Journal•ISSN: 0165-0513

# Recueil des Travaux Chimiques des Pays-Bas

Royal Netherlands Chemical Society

About: Recueil des Travaux Chimiques des Pays-Bas is an academic journal. The journal publishes majorly in the area(s): Alkyl & Catalysis. It has an ISSN identifier of 0165-0513. Over the lifetime, 9289 publications have been published receiving 90642 citations.

Topics: Alkyl, Catalysis, Ring (chemistry), Yield (chemistry), Aqueous solution

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TL;DR: In this paper, it was shown that the abscissa of the intersecting point of the 1/v2 and 1 /v branches, when extrapolated to the transition region, is connected in a characteristic way with the statistical chain element or the length of persistance, which represent two different measures for the stiffness of the chain molecule.

Abstract: In the X-ray scattering curve of chain-molecules in solution, essentially four regions may be distinguished as is shown by a more detailed mathematical discussion:
(1)The scattering at the smallest angles, showing an approximately Gaussean course, whose ordinate, when extrapolated to zero angle, is proportional to the square of the mol. weight. It is due to the diffraction effect of the whole coiled chain-molecule.
(2)This is followed by a region of v-values where the scattering falls off as 1/v2. It is due to parts of the chain molecule which themselves already occur in all possible orientations.
(3)After a transition region (which is also accounted for by the theory) there follows a scattering which is proportional to 1/v. It is to be considered as the scattering of mostly straight parts of the molecule.
(4)The scattering at large angles, caused by smaller parts of the molecule (monomer group and single atoms), which at the same time indicates the periodicity (= length of structural unit in the direction of the chain axis) by a step, at an angle corresponding to Bragg's law. Its sharpness, too, is a measure for the coiling of the molecule.
It can be shown that the abscissa of the intersecting point of the 1/v2 and 1/v branches, when extrapolated to the transition region, is connected in a characteristic way with the statistical chain element or the “length of persistance”, which represent two different measures for the stiffness of the chain molecule.
Measurements with polyvinyl bromide lead to a length of persistance of 11 ± 1 A, which agrees satisfactorily with the value of 13 A for polyvinyl chloride as derived from the birefringence of flow. At large angles two weak steps were found, one of which corresponds to the monomer length of 2.56 A.
Measurements on solutions of cellulose nitrate gave a curve ∼ 1/v without any steeper ascent up to the smallest angles, corresponding to 300 A. We have, therefore, to conclude that the chain-element of cellulose nitrate is in any case larger than 150 A, which again is in agreement with the results of other physical measurements.
Though only a small number of experimental results is available so far, it seems to be established that the procedure yields a direct evaluation of the shape of chain molecules in solution and, in this respect, appears superior to other methods. However, the experimental difficulties are considerable.

1,608 citations

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TL;DR: Propargyl ethers HCCCH2OR [R = alkyl or-CH(CH8)(OC2H5)] have been isomerized with good yields into the corresponding allenyl ether's CH2CCHOR by warming with potassium tert-butoxide at 70°.

Abstract: Propargyl ethers HCCCH2OR [R = alkyl or-CH(CH8)(OC2H5)] have been isomerized with good yields into the corresponding allenyl ethers CH2CCHOR by warming with potassium tert.-butoxide at 70°.
These allenyl ethers can be metallated with butyllithium in ether or alkali amides in liquid ammonia. In ether, subsequent alkylation with alkyl halides R′Hal affords α-substituted allenyl ethers CH2CC(R′)OR. Alkylation in liquid ammonia produces a mixture of this same compound and the γ-substituted product R′CHCCHOR. In both cases reasonable yields are obtained. Sodamide and potassium amide quickly convert allenyl ethers CH2CCHOR into metallated propargyl ethers MCC-CH2OR (M = Na or K). If alkylation is not performed almost simultaneously with the metallation with sodamide or potassium amide, the only alkylation product obtained is R′CCCH2OR.

943 citations

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TL;DR: In this paper, the authors apply Onsager's symmetry relations to the process of diffusion of a solution through a membrane and show that measured osmotic pressures deviate from those calculated thermodynamically in proportion to the permeability of the membrane to the solute molecules.

Abstract: Application of Onsager's symmetry relations to the process of diffusion of a solution through a membrane shows that measured osmotic pressures deviate from those calculated thermodynamically in proportion to the permeability of the membrane to the solute molecules. Therefore little is learned from one dynamic osmotic measurement but by simultaneous measurements of osmotic pressure and permeation at different membranes the entire molecular weight distribution of the solute can be computed.

396 citations

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TL;DR: In this paper, a modification of the Benesi-Hildebrand equation is given to determine the equilibrium constant for complex formation from spectrophotometric measurements, and difficulties arising from the use of either concentrations or mole fractions are discussed.

Abstract: A modification is given of the Benesi-Hildebrand equation to determine the equilibrium constant for complex formation from spectrophotometric measurements. Difficulties arising from the use of either concentrations or mole fractions are discussed.

379 citations