摘要:

The reaction between 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 4-isopropyl-2,6-di-t-butylphenol has been studied by optical and electron spin resonance methods. The concentration of the intermediate 4-isopropyl-2,6-di-t-butylphenoxy radical, determined by electron spin resonance spectroscopy, rises fairly rapidly to a maximum value and then decays relatively slowly. Addition of 2,2-diphenyl-1-picrylhydrazine (DPPH-H) reduces the maximum concentration of phenoxyl but does not significantly change the initial rate of production of the intermediate.The kinetic results are interpreted in terms of a reversible primary reaction between DPPH and the phenol to give DPPH-H and the phenoxy radical. The phenoxyl can disappear by reaction with itself or with a second molecule of DPPH. The rate constant for the primary step at 20 °C is 0.18 ± 0.02 l/(mole s) and for the reverse reaction is 1.34 ± 0.2 l/(mole s); the rate constant for the reaction between 4-isopropyl-2,6-di-t-butylphenoxyl and DPPH is 0.68 ± 0.2 l/(mole s) at 20 °C. The activation energies for the respective reactions are 6.8 ± 0.6, 6.0 ± 1.0, and 6.4 ± 1.5 kcal/mole.

ISSN:0008-4042    

DOI:10.1139/v67-489

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The kinetics of the copper (II)-catalyzed oxidation of carbon monoxide by molecular oxygen, i.e.have been investigated in aqueous solutions at 120 °C. The rate law was found to be of the form −d[O2]/dt=kexpt[O2][CO][Cu(II)]/[H+], wherekexpt = 7.88 × 10−6 M−1s−1in 0.25 Macetate solutions. The apparent activation energy is 29 600 cal/mole. The rate-determining step of the reaction appears to be the oxidation by molecular oxygen of a carbon monoxide insertion complexformed in the pre-equilibrium step.

ISSN:0008-4042    

DOI:10.1139/v67-490

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Measurements were made of the effect of temperature on the rate at which Mg, Fe, and Al were dissolved from clinochlore, a Mg-rich orthochlorite mineral, by acid. The Mg, Fe, and Al were dissolved at the same rate with the same activation energy of 21 kcal/mole. The data indicated that the reaction proceeded from the particle edges inwards and was controlled by diffusion.

ISSN:0008-4042    

DOI:10.1139/v67-491

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Dibenzhydryl oxalate and several of its para-substituted analogs were thermally decomposed in diphenylmethane, diphenyl ether, and in α-chloronaphthalene solution. Evolution of gas (mainly CO2) was approximately first order, both rate and stoichiometry being poorly reproducible. Rates are correlated withσ+-substituent parameters, withρ = −1.6 at 230.2°. The13C/12C and18O/16O isotope effects involved in CO2formation were measured. It is concluded that thermolysis is a radical process with considerable polar character at the transition state and that the slow step involves concerted formation of one CO2molecule, a diarylmethyl radical, and a carbodiarylmethoxy radical. The fate of the latter is primarily decarboxylation, but there is some decarbonylation and some trapping by diarylmethyl radicals. Tetraaryl ethane and CO2are major products, the yield of the latter approaching 2 moles at high temperatures.

ISSN:0008-4042    

DOI:10.1139/v67-492

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Equations for the calculation of isotope effects (k12/k13andk16/k18) in the concerted twobond thermolysis of oxalates are presented. The equations are developed for material of low isotopic abundance such that the presence of doubly labelled molecules can be ignored. No assumption is made about the distribution of18O between the carbonyl and ether functions, other than that the distribution is known. The experimental data required are the ratios CO246/CO244, and CO245/CO244, corrected for the presence of17O and14C, in the CO2obtained from partial decomposition and in the CO2from total decomposition and the fractional extent of reaction.

ISSN:0008-4042    

DOI:10.1139/v67-493

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

The nuclear magnetic resonance technique of preferential solvation analysis developed by Frankel, Stengle, and Langford is applied to determination of the composition of the solvation shell abouttrans-[Cr(NH3)2(NCS)4]−in acetone–water mixtures. The composition of the solvation shell is correlated with the rate of acid hydrolysis of the chromium complex. It emerges that the solvolysis reaction is second order with respect to the solvolytically reactive solvent, water. The mechanistic implications of the rate law are considered as is the significance of analysis of preferential solvation for the determination of kinetic order of solvolytic reactions.

