摘要:

Equilibrium between allene and methylacetylene was studied over iron catalyst in the temperature range of 165 to 200 °C, with allene or methylacetylene as the initial reactant. In both cases similar equilibrium product-distribution (allene 16% and methylacetylene 84%), fairly close to the calculated value, is observed.Kinetics of allene-methylacetylene isomerization was studied between 70 and 165 °C. The order of reaction was always one and temperature independent. Both activity and calculated energy of activation (11.8 and 11.2 kcal/mol over iron and cobalt respectively) were similar for the two catalysts, suggesting that active sites for the reaction were also similar. This similarity, as well as the first order kinetics, are fully explained by a reaction mechanism based on adsorbate migration.

ISSN:0008-4042    

DOI:10.1139/v78-461

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The intense emerald green solutions formed by the reaction of iron salts with alkali metal sulfides at pH 11–13 have been found to contain colloidal MFeS2, M = Li, Na, K. Solid KFeS2and NaFeS2have been recovered from these systems. X-ray powder diffraction studies confirmed the identity of KFeS2, and showed NaFeS2to have a structure different from those of other MFeS2compounds, and related to that of the mineral rasvumite, K3Fe9S14. Some aspects of the crystal structures and chemistry of different MFeS2compounds are discussed. A mechanism for the formation of colloidal MFeS2is proposed on the basis of kinetic data. It is likely that colloidal NaFeS2is responsible for the colour of the "green liquor" of the pulp and paper industry.

ISSN:0008-4042    

DOI:10.1139/v78-462

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Densities of water + tetrahydrofuran mixtures were measured at 5 K intervals of temperature from 288.15 to 308.15 K. Excess thermal expansion coefficients and partial molar excess thermal expansivities at 298.15 K over the whole mole fraction range were derived from the results. The significance of the expansivities is discussed in terms of the structural changes accompanying the formation of the mixture.

ISSN:0008-4042    

DOI:10.1139/v78-463

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The densities and heat capacities per unit volume of aqueous solutions of propionamide, methylacetate, ethylacetate, methylethylketone and diethylketone, and bis(2-ethoxyethyl)ether were measured over the whole solubility range with a flow densimeter and a flow microcalorimeter. Most systems were studied at 10, 25, and 40 °C. Properties of the pure liquids were also measured whenever possible. The derived apparent molal volumesall decrease with concentration in the water-rich region, except with ethyl acetate which increases at high temperature. In general the more hydrophobic the solute the more negative the initial slope. All apparent molal heat capacitiesdecrease as a function of concentration and the decrease is more important for more hydrophobic solutes. The apparent molal expansibilitiesare obtained from. They are positive for all solutes but, at low concentrations, they are smaller than the corresponding molar value of the pure liquid. Various factors affecting hydrophobic interactions are examined.

ISSN:0008-4042    

DOI:10.1139/v78-464

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

When a suspension of nearly monodisperse rigid axisymmetric particles in a Newtonian liquid is sheared, the orientation distributions of the particle undergo damped oscillations of frequency twice that of the rotating particles. If the flow is stopped and then reversed, the oscillations regrow under certain restricted conditions until the initial state is fully restored: the system has perfect memory. Removing some of the restrictions causes imperfect recovery of the initial orientation distribution, so that when the flow is reversed cyclically back and forth, the orientation distribution eventually becomes time-independent: the system has lost all of its memory. A number of sources of memory impairment are considered theoretically, several of which are amenable to experimental verification and are illustrated by numerical calculation.

ISSN:0008-4042    

DOI:10.1139/v78-465

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Experiments on the reversibility of particle orientation distributions in suspensions of nearly monodisperse rigid rods and hardened red blood cells (HRBC) subjected to cyclic shearing are described.The orientation distributions of initially aligned rods measured by direct observation exhibited a gradual loss in memory as flow was reversed back and forth which was attributed mainly to non-reversible particle interactions. When an electric field was applied continuously during cyclic shear flow, the rate of memory loss was increased. However, if an electrical shock was applied momentarily between each reversal of flow, the suspension maintained some memory. These results are generally in agreement with the theory presented in the preceding paper.With suspensions of HRBC, the particles were initially randomly oriented and the light transmittance across the planes of shear was used to measure changes in orientation distribution. Since HRBC are small enough to exhibit appreciable rotary Brownian motion, memory loss was inevitable and increased with the duration of each shear cycle and the cell concentration.Memory loss was also observed for rods and HRBC in non-Newtonian media and was attributed to drift in the rotational orbit constants of the particles.

