Ultrafast photodissociation studies of acetyl cyanide and acetic acid and unimolecular decomposition rates of the acetyl radical products

1999 ◽  
Vol 111 (16) ◽  
pp. 7329-7336 ◽  
Author(s):  
J. C. Owrutsky ◽  
A. P. Baronavski
Keyword(s):  
Acetic Acid ◽  
Unimolecular Decomposition ◽  
Decomposition Rates ◽  
Acetyl Radical

scholarly journals The homogeneous unimolecular decomposition of gaseous alkyl nitrites - IV—The decomposition of Iso -propyl nitrite

1935 ◽  
Vol 151 (874) ◽  
pp. 685-693 ◽  
Keyword(s):  
Activation Energy ◽  
Thermal Decomposition ◽  
Pressure Change ◽  
Methyl Ethyl ◽  
Unimolecular Decomposition ◽  
Decomposition Rates ◽  
Straight Chain ◽  
Alkyl Nitrites ◽  
Branched Chain ◽  
Reaction Vessels

It has already been shown that the first three straight chain members of the nitrite homologous series, i. e ., methyl, ethyl, and n -propyl nitrites, have exhibited in their thermal decomposition the characteristics pertaining to homogeneous unimolecular reactions. This paper deals with the investigation carried out on iso -propyl nitrite decomposition. This member of the series is particularly interesting as it allows comparison to be made between a straight-chain and a branched-chain isomer. The effect of these chemical configurations on the activation energy and the decomposition rates can be very effectively studies as no complications enter into the reactions to confuse measurements. Experimental Reaction velocities were measured as before by observing the rate of pressure change in a system at constant volume. The reaction vessels were Pyrex glass bulbs with a capacity of about 125 cc. The apparatus was similar to that used in previous experiments. The connecting tubing was heated to 105° C to prevent any of the products of the reaction condensing out. Control and measurement of the temperature was carried out as before. The temperature could be maintained constant to within 0·25° C.

scholarly journals Mechanism of 17α,20-Lyase and New Hydroxylation Reactions of Human Cytochrome P450 17A1

2016 ◽  
Vol 291 (33) ◽  
pp. 17143-17164 ◽  
Author(s):  
Francis K. Yoshimoto ◽  
Eric Gonzalez ◽  
Richard J. Auchus ◽  
F. Peter Guengerich
Keyword(s):  
Acetic Acid ◽  
Cytochrome P450 ◽  
Bond Cleavage ◽  
Active Species ◽  
Sterol Biosynthesis ◽  
Compound I ◽  
Human Cytochrome ◽  
Acetyl Radical

Cytochrome P450 (P450) reactions can involve C–C bond cleavage, and several of these are critical in steroid and sterol biosynthesis. The mechanisms of P450s 11A1, 17A1, 19A1, and 51A1 have been controversial, in the context of the role of ferric peroxide (FeO2−) versus perferryl (FeO3+, compound I) chemistry. We reinvestigated the 17α-hydroxyprogesterone and 17α-hydroxypregnenolone 17α,20-lyase reactions of human P450 17A1 and found incorporation of one 18O atom (from 18O2) into acetic acid, consonant with proposals for a ferric peroxide mechanism (Akhtar, M., Lee-Robichaud, P., Akhtar, M. E., and Wright, J. N. (1997) J. Steroid Biochem. Mol. Biol. 61, 127–132; Akhtar, M., Wright, J. N., and Lee-Robichaud, P. (2011) J. Steroid Biochem. Mol. Biol. 125, 2–12). However, the reactions were supported by iodosylbenzene (a precursor of the FeO3+ species) but not by H2O2. We propose three mechanisms that can involve the FeO3+ entity and that explain the 18O label in the acetic acid, two involving the intermediacy of an acetyl radical and one a steroid 17,20-dioxetane. P450 17A1 was found to perform 16-hydroxylation reactions on its 17α-hydroxylated products to yield 16,17α-dihydroxypregnenolone and progesterone, suggesting the presence of an active perferryloxo active species of P450 17A1 when its lyase substrate is bound. The 6β-hydroxylation of 16α,17α-dihydroxyprogesterone and the oxidation of both 16α,17α-dihydroxyprogesterone and 16α,17α-dihydroxypregnenolone to 16-hydroxy lyase products were also observed. We provide evidence for the contribution of a compound I mechanism, although contribution of a ferric peroxide pathway in the 17α,20-lyase reaction cannot be excluded.

scholarly journals Acetyl Radical Formation in X-Irradiated Acetic Acid Single Crystals Studied by ESR Spectroscopy.

1992 ◽  
Vol 46 ◽  
pp. 1140-1145
Author(s):  
N. A. Salih ◽  
O. Awadelkarim ◽  
A. Lund ◽  
Tuomas T. Huuhtanen ◽  
Martti Dahlqvist ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Single Crystals ◽  
Esr Spectroscopy ◽  
Radical Formation ◽  
Acetyl Radical

scholarly journals Unimolecular decomposition rates of a methyl-substituted Criegee intermediate syn-CH3CHOO

RSC Advances ◽  
2020 ◽  
Vol 10 (14) ◽  
pp. 8518-8524 ◽  
Author(s):  
Yu-Lin Li ◽  
Mei-Tsan Kuo ◽  
Jim Jr-Min Lin
Keyword(s):  
Unimolecular Decomposition ◽  
Temperature Dependent ◽  
Decomposition Rates

This work provides temperature dependent unimolecular rates of syn-CH3CHOO at higher pressures.

The unimolecular decomposition rates of energy selected methylnitrite and deuterated methylnitrite ions

1983 ◽  
Vol 78 (6) ◽  
pp. 3767-3773 ◽  
Author(s):  
Jerome P. Gilman ◽  
Tacheng Hsieh ◽  
G. G. Meisels
Keyword(s):  
Unimolecular Decomposition ◽  
Decomposition Rates

THE CHROMIC ACID OXIDATION OF ARYL TRIFLUOROMETHYL ALCOHOLS: ISOTOPE AND SUBSTITUENT EFFECTS

1964 ◽  
Vol 42 (2) ◽  
pp. 439-446 ◽  
Author(s):  
Ross Stewart ◽  
Donald G. Lee
Keyword(s):  
Acetic Acid ◽  
Acid Solution ◽  
Chromic Acid ◽  
Isotope Effects ◽  
Acetic Acid Solution ◽  
Substituent Effects ◽  
Acid Oxidation ◽  
Unimolecular Decomposition ◽  
Chromic Acid Oxidation ◽  
Deuterium Isotope Effects

The mechanism of the chromic acid oxidation of eight aryltrmuoromethylcarbinols has been studied in acetic acid solution. Electron-donating substituents accelerate the reaction and a good correlation of rate with σ+ values has been found. The rho value is −1.01. Deuterium isotope effects for the oxidation of five of these compounds have been determined and the magnitude of the isotope effect has been found to correlate inversely with the ease of oxidation of the alcohol.The results are interpreted in terms of a unimolecular decomposition of the chromate ester of the alcohol.

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