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Molar Yields (molar + yield)

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Chemistry	100%

Selected Abstracts

Kinetics and mechanisms of OH-initiated oxidation of small unsaturated alcohols

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2010
Kenshi Takahashi
Smog chamber relative rate techniques were used to measure rate coefficients of (5.00 ± 0.54) × 10,11, (5.87 ± 0.63) × 10,11, and (6.49 ± 0.82) × 10,11 cm3 molecule,1 s,1 in 700 Torr air at 296 ± 1 K for reactions of OH radicals with allyl alcohol, 1-buten-3-ol, and 2-methyl-3-buten-2-ol, respectively; the quoted uncertainties encompass the extremes of determinations using two different reference compounds. The OH-initiated oxidation of allyl alcohol in the presence of NOx gives glycolaldehyde in a molar yield of 0.85 ± 0.08; the quoted uncertainty is two standard deviations. Oxidation of 2-methyl-3-buten-2-ol gives acetone and glycolaldehyde in molar yields of 0.66 ± 0.06 and 0.56 ± 0.05, respectively. The reaction of OH radicals with allyl alcohol, 1-buten-3-ol, and 2-methyl-3-buten-2-ol proceeds predominately via addition to the >CCH2 double bond with most of the addition occurring to the terminal carbon. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 151,158, 2010 [source]

Preparation of sorbitol from D -glucose hydrogenation in gas,liquid,solid three-phase flow airlift loop reactor

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2004
Jian-Ping Wen
Abstract A new process for D -glucose hydrogenation in 50 wt% aqueous solution, into sorbitol in a 1.5 m3 gas,liquid,solid three-phase flow airlift loop reactor (ALR) over Raney Nickel catalysts has been developed. Five main factors affecting the reaction time and molar yield to sorbitol, including reaction temperature (TR), reaction pressure (PR), pH, hydrogen gas flowrate (Qg) and content of active hydrogen, were investigated and optimized. The average reaction time and molar yield were 70 min and 98.6% under the optimum operating conditions, respectively. The efficiencies of preparation of sorbitol between the gas,liquid,solid three-phase flow ALR and stirred tank reactor (STR) under the same operating conditions were compared. Copyright © 2004 Society of Chemical Industry [source]

Atmospheric chemistry of isopropyl formate and tert -butyl formate

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 8 2010
Andre Silva Pimentel
Formates are produced in the atmosphere as a result of the oxidation of a number of species, notably dialkyl ethers and vinyl ethers. This work describes experiments to define the oxidation mechanisms of isopropyl formate, HC(O)OCH(CH3)2, and tert -butyl formate, HC(O)OC(CH3)3. Product distributions are reported from both Cl- and OH-initiated oxidation, and reaction mechanisms are proposed to account for the observed products. The proposed mechanisms include examples of the ,-ester rearrangement reaction, novel isomerization pathways, and chemically activated intermediates. The atmospheric oxidation of isopropyl formate by OH radicals gives the following products (molar yields): acetic formic anhydride (43%), acetone (43%), and HCOOH (15,20%). The OH radical initiated oxidation of tert -butyl formate gives acetone, formaldehyde, and CO2 as major products. IR absorption cross sections were derived for two acylperoxy nitrates derived from the title compounds. Rate coefficients are derived for the kinetics of the reactions of isopropyl formate with OH (2.4 ± 0.6) × 10,12, and with Cl (1.75 ± 0.35) × 10,11, and for tert -butyl formate with Cl (1.45 ± 0.30) × 10,11 cm3 molecule,1 s,1. Simple group additivity rules fail to explain the observed distribution of sites of H-atom abstraction for simple formates. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 479,498, 2010 [source]

Kinetics and mechanisms of OH-initiated oxidation of small unsaturated alcohols

Gas-phase reaction of hydroxyl radicals with m -, o - and p -cresol

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 9 2006
Cecile Coeur-Tourneur
The gas-phase reaction of oxygenated aromatic compounds m -cresol, o -cresol, and p -cresol with hydroxyl radicals has been studied by GC-MS. Experiments have been performed in a large-volume photoreactor (8000 L) at 294 ± 2 K and atmospheric pressure. The relative kinetic method was used to determine the rate constants for these reactions, with 1,3,5-trimethylbenzene as a reference compound. The rate constants obtained are kOH(m -cresol) = (5.88 ± 0.92) × 10,11 cm3 molecule,1 s,1, kOH(o -cresol) = (4.32 ± 0.52) × 10,11 cm3 molecule,1 s,1, and kOH(p -cresol) = (4.96 ± 0.75) × 10,11 cm3 molecule,1 s,1. The degradation products observed and their respective molar yields were methyl-1,4-benzoquinone 12.4 ± 1.2%, 5-methyl-2-nitrophenol 1.5 ± 0.3%, and 3-methyl-2-nitrophenol 1.4 ± 0.3% from m -cresol, methyl-1,4-benzoquinone 5.6 ± 0.9%, and 6-methyl-2-nitrophenol 4.7 ± 0.8% from o -cresol, and 4-methyl-2-nitrophenol 17.2 ± 2.5% from p -cresol. This kinetic and product data are compared with the literature, and the reaction mechanisms are discussed. Our results are in accordance with the previous studies (Atkinson, J Phys Chem Ref Data 1989, Monograph (1), 1,246; Atkinson and Aschmann, Int J Chem Kinet 1990, 22, 59,67; Atkinson et al., Environ Sci Technol 1992, 26, 1397,1403; Atkinson et al., J Phys Chem 1978, 82, 2759,2805; Olariu et al., Atmos Environ 2002, 36, 3685,3697; Semadeni et al., Int J Chem Kinet 1995, 27, 287,304) and confirm the methyl-1,4-benzoquinone yields determined by a different experimental technique (long-path Fourier transform infrared FT-IR (Olariu et al., 2002)). © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 553,562, 2006 [source]

