And optical rotation

Physical Properties. Oligosaccharide antibiotics are colodess soHds, which are often crystalline and have defined melting poiats and optical rotations, [cc] (see Tables 1 and 2). They have a characteristic uv spectmm resulting from the phenoHc ester residue, 285 nm (s ca 22), which shifts... 

This Oil is obtamcil from che wood of tuilaiuni l rv specitic gravin 0-976S and optical rotation - 23-5 . 

Origanum viilgare yields from O l to 0-5 per oeot. of oil having a speciho gravity 0-870 to 0-010, and optical rotation about - It ccoiains phenols wh ch have not been carefully iovestigatod,... 

Tardy ha.s examined an Algerian oil of specific gravity 0 991 and optical rotation +62°. He found present pinene, pliellandrcne, isnehone, mcthyl-chavicol, auethol, a sesquiterpene, and a little thymo-hydroquinotie. Scliimmcl A Co. find camphene in fennel oil, but are not able to confirm the presence of cymene. Traces ol basic com-ponnds were also detocted. 

Tjganda Hlemi, from Canarimn, hiceinfw lhu, yields about 11 per eect. of essential oil of specific (Travitv () 84.5I and optical rotation + 9 20, It cootaiiis much phellandrene. 

Thoms olituined a vielJ of 7 per cent, of oil from the seeds, which had a specific gravdlv of 08136 and optical rotation - 5S-.5. The oil, from tvhich traces of free acids and pheooH were first removed, was fractionated in yaciio. 

Tilden and Leech have prepared nitrosocyanides of limonene by the action of potassium cyanide on the nitroso compounds. The table on opposite page gives tbe melting-points and optical rotation of the principal of these and other limonene compounds. 

Costol forms an acetic ester, having a specific gravity 0 9889 at 21° and optical rotation + 19°. 

The normal semi-carbazone melts at 240° to 243°. By reduction it yields dihydroumbellulol, CjqHjjO, a liquid of specific gravity 0-931 at 20° and optical rotation — 27° 30. ... 

Turpentine Oil.—This is readily recognised in oils which contain no pinene, as this is the main constituent of turpentine oil. It is usually found in the first distillates, and generally reduces the specific gravity and effects the solubility and optical rotation. Its presence is proved by the formation of pinene hydrochloride (melting-point 125°) and the nitro-sochloride (melting-point 103°). If pinene is a constituent of the oil itself, the addition of turpentine can only be proved by comparison with an authentic sample. 

The physical properties of the synthetic glycosyl derivatives of l-asparagine, L-serine, and L-threonine are reported in Tables I-V. Derivatives characterized otherwise, but without m.p. and optical rotation, have also been included. Whenever more than one reference is given, the physical constants are taken from the references printed in bold letters. The abbreviations used in the m.p. column are as follows foam., foaming dec., decomposing and soft., softening. 

Table 7.1 The isolated yields, ee and optical rotation of the product alcohols on the preparative scale...

Harada et al. started from preparing inclusion complexes by adding an aqueous solution of PEG bisamine (PEG-BA) to a saturated aqueous solution of a-CD at room temperature and then allowing the complexes formed to react with an excess of 2,4-dinitrofluorobenzene. They examined the product by column chromatography on Sephadex G-50, with DMSO as the solvent, and obtained the elution diagram shown in Fig. 46. They identified the first, second, and third fraction, respectively, as the desired product, i.e., a polyrotaxane, dinitrophenyl derivatives of PEG, and uncomplexed a-CD, by measurement of both optical rotation and UV absorbance at 360 nm for the first, UV absorbance at 360 nm for the second, and optical rotation for the third. 

In 1822, the British astronomer Sir John Herschel observed that there was a correlation between hemihedralism and optical rotation. He found that all quartz crystals having the odd faces inclined in one direction rotated the plane of polarized light in one direction, while the enantiomorphous crystals rotate the polarized light in the opposite direction. 

Within this historical setting, the actual birth of stereochemistry can be dated to independent publications by J. H. van t Hoff and J. A. Le Bel within a few months of each other in 1874. Both scientists suggested a three-dimensional orientation of atoms based on two central assumptions. They assumed that the four bonds attached to a carbon atom were oriented tetrahedrally and that there was a correlation between the spatial arrangement of the four bonds and the properties of molecules, van t Hoff and Le Bell proposed that the tetrahedral model for carbon was the cause of molecular dissymmetry and optical rotation. By arguing that optical activity in a substance was an indication of molecular chirality, they laid the foundation for the study of intramolecular and intermolecular chirality. 

A wide range of physical constants, for instance melting point, boiling point, specific gravity, viscosity, refractive index, solubility, polymorphic forms vis-a-vis particle size, in addition to characteristic absorption features and optical rotation play a vital role in characterization of pharmaceutical chemicals and drug substances. These physical constants will be discussed briefly with typical examples as under ... 

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