ISSN:0008-4042    

DOI:10.1139/v78-466

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Crystals of 2,2,4,4,6,8,8-heptamethyl-6-methylamino-1,3,5-triaza-2,4,6,8(PV)-tetraphosphorin are monoclinic,a = 11.639(4),b = 11.957(7),c = 12.114(4) Å, β = 94.07(2) °,Z = 4, space groupP21/n. The structure was solved by direct methods and was refined by full-matrix least-squares procedures toR = 0.032 andRwof 0.041 for 2012 reflections withI ≥ 3σ(I). Crystals of 2,2,4,4,6,8,8-heptamethyl-6-methylamino-7-benzoyl-1,3,5-triaza-2,4,6,8(PV)-tetraphosphorin are triclinic,a = 15.513(1),b = 8.422(1),c = 8.933(1) Å, α = 89.24(1), β = 100.18(1), γ = 107.30(1) °,Z = 2, space group. The structure was solved by Patterson and Fourier syntheses and was refined to a finalRof 0.041 andRwof 0.044 for 3654 reflections withI ≥ 3σ(I). The eight-membered P4N3C rings in both structures hâve 'tub' conformations. The mean bond lengths (corrected for libration) are: P—N(endo), 1.609(9), P—N(exo), 1.679(2), P—C(endo), 1.717(2), and P—C(exo), 1.815(8) Å for Me7(MeNH)P4N3CH and 1.595(4), 1.655(2), 1.763(4), and 1.804(5) Å respectively for Me7(MeNH)P4N3CC(O)Ph. The near-equivalence of the endocyclic P—N bond lengths in the azaphosphorins is discussed in terms of opposing changes in the in-plane and out-of-plane Π-systems.

ISSN:0008-4042    

DOI:10.1139/v78-467

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

The kinetics of the reactions of hydrogen peroxide and cyanide with native horseradish peroxidase, as well as reactions of compounds I and II with ferrocyanide have been studied in ordinary water and in deuterium oxide at 25 °C and ionic strength 0.11 using a stopped-flow apparatus. Rate constants for all reactions were measured over a wide range of acidity in both solvents from which equilibrium and kinetic isotope effects were evaluated. Protonation of an ionizable group on the enzyme with a pKavalue of 4.15 ± 0.05 in water inhibits the reactions with both hydrogen peroxide and cyanide. A significant kinetic isotope effect,kH/kD = 1.6 ± 0.1, was measured for compound I formation whereas no significant kinetic isotope effect was found for cyanide binding. On the basis of these findings, a partial mechanism for compound I formation is proposed in which the group of pKa4.15 plays a crucial role. The pH dependencies of the ferrocyanide reaction in the pH interval 4.5–10.8 confirmed the role of an acid group with a pKaof 5.2 for compound I and for compound II a pKaof 8.6 and another with a value lower than that encompassed by the pH range of the study. Equilibrium isotope effects were found but no kinetic isotope effects for either the reaction of compound I or of compound II This suggests that there are no rate-limiting proton transfers in the reactions between ferrocyanide and compounds I and II of horseradish peroxidase. The only reducing substrates which exhibit positivekH/kDvalues possess a labile proton.

ISSN:0008-4042    

DOI:10.1139/v78-468

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Specific labelling of the title compound was achieved through intermediate3a, methyl 2-(2-phthalimidoethoxy)acetate, derived from methyl bromoacetate-2-14C. Conversion to the corresponding acid (4) was followed with selective diborane reduction which provided 2-(2-phthalimidoethoxy)ethanol-2-14C(5). Treatment with thionyl chloride yielded the chloride6which is identical with the intermediate used in the nonlabelled synthesis and reaction with sodium ethyl phthalimidomalonate provided the title compound after hydrolytic work-up.

ISSN:0008-4042    

DOI:10.1139/v78-469

出版商:NRC Research Press    

年代:1978

数据来源: NRC

摘要:

Nine trialkylamines, triethyl- to trihexylamine trioctyl-, tridodecyl, tri(methyl-2-butyl)-, and dimethyldodecylamine have been used for heats of mixing of the following systems at 298 K:A, fourteen systems made of all the possible binary mixtures (except one) of the six shorter amines;B, twelve systems made of a long chain amine, trioctyl-, tridodecyl- or dimethyldodecylamine with the four shorter members of the series;C, two systems consisting of the mixture of two long-chain compounds, trioctylamine with tridodecyl- and dimethyldodecylamine. Heats for the classAsystems are less than or equal to 40 J/mol, indicating no net effect of the small polarity of the shorter members of the series. The experimentalHEof these mixtures are compared with two theories. The Monte Carlo approach gives good predictions but the heats calculated with the Snider–Herrington theory are too negative. Heats of the classBsystems are suitable for the investigation of two new contributions to the heats of mixing, the positive heat of disordering of long-chainsHE(dis.) and the negative heat found in systems where one of the components is sterically hindered,HE(ster.hindr.).HE(dis.) found with the long-chain amines indicates an orientational order larger than in the case of then-alkane of the same chain-length but equivalent to that found in the tetraalkyltin compounds of the same length. Recent work has shown that the tetrapropyl and tetraethyltin derivatives when mixed with long-chain alkanes or tin derivatives give rise to aHE(ster.hindr.) contribution. From this work and the present study, the steric hindrance contributions of five sterically hindered compounds tetraethyltin and tetrapropyltin, triethyl- and tripropylamine, and 3,3-diethylpentane mixed with different second components are calculated. The steric hindrance contribution is found proportional to the volume of the second component and increasing in the following order of the sterically hindered component: triethyl- < tripropylamine < tetraethyl- < tetrapropyltin < 3,3-diethylpentane. Heats of the classCsystems are small without significant contribution ofHE(dis.) due to the fitting of the long-chains in solution.

ISSN:0008-4042    

DOI:10.1139/v78-470

出版商:NRC Research Press    

年代:1978

数据来源: NRC