Kinetics of the reactions of OH radicals with selected acetates and other esters under simulated atmospheric conditions

The relative hydroxyl radical reaction rate constants from the simulated atmospheric oxidation of selected acetates and other esters have been measured. Reactions were carried out at 297 ± 2 K in 100-liter FEP Teflon®-film bags. The OH radicals were generated from the photolysis of methyl nitrite in pure air. Using a rate constant of 2.63 × 10^?11 cm³ molecule^?1 s^?1 for the reaction of OH radicals with propene, the principal reference organic compound, the rate constants (×10¹² cm³ molecule^?1 s^?1) obtained for the acetates and esters used in this study are:

Kinetics of the reactions of OH radicals with some oxygenated volatile organic compounds under simulated atmospheric conditions

Some relative rate experiments have been carried out at room temperature and at atmospheric pressure. This concerns the OH-oxidation of some oxygenated volatile organic compounds including methanol (k₁), ethanol (k₂), MTBE (k₃), ethyl acetate (k₄), n-propyl acetate (k₅), isopropyl acetate (k₆), n-butyl acetate (k₇), isobutyl acetate (k₈), and t-butyl acetate (k₉). The experiments were performed in a Teflon-film bag smog chamber. The rate constants obtained are (in cm³ molecule⁻¹ s⁻¹): k₁=(0.90±0.08)×10⁻¹²; k₂=(3.88±0.11)×10⁻¹²; k₃=(2.98±0.06)×10⁻¹²; k₄=(1.73±0.20)×10⁻¹²; k₅=(3.56±0.15)×10⁻¹²; k₆=(3.97±0.18)×10⁻¹²; k₇=(5.78±0.15)×10⁻¹²; k₈=(6.77±0.30)×10⁻¹²; and k₉=(0.56±0.11)×10⁻¹². The agreement between the obtained rate constants and some previously published data has allowed for most of the studied compounds to point out a coherent group of values and to suggest recommended values. Atmospheric implications are also discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 839–847, 1998     

Kinetic studies on the reactions of 3‐isothiazolones with 2‐methyl‐2‐propanethiol

The kinetics of the ring‐opening reactions of the 3‐isothiazolones ( 1a–d ) with aqueous 2‐methyl‐2‐propanethiol has been explored at pH 4. The results strongly suggest that the reaction is second order in thiol and third order overall. Extrapolation of the kinetic data gives third‐order rate constants that lie in the order ( 1a ) > ( 1b ) > ( 1c ) > ( 1d ) in line with the known biological activity of these derivatives. The mechanism of the reaction is thought to involve attack by one thiol at the sulfur atom of the isothiazolone with the concomitant hydrogen bonding of a second thiol to the amide nitrogen. Calculations of the structure and electronic properties of the isothiazolones at the RHF 6‐31G** level are supportive. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 254–260, 2005     

Alternative Synthesis of 2‐Hydroxy‐3,5,5‐trimethylcyclopent‐2‐en‐1‐one

The 2‐hydroxy‐3,5,5‐trimethylcyclopent‐2‐en‐1‐one ( 1 ) was synthesized in 42% yield by rearrangement of epoxy ketone 10 on treatment with BF₃⋅Et₂O under anhydrous conditions. Intermediate 10 was available from the known enone 8 , either via direct epoxidation (60% H₂O₂, NaOH, MeOH; yield 50%), or via reduction to the corresponding allylic alcohol 14 (LiAlH₄, THF), followed by epoxidation ([VO(acac)₂], ^tBuOOH) and reoxidation under Swern conditions, in 37% total yield.     

