Molecular weight determination by cryoscopy

On the basis of molecular weight determinations by cryoscopy in THF and conductivity measurements, it was concluded that the polymeric chain breaks up in solution to form smaller aggregates, probably giving rise to solvent-separated... 

In the presence of anhydrous hydrogen fluoride at 30°, cellulose is transformed into a polymeric product, called cellan.77 This substance is water-soluble, strongly dextrorotatory ([mineral acid, and only faintly reducing. Molecular-weight determinations (by cryoscopy) on cellan acetate ([a]n + 128°) and on the regenerated polymer indicated it to have a Pn of 14. 

Molecular weight determinations by cryoscopy in benzene revealed that the MLi2BrAr2 stoichiometry found in the solid state is retained in solution. On the basis of NMR and cryoscopy, it can be concluded that the structural features of the bromoaurate are similar to those of the bromocuprate and -argentate. A multinuclear NMR study shows that the bonding between the [Li-Br-Li] and [Ar-M-Ar] is intermediate between ionic and covalent, with a more covalent Au-C,pjo bond than the Cu-C o or Ag-Cipso ones. A similar trend has also been reported previously by van Koten for tetranuclear compounds of the type [M2Li2 2-CH2NMe2C6H4 4] (M = Cu, Ag, Au).125... 

Molecular Weight and Constitution.—The electrical conductivity of aqueous solutions of potassium perdisulphate supplies distinct evidence of the dibasicity of the corresponding acid.12 This is confirmed by molecular weight determinations made by the cryoscopie method... 

To differentiate monomeric, dimeric, and polymeric products, a molecular weight determination is essential. The usual cryoscopic and osmometric techniques are applicable.In fact, these methods have been used for impure dioxe-tanes and at low temperatures.Furthermore, the dioxetane derived from the acridine (14) by singlet oxygenation (Eq. 27) was shown to be the dimeric peroxide (15) by cryoscopy. ... 

Dibutylperoxide 62) and azobis(isobutyronitrile) in bulk or benzene solution were initiators. The same polymer was obtained 166) by initiation with y-irradiation ( °Co source). The molecular weight of this latter polymer as determined by cryoscopy was approximately 1500. The ratio of x x + y) is a measure of the extent of cyclization that occurred during the reaction. This ratio depends on the experimental conditions used. It was claimed in one instance that the free-radical polymerization of bicyclo[2.2.1]heptadiene yields polymer resulting from l,2 -polymerization only [Eq. (II-5)] (72). 

In many of its reactions, and in its molecular formula, thiocyanogen shows a close analogy with the halogens. Its molecular weight has been determined by the cryoscopie method, allowing a known weight of bromine to react with lead thiocyanate in the presence of bromoform,... 

The 4-nonylphenol methanal resin fiom a methanal/phenol mole ratio = 0.67 reaction is a solid product with an average molecular weight of 1400 g mole, as determined in hexane by cryoscopy. Rheological investigation of all of the resins showed a non-Newtonian rheological behavior [122]. 

The method "was utilized to determine the molar -weights of squalane (against eicosane) [110] and apieson L [111] and the results are in very good agreement with those yielded by osmometry and cryoscopy, respectively. Martire [112] has shown that for molecular weights of about 6000 the error is 15% and that it rises with increasing molecular weight. 

The other methods for determining M, by using the colligative nature of the polymer solutions are ebulliometry and cryoscopy, by both of which the maximum molecular weight obtainable is about 2 x 10. The detailed principles and practical techniques for determination of by these methods are described in refs 12 and 13. Note that these two methods are available only at specific (boiling or melting) temperatures for given solutions and are limited in applications. 

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