ISSN:0008-4042    

DOI:10.1139/v67-494

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Theν2symmetrical deformation vibration for ammonia adsorbed on silica cannot be observed directly, owing to strong absorption arising from the adsorbent. It is possible, however, to calculate a value for this vibrational frequency based on combination bands for the adsorbed ammonia, which occur in regions remote from strong absorption by the silica. The frequency of theν2mode reflects the strength of bonding in both the adsorbed state and in metal–ammine complexes.

ISSN:0008-4042    

DOI:10.1139/v67-495

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

Densities at 10 °C and proton magnetic resonance (p.m.r.) chemical shifts at 0 °C have been measured for aqueous ethylene oxide over the whole solution composition range. Ice freezing points have been determined for solutions containing up to 2 mole % ethylene oxide in water and in deuterium oxide. The deuterium oxide freezing point is 3.809 ± 0.003 °C and its freezing enthalpy is −1510 ± 8 cal. The freezing point measurements show water and deuterium oxide having unexpected negative deviations from Raoult's law. A maximum thermodynamic stabilization of water is found for solutions containing 4 mole % ethylene oxide. Partial molar volume evaluation shows a water volume maximum at 3.2 mole % ethylene oxide and a minimum at about 89%. Proton magnetic resonance measurements indicate weak H-bonding of water to ethylene oxide involving only one lone pair per ethylene oxide molecule. An abnormal shoulder in the direction of lower magnetic field for the water chemical shift is found, with the anomaly maximum at 4 to 6 mole % ethylene oxide.Correlating with the 20 and 24 water molecules encaging ethylene oxide in its clathrate hydrate, these new solution measurements show that when 20 to 30 water molecules are associated with each ethylene oxide at lower temperature, the water solvent exhibits a free energy minimum, a volume maximum, and an anomalous increase of water H-bond strength. At these compositions each ethylene oxide molecule is apparently surrounded by its own H-bonded water coordination shell to which it is weakly H bonded.

ISSN:0008-4042    

DOI:10.1139/v67-496

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

A technique is described for measuring ion lifetimes in irradiated gases. Gases were irradiated continuously, and lifetimes were determined by measuring average ion currents, obtained with an intermittent square-wave applied field, as a function of square-wave period. The dose rates, pressures, and vessel geometry were similar to those commonly used in radiolysis experiments, so that the information obtained can be applied directly to an understanding of radiolysis mechanisms. The theory of the method and analysis of ion-loss processes are discussed in some detail.Measurements in oxygen at pressures from 30 to 300 Torr and dose rates from 1.5 to 56 × 1010 eV cc−1s−1gave mean ion lifetimes ranging from 0.014 to 0.082 s. The dependence of lifetime on dose rate and pressure indicated that ion loss under these conditions was almost entirely by gas-phase combination. Values of α, the gas-phase combination coefficient, are compared with those measured by other methods.

ISSN:0008-4042    

DOI:10.1139/v67-497

出版商:NRC Research Press    

年代:1967

数据来源: NRC

摘要:

An intermittent-field method has been used to measure ion lifetimes in gaseous HCl during irradiation by gamma rays under conditions of pressure, dose rate, and vessel geometry similar to those employed in radiolysis studies. At 23 °C, with HCl pressures from 119 to 660 Torr and dose rates from 5.5 to 86 × 1010 eV cc−1s−1, the ion half-life ranged from 6 to 30 ms. The dependence on dose rate and pressure strongly indicated that ion neutralization occurred almost entirely in the gas phase. Values of α, the gas-phase combination coefficient, were calculated; at pressures above 246 Torr the value was constant and equal to 3.1 ± 0.3 × 10−6 cc ions−1s−1. The addition of SF6had little effect on α, while reducing the temperature to −79 °C increased α to 5.1 × 10−6.

ISSN:0008-4042    

DOI:10.1139/v67-498

出版商:NRC Research Press    

年代:1967

数据来源: NRC