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  • Articles  (16)
  • Physical Chemistry  (16)
  • 1
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The title sulphenamides were pyrolysed in a stirred-flow reactor at temperatures of 310-410°C, pressures of 8-15 Torr and residence times of 0·4-2 s using toluene as the carrier gas. N-(tert-Butylthio)allylamine formed 73 ± 4% isobutene, 23 ± 3% propene and N-allylthiohydroxylamine. The first-order rate coefficients for the formation of isobutene and propene, respectively, followed the Arrhenius equations kC4(s-1) = 1012·52 ± 0·36 exp(-163 ± 5 kJ mol-1 RT) and kC3(s-1) = 1010·99 ± 0·29 exp(-151 ± 4 kJ mol-1 RT) N-(tert-Butylthio)diethylamine gave 97 ± 1% isobutene, 1·9 ± 0·4% isobutane and N,N-diethylthiohydroxylamine. The first-order rate coefficients for isobutene elimination followed the Arrhenius equation k(s-1) = 1013·45 ± 0·24 exp(-164 ± 3 kJ mol-1 RT). The formation of the products is interpreted in terms of an elimination reaction with a unimolecular, four-centered, cyclic transition state. The reactivity of these sulphenamides was found to be much higher than that of previously studied alkyl or aryl tert-butyl sulphides and disulphides.
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 4 (1991), S. 579-585 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The pyrolysis kinetics of RC6H4SS—t—C4H9 (R=H, p-NO2, p-Cl, p-F) were determined at 390-450°C and 7-15 Torr in a stirred-flow reactor using toluene as carrier gas. The reaction products were 95% isobutene, 5% isobutane and the corresponding RC6H4SSH disulphanes. The first-order rate constants, k (s-1), based on isobutene production, followed the Arrhenius equations: phenyl tert-butyl disulphide, k = 1013.49±0.31 exp (- 182 ± 4 kJ mol-1)(RT)-1; pnitrophenyl tert-butyl disulphide, k = 1013.46 ± 0.32 [exp(- 185 ± 5 kJ mol-1)(RT)-1]; p-chlorophenyl tert-butyl disulphide, k = 1014.44 ± 0.66 [exp(- 196 ± 9 kJ mol-1)(RT)-1; p-fluorophenyl tert-butyl disulphide, k = 1010.80 ± 0.16 exp(- 144.5 ± 2 kJ mol -1)(RT)-1]; The observed reactivities, within the above temperature range, follow the order p—F 〉 H 〉 p—Cl 〉 p—NO2. A four-centre, cuadrupolar cyclic transition state mechanism is proposed for the formation of the isobutene and aryldisulphane products. The optimized ground-state molecular geometries of the reactants were calculated by using the MINDO/3 procedure.
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  • 3
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrolyses of cyanomethyl t-butyl sulfide and its oxygen homologue have been studied in a stirred-flow system over the temperature range 490-540°C and pressures between 5 and 14 Torr. In both cases, isobutene is formed as product in over 97% yield. Hydrogen sulfide is obtained in about half the amount of isobutene in the pyrolysis of the sulfide. Hydrogen cyanide is formed in the pyrolysis of the ether. The first-order rate coefficients for the consumption of the reactants followed the Arrhenius equations Cyanomethyl t-butyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{ - 1}) = 10^{12.63 \pm 0.23} \exp (- 201.7 \pm 3.5)\,{\rm kj}/{\rm mol }\,RT $$\end{document} Cyanomethyl t-butyl ether: \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{ - 1}) = 10^{11.27 \pm 0.30} \exp (- 186 \pm 5)\,{\rm kj}/{\rm mol }\,RT $$\end{document}A molecular mechanism involving polar four-centered cyclic transition states is proposed for both reactions, with the CN group stabilizing the partial negative charge developed at the S and O atoms.
