Benzyne

Formula: C₆H₄
Molecular weight: 76.0960
IUPAC Standard InChI: InChI=1S/C6H4/c1-2-4-6-5-3-1/h1-4H
IUPAC Standard InChIKey: KLYCPFXDDDMZNQ-UHFFFAOYSA-N
CAS Registry Number: 462-80-6
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.
Permanent link for this species. Use this link for bookmarking this species for future reference.
Information on this page:
Other data available:
- Gas phase ion energetics data
Data at other public NIST sites:
- Microwave spectra (on physics lab web site)
- Gas Phase Kinetics Database
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Gas 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°_gas	105. ± 2.4	kcal/mol	Ion	Riveros, Ingeman, et al., 1991	Bracketing technique
Δ_fH°_gas	106. ± 3.	kcal/mol	Ion	Wenthold, Paulino, et al., 1991	collision-induced dissociation
Δ_fH°_gas	118. ± 5.	kcal/mol	Ion	Pollack and Hehre, 1980

Reaction thermochemistry data

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Data compiled by: John E. Bartmess

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

+ = Benzyne

By formula: C₆H₃^- + H⁺ = C₆H₄

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	378.7 ± 3.1	kcal/mol	G+TS	Guo and Grabowski, 1991	gas phase; Acidity between MeOH and tBuOH, comparable to EtOH
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	371.0 ± 3.0	kcal/mol	IMRB	Guo and Grabowski, 1991	gas phase; Acidity between MeOH and tBuOH, comparable to EtOH
Δ_rG°	372.0 ± 5.0	kcal/mol	IMRB	Gronert and DePuy, 1989	gas phase

(CAS Reg. No. 72863-53-7 • 4294967295 Benzyne ) + Benzyne = CAS Reg. No. 72863-53-7

By formula: (CAS Reg. No. 72863-53-7 • 4294967295C₆H₄) + C₆H₄ = CAS Reg. No. 72863-53-7

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	19.5 ± 4.1	kcal/mol	N/A	Andrade and Riveros, 1996	gas phase
Δ_rH°	16.7 ± 3.7	kcal/mol	Ther	Wenthold and Squires, 1995	gas phase
Δ_rH°	15.7 ± 3.0	kcal/mol	CIDT	Wenthold, Paulino, et al., 1991, 2	gas phase; Between PhF, furan

(CAS Reg. No. 77748-26-6 • 4294967295 Benzyne ) + Benzyne = CAS Reg. No. 77748-26-6

By formula: (CAS Reg. No. 77748-26-6 • 4294967295C₆H₄) + C₆H₄ = CAS Reg. No. 77748-26-6

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	54.1 ± 4.4	kcal/mol	N/A	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.

Vibrational and/or electronic energy levels

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, References, Notes

Data compiled by: Marilyn E. Jacox

State: ?

Energy (cm^-1)	Med.	References


T_x = 50200	Ar	Munzel and Schweig, 1988
		Simon, Munzel, et al., 1990

State: ?

Energy (cm^-1)	Med.	References


T_x = 40600	Ar	Munzel and Schweig, 1988
		Simon, Munzel, et al., 1990

State: ?

Energy (cm^-1)	Med.	References


T_x = 28730	Ne	Radziszewski, Hess, et al., 1992

State: ?

Energy (cm^-1)	Med.	References


T_x = 26300	Ar	Munzel and Schweig, 1988

State: a

Energy (cm^-1)	Med.	References


T_o = 13140 ± 50	gas	Leopold, Stevens-Miller, et al., 1986
		Wenthold, Squires, et al., 1998

Vib. sym.	cm^-1	Med.	Method	References


a₁	1520 ± 40	gas	PE	Wenthold, Squires, et al., 1998
	1395 ± 30	gas	PE	Leopold, Stevens-Miller, et al., 1986 Wenthold, Squires, et al., 1998
	1275 ± 30	gas	PE	Wenthold, Squires, et al., 1998
	560 ± 20	gas	PE	Leopold, Stevens-Miller, et al., 1986 Wenthold, Squires, et al., 1998

