Methanethiol

Formula: CH₄S
Molecular weight: 48.107
IUPAC Standard InChI:
InChI=1S/CH4S/c1-2/h2H,1H3

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IUPAC Standard InChIKey: LSDPWZHWYPCBBB-UHFFFAOYSA-N
CAS Registry Number: 74-93-1
Chemical structure:
This structure is also available as a 2d Mol file or as a computed 3d SD file
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Other names: Methyl mercaptan; Mercaptomethane; CH3SH; Methyl sulfhydrate; Methyl thioalcohol; Mercaptan methylique; Methaanthiol; Methanthiol; Methvtiolo; Methylmercaptaan; Metilmercaptano; Rcra waste number U153; Thiomethanol; UN 1064; Methanethiole
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Reaction thermochemistry data

Go To: Top, References, Notes

Data compiled as indicated in comments:
B - John E. Bartmess
M - Michael M. Meot-Ner (Mautner) and Sharon G. Lias
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein

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Individual Reactions

+ Methanethiol = ( )

By formula: F^- + CH₄S = (F^- CH₄S)

Quantity	Value	Units	Method	Reference	Comment
_rH°	143. ± 8.4	kJ/mol	IMRE	Larson and McMahon, 1983	gas phase; These relative affinities are ca. 10 kcal/mol weaker than threshold values (see Wenthold and Squires, 1995) for donors greater than ca. 27 kcal/mol in free energy. This discrepancy has not yet been resolved, though the stronger value appears preferable.; B,M
Quantity	Value	Units	Method	Reference	Comment
_rS°	97.1	J/mol*K	N/A	Larson and McMahon, 1983	gas phase; switching reaction(F-)H2O, Entropy change calculated or estimated; Arshadi, Yamdagni, et al., 1970; M
Quantity	Value	Units	Method	Reference	Comment
_rG°	114. ± 8.4	kJ/mol	IMRE	Larson and McMahon, 1983	gas phase; These relative affinities are ca. 10 kcal/mol weaker than threshold values (see Wenthold and Squires, 1995) for donors greater than ca. 27 kcal/mol in free energy. This discrepancy has not yet been resolved, though the stronger value appears preferable.; B,M

+ = Methanethiol

By formula: CH₃S^- + H⁺ = CH₄S

Quantity	Value	Units	Method	Reference	Comment
_rH°	1496. ± 8.4	kJ/mol	D-EA	Schwartz, Davico, et al., 2000	gas phase; B
_rH°	1496. ± 8.4	kJ/mol	D-EA	Moran and Ellison, 1988	gas phase; B
_rH°	1493. ± 9.2	kJ/mol	G+TS	Bartmess, Scott, et al., 1979	gas phase; value altered from reference due to change in acidity scale; B
Quantity	Value	Units	Method	Reference	Comment
_rG°	1467. ± 8.4	kJ/mol	IMRE	Bartmess, Scott, et al., 1979	gas phase; value altered from reference due to change in acidity scale; B

CH₃S^- + = Methanethiol

By formula: CH₃S^- + H⁺ = CH₄S

Quantity	Value	Units	Method	Reference	Comment
_rH°	1654. ± 11.	kJ/mol	G+TS	Kass, Guo, et al., 1990	gas phase; Acidity between D2O and Me2NH.; B
_rH°	1638. ± 32.	kJ/mol	D-EA	Kass, Guo, et al., 1990	gas phase; Between O2 and SO2. Explains bad anchor in McIver Jr. and Fukuda, 1982; B
Quantity	Value	Units	Method	Reference	Comment
_rG°	1624. ± 10.	kJ/mol	IMRB	Kass, Guo, et al., 1990	gas phase; Acidity between D2O and Me2NH.; B

(CH₆N⁺ 2) + Methanethiol = (CH₆N⁺ 2)

By formula: (CH₆N⁺ 2C₂H₃N) + CH₄S = (CH₆N⁺ CH₄S 2C₂H₃N)

Quantity	Value	Units	Method	Reference	Comment
_rH°	33.	kJ/mol	PHPMS	Meot-Ner (Mautner) and Sieck, 1985	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
_rS°	84.	J/mol*K	N/A	Meot-Ner (Mautner) and Sieck, 1985	gas phase; Entropy change calculated or estimated; M

Free energy of reaction

_rG° (kJ/mol)	T (K)	Method	Reference	Comment
10.	270.	PHPMS	Meot-Ner (Mautner) and Sieck, 1985	gas phase; Entropy change calculated or estimated; M

+ Methanethiol = ( )

By formula: Cl^- + CH₄S = (Cl^- CH₄S)

Quantity	Value	Units	Method	Reference	Comment
_rH°	65. ± 13.	kJ/mol	IMRB	Staneke, Groothuis, et al., 1995	gas phase; Chloride affinity comparable to that of CHCl3; B
Quantity	Value	Units	Method	Reference	Comment
_rG°	45. ± 13.	kJ/mol	IMRB	Staneke, Groothuis, et al., 1995	gas phase; Chloride affinity comparable to that of CHCl3; B

+ Methanethiol = ( )

By formula: C₂H₃O₂^- + CH₄S = (C₂H₃O₂^- CH₄S)

Quantity	Value	Units	Method	Reference	Comment
_rH°	62.3 ± 4.2	kJ/mol	TDAs	Meot-ner, 1988	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
_rS°	95.4	J/mol*K	PHPMS	Meot-ner, 1988	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
_rG°	34. ± 4.2	kJ/mol	TDAs	Meot-ner, 1988	gas phase; B

(CH₆N⁺ ) + Methanethiol = (CH₆N⁺ )

