摘要:

It has been suggested that the pressure coefficient of the rate constant of some reactions may be influenced by the formation of intermolecular or intramolecular conformations prior to reaction. This has been examined theoretically and the relevant experimental evidence has been discussed. No examples of an effect in which the conformations are at equilibrium are known with certainty, but the effect of pressure on termination in the polymerization of styrene appears to be an example of a conformational effect when the conformations are not at equilibrium.The pressure coefficient of the rate constant for the isomerization of citraldehyde to 3,8-carvomenthenediol is not consistent with a unimolecular slow step, but it is consistent with either a bimolecular or a termolecular slow step. It is pointed out that the pressure coefficient of rate constants may be very useful in determining the molecularity of some reactions.

ISSN:0008-4042    

DOI:10.1139/v58-031

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The reduction of nitro compounds to amines by ethanolic hydrazine and palladized charcoal probably proceeds through the nitroso and hydroxylamine derivatives. This reagent is shown to be useful for the reduction of azo to hydrazo compounds.

ISSN:0008-4042    

DOI:10.1139/v58-032

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

A series of triarylmethane dyes were made by varying the substituents in the thiophene ring of the dye [4-(p-dimethylamino-α-2-thienylbenzylidene)-2,5-cyclohexadiene-1-ylidene]-dimethylammonium chloride. The spectra of the zinc salts of these dyes were shown to be similar to that of the dye formed in the Schoenemann reaction when the parent triarylmethane compound was used as an indicator. Neither of the absorption bands occurring in the 475 mμ or 625 mμ regions is affected by pH or buffer salts in the pH range 2.4 to 6.4 but both bands are hypsochromically shifted when the pH is lowered to 0.5. The substitution of 5-nitro and 5-acetamido groups in the thiophene ring results in the largest bathochromic and hypsochromic shifts respectively. Interpretation of the effect of substitution and pH was attempted employing existing theories on the relation between color and constitution.

ISSN:0008-4042    

DOI:10.1139/v58-033

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The photochemical oxidation of acetaldehyde has been studied in the gaseous phase at 20 °C. and a wavelength of 3130 Å. It has been established that when the pressure of oxygen is between 0.5 mm. and 150 mm. the reaction obeys the kinetic law:wherek3is the velocity constant for the propagating reaction [3]:andk6is the velocity constant for the terminating reaction [6]:is the rate of initiation of the photooxidation, i.e. the rate of formation of acetyl radicals, which are thought to be produced in one or both of the following ways:

ISSN:0008-4042    

DOI:10.1139/v58-034

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

The photochemical oxidation of propionaldehyde has been studied in the gaseous phase at 23 °C. and a wavelength of 3130 Å. With pressures of oxygen varying from 0.3 mm. to 100 mm. Hg it has been established that the reaction obeys the same kinetic law as that found for the corresponding reaction with acetaldehyde, namely:wherek3is the velocity constant for the propagating reaction [3]:andk6is the velocity constant for the terminating reaction [6]:is the rate of initiation and it is regarded as being a composite quantity representing the rate of formation of propionyl radicals, which are thought to be the initiators of the oxidation chain. The propionyl radicals are thought to be formed by two processes: (a) from the subsequent reactions of free radicals produced in the primary free radical process which occurs when propionaldehyde absorbs a quantum of radiation at 3130 Å, and (b) from the subsequent reactions, with oxygen, of excited states of propionaldehyde, which are also thought to be formed by the absorption of light of wavelength 3130 Å.

ISSN:0008-4042    

DOI:10.1139/v58-035

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

It has been established (Parts I and II) that the photochemical oxidation of acetaldehyde and propionaldehyde obeys the kinetic expressionwhere RCHO represents the aldehyde and RCO3H the corresponding peracid.k3is the velocity constant for the propagating reaction, andk6that for the terminating reaction involving the mutual interaction of two RCO3radicals.represents the rate of initiation of the photooxidation.Alcohols have been found to retard the photooxidation and it has been shown that the retarded reaction obeys the kinetic expression:It has thus been possible to determine the rates of initiationfor each of the photooxidations. Application of the rotating sector technique has enabled the lifetime of the oxidation chains to be measured. These data together with the information given in Parts I and II have been used to calculate the absolute values for the velocity constants for the propagating and terminating reactions,k3andk6:in the gas-phase photooxidations of acetaldehyde and propionaldehyde.The values of the respective velocity constants are: acetaldehyde at 20°,k3 = 8.05( ±2.04) × 1031. mole−1sec−1,k6 = 8.93( ±4.20) × 10101. mole−1sec−1; propionaldehyde at 22°,k3 = 4.35( ±0.9) × 1041. mole−1sec−1,k6 = 2.69( ±1.35) × 10101 mole−1sec−1.These values for the velocity constants for the "recombination" reactions of the peracetic and perpropionic radicals indicate that for these radicals reaction [6] is very efficient.

ISSN:0008-4042    

DOI:10.1139/v58-036

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

not available

ISSN:0008-4042    

DOI:10.1139/v58-038

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

not available

ISSN:0008-4042    

DOI:10.1139/v58-039

出版商:NRC Research Press    

年代:1958

数据来源: NRC

摘要:

not available

ISSN:0008-4042    

DOI:10.1139/v58-040

出版商:NRC Research Press    

年代:1958

数据来源: NRC