State: X

Vib. sym.	No.	Approximate type of mode	cm^-1		Med.	Method	References


a₁	1	CH stretch	3094	w m	Ne	IR	Radziszewski, Hess, et al., 1992
	1	CH stretch	3088		N₂	IR	Dunkin and MacDonald, 1979
	2	CH stretch	3071	w	Ne	IR	Radziszewski, Hess, et al., 1992
	3	CC stretch	1860 ± 15		gas	PE	Leopold, Stevens-Miller, et al., 1986 Wenthold, Squires, et al., 1998
	3	CC stretch	1846	w	Ne	IR	Radziszewski, Hess, et al., 1992
	4	Mixed	1415	w	Ne	IR	Radziszewski, Hess, et al., 1992
	5	Mixed	1271	w	Ne	IR	Radziszewski, Hess, et al., 1992
	6	CH deform.	1055	w m	Ne	IR	Radziszewski, Hess, et al., 1992
	6	CH deform.	1053	m	Ar	IR	Chapman, Mattes, et al., 1973
	6	CH deform.	1056		N₂	IR	Dunkin and MacDonald, 1979 Nam and Leroi, 1987
	7	Ring stretch	1010 ± 40		gas	PE	Leopold, Stevens-Miller, et al., 1986 Wenthold, Squires, et al., 1998
	7	Ring stretch	1039	m	Ne	IR	Radziszewski, Hess, et al., 1992
	7	Ring stretch	1038	m	Ar	IR	Chapman, Mattes, et al., 1973
	7	Ring stretch	1039		N₂	IR	Dunkin and MacDonald, 1979 Nam and Leroi, 1987
	8	Ring stretch	982	w m	Ne	IR	Radziszewski, Hess, et al., 1992
	9	Ring deform.	600 ± 15		gas	PE	Leopold, Stevens-Miller, et al., 1986 Wenthold, Squires, et al., 1998
	9	Ring deform.	589	w	Ne	IR	Radziszewski, Hess, et al., 1992
b₁	14	CH wag	838	w	Ne	IR	Radziszewski, Hess, et al., 1992
	15	CH wag	737	s	Ne	IR	Radziszewski, Hess, et al., 1992
	15	CH wag	736	vs	Ar	IR	Chapman, Mattes, et al., 1973
	15	CH wag	743		N₂	IR	Dunkin and MacDonald, 1979 Nam and Leroi, 1987
	16	Ring torsion	388	w m	Ne	IR	Radziszewski, Hess, et al., 1992
b₂	17	CH stretch	3086	m	Ne	IR	Radziszewski, Hess, et al., 1992
	18	CH stretch	3049	w	Ne	IR	Radziszewski, Hess, et al., 1992
	19	Ring stretch	1451	m	Ne	IR	Radziszewski, Hess, et al., 1992
	19	Ring stretch	1451	m	Ar	IR	Chapman, Mattes, et al., 1973
	19	Ring stretch	1448		N₂	IR	Dunkin and MacDonald, 1979 Nam and Leroi, 1987
	20	Mixed	1394	w m	Ne	IR	Radziszewski, Hess, et al., 1992
	20	Mixed	1395		N₂	IR	Nam and Leroi, 1987
	20	Mixed	1355		N₂	IR	Nam and Leroi, 1987
	21	Mixed	1307	w	Ne	IR	Radziszewski, Hess, et al., 1992
	22	Mixed	1094	w	Ne	IR	Radziszewski, Hess, et al., 1992
	23	Ring deform.	849	m s	Ne	IR	Radziszewski, Hess, et al., 1992
	23	Ring deform.	849	s	Ar	IR	Chapman, Mattes, et al., 1973
	23	Ring deform.	847		N₂	IR	Dunkin and MacDonald, 1979 Nam and Leroi, 1987
	24	Ring deform.	472	vs	Ne	IR	Radziszewski, Hess, et al., 1992
	24	Ring deform.	469	vs	Ar	IR	Chapman, Mattes, et al., 1973
	24	Ring deform.	472		N₂	IR	Dunkin and MacDonald, 1979 Nam and Leroi, 1987

