Neopentane

Formula: C₅H₁₂
Molecular weight: 72.1488
IUPAC Standard InChI: InChI=1S/C5H12/c1-5(2,3)4/h1-4H3
IUPAC Standard InChIKey: CRSOQBOWXPBRES-UHFFFAOYSA-N
CAS Registry Number: 463-82-1
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: Propane, 2,2-dimethyl-; tert-Pentane; Tetramethylcarbon; Tetramethylmethane; 1,1,1-Trimethylethane; 2,2-Dimethylpropane; Neo-C5H12; UN 2044; Dimethylpropane
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Gas phase thermochemistry data

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

Data compiled as indicated in comments:
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
GT - Glushko Thermocenter, Russian Academy of Sciences, Moscow

Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	-40.14 ± 0.15	kcal/mol	Ccb	Good, 1970	ALS
Δ_fH°_gas	-40.27 ± 0.24	kcal/mol	Cm	Pilcher and Chadwick, 1967	ALS
Δ_fH°_gas	-39.67 ± 0.25	kcal/mol	Ccb	Prosen and Rossini, 1945	ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_gas	-839.88 ± 0.23	kcal/mol	Cm	Pilcher and Chadwick, 1967	Corresponding Δ_fHº_gas = -40.27 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS

Constant pressure heat capacity of gas

C_p,gas (cal/mol*K)	Temperature (K)	Reference	Comment
28.877 ± 0.060	298.15	Hossenlopp I.A., 1981	GT
30.970 ± 0.062	323.15
33.081 ± 0.067	348.15
35.148 ± 0.069	373.15
37.156 ± 0.074	398.15
39.082 ± 0.076	423.15
40.980 ± 0.081	448.15
42.770 ± 0.086	473.15
44.555 ± 0.088	498.15
46.219 ± 0.093	523.15

Constant pressure heat capacity of gas

C_p,gas (cal/mol*K)	Temperature (K)	Reference	Comment
19.25	200.	Scott D.W., 1974	Recommended values were obtained from the consistent correlation scheme for alkanes [ Scott D.W., 1974, 2, Scott D.W., 1974]. This approach gives a better agreement with experimental data than the statistical thermodynamics calculation [ Pitzer K.S., 1946].; GT
26.680	273.15
28.879 ± 0.060	298.15
29.051	300.
37.280	400.
44.689	500.
51.300	600.
57.101	700.
62.400	800.
67.000	900.
71.200	1000.
74.900	1100.
78.200	1200.
80.999	1300.
84.001	1400.
85.999	1500.

Condensed phase thermochemistry data

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

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	-45.49 ± 0.15	kcal/mol	Ccb	Good, 1970	ALS
Δ_fH°_liquid	-44.98 ± 0.25	kcal/mol	Ccb	Prosen and Rossini, 1945	ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_liquid	-834.71 ± 0.14	kcal/mol	Ccb	Good, 1970	Reanalyzed by Pedley, Naylor, et al., 1986, Original value = -834.66 ± 0.12 kcal/mol; Corresponding Δ_fHº_liquid = -45.44 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS
Δ_cH°_liquid	-835.18 ± 0.24	kcal/mol	Ccb	Prosen and Rossini, 1945	Corresponding Δ_fHº_liquid = -44.97 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS
Quantity	Value	Units	Method	Reference	Comment
S°_liquid	51.819	cal/mol*K	N/A	Enokida, Shinoda, et al., 1969	At normal boiling point.; DH
S°_liquid	52.29	cal/mol*K	N/A	Aston and Messerly, 1936	DH

Constant pressure heat capacity of liquid

C_p,liquid (cal/mol*K)	Temperature (K)	Reference	Comment
36.589	259.93	Enokida, Shinoda, et al., 1969	T = 4 to 260 K. Value is unsmoothed experimental datum.; DH
39.171	278.92	Aston and Messerly, 1936	T = 13 to 283 K. Value is unsmoothed experimental datum.; DH

Gas phase ion energetics data

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Data evaluated as indicated in comments:
L - 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

