- Oh radical-initiated oxidation of 2-butoxyethanol under laboratory conditions related to the troposphere: Product studies and proposed mechanism
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This type of study provides information on the reaction mechanism of the conversion of a substrate molecule, in this case a glycol ether, into its oxidation products under polluted tropospheric conditions. Such detailed pathways for the breakdown of the substrate molecule lead to the generation of photooxidants, mainly ozone, and are essential input data for computer modeling studies used to derive ozone-creating potentials of volatile organic compounds released into the atmosphere. The products formed by the hydroxyl radical-initiated oxidation of 2-butoxyethanol (C4H9OCH2CH2OH) have been investigated by irradiating synthetic air mixtures containing the substrate, methyl nitrite, and nitric oxide at ppm levels in a Teflon bag reactor at room temperature. The decay of reactant and the formation of products were monitored by gas chromatography and by mass spectrometry. The molar yields of the major products (mol of product formed/mol of 2-butoxyethanol consumed) were as follows: butyl formate (HC(O)OCH2CH2CH2CH3), 0.35 ± 0.11; ethylene glycol monoformate (HC(O)OCH2CH2OH), 0.39 ± 0.18; butoxyacetaldehyde (CH3CH2CH2CH2OCH2C(O)H), 0.12 ± 0.09; 3-hydroxybutyl formate (HC(O)OCH2CH2CHOHCH3), ~0.20; and propionaldehyde, ~0.2-0.3. The yields of minor products were as follows: 2-propyl-1,3-dioxolane (CH3CH2CH2CHOCH2CH2O), 0.025 ± 0.005; ethylene glycol monobutyrate (CH3CH2CH2C(O)OCH2CH2OH), ~0.02-0.03; 2-hydroxybutyl formate (HC(O)OCH2CHOHCH2CH3), ~0.05, acetaldehyde, 2- groups in 2- butoxyethanol followed by the subsequent reactions of the resulting alkyl and alkoxy radicals. The mechanism is analogous to that proposed for 2- ethoxyethanol (Stemmler et al. Environ. Sci. Technol. 1996, 20, 3385-3391), in which the alkoxy radicals predominantly undergo decomposition reactions, but also includes isomerization reactions for the alkoxy radicals that are derived from the butyl side chain in 2-butoxyethanol. The observed products, in conjunction with the proposed mechanism, account for a total molar yield of about 1.1, indicating that all the main routes are accounted for in the degradation of this hydroxy ether. Rate coefficients at room temperature for the reactions of OH radicals with butoxyacetaldehyde and 2-propyl-1,3- dioxolane have been determined to be 20.6 x 10-12 and 10.8 x 10-12 cm3 molecule-1 s-1, respectively, with error limits of about ±40%, in each case.
- Stemmler, Konrad,Mengon, Wolfgang,Kinnison, David J.,Kerr, J. Alistair
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- Oxoammonium salt oxidations of alcohols in the presence of pyridine bases
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Oxoammonium salt oxidations (using 4-acetylamino-2,2,6,6- tetramethylpiperidine-1-oxoammonium tetrafluoroborate) of alcohols containing a β-oxygen atom in the presence of pyridine yield dimeric esters, while in the presence of 2,6-lutidine the product is a simple aldehyde. The formation of a betaine between pyridine and an aldehyde is presented to explain this disparity in reactivity. The betaine is oxidized by the oxoammonium salt to give an N-acylpyridinium ion that serves as an acylating agent for ester formation. Steric effects deter the formation of such a betaine with 2,6-disubstituted pyridines. A series of alcohols containing a β-oxygen substituent were oxidized to aldehydes in the presence of 2,6-lutidine, and a short study of the relative reactivity of various alcohols is given. An overall mechanism for oxoammonium cation oxidations is suggested, premised on nucleophilic additions to the oxygen atom of the positively charged nitrogen-oxygen double bond. Possible mechanisms for both dimeric oxidations and simple oxidations are given.
- Bobbitt, James M.,Bartelson, Ashley L.,Bailey, William F.,Hamlin, Trevor A.,Kelly, Christopher B.
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supporting information
p. 1055 - 1067
(2014/03/21)
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- 2-Butoxyethanol and benzyl alcohol reactions with the nitrate radical: Rate coefficients and gas-phase products
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The bimolecular rate coefficients k NO 3 ? + 2-butoxyethanol and k NO 3 ? + benzyl alcohol were measured using the relative rate technique at (297 ± 3) K and 1 atmosphere total pressure. Values of (2.7 ± 0.7) and (4.0 ± 1.0) × 10-15 cm3/s
- Harrison, Joel C.,Wells
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p. 778 - 788
(2013/01/15)
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