Additional references: Jacox, 1994, page 386; Jacox, 2003, page 364; Brown, Godfrey, et al., 1986; Robertson, Godfrey, et al., 2003; Kukolich, Tanjaroon, et al., 2003; Kukolich, McCarthy, et al., 2004

Notes

Weak

Medium

Strong

Very strong

Energy separation between the v = 0 levels of the excited and electronic ground states.

Energy separation between the band maximum of the excited electronic state and the v = 0 level of the ground state.

References

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Vibrational and/or electronic energy levels, Notes

Riveros, Ingeman, et al., 1991
Riveros, J.M.; Ingeman, S.; Nibbering, N.M.M., Formation of gas-phase solvated Br-and I- ion/molecule reactions of halobenzenes. Revised heat of formation of benzyne, J. Am. Chem. Soc., 1991, 113, 1053. [all data]

Wenthold, Paulino, et al., 1991
Wenthold, P.G.; Paulino, J.A.; Squires, R.R., The absolute heats of formation of o-,m-, and p-benzyne, J. Am. Chem. Soc., 1991, 113, 7414-7415. [all data]

Pollack and Hehre, 1980
Pollack, S.K.; Hehre, W.J., Determination of the heat of formation of ortho-benzyne by ion cyclotron resonance spectroscopy, Tetrahedron Lett., 1980, 21, 2483-2486. [all data]

Guo and Grabowski, 1991
Guo, Y.L.; Grabowski, J.J., Reactions of the Benzyne Radical Anion in the Gas Phase, the Acidity of the Phenyl Radical, and the Heat of Formation of ortho-Benzyne, J. Am. Chem. Soc., 1991, 113, 16, 5923, https://doi.org/10.1021/ja00016a001 . [all data]

Gronert and DePuy, 1989
Gronert, S.; DePuy, C.H., The Dehydrophenyl Anion and the Gas Phase Ion Chemistry of Benzyne, J. Am. Chem. Soc., 1989, 111, 26, 9253, https://doi.org/10.1021/ja00208a032 . [all data]

Andrade and Riveros, 1996
Andrade, P.B.M.; Riveros, J.M., Relative Gas-phase Acidities of Fluoro- and Chlorobenzene, J. Mass Spectrom., 1996, 31, 7, 767, https://doi.org/10.1002/(SICI)1096-9888(199607)31:7<767::AID-JMS345>3.0.CO;2-Q . [all data]

Wenthold and Squires, 1995
Wenthold, P.G.; Squires, R.R., Determination of the gas-phase acidities of halogen-substituted aromatic compounds using the silane-cleavage method, J. Mass Spectrom., 1995, 30, 1, 17, https://doi.org/10.1002/jms.1190300105 . [all data]

Wenthold, Paulino, et al., 1991, 2
Wenthold, P.G.; Paulino, J.A.; Squires, R.R., The Absolute Heats of Formation of ortho-Benzyne, meta-Benzyne, and para-Benzyne, J. Am. Chem. Soc., 1991, 113, 19, 7414, https://doi.org/10.1021/ja00019a044 . [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]

Munzel and Schweig, 1988
Munzel, N.; Schweig, A., UV/VIS absorption spectrum, geometry and electronic structure of transient o-benzyne, Chem. Phys. Lett., 1988, 147, 2-3, 192, https://doi.org/10.1016/0009-2614(88)85082-6 . [all data]

Simon, Munzel, et al., 1990
Simon, J.G.G.; Munzel, N.; Schweig, A., Matrix isolation photochemistry: photoequilibrium between transient o-benzyne, carbon monoxide and transient cyclopentadienylideneketene in an argon matrix, Chem. Phys. Lett., 1990, 170, 2-3, 187, https://doi.org/10.1016/0009-2614(90)87113-6 . [all data]