Kinetics of the reaction of OH radicals with a series of ethers under simulated atmospheric conditions at 295 K

Ethers are being increasingly used as motor fuel additives to increase the octane number and to reduce CO emissions. Since their reaction with hydroxyl radicals (OH) is a major loss process for these oxygenated species in the atmoshpere, we have conducted a relative rate study of the kinetics of the reactions of OH radicals with a series of ethers and report the results of these measurements here. Experiments were performed under simulated atmospheric conditions; atmospheric pressure (? 740 torr) in synthetic air at 295 K. Using rate constants of 2.53 × 10^?12, and 1.35 × 10^?11 cm³ molecule^?1 s^?1 for the reaction of OH radicals with n-butane and diethyl ether, the following rate constants were derived, in units of 10^?11 cm³ molecule^?1 s^?1: dimethylether, (0.232 ± 0.023); di-n-propylether, (1.97 ± 0.08); di-n-butylether, (2.74 ± 0.32); di-n-pentylether, (3.09 ± 0.26); methyl-t-butylether, (0.324 ± 0.008); methyl-n-butylether, (1.29 ± 0.03); ethyl-n-butylether, (2.27 ± 0.09); and ethyl-t-butylether, (0.883 ± 0.026). Quoted errors represent 2σ from the least squares analysis and do not include any systematic errors associated with uncertainties in the reference rate constants used to place our relative measurements on an absolute basis. The implications of these results for the atmospheric chemistry of ethers are discussed.     

Measurements of the kinetics of the OH + α‐pinene and OH + β‐pinene reactions at low pressure

The rate constants for the OH + α‐pinene and OH + β‐pinene reactions have been measured in 5 Torr of He using discharge‐flow systems coupled with resonance fluorescence and laser‐induced fluorescence detection of the OH radical. At room temperature, the measured effective bimolecular rate constant for the OH + α‐pinene reaction was (6.08 ± 0.24) × 10^?11 cm³ molecule^?1 s^?1. These results are in excellent agreement with previous absolute measurements of this rate constant, but are approximately 13% greater than the value currently recommended for atmospheric modeling. The measured effective bimolecular rate constant for the OH + β‐pinene reaction at room temperature was (7.72 ± 0.44) × 10^?11 cm³ molecule^?1 s^?1, in excellent agreement with previous measurements and current recommendations. Above 300 K, the effective bimolecular rate constants for these reactions display a negative temperature dependence suggesting that OH addition dominates the reaction mechanisms under these conditions. This negative temperature dependence is larger than that observed at higher pressures. The measured rate constants for the OH + α‐pinene and OH + β‐pinene reactions are in good agreement with established reactivity trends relating the rate constant for OH + alkene reactions with the ionization potential of the alkene when ab initio calculated energies for the highest occupied molecular orbital are used as surrogates for the ionization potentials for α‐ and β‐pinene. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 300–308, 2002     

Kinetics of the gas‐phase reaction of CF3CF2CH2OH with OH radicals and its atmospheric lifetime

CF₃CF₂CH₂OH is a new chlorofluorocarbon (CFC) alternative. However, there are few data about its atmospheric fate. The kinetics of its atmospheric oxidation, the OH radical reaction of CF₃CF₂CH₂OH, has been investigated in a 2‐liter Pyrex reactor in the temperature range of 298 ∼ 356 K using gas chromatography (GC)–mass spectrometry (MS) for analysis in this study. The rate coefficient of k₁ = (2.27) × 10⁻¹² exp[−(900 ± 70)/T] cm³ molecule⁻¹ s⁻¹ was determined using the relative rate method. The results are in good agreement with the literature values and the prediction of Atkinson's structure–activity relationship (SAR) model. From these results, the atmospheric lifetime of CF₃CF₂CH₂OH in the troposphere was deduced to be 0.34 year, which is 250 and 6 times shorter than those of CFC‐113 and hydrochlorofluorocarbons (HCFC‐225ca), respectively. Therefore CF₃CF₂CH₂OH has significant potential for the replacement of CFC‐113 and HCFC‐225ca. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 73–78, 2000     

Methoxylation of 4,5‐Dichloro‐2‐methyl‐6‐nitropyridazin‐3‐one

This paper presents the methoxylation of 4,5‐dichloro‐2‐methyl‐6‐nitropyridazin‐3‐one with potassium carbonate/methanol.     

