Electronic factors in the elimination kinetics of 2‐halosubstituted methanesulphonates in the gas phase

Alvarez, G Jaime; Chuchani, Gabriel

doi:10.1002/poc.610030707

Cited by 3 publications

(1 citation statement)

References 6 publications

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“…t -BuS(O)S t -Bu can also dissociate directly to tert -butanethiosulfonic acid ( t -BuS(OH)S) and 2-methylpropene via β-elimination mechanism involving a six-membered transition state TS2. The internal elimination mechanism of the title compound via a six-membered TS pathway can be compared to the gas phase pyrolysis of alkyl sufonates through six-membered ring transition state to give olefin and sulfonic acid. − From the generalized work of McCulla et al it can be found that the pyrolytic elimination reactions of sulfinate and sulfonate esters via six-membered TS pathway yield the same. The energy barrier 43.34 kcal/mol (G3B3 value) for the six-centered elimination of t- BuS(O)S t- Bu is comparable with 50.6 kcal/mol (MP2/6-311+G(3df,2p)//MP2/6-31G(d,p) value) for its analogue CH 3 S(O)OCH 2 CH 3 .…”

Section: Resultsmentioning

confidence: 99%

Pyrolysis of tert-Butyl tert-Butanethiosulfinate, t-BuS(O)St-Bu: A Computational Perspective of the Decomposition Pathways

2011

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A systematic theoretical study has been performed on the low pressure thermal decomposition pathways of t-BuS(O)St-Bu using the CCSD(T)/cc-pV(D+d)Z//B3LYP/6-311++G(2d,2p), CCSD(T)/cc-pV(D+d)Z//PBEPBE/6-311++G(2d,2p), and G3B3 level of theories. Rate constants for the unimolecular decomposition pathways are calculated using Rice−Ramsperger−Kassel−Marcus (RRKM) theory. On the basis of the experimental observation and theoretical predictions, the pyrolysis channels are considered as primary and secondary pyrolysis reactions. The primary decomposition via a five-membered transition state leads to the formation of tert-butanethiosulfoxylic acid (t-BuSSOH) and 2-methylpropene (C4H8) almost exclusively having low-pressure limit rate constant k(1)(0) = 4.67 × 10(−6)T(−4.67) exp(−11.64 kcal mol(−1)/RT) cm3 mol(−1) s(−1) (T = 500−800 K). The primary decomposition via a six-membered transition state is also identified, and that leads to the tert-butanethiosulfinic acid t-BuS(OH)S, which is the branched chain isomer of t-BuSSOH. The formation of t-BuSSOH is thermodynamically as well as kinetically favorable over t-BuS(OH)S formation, and therefore the second product could not be found experimentally. Furthermore, calculation on secondary pyrolysis pathways involving the decomposition of t-BuSSOH leads to the formation of 1-oxatrisulfane (trans-HSSOH and cis-HSSOH) and their branched isomer S(SH)OH. These three secondary product formation rates are competitive, but thermodynamics do not favor the formation of the branched isomer. Among the secondary pyrolysis products, trans-HSSOH is the most stable one, and its formation rate constant at low pressure is calculated to be k(3)(0) = 5.49 × 10(28)T(−10.70) exp(−36.22 kcal mol(−1)/RT) cm3 mol(−1) s(−1) (T = 800−1500 K). Finally, the secondary pyrolysis pathway from less stable product t-BuS(OH)S is also predicted, and that leads to trans-HSSOH and cis-HSSOH products with almost equal rates. A bond-order analysis using Wiberg bond indexes obtained by natural bond orbital (NBO) calculation predicts that the primary and secondary pyrolysis of t-BuS(O)St-Bu occur via E1-like mechanism.

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Section: Resultsmentioning

confidence: 99%

Pyrolysis of tert-Butyl tert-Butanethiosulfinate, t-BuS(O)St-Bu: A Computational Perspective of the Decomposition Pathways

2011

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Pyrolytic elimination reactions of sulfinate and sulfonate esters

McCulla

Cubbage

Jenks

2001

J of Physical Organic Chem

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The barriers to pyrolytic unimolecular elimination by ethyl methanesulfonate and ethyl methanesulfinate were calculated for both five‐membered ring eliminations that yield acetaldehyde and six‐membered ring eliminations that yield ethylene. The experimental observation that related sulfinates undergo the five‐centered elimination and sulfonates the six‐centered elimination is reproduced by the calculations and rationalized in terms of a nucleophilicity/electrophilicity matching issue in the former and a charge‐separated transition state in the latter. Copyright © 2001 John Wiley & Sons, Ltd.

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Correlation of alkyl and polar substituents in the elimination kinetics of 2‐substituted ethyl methanesulphonates in the gas phase

Chuchani

Martín

1991

J of Physical Organic Chem

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The kinetics of the elimination of several polar 2‐substituted ethyl methanesulphonates in the gas phase were determined in a static system, seasoned with allylbromide, and in the presence of at least equal amount of the freeradical suppressor propene and/toluene. The working temperature and pressure ranges were 290–360°C and 31°199 Torr (1 Torr = 133.3 Pa), respectively. The reactions are homogeneous, unimolecular, show a first‐order rate law and take place according to the following equations: for 3‐chloropropyl methanesulphonate, log k1 (s−1) = (12.01 ± 0.18) ‐ (171.7 ± 2.1) kJ mol−1 (2.303RT)−1; for 4‐chlorobutyl methanesulphonate, log k1 (S−1) = (11.78 ± 0.31) ‐ (166.1 ± 3.5) kJ mol−1 (2.303RT)−1; for 3‐methoxypropyl methanesulphonate, log k1 (s−1) = (11.50 ± 0.36) ‐ (163.3 ± 4.0) kJ Mol−1 (2.303RT)−1; and for 2‐ethoxyethyl methanesulphonate, log k1 (s−1) = (11.52 ± 0.37) ‐ (167.3 ± 4.1) kJ mol−1 (2.303RT)−1. The present data together with those reported in the literature show that alkyl 2‐substituted ethyl methanesulphonates give an approximate straight line when log k/ko vs σ* values (ρ* = −0.82 ± 0.088, intercept = 0.0084 ± 0.0209 and correlation coefficient r = 0.967 at 320°C) are plotted. However, polar substituents at the 2‐position of ethyl methanesulphonates give rise to an inflection point at σ*(CH3) = 0.00 into another very good straight line (σ* = −0.29 ± 0.013, intercept = −0.0065 ± 0.0213 and r = 0.994 at 320°C). The mechanism of these reactions is considered to be heterolytic in nature, proceeding in terms of an intimate ion‐pair intermediate.

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Electronic factors in the elimination kinetics of 2‐halosubstituted methanesulphonates in the gas phase

Cited by 3 publications

References 6 publications

Pyrolysis of tert-Butyl tert-Butanethiosulfinate, t-BuS(O)St-Bu: A Computational Perspective of the Decomposition Pathways

Pyrolysis of tert-Butyl tert-Butanethiosulfinate, t-BuS(O)St-Bu: A Computational Perspective of the Decomposition Pathways

Pyrolytic elimination reactions of sulfinate and sulfonate esters

Correlation of alkyl and polar substituents in the elimination kinetics of 2‐substituted ethyl methanesulphonates in the gas phase

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