Radziszewski, Hess, et al., 1992
Radziszewski, J.G.; Hess, B.A., Jr.; Zahradnik, R., Infrared spectrum of o-benzyne: experiment and theory, J. Am. Chem. Soc., 1992, 114, 1, 52, https://doi.org/10.1021/ja00027a007 . [all data]

Leopold, Stevens-Miller, et al., 1986
Leopold, D.G.; Stevens-Miller, A.E.; Linebergr, W.C., Determination of the singlet-triplet splitting and electron affinity of o-benzyne by negative ion photoelectron spectroscopy, J. Am. Chem. Soc., 1986, 108, 7, 1379, https://doi.org/10.1021/ja00267a003 . [all data]

Wenthold, Squires, et al., 1998
Wenthold, P.G.; Squires, R.R.; Lineberger, W.C., Ultraviolet Photoelectron Spectroscopy of the, J. Am. Chem. Soc., 1998, 120, 21, 5279, https://doi.org/10.1021/ja9803355 . [all data]

Dunkin and MacDonald, 1979
Dunkin, I.R.; MacDonald, J.G., J. Chem. Soc., 1979, Chem. Commun. 772. [all data]

Chapman, Mattes, et al., 1973
Chapman, O.L.; Mattes, K.; McIntosh, C.L.; Pacansky, J.; Calder, G.V.; Orr, G., Photochemical transformations. LII. Benzyne, J. Am. Chem. Soc., 1973, 95, 18, 6134, https://doi.org/10.1021/ja00799a060 . [all data]

Nam and Leroi, 1987
Nam, H.-H.; Leroi, G.E., On the vibrational spectrum of matrix isolated o-benzyne, J. Mol. Struct., 1987, 157, 1-3, 301, https://doi.org/10.1016/0022-2860(87)87100-4 . [all data]

Jacox, 1994
Jacox, M.E., Vibrational and electronic energy levels of polyatomic transient molecules, American Chemical Society, Washington, DC, 1994, 464. [all data]

Jacox, 2003
Jacox, M.E., Vibrational and electronic energy levels of polyatomic transient molecules: supplement B, J. Phys. Chem. Ref. Data, 2003, 32, 1, 1-441, https://doi.org/10.1063/1.1497629 . [all data]

Brown, Godfrey, et al., 1986
Brown, R.D.; Godfrey, P.D.; Rodler, M., Microwave spectrum of benzyne, J. Am. Chem. Soc., 1986, 108, 6, 1296, https://doi.org/10.1021/ja00266a028 . [all data]

Robertson, Godfrey, et al., 2003
Robertson, E.G.; Godfrey, P.D.; McNaughton, D., The microwave spectrum of o-benzyne measured in a novel Stark modulated spectrometer for transient molecules, J. Mol. Spectrosc., 2003, 217, 1, 123, https://doi.org/10.1016/S0022-2852(02)00021-8 . [all data]

Kukolich, Tanjaroon, et al., 2003
Kukolich, S.G.; Tanjaroon, C.; McCarthy, M.C.; Thaddeus, P., Microwave spectrum of o-benzyne produced in a discharge nozzle, J. Chem. Phys., 2003, 119, 8, 4353, https://doi.org/10.1063/1.1593015 . [all data]

Kukolich, McCarthy, et al., 2004
Kukolich, S.G.; McCarthy, M.C.; Thaddeus, P., Molecular Structure of, J. Phys. Chem. A, 2004, 108, 14, 2645, https://doi.org/10.1021/jp031344p . [all data]

Notes

Go To: Top, Gas phase thermochemistry data, Reaction thermochemistry data, Vibrational and/or electronic energy levels, References

Symbols used in this document:

Δ_fH°_gas Enthalpy of formation of gas 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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Δ_fH°_gas	Enthalpy of formation of gas at standard conditions
Δ_rG°	Free energy of reaction at standard conditions
Δ_rH°	Enthalpy of reaction at standard conditions