Synthesis and reactions of 3‐amino‐2‐methyl‐3H‐[1,2,4]triazolo[5,1‐b]‐quinazolin‐9‐one and 2‐hydrazino‐3‐phenylamino‐3H‐quinazolin‐4‐one

The reaction of 3‐N‐(2‐mercapto‐4‐oxo‐4H‐quinazolin‐3‐yl)acetamide ( 1 ) with hydrazine hydrate yielded 3‐amino‐2‐methyl‐3H‐[1,2,4]triazolo[5,1‐b]quinazolin‐9‐one ( 2 ). The reaction of 2 with o‐chlorobenzaldehyde and 2‐hydroxy‐naphthaldehyde gave the corresponding 3‐arylidene amino derivatives 3 and 4 , respectively. Condensation of 2 with 1‐nitroso‐2‐naphthol afforded the corresponding 3‐(2‐hydroxy‐naphthalen‐1‐yl‐diazenyl)‐2‐methyl‐3H‐[1,2,4]triazolo[5,1‐b]quinazolin‐9‐one ( 5 ), which on subsequent reduction by SnCl₂ and HCl gave the hydrazino derivative 6. Reaction of 2 with phenyl isothiocyanate in refluxing ethanol yielded thiourea derivative 7. Ring closure of 7 subsequently cyclized on refluxing with phencyl bromide, oxalyl dichloride and chloroacetic acid afforded the corresponding thiazolidine derivatives 8, 9 and 10 , respectively. Reaction of 2‐mercapto‐3‐phenylamino‐3H‐quinazolin‐4‐one ( 11 ) with hydrazine hydrate afforded 2‐hydrazino‐3‐phenylamino‐3H‐quinazolin‐4‐one ( 12 ). The reactivity 12 towards carbon disulphide, acetyl acetone and ethyl acetoacetate gave 13, 14 and 15 , respectively. Condensation of 12 with isatin afforded 2‐[N‐(2‐oxo‐1,2‐dihydroindol‐3‐ylidene)hydrazino]‐3‐phenylamino‐3H‐quinazolin‐4‐one ( 16 ). 2‐(4‐Oxo‐3‐phenylamino‐3,4‐dihydroquinazolin‐2‐ylamino)isoindole‐1,3‐dione ( 17 ) was synthesized by the reaction of 12 with phthalic anhydride. All isolated products were confirmed by their ir, ¹H nmr, ¹³C nmr and mass spectra.     

Kinetics of the gas-phase reactions of β-phellandrene with OH and NO3 radicals and O3 at 297 ± 2 K

Rate constants for the gas-phase reactions of the biogenically emitted monoterpene β-phellandrene with OH and NO₃ radicals and O₃ have been measured at 297 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained were (in cm³ molecule^?1 s^?1 units): for reaction with the OH radical, (1.68 ± 0.41) × 10^?10; for reaction with the NO₃ radical, (7.96 ± 2.82) × 10^?12; and for reaction with O₃, (4.77 ± 1.23) × 10^?17, where the error limits include the estimated uncertainties in the reference reaction rate constants. Using these rate constants, the lifetime of β-phellandrene in the lower troposphere due to reaction with these species is calculated to be in the range of ca. 1–8 h, with the OH radical reaction being expected to dominate over the O₃ reaction as a loss process for β-phellandrene during daylight hours.     

Kinetics of the reactions of OH radicals with 2‐methoxy‐6‐(trifluoromethyl)pyridine,diethylamine, and 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol at 298 ± 2 K