By formula: (CH₆N⁺ C₂H₃N) + CH₄S = (CH₆N⁺ CH₄S C₂H₃N)

Quantity	Value	Units	Method	Reference	Comment
_rH°	41.	kJ/mol	PHPMS	Meot-Ner (Mautner) and Sieck, 1985	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
_rS°	83.7	J/mol*K	PHPMS	Meot-Ner (Mautner) and Sieck, 1985	gas phase; M

CH₆N⁺ + Methanethiol = (CH₆N⁺ )

By formula: CH₆N⁺ + CH₄S = (CH₆N⁺ CH₄S)

Quantity	Value	Units	Method	Reference	Comment
_rH°	56.1	kJ/mol	PHPMS	Meot-Ner (Mautner) and Sieck, 1985	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
_rS°	92.5	J/mol*K	PHPMS	Meot-Ner (Mautner) and Sieck, 1985	gas phase; M

+ = Methanethiol +

By formula: HI + CH₃IS = CH₄S + I₂

Quantity	Value	Units	Method	Reference	Comment
_rH°	-12.0 ± 2.3	kJ/mol	Eqk	Shum and Benson, 1983	gas phase; ALS

References

Go To: Top, Reaction thermochemistry data, Notes

Larson and McMahon, 1983
Larson, J.W.; McMahon, T.B., Strong hydrogen bonding in gas-phase anions. An ion cyclotron resonance determination of fluoride binding energetics to bronsted acids from gas-phase fluoride exchange equilibria measurements, J. Am. Chem. Soc., 1983, 105, 2944. [all data]

Wenthold and Squires, 1995
Wenthold, P.G.; Squires, R.R., Bond dissociation energies of F2(-) and HF2(-). A gas-phase experimental and G2 theoretical study, J. Phys. Chem., 1995, 99, 7, 2002, https://doi.org/10.1021/j100007a034 . [all data]

Arshadi, Yamdagni, et al., 1970
Arshadi, M.; Yamdagni, R.; Kebarle, P., Hydration of Halide Negative Ions in the Gas Phase. II. Comparison of Hydration Energies for the Alkali Positive and Halide Negative Ions, J. Phys. Chem., 1970, 74, 7, 1475, https://doi.org/10.1021/j100702a014 . [all data]

Schwartz, Davico, et al., 2000
Schwartz, R.L.; Davico, G.E.; Lineberger, W.C., Negative-ion photoelectron spectroscopy of CH3S-, J. Electron Spectros. Rel. Phenom., 2000, 108, 1-3, 163-168, https://doi.org/10.1016/S0368-2048(00)00125-0 . [all data]

Moran and Ellison, 1988
Moran, S.; Ellison, G.B., Photoelectron Spectroscopy of Sulfur Ions, J. Phys. Chem., 1988, 92, 7, 1794, https://doi.org/10.1021/j100318a021 . [all data]

Bartmess, Scott, et al., 1979
Bartmess, J.E.; Scott, J.A.; McIver, R.T., Jr., The gas phase acidity scale from methanol to phenol, J. Am. Chem. Soc., 1979, 101, 6047. [all data]

Kass, Guo, et al., 1990
Kass, S.R.; Guo, H.-Z.; Dahlke, G.D., The Thiomethyl Anion: Formation, Reactivity, and Thermodynamic Properties, J. Am. Soc. Mass Spectrom., 1990, 1, 5, 366, https://doi.org/10.1016/1044-0305(90)85016-F . [all data]

McIver Jr. and Fukuda, 1982
McIver Jr.; Fukuda, E.K., Equilibrium Electron Affinities, Lec. Notes in Chem., 1982, 31, 165. [all data]

Meot-Ner (Mautner) and Sieck, 1985
Meot-Ner (Mautner), M.; Sieck, L.W., The Ionic Hydrogen Bond and Ion Solvation. 4. SH+ O and NH+ S Bonds. Correlations with Proton Affinity. Mutual Effects of Weak and Strong Ligands in Mixed Clusters, J. Phys. Chem., 1985, 89, 24, 5222, https://doi.org/10.1021/j100270a021 . [all data]

Staneke, Groothuis, et al., 1995
Staneke, P.O.; Groothuis, G.; Ingemann, S.; Nibbering, N.M.M., Formation, stability and structure of radical anions of chloroform, tetrachloromethane and fluorotrichloromethane in the gas phase, Int. J. Mass Spectrom. Ion Proc., 1995, 142, 1-2, 83, https://doi.org/10.1016/0168-1176(94)04127-S . [all data]

Meot-ner, 1988
Meot-ner, M., Ionic Hydrogen Bond and Ion Solvation. ₆. Interaction Energies of the Acetate Ion with Organic Molecules. Comparison of CH₃COO^- with Cl^-, CN^-, and SH^-, J. Am. Chem. Soc., 1988, 110, 12, 3854, https://doi.org/10.1021/ja00220a022 . [all data]

Shum and Benson, 1983
Shum, L.G.S.; Benson, S.W., Thermochemnistry and kinetics of the reaction of methyl mercaptan with iodine, Int. J. Chem. Kinet., 1983, 15, 433-453. [all data]

Notes

Go To: Top, Reaction thermochemistry data, References

Symbols used in this document:

T Temperature

_rG° Free energy of reaction at standard conditions

_rH° Enthalpy of reaction at standard conditions

_rS° Entropy of reaction at standard conditions
Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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T	Temperature
_rG°	Free energy of reaction at standard conditions
_rH°	Enthalpy of reaction at standard conditions
_rS°	Entropy of reaction at standard conditions