Pyridine, 4-methyl-

Formula: C₆H₇N
Molecular weight: 93.1265
IUPAC Standard InChI: InChI=1S/C6H7N/c1-6-2-4-7-5-3-6/h2-5H,1H3
IUPAC Standard InChIKey: FKNQCJSGGFJEIZ-UHFFFAOYSA-N
CAS Registry Number: 108-89-4
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: 4-Picoline; γ-Methylpyridine; γ-Picoline; p-Methylpyridine; p-Picoline; Ba 35846; 4-Methylpyridine; para-Methylpyridine; gamma-Picoline; NSC 18252
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Condensed phase thermochemistry data

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Data compiled as indicated in comments:
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
DH - Eugene S. Domalski and Elizabeth D. Hearing

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_liquid	59.20 ± 0.88	kJ/mol	Ccb	Good, 1972	ALS
Δ_fH°_liquid	56.78 ± 0.63	kJ/mol	Ccb	Cox, Challoner, et al., 1954	ALS
Δ_fH°_liquid	48.07	kJ/mol	Ccb	Constam and White, 1903	ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_liquid	-3420.7 ± 0.84	kJ/mol	Ccb	Good, 1972	ALS
Δ_cH°_liquid	-3418.3 ± 0.63	kJ/mol	Ccb	Cox, Challoner, et al., 1954	ALS
Δ_cH°_liquid	-3417.	kJ/mol	Ccb	Constam and White, 1903	ALS
Quantity	Value	Units	Method	Reference	Comment
S°_liquid	209.091	J/mol*K	N/A	Messerly, Todd, et al., 1988	DH
S°_liquid	208.22	J/mol*K	N/A	Messerly, Todd, et al., 1987	DH
S°_liquid	208.22	J/mol*K	N/A	Steele, Chirico, et al., 1986	DH

Constant pressure heat capacity of liquid

C_p,liquid (J/mol*K)	Temperature (K)	Reference	Comment
158.988	298.150	Messerly, Todd, et al., 1988	T = 10 to 400 K.; DH
158.99	298.15	Messerly, Todd, et al., 1987	T = 10 to 410 K.; DH
158.99	298.15	Steele, Chirico, et al., 1986	T = 10 to 410 K.; DH

Reaction thermochemistry data

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Data compiled as indicated in comments:
B - John E. Bartmess
RCD - Robert C. Dunbar

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. A general reaction search form is also available. Future versions of this site may rely on reaction search pages in place of the enumerated reaction displays seen below.

Individual Reactions

C₆H₆N^- + = Pyridine, 4-methyl-

By formula: C₆H₆N^- + H⁺ = C₆H₇N

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1547. ± 21.	kJ/mol	G+TS	Meot-ner and Kafafi, 1988	gas phase; anchored to 88MEO scale, not the "87 acidity scale". The Kiefer, Zhang, et al., 1997 BDE is for ortho.; B
Δ_rH°	1568. ± 13.	kJ/mol	G+TS	DePuy, Kass, et al., 1988	gas phase; Acid: p-methylpyridine. Between iPrOH, MeCN.; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1518. ± 21.	kJ/mol	IMRB	Meot-ner and Kafafi, 1988	gas phase; anchored to 88MEO scale, not the "87 acidity scale". The Kiefer, Zhang, et al., 1997 BDE is for ortho.; B
Δ_rG°	1540. ± 13.	kJ/mol	IMRB	DePuy, Kass, et al., 1988	gas phase; Acid: p-methylpyridine. Between iPrOH, MeCN.; B

+ Pyridine, 4-methyl- = ( • )

By formula: Li⁺ + C₆H₇N = (Li⁺ • C₆H₇N)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	196. ± 14.	kJ/mol	CIDT	Rodgers, 2001	RCD

+ Pyridine, 4-methyl- = ( • )

By formula: Na⁺ + C₆H₇N = (Na⁺ • C₆H₇N)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	133. ± 4.	kJ/mol	CIDT	Rodgers, 2001	RCD

+ Pyridine, 4-methyl- = ( • )

