet radiation on substances of physio­logical importance under conditions which may approximate to those in vivo. In this paper the photochemical properties of the ketoimino linkage are examined. Singularly little has been recorded on the photochemistry of simple compounds containing the ketoimino linkage. In 1926 Abderhalden and Haas (1926) found that irradiation for 12 hr. with the total radiation from a quartz mercury vapour lamp produced no change in the optical rotation of solutions of glycyl-d-leucine and d-leucyl-glycine, in the presence or absence of oxygen. In the case of d-leucyl-glycine anhydride no change occurred in the absence of oxygen, but when oxygen was present the specific rotation fell rapidly, reaching a steady value in 4 hr., and CO2 and NH3 appeared in the solution. Eckstein and Lieben (1933) irradiated M/200 solutions of glycyl-glycine, glycyl-l-leucine and dl-leucyl-glycyl-glycine with the total radiation from a mercury vapour lamp for 2 hr. and found no change in amino-nitrogen as determined by Van Slyke’s method. Guillaume and Tanret (1935) found that solutions of glycyl-glycine, alanyl-glycine, glycyl-tyrosine and ovalbumin were unchanged by irradiation, presumably in the absence of oxygen, with the total radiation from a mercury vapour lamp. The photolysis of amides and amino-acids by sunlight in the presence of oxygen has been studied by Rao and Dhar (1934), and it is of interest that no changes were observed with hippuric acid.