Solvents Trouton constants

After evaporating the solvents and hydrogen halides the free acids can be purified by fractional distillation in vacuo. It was not possible to isolate the acid with X = J (7). The high value of the Trouton constant (25.1 cal/Mol °K) (7) seems to indicate, that H[P02FC1] and H[P02pBr] as well are associated over hydrogen bridges. 

This rule works best for apolar, quasi-spherical molecules. Large deviations occur when chemical association is involved (e.g., carboxylic acids), from molecular dipolarity (e.g., dimethyl sulfoxide), and from molecular asphericity (e.g., neopentane/ -pentane). Strongly associating solvents (e.g., HF, H2, NH3, alcohols, carboxylic acids) have Trouton constants which are higher than the average value of 88 J mol K" found for nonassociating solvents such as diethyl ether and benzene. 

Dimethylformamide and related solvents, such as dimethyl sulphoxide, have high Trouton constants and high dipole moments (Table 1, and... 

Table 4.1 The structuredness of solvents, measured by their Trouton s constant, the entropy deficit, the dipole orientation correlation coefficient, and the heat capacity density...

From these relationships, the following values are obtained 4 heat of fusion, 3.5 kcal./mol normal boiling point, 233° Trouton s constant, 25.5 cal./deg. mol. The liquid and vapor are both associated.4 Cryoscopic measurements upon benzene solutions give apparent molecular weights ranging from 158 (mol fraction = 0.0016) to 230 (mol fraction = 0.0060). At room temperature the solubility of the compound in benzene is 0.995 g./lOO g. of solvent.3... 

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