Rotatory power, free

Configurational stability (or persistence) is one of the important properties of a chiral material. The definition of the lower limit for the free energy barrier for racemization may depend on the specific application. For optoelectronic applications, accelerated aging tests may provide very approximate guidelines [114]. For the purpose of estimating the free energy barrier for racemization, we will assume that the less than 1 % conversion of the major enantiomer to the minor enantiomer in such aging tests is tolerable, i.e. Aa / a < 0.02, where a (in units °mm 1) denotes rotatory power of thin-film material. With these assumptions,... 

The pure laevo-mandelic cannot be obtained readily from small quantities of mandelic acid but a preparation showing to a slight extent laevo-rotatory power may be obtained in the following way The filtrate A is worked up for the free acid exactly as in the method described for pure dextro-cinchonine mandelate since a portion of the d-modification has been removed from the solution, it should be laevo-rotatory. 

As already remarked the imaginary part of the pseudo-scalar i determines the optical rotatory power. X m is a polar vector perpendicular to the electric dipole direction and 2 - - its (scalar) magnitude. In both the averages to be discussed the contribution by R- averages to zero. Where the molecules are locked with electric dipole directions fixed, but are each free to rotate independently about these axes, the averaged discriminating term is given by expression (III. 15)... 

The rotation of individual parts of the molecule plays a role which is especially prominent in larger molecules. This is particularly true in organic molecules, where, in consequence of the possibility of free rotatory power around the simple primary valence bonds, the components of a molecule may be moved toward one another without causing appreciable... 

Fuchs and Tiganik have devised a formula by which the total moment of a molecule can be calculated if it possesses two separate moments, fn and which are able to rotate freely round certain axes fixed in space. In substituted benzenes, it is possible, by comparing experimental results with the requirements of this formula, to decide whether the rotary power of the polar groups is free or impeded. In m- and p-derivatives, e.g. in the chlorophenols, bromophenols, nitrophenols, etc., essentially unimpeded rotatory power of the OH-dipole round the C—0 bond occurs, while in the o-derivatives, the mutual interaction of the substituents is so considerable that mobility is greatly impeded. There is experimental evidence... 

Valence angle, free rotatory power, symmetry in free state, group moments... 

Free rotatory power, deformability and natural vibrations... 

Every advance won by applying exact physical methods to the field of atomic and molecular structure should be made use of immediately in considering the high polymers. The distance rules for primar and secondary valences, the free rotatory power, the dipole properties of molecules, their natural vibrations and their optical behavior, all this is to be drawn on to the last detail in the discussion of high polymers. The experimental methods and also the quantitative results obtained with low molecular substances should be applied to the high polymers. 

Figure 1. Variation of mean residue optical rotatory power [m] with pH for optically active partially quaternized poly(N-N-diethyl aminomethyl thiirane] with 17% N-methylated units in salt-free water (T j = 1 x 10 2 N titrating reagent 1 M HCl).

In salt-free water, no dependance of the rotatory power (a= 1) on the counter-ion has been found except for Bu4N" (Figure 1). As shown in Table IV, in the presence of salts, the same counter-ion dependance on the optical properties as for viscosity is observed. 

Muckiger and Power isolated two laevo-rotatory terpenes from English peppermint oil, but their purity is doubtful. It is probable that they were mixtures of pinene, phellai rene, and limonene. A dextrorotatory sesquiterpene.(cadinene ) is also psresent, as well as menthone,. and menthol, both in the free state and as acetate and isovalerianate. 

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