Index of content:
Volume 12, Issue 10, 01 October 1944
12(1944); http://dx.doi.org/10.1063/1.1723879View Description Hide Description
Raman frequencies and relative intensities are reported for dimethyldiacetylene, diethyldiacetylene, dipropyldiacetylene, dibutyldiacetylene, and diamyldiacetylene. Depolarization factors also were obtained except for diethyldiacetylene. The relative intensities and depolarization factors were obtained with the use of a Gaertner microdensitometer. A tentative assignment was made of all the observed Raman frequencies of dimethyldiacetylene, assuming that it has the symmetry D′3h . Using the chain and methyl group frequencies thus established for dimethyldiacetylene, a comparison was made with the other spectra in order to determine how these frequencies are affected by introducing additional CH2 groups into the dimethyldiacetylene molecule. A comparison was made of the Raman spectra of the disubstituted diacetylenes with those of the corresponding acetylenes. For dimethyldiacetylene, three cases of Fermi resonance occurred, but there were also two cases where only a single line was observed, in spite of the fact that the frequency and symmetry conditions for resonance were satisfied. The carbon‐carbon triple‐bond frequency, which appears at 2183 cm−1 for diacetylene, increases to 2264 for dimethyldiacetylene, then drops to 2251–2257 for the other four compounds.
12(1944); http://dx.doi.org/10.1063/1.1723880View Description Hide Description
An experimental method for determining directly the bond energies in some polyatomic molecules is suggested, and the experimental data obtained in applying it to the case of carbon‐chlorine bond in methyl chloride are presented and discussed. The decomposition of methyl chloride and carbon tetrachloride on hot tungsten is shown to be quite inefficient.
12(1944); http://dx.doi.org/10.1063/1.1723881View Description Hide Description
Systems of linear polymer molecules are characterized by favorable heats of polymerization counterbalanced by unfavorable entropies of polymerization. Long chains are therefore formed and are stable at low temperatures while at sufficiently high temperature appreciable amounts of monomeric units split off. At any given temperature there exists a definite equilibrium distribution in sizes. This distribution is derived here by statistical methods and proves to be a very simple function of the heat of polymerization.
12(1944); http://dx.doi.org/10.1063/1.1723883View Description Hide Description
The thermodynamic properties of sulfur trioxide in the ideal gas state are calculated from molecular data. To obtain satisfactory agreement with the equilibrium data for the reaction SO2+½O2=SO3, it is necessary to include vibrational anharmonicities, which are somewhat larger than usual because of an accidental degeneracy involving two of the normal frequencies. The standard entropy of SO3(g) at 25°C is 61.2±0.2 E.U., and its standard heat and free energy of formation from the elements are ΔH°298.16=−94.43±0.15 and ΔF°298.16=−88.48±0.20 kcal./mole.
12(1944); http://dx.doi.org/10.1063/1.1723884View Description Hide Description
Elongation of swollen vulcanized rubber, or other polymeric materials possessing random network structures, should increase the amount of liquid absorbed (dissolved) at equilibrium with an excess of the swelling agent. According to a previously published equation relating to the thermodynamics of stretching and swelling of rubber, the relative volume of the swollen rubber at equilibrium should equal the square root of the relative stretched length. Experiments with butyl rubber vulcanizates in xylene support these predictions of theory.
12(1944); http://dx.doi.org/10.1063/1.1723885View Description Hide Description
The electrolytic reduction of acetone in alkaline aqueous solutions at a mercury surface has been studied with the object of determining the kinetics of the formation of isopropyl alcohol and pinacol. The reduction rate has been studied at various acetone concentrations, in varying concentrations of sodium hydroxide, in solutions of sodium sulfate, sodium chloride, barium hydroxide, and potassium hydroxide. During electrolysis the rates of formation of isopropyl alcohol and pinacol were followed continuously. It is found that at low acetone concentrations the rate of formation of isopropyl alcohol is proportional to the acetone concentration, while the rate of formation of pinacol is proportional to the square of the acetone concentration. At somewhat higher acetone concentrations the pinacol rate becomes linear in acetone concentration, and near saturation the isopropyl alcohol rate becomes practically independent of acetone concentration. At constant current density, increasing the sodium hydroxide concentration decreases the yield of isopropyl alcohol and increases the yield of pinacol (except at high concentrations of acetone and sodium hydroxide). Substitution of chloride or sulfate for hydroxide causes an increase in the alcohol rate but lowers the pinacol rate. Substitution of barium for sodium stops the reduction completely. Substitution of potassium for sodium increases both yields. Increasing the current density is accompanied by a decrease in the fraction of the current which goes into isopropyl alcohol formation and pinacol formation. It is shown that these experimental results can be explained by a modification of the mechanism proposed by Müller. The acetone is first adsorbed on the mercury with the formation of a covalent bond. The product of the adsorption may dissociate from the surface as a free radical, in which case pinacol is the final product, or it may first add on a proton and then dissociate from the surface as an ion which adds a second proton to become isopropyl alcohol.