RECENT ADVANCES IN SCIENCE--ORGANIC CHEMISTRY.

Abstract

The proof of the equivalence of the four valencies of the carbon atom which was originally furnished by Henry (Bull. Acad. Roy. Belg. 1886, Classe des Sciences, 12, (111), 644, 1888,15, 333 and 1906, 722) can no longer be regarded as rigid in view of the possibilities of intramolecular rearrangement on the lines of the so-called Walden inversion. Fischer and Brieger (Berichte, 1915, 48, 1517) have accordingly taken up this question once more, making use of a series of reactions in which no substitutions are called into play and which all take place at low temperatures, thereby reducing the chances of a Walden inversion to a minimum. Starting with the optically active half amide of ethyl isopropyl malonic acid [FORMULA NOT REPRODUCIBLE IN ASCII] they have obtained by the action of nitrous acid the optically inactive ethyl isopropyl malonic acid, thus demonstrating the equivalence of the two carboxyl groups. Similarly, dextrorotatory allyl propyl cyanacetic acid [FORMULA NOT REPRODUCIBLE IN ASCII] on reduction has yielded the inactive dipropyl cyanacetic acid which proves the equivalence of the two alkyl groups. It is proposed next to prepare the optically active form of vinyl ethyl cyanacetic acid [FORMULA NOT REPRODUCIBLE IN ASCII] and to reduce a portion of it to the inactive diethyl cyanacetic acid and also if possible to oxidise some of it to ethyl cyanomalonic acid [FORMULA NOT REPRODUCIBLE IN ASCII] If these latter reactions are successfully accomplished the equivalence of all the four valencies will have been established. The intricate question of the assimilation of carbon dioxide by the plant forms the subject of an interesting paper by Willstatter and Stoll (Berichte, 1915, 48, 1540). The authors' method of experimenting was to pass a regular stream of air containing a known amount of carbon dioxide through a small illuminated glass vessel immersed in a constant temperature water bath and containing from 5 to 20 grams of leaves. By estimating the amount of carbon dioxide in the issuing gas and the amount of chlorophyll in the leaves they determined the ratio between the number of grams of carbon dioxide assimilated in one hour and the weight of chlorophyll concerned, to which ratio they gave the name of assimilation number. Experiments with normal, autumnal, and etiolated leaves showed that the assimilative effect is not always proportional to the chlorophyll content, which is explained by assuming that the process of assimilation is to some extent effected by an enzyme, probably acting at the surface of contact between the chloroplast and the plasma. The fact that in leaves rich in chlorophyll an increase in illumination produces no effect on assimilation, whereas a rise in temperature brings about increased assimilation is explained by the accelerating effect of a rise of temperature upon the enzyme action. In the case of leaves deficient in chlorophyll a rise of temperature has but little influence, whereas increased illumination has a very marked effect. The explanation offered in this case is that there is more than sufficient enzyme present for the chlorophyll present, but that the greatest assimilative effect can only be attained when all the chlorophyll is exerting its maximum activity. All attempts to bring about assimilation by means of chlorophyll isolated from the leaf failed, in all probability owing to absence of enzyme. …