Rate coefficients and mechanisms of the reaction of cl-atoms with a series of unsaturated hydrocarbons under atmospheric conditions

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 8 2003
John J. Orlando
Rate coefficients and/or mechanistic information are provided for the reaction of Cl-atoms with a number of unsaturated species, including isoprene, methacrolein (MACR), methyl vinyl ketone (MVK), 1,3-butadiene, trans -2-butene, and 1-butene. The following Cl-atom rate coefficients were obtained at 298 K near 1 atm total pressure: k(isoprene) = (4.3 ± 0.6) × 10,10cm3 molecule,1 s,1 (independent of pressure from 6.2 to 760 Torr); k(MVK) = (2.2 ± 0.3) × 10,10 cm3 molecule,1 s,1; k(MACR) = (2.4 ± 0.3) × 10,10 cm3 molecule,1 s,1; k(trans -2-butene) = (4.0 ± 0.5) × 10,10 cm3 molecule,1 s,1; k(1-butene) = (3.0 ± 0.4) × 10,10 cm3 molecule,1 s,1. Products observed in the Cl-atom-initiated oxidation of the unsaturated species at 298 K in 1 atm air are as follows (with % molar yields in parentheses): CH2O (9.5 ± 1.0%), HCOCl (5.1 ± 0.7%), and 1-chloro-3-methyl-3-buten-2-one (CMBO, not quantified) from isoprene; chloroacetaldehyde (75 ± 8%), CO2 (58 ± 5%), CH2O (47 ± 7%), CH3OH (8%), HCOCl (7 ± 1%), and peracetic acid (6%) from MVK; CO (52 ± 4%), chloroacetone (42 ± 5%), CO2 (23 ± 2%), CH2O (18 ± 2%), and HCOCl (5%) from MACR; CH2O (7 ± 1%), HCOCl (3%), acrolein (,3%), and 4-chlorocrotonaldehyde (CCA, not quantified) from 1,3-butadiene; CH3CHO (22 ± 3%), CO2 (13 ± 2%), 3-chloro-2-butanone (13 ± 4%), CH2O (7.6 ± 1.1%), and CH3OH (1.8 ± 0.6%) from trans -2-butene; and chloroacetaldehyde (20 ± 3%), CH2O (7 ± 1%), CO2 (4 ± 1%), and HCOCl (4 ± 1%) from 1-butene. Product yields from both trans -2-butene and 1-butene were found to be O2 -dependent. In the case of trans -2-butene, the observed O2 -dependence is the result of a competition between unimolecular decomposition of the CH3CH(Cl)CH(O,)CH3 radical and its reaction with O2, with kdecomp/kO2 = (1.6 ± 0.4) × 1019 molecule cm,3. The activation energy for decomposition is estimated at 11.5 ± 1.5 kcal mol,1. The variation of the product yields with O2 in the case of 1-butene results from similar competitive reaction pathways for the two ,-chlorobutoxy radicals involved in the oxidation, ClCH2CH(O,)CH2CH3 and ,OCH2CHClCH2CH3. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 334,353, 2003 [source]

CF3CH(ONO)CF3: Synthesis, IR spectrum, and use as OH radical source for kinetic and mechanistic studies

INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 4 2003
M. P. Sulbaek Andersen
The synthesis, IR spectrum, and first-principles characterization of CF3CH(ONO)CF3 as well as its use as an OH radical source in kinetic and mechanistic studies are reported. CF3CH(ONO)CF3 exists in two conformers corresponding to rotation about the RCONO bond. The more prevalent trans conformer accounts for the prominent IR absorption features at frequencies (cm,1) of 1766 (NO stretch), 1302, 1210, and 1119 (CF stretches), and 761 (ONO bend); the cis conformer contributes a number of distinct weaker features. CF3CH(ONO)CF3 was readily photolyzed using fluorescent blacklamps to generate CF3C(O)CF3 and, by implication, OH radicals in 100% yield. CF3CH(ONO)CF3 photolysis is a convenient source of OH radicals in the studies of the yields of CO, CO2, HCHO, and HC(O)OH products which can be difficult to measure using more conventional OH radical sources (e.g., CH3ONO photolysis). CF3CH(ONO)CF3 photolysis was used to measure k(OH + C2H4)/k(OH + C3H6) = 0.29 ± 0.01 and to establish upper limits of 16 and 6% for the molar yields of CO and HC(O)OH from the reaction of OH radicals with benzene in 700 Torr of air at 296 K. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 35: 159,165, 2003 [source]