Methyl isocyanide

Formula: C₂H₃N
Molecular weight: 41.0519
IUPAC Standard InChI: InChI=1S/C2H3N/c1-3-2/h1H3
IUPAC Standard InChIKey: ZRKSVHFXTRFQFL-UHFFFAOYSA-N
CAS Registry Number: 593-75-9
Chemical structure:
This structure is also available as a 2d Mol file
Other names: Methane, isocyano-; Isocyanomethane; Methyl isonitrile; CH3NC
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Condensed phase thermochemistry data

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Data compiled by: Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_liquid	132.7 ± 7.3	kJ/mol	Cm	Baghal-Vayjooee, Collister, et al., 1977	Reanalyzed by Pedley, Naylor, et al., 1986, Original value = 142.0 ± 1.5 kJ/mol; Heat of isomerization
Δ_fH°_liquid	112.	kJ/mol	Ccb	Lemoult, 1906
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_liquid	-1333.	kJ/mol	Ccb	Lemoult and Jungfleisch, 1909
Δ_cH°_liquid	-1333.	kJ/mol	Ccb	Lemoult, 1906

Reaction thermochemistry data

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Data compiled as indicated in comments:
B - John E. Bartmess
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein

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Individual Reactions

C₂H₂N^- + = Methyl isocyanide

By formula: C₂H₂N^- + H⁺ = C₂H₃N

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1592. ± 8.8	kJ/mol	G+TS	Matimba, Crabbendam, et al., 1992	gas phase; B
Δ_rH°	1567. ± 8.8	kJ/mol	G+TS	Filley, DePuy, et al., 1987	gas phase; Matimba, Crabbendam, et al., 1992 indicate that CN- loss interfered with equilibrium here.; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1561. ± 8.4	kJ/mol	IMRE	Matimba, Crabbendam, et al., 1992	gas phase; B
Δ_rG°	1536. ± 8.4	kJ/mol	IMRE	Filley, DePuy, et al., 1987	gas phase; Matimba, Crabbendam, et al., 1992 indicate that CN- loss interfered with equilibrium here.; B

Methyl isocyanide =

By formula: C₂H₃N = C₂H₃N

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-99.16 ± 0.59	kJ/mol	Cm	Baghal-Vayjooee, Collister, et al., 1977	gas phase; Heat of isomerization; ALS

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
MM - Michael M. Meot-Ner (Mautner)
LBLHLM - Sharon G. Lias, John E. Bartmess, Joel F. Liebman, John L. Holmes, Rhoda D. Levin, and W. Gary Mallard
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 C₂H₃N⁺ (ion structure unspecified)

Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	839.1	kJ/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	806.6	kJ/mol	N/A	Hunter and Lias, 1998	HL

Gas basicity at 298K

Gas basicity (review) (kJ/mol)	Reference	Comment
848.6 ± 5.3	Witt and Grutzmacher, 1997	T = 298K; Equilibrium constant measured directly. Data readjusted to 98 HUN/LIA; MM

Ionization energy determinations

IE (eV)	Method	Reference	Comment
11.53 ± 0.04	EI	Harland and McIntosh, 1985	LBLHLM
11.5 ± 0.25	EI	Chess, Lapp, et al., 1982	LBLHLM
11.24	PE	Bevan, Sandorfy, et al., 1981	LLK
11.24	PE	Lake and Thompson, 1971	LLK
11.83	EI	Heerma and deRidder, 1970	RDSH
11.27	PE	Bevan, Sandorfy, et al., 1981	Vertical value; LLK
11.32	PE	Asbrink, Von Niessen, et al., 1980	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
CH₃⁺	14.76	CN	EI	Heerma and deRidder, 1970	RDSH
C₂HN⁺	14.56 ± 0.08	?	EI	Harland and McIntosh, 1985	LBLHLM
C₂HN⁺	14.46	H₂	EI	Heerma and deRidder, 1970	RDSH
C₂H₂N⁺	13.21 ± 0.04	H	EI	Harland and McIntosh, 1985	LBLHLM
C₂H₂N⁺	13.21	H	EI	Heerma and deRidder, 1970	RDSH
C₂N⁺	18.33 ± 0.06	?	EI	Harland and McIntosh, 1985	LBLHLM
C₂N⁺	18.28	?	EI	Heerma and deRidder, 1970	RDSH