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  • 4
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-cyanomethyl-N-ethyl aniline (CEAN) and N-cyanomethyl-N-ethyl-p-anisidine (CEPA) have been thermolyzed in a stirred-flow reactor, in the range of 510-560 °C, pressures of 7-11 torr and residence times of 0.5-0.9 s, using toluene as carrier gas. N-cyanomethyl-N-ethyl-p-nitroaniline (ECNA) was thermolyzed at 640°C and 13% conversion. Ethylene and HCN formed in 43% yield each as products from all three starting materials. Phenyl methanaldimine and p-anisidyl methanaldimine were also products of CEAN and CEPA, respectively. The consumption of CEAN and CEPA showed first-order kinetics for a three-fold increase of reactant inflow and initial conversions of up to 40 percent. The following Arrhenius equations were obtained from the rate coefficients for the production of ethylene: CEAN: k=1015.10±0.74 exp(-238±11 kJ/mol·RT); CEPA: k=1015.61±0.29 exp(-246±4 kJ/mol·RT). The results are explained by means of radical, nonchain thermolysis mechanisms. The thermochemistry of relevant reaction steps has been estimated from thermochemical parameters calculated by using the semiempirical AM1 method. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet: 30: 451-456, 1998
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrolysis of di-tert-butyl sulfide has been investigated in static and stirred-flow systems at subambient pressures. The rate of consumption of the sulfide was measured in some experiments, and the rate of pressure increase was followed in others. The results suggest that the reaction is essentially homogeneous in a seasoned reactor and proceeds through a free radical mechanism. In the initial stages, the decomposition rate follows first-order kinetics, and the rate coefficient in the absence of an inhibitor is given by \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{^u} (\sec ^{ - 1}) = 10^{15.1 \pm 0.6} \exp \left[{\left({ - 229 \pm 8} \right){\rm kJ/mol/RT}} \right] $$\end{document} between 360 and 413°C. The stoichiometry of the uninhibited reaction at 380°C and 50% decomposition is approximately \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm t}^{\rm \_} {\rm C}_{\rm 4} {\rm H}_{{\rm 9}^{\rm -}} {\rm S}_{\rm -} {\rm t}_{\rm -} {\rm C}_{\rm 4} {\rm H}_{\rm 9} = 1.72i_ - {\rm C}_{\rm 4} {\rm H}_{\rm 8} + 0.88{\rm H}_{\rm 2} {\rm S} + 0.29i_ - {\rm C}_{\rm 4} {\rm H}_{{\rm 10}} + 0.11t_ - {\rm C}_{\rm 4} {\rm H}_{\rm 9} {\rm SH} $$\end{document} between 360 and 413°C. The stoichiometry of the uninhibited reaction at 380°C and 50% decomposition is approximately.
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  • 6
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrolyses of four alkyl allyl sulfides with substituents on the α—C atom of the alkyl moiety have been studied in a stirred-flow system over the temperature range 340-400°C and pressures between 2 and 12 torr. The only products formed are propene and thioaldehydes. The reactions showed first-order kinetics with the rate coefficients following the Arrhenius equations: Chloromethyl allyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{{\rm - 1}}) = 10^{10.74 \pm 0.23} \exp ( - 144 \pm 3){\rm kJ/mol}RT $$\end{document} Cyanomethyl allyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{{\rm - 1}}) = 10^{10.20 \pm 0.19} \exp ( - 129 \pm 2){\rm kJ/mol}RT $$\end{document} 1-cyanoethyl allyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{{\rm - 1}}) = 10^{11.09 \pm 0.18} \exp ( - 141.5 \pm 2.2){\rm kJ/mol}RT $$\end{document} Neopentyl allyl sulfide: \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{{\rm - 1}}) = 10^{10.54 \pm 0.24} \exp ( - 144 \pm 3){\rm kJ/mol}RT $$\end{document}The effects of these and other substituents on the reactivity is discussed in relation with the stabilization of a polar six-centered transition state. The results support a non-concerted mechanism where the 1-5 α—H atom shift is assisted by its acidic character.
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  • 7
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title amines have been pyrolyzed in a stirred-flow reactor, at temperatures of 360-500°C, pressures of 7-16 torr, and residence times of 0.5-2.9 s, using toluene as carrier gas. The reaction products were allene, propene, and the corresponding imines. The ratio allene:propene varied in the range 6.7-1.6. The amines with CH2CN and SO2CH3 substituents also formed HCN and SO2. These appear to arise from complex free radical decomposition of the imine product. The first-order rate coefficients for the production of allene plus propene followed the Arrhenius equations: Allyl propargl amine: \documentclass{article}\pagestyle{empty}\begin{document}$$ k\left({{\rm s}^{- 1}} \right) = 10^{10.07 \pm 0.31} \exp \left({- 133 \pm 4{\rm kj/mol\,}RT} \right) $$\end{document} Allyl cyanomethyl propargyl amine: \documentclass{article}\pagestyle{empty}\begin{document}$$ k\left({{\rm s}^{- 1}} \right) = 10^{10.73 \pm 0.30} \exp \left({- 146 \pm 4{\rm kj/mol\,}RT} \right) $$\end{document} Allyl propargyl 2-thiapropyl amine: \documentclass{article}\pagestyle{empty}\begin{document}$$ k\left({{\rm s}^{- 1}} \right) = 10^{12.55 \pm 0.38} \exp \left({- 166 \pm 5{\rm kj/mol\,}RT} \right) $$\end{document} Allyl methanesulfonyl propargyl amine: \documentclass{article}\pagestyle{empty}\begin{document}$$ k\left({{\rm s}^{- 1}} \right) = 10^{12.56 \pm 0.34} \exp \left({- 184 \pm 5{\rm kj/mol\,}RT} \right) $$\end{document} Nonconcerted mechanisms, involving polar six center cyclic transition states, are suggested for the elimination of allene and propene. © 1994 John Wiley & Sons, Inc.