Rate constants for the reactions of 2‐methoxy‐6‐(trifluoromethyl)pyridine, diethylamine, and 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol with OH radicals have been measured at 298 ± 2 K using a relative rate method. The measured rate constants (cm³ molecule^?1 s^?1) are (1.54 ± 0.21) × 10^?12 for 2‐methoxy‐6‐(trifluoromethyl)pyridine, (1.19 ± 0.25) × 10^?10 for diethylamine, and (1.76 ± 0.38) × 10^?12 for 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol, where the indicated errors are the estimated overall uncertainties including those in the rate constants for the reference compounds. No reaction of 2‐methoxy‐6‐(trifluoromethyl)pyridine with gaseous nitric acid was observed, and an upper limit to the rate constant for the reaction of 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol with O₃ of <7 × 10^{? 20} cm³ molecule^?1 s^?1 was determined. Using a 12‐h average daytime OH radical concentration of 2 × 10⁶ molecule cm^?3, the lifetimes of the volatile organic compounds studied here with respect to reaction with OH radicals are 7.5 days for 2‐methoxy‐6‐(trifluoromethyl)pyridine, 1.2 h for diethylamine, and 6.6 days for 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol. Likely reaction mechanisms are discussed. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 631–638, 2011     

3‐Cyano‐6‐methyl‐4‐(2‐naphthyl­ethenyl)‐1‐benzo­pyran‐2‐one

In the title compound, C₂₃H₁₅NO₂, the naphthyl unit is planar and the benzo­pyran unit is nearly planar. These two moieties are inclined at an angle of 9.10 (6)° with respect to one another.     

Full Characterization and some reactions of 1‐(2‐adamantyl)‐3‐(1‐adamantyl)aziridin‐2‐one

We found that 1‐(2‐adamantyl)‐3‐tert‐butylaziridin‐2‐one ( 5a ) is unstable. It slowly decomposes at room temperature, although detectable by IR spectroscopy (1840 cm^?1 band in CCl₄). On the other hand, a closely related analogue, 1‐(2‐adamantyl)‐3‐(1‐adamantyl)aziridin‐2‐one ( 5b ), is very stable, in concurrence with an earlier report [1]. We fully characterized aziridinone 5b , identified its thermal decomposition products ( 7 and 8 ) and reacted it with two aprotic ionic (tBuO^? and HO^?) and one protic non‐ionic nucleophile (benzylamine). All three products ( 9b , 10 , and 11 ) result from exclusive cleavage of the lactam (1‐2) bond.     

Kinetics of the gas-phase reactions of OH radicals with a series of α,β-unsaturated carbonyls at 299 ± 2 K

Relative rate constants for the reaction of OH radicals with a series of α,β-unsaturated carbonyls have been determined at 299 ± 2 K, using methyl nitrite photolysis in air as a source of OH radicals. Using a rate constant for the reaction of OH radicals with propene of 2.52 × 10^?11 cm³/molec·s, the rate constants obtained are (× 10¹¹ cm³/molec·s: acrolein, 1.83 ± 0.13; crotonaldehyde, 3.50 ± 0.40; methacrolein, 2.85 ± 0.23; and methylvinylketone, 1.88 ± 0.14). These data, which are necessary input to chemical computer models of the NO_x–air photooxidations of conjugated dialkenes, are discussed and compared with literature values.     

Syntheses of N‐[3‐(1‐methyl‐1H‐2‐imidazolyl)propyl]benzamides and N‐[3‐(1‐methyl‐1H‐2‐imidazolyl)propyl]benzenesulfonamides

A series of substituted N‐(4‐substituted‐benzoyl)‐N‐[3‐(1‐methyl‐1H‐imidazol‐2‐yl)propyl]amines ( 13 ) and N‐arylsulfonyl‐N‐[3‐(1‐methyl‐1H‐imidazol‐2‐yl)propyl]amines ( 14 ) were prepared from the reaction of 3‐(1‐methyl‐1H‐imidazol‐2‐yl)propan‐1‐amine ( 7 ) with substituted benzoyl chloride or substituted‐benzene sulfonyl chloride respectively. Compound 7 was prepared by two independent methods.     

Crystallographic report: Bis(3‐methyl‐2‐cyclopenten‐1‐one)dichloro‐oxovanadium(IV)

The crystal structure of the oxovanadium(IV) complex (CH₃C₅H₅O)₂VOCl₂ was determined. The molecule has trigonal bipyramidal geometry, with oxygen atoms of cyclopentenones in axial positions and oxygen and two chlorine atoms in equatorial positions. Copyright © 2005 John Wiley & Sons, Ltd.     