By formula: K⁺ + C₆H₇N = (K⁺ • C₆H₇N)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	98.7 ± 4.2	kJ/mol	CIDT	Rodgers, 2001	RCD

Gas phase ion energetics data

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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
RDSH - Henry M. Rosenstock, Keith Draxl, Bruce W. Steiner, and John T. Herron

View reactions leading to C₆H₇N⁺ (ion structure unspecified)

Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	947.2	kJ/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	915.3	kJ/mol	N/A	Hunter and Lias, 1998	HL

Ionization energy determinations

IE (eV)	Method	Reference	Comment
9.46 ± 0.05	EI	Zaretskii, Oren, et al., 1976	LLK
9.5 ± 0.1	EI	Stefanovic and Grutzmacher, 1974	LLK
9.55 ± 0.05	EI	Distefano, Foffani, et al., 1971	LLK
9.55	EI	Distefano, Foffani, et al., 1971, 2	LLK
9.04 ± 0.03	PI	Watanabe, Nakayama, et al., 1962	RDSH
9.41	PE	Klasinc, Novak, et al., 1978	Vertical value; LLK
9.50 ± 0.05	PE	Heilbronner, Hornung, et al., 1972	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
C₅H₆⁺	12.86 ± 0.05	HCN	EI	Zaretskii, Oren, et al., 1976	LLK
C₆H₆N⁺	12.2 ± 0.1	H	EI	Palmer and Lossing, 1963	RDSH

De-protonation reactions

C₆H₆N^- + = Pyridine, 4-methyl-

By formula: C₆H₆N^- + H⁺ = C₆H₇N

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1547. ± 21.	kJ/mol	G+TS	Meot-ner and Kafafi, 1988	gas phase; anchored to 88MEO scale, not the "87 acidity scale". The Kiefer, Zhang, et al., 1997 BDE is for ortho.; B
Δ_rH°	1568. ± 13.	kJ/mol	G+TS	DePuy, Kass, et al., 1988	gas phase; Acid: p-methylpyridine. Between iPrOH, MeCN.; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1518. ± 21.	kJ/mol	IMRB	Meot-ner and Kafafi, 1988	gas phase; anchored to 88MEO scale, not the "87 acidity scale". The Kiefer, Zhang, et al., 1997 BDE is for ortho.; B
Δ_rG°	1540. ± 13.	kJ/mol	IMRB	DePuy, Kass, et al., 1988	gas phase; Acid: p-methylpyridine. Between iPrOH, MeCN.; B

References

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Good, 1972
Good, W.D., Enthalpies of combustion of nine organic nitrogen compounds related to petroleum, J. Chem. Eng. Data, 1972, 17, 28-31. [all data]

Cox, Challoner, et al., 1954
Cox, J.D.; Challoner, A.R.; Meetham, A.R., The heats of combustion of pyridine and certain of its derivatives, J. Chem. Soc., 1954, 265-271. [all data]

Constam and White, 1903
Constam, E.J.; White, J., Physico-chemical investigations in the pyridine series, Am. Chem. J., 1903, 29, 1-49. [all data]

Messerly, Todd, et al., 1988
Messerly, J.F.; Todd, S.S.; Finke, H.L.; Good, W.D.; Gammon, B.E., Condensed-phase heat-capacity studies and derived thermodynamic properties for six cyclic nitrogen compounds, J. Chem. Thermodynam., 1988, 20, 209-224. [all data]

Messerly, Todd, et al., 1987
Messerly, J.F.; Todd, S.S.; Finke, H.L.; Gammon, B.E., Thermodynamic properties of organic nitrogen compounds that occur in shale oil and heavy petroleum-topical report, NIPER Report, 1987, 83, 37p. [all data]

Steele, Chirico, et al., 1986
Steele, W.V.; Chirico, R.D.; Collier, W.B.; Hossenlopp, I.A.; Nguyen, A.; Strube, M.M., Thermochemical and thermophysical properties of organic nitrogen compounds found in fossil materials, NIPER Report, 1986, 188, 112p. [all data]