De-protonation reactions

C₂H₂N^- + = Methyl isocyanide

By formula: C₂H₂N^- + H⁺ = C₂H₃N

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1592. ± 8.8	kJ/mol	G+TS	Matimba, Crabbendam, et al., 1992	gas phase; B
Δ_rH°	1567. ± 8.8	kJ/mol	G+TS	Filley, DePuy, et al., 1987	gas phase; Matimba, Crabbendam, et al., 1992 indicate that CN- loss interfered with equilibrium here.; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1561. ± 8.4	kJ/mol	IMRE	Matimba, Crabbendam, et al., 1992	gas phase; B
Δ_rG°	1536. ± 8.4	kJ/mol	IMRE	Filley, DePuy, et al., 1987	gas phase; Matimba, Crabbendam, et al., 1992 indicate that CN- loss interfered with equilibrium here.; B

References

Go To: Top, Condensed phase thermochemistry data, Reaction thermochemistry data, Gas phase ion energetics data, Notes

Baghal-Vayjooee, Collister, et al., 1977
Baghal-Vayjooee, M.H.; Collister, J.L.; Pritchard, H.O., The enthalpy of isomerisation of methyl isocyanide, Can. J. Chem., 1977, 55, 2634-2636. [all data]

Pedley, Naylor, et al., 1986
Pedley, J.B.; Naylor, R.D.; Kirby, S.P., Thermochemical Data of Organic Compounds, Chapman and Hall, New York, 1986, 1-792. [all data]

Lemoult, 1906
Lemoult, P., Carbylamines et nitriles., Compt. Rend., 1906, 143, 902-904. [all data]

Lemoult and Jungfleisch, 1909
Lemoult, M.P.; Jungfleisch, M.E., Thermochimie. - Comparaisons entre les nitriles et les carbylamines, Compt. Rend., 1909, 148, 1602-1604. [all data]

Matimba, Crabbendam, et al., 1992
Matimba, H.E.K.; Crabbendam, A.M.; Ingemann, S.; Nibbering, N.M.M., Gas-phase Bimolecular Chemistry of the .-CHNC and .-CHCN Radical Anions, Int. J. Mass Spectrom. Ion Proc., 1992, 114, 1-2, 85, https://doi.org/10.1016/0168-1176(92)85024-T . [all data]

Filley, DePuy, et al., 1987
Filley, J.; DePuy, C.H.; Bierbaum, V.M., Gas-Phase Negative Ion Chemistry of Methyl Isocyanide, J. Am. Chem. Soc., 1987, 109, 20, 5992, https://doi.org/10.1021/ja00254a017 . [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]

Witt and Grutzmacher, 1997
Witt, M.; Grutzmacher, H.F., The gas phase basicity and proton affinity of propionamide: a comparison of methods, Int. J. Mass Spectrom. Ion. Processes, 1997, 164, 93. [all data]

Harland and McIntosh, 1985
Harland, P.W.; McIntosh, B.J., Enthalpies of formation for the isomeric ions H_xCCN⁺ and H_xCNC⁺ (x = 0-3) by monochromatic electron impact on C₂N₂, CH₃CN and CH₃NC., Int. J. Mass Spectrom. Ion Processes, 1985, 67, 29. [all data]

Chess, Lapp, et al., 1982
Chess, E.K.; Lapp, R.L.; Gross, M.L., The question of tautomerism of alkylnitrile and isonitrile radical cations, Org. Mass Spectrom., 1982, 17, 475. [all data]

Bevan, Sandorfy, et al., 1981
Bevan, J.W.; Sandorfy, C.; Pang, F.; Bogg, J.E., The photoelectron spectrum of methylisocyanide-borane, Spectrochim. Acta A:, 1981, 37, 601. [all data]

Lake and Thompson, 1971
Lake, R.F.; Thompson, H.W., The photoelectron spectra of methyl isocyanide and trideuteromethyl isocyanide, Spectrochim. Acta, 1971, 27A, 783. [all data]

Heerma and deRidder, 1970
Heerma, W.; deRidder, J.J., The electron-impact induced fragmentation of some alkyl isocyanides and alpha-branched alkyl cyanides, Org. Mass Spectrom., 1970, 3, 1439. [all data]

Asbrink, Von Niessen, et al., 1980
Asbrink, L.; Von Niessen, W.; Bieri, G., 30.4-nm He(II) photoelectron spectra of organic molecules, J. Electron Spectrosc. Relat. Phenom., 1980, 21, 93. [all data]

Notes

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Symbols used in this document:

AE	Appearance energy
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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