Methylation of Thioanisoles and Anilines by 1-Methyl-2,5-diphenyl-1,4-dithiinium Tetrafluoroborate. Kinetics and Correlations

Thomas E. Young, Alan R. Oyler

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

The kinetics of methyl transfer from 1-methyl-2,5-diphenyl-1,4-dithiinium tetrafluoroborate (1) to a series of thioanisoles (2) and to a comparable series of anilines (5) have been followed spectrophotometrically in acetonitrile under pseudo-first-order conditions at four temperatures for each compound. Derived second-order rate constants, Arrhenius equation constants, and activation thermodynamic parameters have been calculated for intra- and inter-series comparison. Both series exhibited well-defined Hammett correlations (ρS = -1.58 ± 0.04; corr coeff = 0.999 for the thioanisoles, and ρN = -1.95 ± 0.05; corr coeff = 0.998 for the anilines) in which the ρ values were essentially constant over the range 25-80 °C. Specific rate constants for the thioanisole set (k S X ) correlated well with those of the aniline set (k N X ) via a linear equation: log k S X = m log k N X + constant, where the slope m is approximated by the ratio of Hammett ρ values (ρS/ρN)· Comparisons with literature data show that dimethyl sulfate is 2.3 times as reactive as 1 toward the thioanisoles, and that 1 is about 10 times as reactive as Mel toward the anilines.

Original languageEnglish (US)
Pages (from-to)2753-2759
Number of pages7
JournalJournal of Organic Chemistry
Volume41
Issue number16
DOIs
StatePublished - Aug 1 1976

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Aniline Compounds
Methylation
Kinetics
Rate constants
Linear equations
Chemical activation
Thermodynamics
methylphenylsulfide
diphenyl

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Methylation of Thioanisoles and Anilines by 1-Methyl-2,5-diphenyl-1,4-dithiinium Tetrafluoroborate. Kinetics and Correlations. / Young, Thomas E.; Oyler, Alan R.

In: Journal of Organic Chemistry, Vol. 41, No. 16, 01.08.1976, p. 2753-2759.

Research output: Contribution to journalArticle

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abstract = "The kinetics of methyl transfer from 1-methyl-2,5-diphenyl-1,4-dithiinium tetrafluoroborate (1) to a series of thioanisoles (2) and to a comparable series of anilines (5) have been followed spectrophotometrically in acetonitrile under pseudo-first-order conditions at four temperatures for each compound. Derived second-order rate constants, Arrhenius equation constants, and activation thermodynamic parameters have been calculated for intra- and inter-series comparison. Both series exhibited well-defined Hammett correlations (ρS = -1.58 ± 0.04; corr coeff = 0.999 for the thioanisoles, and ρN = -1.95 ± 0.05; corr coeff = 0.998 for the anilines) in which the ρ values were essentially constant over the range 25-80 °C. Specific rate constants for the thioanisole set (k S X ) correlated well with those of the aniline set (k N X ) via a linear equation: log k S X = m log k N X + constant, where the slope m is approximated by the ratio of Hammett ρ values (ρS/ρN)· Comparisons with literature data show that dimethyl sulfate is 2.3 times as reactive as 1 toward the thioanisoles, and that 1 is about 10 times as reactive as Mel toward the anilines.",
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N2 - The kinetics of methyl transfer from 1-methyl-2,5-diphenyl-1,4-dithiinium tetrafluoroborate (1) to a series of thioanisoles (2) and to a comparable series of anilines (5) have been followed spectrophotometrically in acetonitrile under pseudo-first-order conditions at four temperatures for each compound. Derived second-order rate constants, Arrhenius equation constants, and activation thermodynamic parameters have been calculated for intra- and inter-series comparison. Both series exhibited well-defined Hammett correlations (ρS = -1.58 ± 0.04; corr coeff = 0.999 for the thioanisoles, and ρN = -1.95 ± 0.05; corr coeff = 0.998 for the anilines) in which the ρ values were essentially constant over the range 25-80 °C. Specific rate constants for the thioanisole set (k S X ) correlated well with those of the aniline set (k N X ) via a linear equation: log k S X = m log k N X + constant, where the slope m is approximated by the ratio of Hammett ρ values (ρS/ρN)· Comparisons with literature data show that dimethyl sulfate is 2.3 times as reactive as 1 toward the thioanisoles, and that 1 is about 10 times as reactive as Mel toward the anilines.

AB - The kinetics of methyl transfer from 1-methyl-2,5-diphenyl-1,4-dithiinium tetrafluoroborate (1) to a series of thioanisoles (2) and to a comparable series of anilines (5) have been followed spectrophotometrically in acetonitrile under pseudo-first-order conditions at four temperatures for each compound. Derived second-order rate constants, Arrhenius equation constants, and activation thermodynamic parameters have been calculated for intra- and inter-series comparison. Both series exhibited well-defined Hammett correlations (ρS = -1.58 ± 0.04; corr coeff = 0.999 for the thioanisoles, and ρN = -1.95 ± 0.05; corr coeff = 0.998 for the anilines) in which the ρ values were essentially constant over the range 25-80 °C. Specific rate constants for the thioanisole set (k S X ) correlated well with those of the aniline set (k N X ) via a linear equation: log k S X = m log k N X + constant, where the slope m is approximated by the ratio of Hammett ρ values (ρS/ρN)· Comparisons with literature data show that dimethyl sulfate is 2.3 times as reactive as 1 toward the thioanisoles, and that 1 is about 10 times as reactive as Mel toward the anilines.

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