Meot-ner and Kafafi, 1988
Meot-ner, M.; Kafafi, S.A., Carbon Acidities of Aromatic Compounds, J. Am. Chem. Soc., 1988, 110, 19, 6297, https://doi.org/10.1021/ja00227a003 . [all data]

Kiefer, Zhang, et al., 1997
Kiefer, J.H.; Zhang, Q.; Kern, R.D.; Yao, J.; Jursic, B., Pyrolysis of Aromatic Azines: Pyrazine, Pyrimidine, and Pyridine, J. Phys. Chem. A, 1997, 101, 38, 7061, https://doi.org/10.1021/jp970211z . [all data]

DePuy, Kass, et al., 1988
DePuy, C.H.; Kass, S.R.; Bean, G.P., Formation and Reactions of Heteroaromatic Anions in the Gas Phase, J. Org. Chem., 1988, 53, 19, 4427, https://doi.org/10.1021/jo00254a001 . [all data]

Rodgers, 2001
Rodgers, M.T., Substituent Effects in the Binding of Alkali Metal Ions to Pyridines, Studied by Threshold Collision-Induced Dissociation and ab Initio Theory: The Methylpyridines, J. Phys. Chem. A, 2001, 105, 11, 2374, https://doi.org/10.1021/jp004055z . [all data]

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]

Zaretskii, Oren, et al., 1976
Zaretskii, Z.V.I.; Oren, D.; Kelner, L., Automatic method for the measurement of the electron impact ionization and appearance potentials, Appl. Spectrosc., 1976, 30, 366. [all data]

Stefanovic and Grutzmacher, 1974
Stefanovic, D.; Grutzmacher, H.F., The ionisation potential of some substituted pyridines, Org. Mass Spectrom., 1974, 9, 1052. [all data]

Distefano, Foffani, et al., 1971
Distefano, G.; Foffani, A.; Innorta, G.; Pignataro, S., Mass spectrometric study of transition metal complexes with ligands having nitrogen or sulphur as donor atom, Adv. Mass Spectrom., 1971, 5, 696. [all data]

Distefano, Foffani, et al., 1971, 2
Distefano, G.; Foffani, A.; Innorta, G.; Pignataro, S., Electron impact ionization potentials of some manganese, chromium and tungsten organometallic derivatives, Int. J. Mass Spectrom. Ion Phys., 1971, 7, 383. [all data]

Watanabe, Nakayama, et al., 1962
Watanabe, K.; Nakayama, T.; Mottl, J., Ionization potentials of some molecules, J. Quant. Spectry. Radiative Transfer, 1962, 2, 369. [all data]

Klasinc, Novak, et al., 1978
Klasinc, L.; Novak, I.; Scholz, M.; Kluge, G., Photoelektronenspektren substituierter Pyridine und Benzole und ihre Interpretation durch die CNDO/SWW-Methode, Croat. Chem. Acta, 1978, 51, 43. [all data]

Heilbronner, Hornung, et al., 1972
Heilbronner, E.; Hornung, V.; Pinkerton, F.H.; Thames, S.F., 31. Photoelectron spectra of azabenzenes and azanaphthalenes: III. The orbital sequence in methyl- and trimethylsilyl- substituted pyridines, Helv. Chim. Acta, 1972, 55, 289. [all data]

Palmer and Lossing, 1963
Palmer, T.F.; Lossing, F.P., Free radicals by mass spectrometry. XXX. Ionization potentials of anilino and 2-, 3-, and 4-pyridylmethyl radicals, J. Am. Chem. Soc., 1963, 85, 1733. [all data]

Notes

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Symbols used in this document:

AE	Appearance energy
C_p,liquid	Constant pressure heat capacity of liquid
S°_liquid	Entropy of liquid at standard conditions
Δ_cH°_liquid	Enthalpy of combustion of liquid at standard conditions
Δ_fH°_liquid	Enthalpy of formation of liquid at standard conditions
Δ_rG°	Free energy of reaction at standard conditions
Δ_rH°	Enthalpy of reaction at standard conditions

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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