摘要:

C14carboxyl-labeled phenylalanine has been synthesized by a modified Strecker reaction. A yield of 27.6% based on sodium carbonate (C14) has been obtained and the distribution of the remainder of the activity in the by-products determined.

ISSN:0008-4042    

DOI:10.1139/v51-028

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

An investigation has been made of the mercury photosensitized decomposition of benzene at high temperatures. Practically no reaction occurs at room temperature. At higher temperatures the main product is diphenyl although even at 400°C. the maximum value ofis 0.1. Ediphenylhas been found to be 13 kcal. mole−1. There is evidence that an activated molecule mechanism occurs. The secondary reactions are complex and it is not possible to arrive at a detailed mechanism, but the probable main reaction steps have been pointed out.

ISSN:0008-4042    

DOI:10.1139/v51-029

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

The velocity and absorption of ultrasound (600 kc.) has been measured throughout the critical temperature region of sulphur hexafluoride. Measurements were carried out for the coexisting liquid phase and vapor phase belowTc, and for the supercritical gas, and simultaneously, observations of the meniscus behavior in the neighborhood ofTcwere made. The sound velocity for both liquid and vapor phases belowTcdecreased with increasing temperature and became equal atTc, the velocity at this point being 121.5 m. per sec. In the temperature range from 0.6° belowTctoTcthe velocity in the vapor was greater than that in the liquid. A very high absorption of sound was observed, having a maximum value atTcand extending over a temperature range of approximately 1°. In the temperature range fromTcto 0.6° belowTc, the absorption in the liquid phase was greater than that in the vapour.

ISSN:0008-4042    

DOI:10.1139/v51-030

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

The copolymerization of butadiene and acrylonitrile is very similar to the copolymerization of butadiene and styrene. Polymers predominantly butadiene may be studied by conventional solution techniques but the study of polymers rich in acrylonitrile requires improved solvents for these materials. Polymerization rates are greatest for monomer ratios approximating equal proportions. The mercaptan modifier disappears much more slowly than in the butadiene–styrene system, the regulating index approximating unity. The number average molecular weights calculated from the mercaptan disappearance curves indicate uniform polymer molecular weights to relatively high conversions after which there is a decrease. The viscosity data indicate a rise in viscosity with conversion, which effect is overcome for charges rich in acrylonitrile by the lessening of branching, the more rapid disappearance of mercaptan at high conversion, and the tendency of polymers containing over 50% acrylonitrile to show very low dilute solution viscosities in the solvents tested. Viscosity molecular weights have been calculated and estimates of the molecular weight distribution made. These distributions appear to be quite narrow and the usual broadening at higher conversions is prevented by the increased modifier consumption and increased vinyl content of the polymer prepared with 50 parts acrylonitrile in the charge. The bound acrylonitrile has been determined at various conversions and the reactivity ratios have been found to ber1 = 0.28 andr2 = 0.02 for emulsions andr1 = 0.18 andr2 = 0.03 for oil phase portion only.Qis 0.74 andeis 1.47 as calculated by the Alfrey–Price equations.

ISSN:0008-4042    

DOI:10.1139/v51-031

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

A study has been made of butadiene-styrene copolymers formed at −18°C. From analyses for bound styrene in the product for various conversions and initial butadiene-styrene ratios the reactivity ratios were calculated to ber1 = 1.37 andr2 = 0.38 compared with 1.8 and 0.6 at 45°C.Qandefor butadiene were 1.38 and 0.008 relative to styrene at 1 and −0.8. Increment bound styrene curves calculated for each stage of the reaction indicated that the polymers were remarkably homogeneous at low conversions. The chain transfer reaction using mixed tertiary mercaptans as the modifier was studied. Regulating indices were found to have decreased with polymerization temperature. Number averageand viscosity averagemolecular weights were calculated from mercaptan disappearance and vistex intrinsic viscosity data respectively. The molecular weight heterogeneity increased with increasing conversion and initial mercaptan content. The increment number average molecular weights were found to diminish with conversions, whereas the increment viscosity average increased at higher conversions as conversion increased.

ISSN:0008-4042    

DOI:10.1139/v51-032

出版商:NRC Research Press    

年代:1951

数据来源: NRC

摘要:

An expression for the change in vibrational frequency in terms of changes in the kinetic and potential energy of a molecule has been derived.For numerical calculations approximations are given. The change in frequency due to configurational changes has also been estimated in a qualitative manner. Finally, an approximate relation between the frequencies observed for a certain symmetry type and those calculated by means of force constants derived from some other symmetry type is given as an aid in assigning vibrational spectra.

ISSN:0008-4042    

DOI:10.1139/v51-033

出版商:NRC Research Press    

年代:1951

数据来源: NRC