Melting points molecular-weight determination

Logarithm of intrinsic solubility (mol L ) experimentally determined (pSOL) also logSexp Melting point Molecular weight... 

The cryoscopic constant Kj gives the depression of the melting point AT (in degrees Celsius) produced when 1 mol of solute is dissolved in 1000 g of a solvent. It is applicable only to dilute solutions for which the number of moles of solute is negligible in comparison with the number of moles of solvent. It is often used for molecular weight determinations. 

Pouradier and Venet (14) showed that the molecular weights (determined by osmometry) of fractions of a gelatin sample could be associated with their melting points. The relationship Tf = A — B/M was found to hold for dif-... 

The aluminum derivative of ethyl acetoacetate is a white crystalHne material, reported to melt at 76°, or 78 to 79°. It supercools readily from the melt to a straw-colored, very viscous liquid. Molecular weight determinations in carbon disulfide indicate that the compound is not associated in that solvent. The aluminmn derivative of ethyl acetoacetate is very soluble in benzene, ether, and carbon disulfide. It is less soluble in petroleum ether or cyclohexane and is insoluble in water. The compound boils at 190 to 200° at 11 mm. The reported dipole moment, in benzene, is 3.96 Debye. Surface tension and density values for the liquid above the melting point have been reported by Robinson and Peak. ... 

Bis(4-imino-2-pentanonato)nickel(II) crystallizes from a benzene-petroleum ether mixture as dark red needles or as fine red-orange needles. The two forms have identical melting points. The compound is very soluble in chloroform, but less soluble in benzene, pyridine, and carbon tetrachloride, and very insoluble in water. The compound crystallizes from pyridine without adduct formation. The compound is diamagnetic and apparently has the trans configuration. Partial resolution in optically active fractions has been achieved by means of a chromatographic technique. Molecular weight determinations indicate that the compound is monomeric in chloroform and benzene solution. The visible absorption spectrum of this compound in chloroform is characterized by a band centered at 552 m/i (e = 43). The ultraviolet absorption maxima for solutions in 1 1 benzene-petroleum ether occur at 298, 348, and 364 m x (e = 4150, 4760, and 4460, respectively). ... 

In 1920 Ray published the first of a series of papers on 9S3 [41, 42, 43]. He reported that preparation of ethanedithiol (by reaction of ethylene bromide with potassium hydrosulfide) leaves behind 9S3 after distillation (Table 4). In contemporaneous work Bennett [44] and coworkers [45] used mixed melting point and cryoscopic molecular weight determination to show that Ray s product was in fact p-dithiane, not 9S3. In a similarly convincing fashion they also disproved Mansfeld s earlier claim for 9S3. Tucker and Reid [46] were also unable to repeat Ray s work. 

The products mentioned in Section V,C are mostly isolated in a pure form and identified not only by analysis and melting points, but also by IR and NMR spectroscopic investigations and often by isolating the products of hydrolysis. Molecular weight determinations show that the plumbyl compounds (XXI)-(XXVII) are monomeric in solution 42, 44). 

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