Kinetics and mechanism of the oxidation of 4‐methyl‐3‐thiosemicarbazide by acidic bromate

The oxidation of 4‐methyl‐3‐thiosemicarbazide (MTSC) by bromate and bromine was studied in acidic medium. The stoichiometry of the reaction is extremely complex, and is dependent on the ratio of the initial concentrations of the oxidant to reductant. In excess MTSC and after prolonged standing, the stoichiometry was determined to be H₃CN(H)CSN(H)NH₂ + 3BrO₃^? → 2CO₂ + NH₄⁺ + SO₄^2? + N₂ + 3Br^? + H⁺ (A). An interim stoichiometry is also obtained in which one of the CO₂ molecules is replaced by HCOOH with an overall stoichiometry of 3H₃CN(H)CSN(H)NH₂ + 8BrO₃^? → CO₂ + NH₄⁺ + SO₄^2? + HCOOH + N₂ + 3Br^? + 3H⁺ (B). Stoichiometry A and B are not very different, and so mixtures of the two were obtained. Compared to other oxidations of thiourea‐based compounds, this reaction is moderately fast and is first order in both bromate and substrate. It is autocatalytic in HOBr. The reaction is characterized by an autocatalytic sigmoidal decay in the consumption of MTSC, while in excess bromate conditions the reaction shows an induction period before autocatalytic formation of bromine. In both cases, oxybromine chemistry, which involves the initial formation of the reactive species HOBr and Br₂, is dominant. The reactions of MTSC with both HOBr and Br₂ are fast, and so the overall rate of oxidation is dependent upon the rates of formation of these reactive species from bromate. Our proposed mechanism involves the initial cleavage of the C? N bond on the azo‐side of the molecule to release nitrogen and an activated sulfur species that quickly and rapidly rearranges to give a series of thiourea acids. These thiourea acids are then oxidized to the sulfonic acid before cleavage of the C? S bond to give SO₄^2?, CO₂, and NH₄⁺. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 237–247, 2002     

5,5‐Dimethyl‐3‐(5‐methyl‐1H‐pyrazol‐3‐ylamino)cyclohex‐3‐en‐1‐one

The mol­ecules of the title compound, C₁₂H₁₇N₃O, are linked by two N—H?O hydrogen bonds to form a three‐dimensional network. The N?O distances are 2.804 (3) and 2.766 (3) Å, both involving a common acceptor O atom.     

New synthesis and reactivity of 3‐bromoacetyl‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one with binucleophilic amines

3‐(Bromoacetyl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one was synthesized by the reaction of dehydroacetic acid (DHAA) with bromine in glacial acetic acid. Novel heterocyclic products were synthesized from the reaction of bromo‐DHAA with alkanediamines, phenylhydrazines, ortho‐phenylenediamines, and ortho‐aminobenzenethiol. The obtained new products 3‐(2‐N‐substituted‐acetyl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐ones, 4‐hydroxy‐3‐[1‐hydroxy‐2‐(2‐phenylhydrazinyl)vinyl]‐6‐methyl‐2H‐pyran‐2‐one, 1‐(2,4‐dinitrophenyl)‐7‐methyl‐2,3‐dihydro‐1H‐pyrano[4,3‐c]pyridazine‐4,5‐dione, 3‐(3,4‐dihydroquinoxalin‐2‐yl)‐4‐hydroxy‐6‐methyl‐2H‐pyran‐2‐one/3‐(3,4‐dihydroquinoxalin‐2‐yl)‐6‐methyl‐2H‐pyran‐2,4(3H)‐dione, 6‐methyl‐3‐(3,4‐dihydroquinoxalin‐2‐yl)‐2H‐pyran‐2,4(3H)‐dione, and (E)‐3‐(2H‐benzo[b][1,4]thiazin‐3(4H)‐ylidene)‐6‐methyl‐2H‐pyran‐2,4(3H)‐dione were fully characterized by IR, ¹H and ¹³C NMR, and mass spectra. J. Heterocyclic Chem., 2011.