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  • 8
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title amines were pyrolyzed in a stirred-flow reactor at 380-510°C, pressures of 8-15 torr and residence times of 0.3-2.4 s, using toluene as carrier gas. The substrates with an allyl group yielded propene and iminonitriles as reaction products. HCN is formed by decomposition of the iminonitriles. The first-order rate coefficients for propene formation fit the Arrhenius equations Allyl cyanomethyl amine:\documentclass{article} \pagestyle{empty} \begin{document} $$ k({\rm s}^{ - {\rm 1}}) = 10^{13.29 \pm 0.35} {\rm exp(} - {\rm 189} \pm 5{\rm kJ/mol }RT{\rm)} $$ \end{document}Diallyl cyanomethyl amine:\documentclass{article} \pagestyle{empty} \begin{document} $$ k({\rm s}^{ - {\rm 1}}) = 10^{13.00 \pm 0.20} {\rm exp(} - {\rm 183} \pm 3{\rm kJ/mol }RT{\rm)} $$ \end{document} Diethyl cyanomethyl amine gave a 20:1 gas mixture of ehylene and ethane, plus HCN. The liquid product fraction contained mainly N-ethyl methanaldimine. The first-order rate coefficients for ethylene formation followed the Arrhenius equation \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{ - {\rm 1}}) = 10^{15.30 \pm 0.24} {\rm exp(} - {\rm 226} \pm 3{\rm kJ/mol }RT{\rm)} $$\end{document} Diethyl propargyl amine decomposed cleanly into allene and N-ethyl ethanaldimine. The first-order rate coefficients for allene formation fit the Arrhenius equation \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{ - {\rm 1}}) = 10^{12.84 \pm 0.30} {\rm exp(} - {\rm 168} \pm 4{\rm kJ/mol }RT{\rm)} $$\end{document} The results suggest that the above allyl and propargyl amines decompose unimolecularly by mechanisms involving six-center cyclic transition states. For diethyl cyanomethyl amine, a nonchain free radical mechanism is proposed. © 1995 John Wiley & Sons, Inc.
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  • 9
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The amide derivatives of t-butylsulfenic acid mentioned in the title have been thermolyzed in a stirred-flow reactor at temperatures of 273-390°C and pressures of 7-15 torr, using toluene as carrier gas, at residence times of 0.4-2 s. Isobutene formed in 95-99% yields, through order one reactions, following the Arrhenius equations: N, N-dimethyl t-butylsulfenamide: $$k(s^{-1})=10^{14.45\pm 0.46}\exp(-175\pm 5 {\rm kJ/mol}\,{\bf RT})$$ 2,6-dimethylpiperidyl t-butylsulfenamide: $$k(s^{-1})=10^{14.38\pm 0.26}\exp(-161\pm 3 {\rm kJ/mol}\,{\bf RT})$$ N-t-butyl t-butylsulfenamide: $$k(s^{-1})=10^{14.75\pm 0.37}\exp(-184\pm 7 {\rm kJ/mol}\,{\bf RT})$$These thermolyses are considered to take place through unimolecular, four-center cyclic transition-state reaction mechanisms, giving rise to isobutene plus the corresponding S-unsubstituted thiohydroxylamines. The latter decompose outside the reactor at temperatures above -78°C forming free sulfur and dimethylamine, 2,6-dimethylpiperidine, and t-butylamine, respectively. © 1996 John Wiley & Sons, Inc.
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  • 10
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrolysis of n-butyl 2-propenyl sulfide has been investigated in a static system in the initial pressure range of 50-350 torr. The reaction was found to be homogeneous and first order. The rate coefficients are given by the Arrhenius equation \documentclass{article}\pagestyle{empty}\begin{document}$$ k{\rm}(s^{- 1}) = 10^{11.42 \pm 0.28} \exp [(- 155 \pm 3){\rm kJ/mol/}RT] $$\end{document} between 262 and 293°C. The rate of the reaction remains unchanged in the presence of cyclohexene as radical inhibitor. The main reaction products were propene and a trimer of n-butyl thioaldehyde. The results are interpreted in terms of a molecular mechanism involving a cyclic six-centered transition state. This mechanism is supported by the pyrolysis of 1,1-dideutero-n-butyl 2-propenyl sulfide at 281°C. The kinetic deuterium isotope effect had a value of 2.7 ± 0.2. Nuclear magnetic resonance and mass spectroscopic analysis of the reaction products showed the deuterium to be distributed as expected from the proposed reaction mechanism.
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