Rotatory power

In view of the indefinite melting-points of many sugars and of their readily obtainable derivatives e.g., osazones, cf. p. 139), their identification should be based primarily on their chemical properties. Their rotatory power can often be used for identification purposes, but is not considered in this book. 

Determination of Rotatory Power. —The 1 otatory p o < 1 of ethyl tartiate, which is an optically active substance, is determined by means of a polarimetcr. One of these insti U-ments known as Laurent s polarimeter is shown in l- igs. 71 and 72. 

Normal measurements of optical activity are concerned with the ability of the optically active substance to rotate the plane of polarization of plane polarized light, its specific optical rotatory power ( ) being given by... 

Charabot and Pdlet have prepared two samples of Spaoish vervain nil, the one distilled from the dried leaves, the other from the flowers, the respeetive yield being 0T 4 per ceut. and 0-878 per oeal, The oil from the leaves had a rotatory power of - 10° 30 , that from the flowers + fi 50 , This laUer appeared to ha more rich in citral than the former, containing 70 per cent, and about 10 por cent, of alcohols,... 

By oxidation of d- and Z-pinene of high rotatory power, Barbier and Grignard obtained the optically active forms of pinonic acid. Z-pinene from French turpentine oil (boiling-point 155 to 157 , od - 37 2 157 to 160 , tto - 32 3°) was oxidised with permanganate. From the product of oxidation, which (after elimination of the volatile acids and of nopinic acid) boiled at 189 to 195 under 18 mm. pressure, Z-pinonic acid separated out in long crystalline needles, which, after recrystallisation from a mixture of ether and petroleum ether, melted at 67° to 69 . The acid was easily soluble in water and ether, fairly soluble in chloroform, and almost insoluble in petroleum ether. Its specific rotation is [a]o - 90-5 in chloroform solution. Oximation produced two oximes one, laevo-rotatory, melting-point 128 and the other, dextro-rotatory, melting-point 189° to 191°. 

No crystalline hydrochlorides eould be obtained from either santalene. tt-Santalene forms a liquid dihydrochloride of optical rotation -n 6°, when dry hydrochloric acid is passed through its ethereal solution. It also forms a crystalline nitrosochloride melting with decomposition at 122°, and a nitrol-piperidide melting at 108° to 109°. /3-santalene forms corresponding compounds, the dihydrochloride having a rotatory power -H 8°. It forms, however, two isomeric nitrosochlorides, CigHj NOCl. They may be separated by fractional crystallisation from alcohol. One melts at 106°, the other at 152°. The corresponding nitrol-piperidides melt at 105° and 101° respectively. 

The treatment of menthylamine by nitrous acid yielded a d-isomenthol still more strongly dextro-rotatory. A d-isomenthylamine hydrochloride, having a rotatory power of [a]o = -1- 17 7°, yielded a d-isomenthol having [a]o = + 25-6°. 

The angle of rotation is, of course, directly proportional to the thickness of the layer of active substance through which the polarised light passes. The expression optical rotation or rotatory power is universally understood to be the observed angle of rotation produced by a column of 100 mm. of the optically active substance. If tubes of other lengths be... 

Drehungs-grad, m. degree of rotation, -kraft, /, rotatory power, -schwingtmg, /, torsional vibration, -streuung, /, rotatory dispersion, -vermogen, n, rotatory power, -winkel, m. angle of rotation. 

O.D., abbrev. (optisches Drehungavermogen) optical rotatory power, od. dgL, abbrev. (oder dergleichen) or the like, bde, a. waste, deserted. 

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