Molecular weight determination 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... 

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... 

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... 

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. ... 

The number average molecular weight determines the colligative properties (i.e., those which depend only on the number of dissolved molecules) of polymer solutions. Measurements of freezing point depression (cryoscopy) or... 

Methods for the determination of Molecular weight based on colligative property are vapour-pressure lowering, boiling point elevation (ebulliometry), freezing-point depression (cryoscopy), and the Osmotic pressure (osmometry). 

The most serious obstacle for the free radical nature of triphenylmethyl was the series of experiments carried out to determine the molecular weight of triphenylmethyl . Cryoscopy was performed in a range of solvents and invariably showed that the molecular weight corresponded to that of the dimer, 486. Only in naphthalene, which in admixture with triphenylmethyl froze at about 80°C, was a lower value obtained, 410. This was a serious dilemma, but Gomberg in 1904 had a reasonable suggestion involving an equilibrium between a dimer and the free triphenylmethyl. 

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,... 

In lyophilic colloidal systems, e.g. in polymer solutions, the disperse phase concentration may be sufficiently high, and the osmotic pressure reaches values that can be reliably measured. In this case osmotic pressure measurements, along with the application of osmosis-related phenomena, such as cryoscopy and ebullioscopy, provide methods for the study of such systems. For example, these methods allow one to determine the molecular weights of polymers. 

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