Handbook of the polariscope and its pracitcal applications / adapted from the German editon of H. Landolt, by D.C. Robb and V.H. Veley.

  • Hans Heinrich Landolt
Date:
1882
Catalogue details

Licence: Public Domain Mark

Credit: Handbook of the polariscope and its pracitcal applications / adapted from the German editon of H. Landolt, by D.C. Robb and V.H. Veley. Source: Wellcome Collection.

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    has shown that nearly perfectly inactive mannite solutions become strongly dextro-rotatory on the addition of borax. Again, ac- cording to Muntz and Aubin,1 inactive glucose becomes strongly dextro-rotatory on the addition of sodium sulphate, and still more so of borax; addition of sodium carbonate produces, on the contrary, left-rotation. Moreover, the activity of organic acids and also of alkaloids is in most cases increased by their conversion into salts, and sometimes very considerably. The reverse also happens, as, for example, in the case of chloride of laudanine, which Hesse2 reports as inactive, although the free base is lsevo-rotatory. Papaverine exhibits the same property. 4. In the preceding cases we have spoken only of the synthesis of bodies the chemical structure of which is identical with that of the natural substances, but where structural differences exist there will obviously be dissimilarity of optical power. Thus inactive paraconine from butyric-aldehyde is not an imide base like the active natural conine (Schiff3), and accordingly differs from it in its other structural properties. § 16. Optical Properties of Derivatives of Active Substances.— It has long been observed that when optically-active substances undergo chemical changes, some of their derivatives exhibit rotatory powers whilst others do not. Where the molecular constitution remains unaltered, as in the conversion of acids into salts, ethers, amides, &c., or in the combination of alkaloids with acids, the activity is usually retained.4 On the other hand, where there is actual chemical decomposition, active and inactive derivatives are obtained with an apparent absence of all rule. If, however, the hypothesis of asymmetrical carbon-atoms be called into aid, the apparent irregularity vanishes, and the conditions, as van’t Hoff5 has shown, resolve themselves into the following :— 1. The rotatory powers of active substances are obliterated m such of their derivatives as are wanting in asymmetrical carbon- atoms. 1 Muntz and Aubin: Ann. Chim. Phys. [5] 10, 564. 2 Hesse: Liebig's Ann. 176, 198, 201. 3 Schiff: Liebig's Ann. 157, 352; 166, 94. 4 Exceptions exist in laudanine and papaverine, which, as mentioned in § 15, when free are optically - active, but in the form of chlorides are inactive (Hesse). 5 J. van’t Hoff: see the two pamphlets mentioned in note 7, p. 24 of the present work; also Per. d. deutsch. chem. Gesell. 1877, 1620. D 2