Thermodynamics of the Ionization of Some Thiols in Aqueous Solution.

Goursot, Paul; Wadsö, Ingemar; Mooney, R. W.; Kristiansen, L. A.; Brünvoll, J.; Bunnenberg, E.; Djerassi, Carl; Records, Ruth

doi:10.3891/acta.chem.scand.18-0769

Cited by 70 publications

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“…The experimental pK a 's for this set of organic thiols are listed in Table 1 and range from 4 to 12 pK a units. [65][66][67][68][69][70][71][72][73][74][75][76] The test calculations in Figure 1 indicate that there is a large error in the calculation of the pK a 's for simple thiols. In previous studies on nucleobases, we found that the methods that performed well for pK a 's of cation-neutral pairs often performed poorly for pK a 's of neutral-anion pairs.…”

Section: Resultsmentioning

confidence: 99%

Density Functional Theory Calculation of pK_a’s of Thiols in Aqueous Solution Using Explicit Water Molecules and the Polarizable Continuum Model

2016

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The pKa's of substituted thiols are important for understanding their properties and reactivities in applications in chemistry, biochemistry, and material chemistry. For a collection of 175 different density functionals and the SMD implicit solvation model, the average errors in the calculated pKa's of methanethiol and ethanethiol are almost 10 pKa units higher than for imidazole. A test set of 45 substituted thiols with pKa's ranging from 4 to 12 has been used to assess the performance of 8 functionals with 3 different basis sets. As expected, the basis set needs to include polarization functions on the hydrogens and diffuse functions on the heavy atoms. Solvent cavity scaling was ineffective in correcting the errors in the calculated pKa's. Inclusion of an explicit water molecule that is hydrogen bonded with the H of the thiol group (in neutral) or S(-) (in thiolates) lowers error by an average of 3.5 pKa units. With one explicit water and the SMD solvation model, pKa's calculated with the M06-2X, PBEPBE, BP86, and LC-BLYP functionals are found to deviate from the experimental values by about 1.5-2.0 pKa units whereas pKa's with the B3LYP, ωB97XD and PBEVWN5 functionals are still in error by more than 3 pKa units. The inclusion of three explicit water molecules lowers the calculated pKa further by about 4.5 pKa units. With the B3LYP and ωB97XD functionals, the calculated pKa's are within one unit of the experimental values whereas most other functionals used in this study underestimate the pKa's. This study shows that the ωB97XD functional with the 6-31+G(d,p) and 6-311++G(d,p) basis sets, and the SMD solvation model with three explicit water molecules hydrogen bonded to the sulfur produces the best result for the test set (average error -0.11 ± 0.50 and +0.15 ± 0.58, respectively). The B3LYP functional also performs well (average error -1.11 ± 0.82 and -0.78 ± 0.79, respectively).

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Section: Resultsmentioning

confidence: 99%

Density Functional Theory Calculation of pK_a’s of Thiols in Aqueous Solution Using Explicit Water Molecules and the Polarizable Continuum Model

2016

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“…9 We have, therefore, measured the acidities of several thiols in the gas phase to determine the intrinsic effect of alkyl groups on acidity and to compare gas-phase acidities with aqueous acidities where ion-pairing is absent. 9 We have, therefore, measured the acidities of several thiols in the gas phase to determine the intrinsic effect of alkyl groups on acidity and to compare gas-phase acidities with aqueous acidities where ion-pairing is absent.…”

Section: Sirmentioning

confidence: 99%

Gas-phase acidities: alkanethiols

Bartmess¹,

McIver²

1977

J. Am. Chem. Soc.

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“…At present, there are not enough data available to make that evaluation. The only data available for ionic organic sulfur species are for ionization of thiols (Irving et al 1964;Tsonopoulos et al 1976), which are not considered in this paper. These studies indicate, however, that thiols are very weak acids; this means that ionization would have a significant effect only in alkaline solutions such as those found in ultramafic rocks.…”

Section: Discussionmentioning

confidence: 98%

Organic Sulfides in Hydrothermal Solution: Standard Partial Molal Properties and Role in Organic Geochemistry of Hydrothermal Environments

Schulte

2010

Aquat Geochem

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Thermodynamic properties for aqueous alkyl sulfides have been compiled and/ or estimated through established methods. These properties are used to investigate reactions among various sulfur compounds in a variety of geological environments, ranging from sea floor hydrothermal systems to organic-rich sludge. Using thermodynamic data and the revised Helgeson-Kirkham-Flowers (HKF) equations of state, along with geochemical constraints imposed by the environment, it is possible to estimate the abiotic production of this class of organic sulfur compounds. For example, in hydrothermal systems in which H 2 and H 2 S concentrations are buffered by the pyrite-pyrrhotite-magnetite (PPM) mineral assemblage, calculated equilibrium activities of dimethyl sulfide (DMS) are as high as 10 -3 through formation reactions in which the environment contains millimolal concentrations of CO 2 . Higher activities are obtained when DMS formation from CO is considered and when more reducing mineral assemblages are present.

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Thermodynamics of the Ionization of Some Thiols in Aqueous Solution.

Cited by 70 publications

References 0 publications

Density Functional Theory Calculation of pK_a’s of Thiols in Aqueous Solution Using Explicit Water Molecules and the Polarizable Continuum Model

Density Functional Theory Calculation of pK_a’s of Thiols in Aqueous Solution Using Explicit Water Molecules and the Polarizable Continuum Model

Gas-phase acidities: alkanethiols

Organic Sulfides in Hydrothermal Solution: Standard Partial Molal Properties and Role in Organic Geochemistry of Hydrothermal Environments

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Thermodynamics of the Ionization of Some Thiols in Aqueous Solution.

Cited by 70 publications

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Density Functional Theory Calculation of pKa’s of Thiols in Aqueous Solution Using Explicit Water Molecules and the Polarizable Continuum Model

Density Functional Theory Calculation of pKa’s of Thiols in Aqueous Solution Using Explicit Water Molecules and the Polarizable Continuum Model

Gas-phase acidities: alkanethiols

Organic Sulfides in Hydrothermal Solution: Standard Partial Molal Properties and Role in Organic Geochemistry of Hydrothermal Environments

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Product

Resources

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Density Functional Theory Calculation of pK_a’s of Thiols in Aqueous Solution Using Explicit Water Molecules and the Polarizable Continuum Model

Density Functional Theory Calculation of pK_a’s of Thiols in Aqueous Solution Using Explicit Water Molecules and the Polarizable Continuum Model