Benzoic acid, 4-methyl-
- Formula: C8H8O2
- Molecular weight: 136.1479
- IUPAC Standard InChIKey: LPNBBFKOUUSUDB-UHFFFAOYSA-N
- CAS Registry Number: 99-94-5
- Chemical structure:
This structure is also available as a 2d Mol file or as a computed 3d SD file
The 3d structure may be viewed using Java or Javascript. - Other names: p-Toluic acid; p-Methylbenzoic acid; p-Toluylic acid; Crithminic acid; 4-Methylbenzoic acid; 4-Toluic acid; para-Toluic acid; NSC 2215; p-Carboxytoluene; p-Tolylcarboxylic acid
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Gas phase ion energetics data
Go To: Top, References, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
Data compiled as indicated in comments:
B - John E. Bartmess
LLK - Sharon G. Lias, Rhoda D. Levin, and Sherif A. Kafafi
View reactions leading to C8H8O2+ (ion structure unspecified)
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
Proton affinity (review) | 836.7 | kJ/mol | N/A | Hunter and Lias, 1998 | HL |
Quantity | Value | Units | Method | Reference | Comment |
Gas basicity | 805.7 | kJ/mol | N/A | Hunter and Lias, 1998 | HL |
Ionization energy determinations
IE (eV) | Method | Reference | Comment |
---|---|---|---|
9.2 ± 0.2 | EI | Benoit, 1973 | LLK |
9.4 | PE | Meeks, Wahlborg, et al., 1981 | Vertical value; LLK |
Appearance energy determinations
Ion | AE (eV) | Other Products | Method | Reference | Comment |
---|---|---|---|---|---|
C7H7+ | 12.6 ± 0.2 | COOH | EI | Benoit, 1973 | LLK |
C8H7O+ | 12.1 ± 0.2 | OH | EI | Benoit, 1973 | LLK |
De-protonation reactions
C8H7O2- + =
By formula: C8H7O2- + H+ = C8H8O2
Quantity | Value | Units | Method | Reference | Comment |
---|---|---|---|---|---|
ΔrH° | 1427. ± 8.8 | kJ/mol | G+TS | Kebarle and McMahon, 1977 | gas phase; B |
ΔrH° | 1425. ± 8.8 | kJ/mol | G+TS | Decouzon, Exner, et al., 1996 | gas phase; relative to benzoate at 333.0 kcal/mol; B |
Quantity | Value | Units | Method | Reference | Comment |
ΔrG° | 1397. ± 8.4 | kJ/mol | IMRE | Kebarle and McMahon, 1977 | gas phase; B |
ΔrG° | 1396. ± 8.4 | kJ/mol | IMRE | Decouzon, Exner, et al., 1996 | gas phase; relative to benzoate at 333.0 kcal/mol; B |
References
Go To: Top, Gas phase ion energetics data, Notes
Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.
Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G.,
Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update,
J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018
. [all data]
Benoit, 1973
Benoit, F.,
Substituent effects in mass spectrometry. III. Substituent effects in the dissociation of the molecular ions of para and meta subtituted benzoic acids,
Org. Mass Spectrom., 1973, 7, 295. [all data]
Meeks, Wahlborg, et al., 1981
Meeks, J.; Wahlborg, A.; McGlynn, S.P.,
Photoelectron spectroscopy of carbonyls: Benzoic acid and its derivatives,
J. Electron Spectrosc. Relat. Phenom., 1981, 22, 43. [all data]
Kebarle and McMahon, 1977
Kebarle, P.; McMahon, T.B.,
Intrinsic Acidities of Substituted Phenols and Benzoic Acids Determined by Gas Phase Proton Transfer Equilibria,
J. Am. Chem. Soc., 1977, 99, 7, 2222, https://doi.org/10.1021/ja00449a032
. [all data]
Decouzon, Exner, et al., 1996
Decouzon, M.; Exner, O.; Gal, J.-F.; Maria, P.-C.,
Non-classical Buttressing Effect: Gas-phase Ionization of Some Methyl Substituted Benzoic Acids,
J. Chem. Soc. Perkin Trans., 1996, 2, 4, 475, https://doi.org/10.1039/p29960000475
. [all data]
Notes
Go To: Top, Gas phase ion energetics data, References
- Symbols used in this document:
AE Appearance energy ΔrG° Free energy of reaction at standard conditions ΔrH° Enthalpy of reaction at standard conditions - Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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