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	≤10.30 ± 0.08	eV	N/A	N/A	L

Ionization energy determinations

IE (eV)	Method	Reference	Comment
10.21 ± 0.04	PE	Jonas, Schweitzer, et al., 1973	LLK
10.3 ± 0.1	PE	Evans, Green, et al., 1972	LLK
10.40	PE	Dewar and Worley, 1969	RDSH
10.35	PI	Watanabe, Nakayama, et al., 1962	RDSH
10.90	PE	Kimura, Katsumata, et al., 1981	Vertical value; LLK
10.9 ± 0.1	PE	Bieri, Burger, et al., 1977	Vertical value; LLK
11.3	PE	Schmidt and Wilkins, 1972	Vertical value; LLK
11.3	PE	Murrell and Schmidt, 1972	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
CH₃⁺	29.5 ± 0.2	?	EI	Olmsted, Street, et al., 1964	RDSH
CH₃⁺	13.14	?	EI	Lampe and Field, 1959	RDSH
C₂H₃⁺	17.95	?	EI	Lampe and Field, 1959	RDSH
C₂H₅⁺	13.81	?	EI	Lampe and Field, 1959	RDSH
C₃H₃⁺	17.08	?	EI	Lampe and Field, 1959	RDSH
C₃H₅⁺	13.13	?	EI	Lampe and Field, 1959	RDSH
C₄H₈⁺	10.39 ± 0.02	CH₄	PI	Steiner, Giese, et al., 1961	RDSH
C₄H₉⁺	10.35	CH₃	PI	Chesnavich, Su, et al., 1978	LLK
C₄H₉⁺	10.56	CH₃	EI	Lossing and Semeluk, 1970	RDSH
C₄H₉⁺	10.57 ± 0.02	CH₃	PI	Steiner, Giese, et al., 1961	RDSH

De-protonation reactions

C₅H₁₁^- + = Neopentane

By formula: C₅H₁₁^- + H⁺ = C₅H₁₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	408.9 ± 2.0	kcal/mol	Bran	DePuy, Gronert, et al., 1989	gas phase; B
Δ_rH°	411. ± 10.	kcal/mol	CIDT	Graul and Squires, 1990	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	400.1 ± 2.1	kcal/mol	H-TS	DePuy, Gronert, et al., 1989	gas phase; B

References

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

Good, 1970
Good, W.D., The enthalpies of combustion and formation of the isomeric pentanes, J. Chem. Thermodyn., 1970, 2, 237-244. [all data]

Pilcher and Chadwick, 1967
Pilcher, G.; Chadwick, J.D.M., Measurements of heats of combustion by flame calorimetry. Part 4.-n-Pentane, isopentane, neopentane, Trans. Faraday Soc., 1967, 63, 2357-2361. [all data]

Prosen and Rossini, 1945
Prosen, E.J.; Rossini, F.D., Heats of combustion and formation of the paraffin hydrocarbons at 25° C, J. Res. NBS, 1945, 263-267. [all data]

Hossenlopp I.A., 1981
Hossenlopp I.A., Vapor heat capacities and enthalpies of vaporization of five alkane hydrocarbons, J. Chem. Thermodyn., 1981, 13, 415-421. [all data]

Scott D.W., 1974
Scott D.W., Chemical Thermodynamic Properties of Hydrocarbons and Related Substances. Properties of the Alkane Hydrocarbons, C1 through C10 in the Ideal Gas State from 0 to 1500 K. U.S. Bureau of Mines, Bulletin 666, 1974. [all data]

Scott D.W., 1974, 2
Scott D.W., Correlation of the chemical thermodynamic properties of alkane hydrocarbons, J. Chem. Phys., 1974, 60, 3144-3165. [all data]

Pitzer K.S., 1946
Pitzer K.S., The entropies and related properties of branched paraffin hydrocarbons, Chem. Rev., 1946, 39, 435-447. [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]

Enokida, Shinoda, et al., 1969
Enokida, H.; Shinoda, T.; Mashiko, Y., Thermodynamic properties of neopentane from 4K to the melting point and comparison with spectroscopic data, Bull. Chem. Soc. Japan, 1969, 42, 84-91. [all data]

Aston and Messerly, 1936
Aston, J.G.; Messerly, G.H., Heat capacities and entropies of organic compounds. II. Thermal and vapor pressure data for tetramethylmethane from 13.22°K to the boiling point. The entropy from its Raman spectrum, J. Am. Chem. Soc., 1936, 58, 2354-2361. [all data]

Jonas, Schweitzer, et al., 1973
Jonas, A.E.; Schweitzer, G.K.; Grimm, F.A.; Carlson, T.A., The photoelectron spectra of the tetrafluoro and tetramethyl compounds of the group IV elements, J. Electron Spectrosc. Relat. Phenom., 1973, 1, 29. [all data]

Evans, Green, et al., 1972
Evans, S.; Green, J.C.; Joachim, P.J.; Orchard, A.F.; Turner, D.W.; Maier, J.P., Electronic structures of the Group IV_B tetramethyls by helium-(I) photoelectron spectroscopy, J. Chem. Soc. Faraday Trans. 2, 1972, 68, 905. [all data]

Dewar and Worley, 1969
Dewar, M.J.S.; Worley, S.D., Photoelectron spectra of molecules. I. Ionization potentials of some organic molecules and their interpretation, J. Chem. Phys., 1969, 50, 654. [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]

Kimura, Katsumata, et al., 1981
Kimura, K.; Katsumata, S.; Achiba, Y.; Yamazaki, T.; Iwata, S., Ionization energies, Ab initio assignments, and valence electronic structure for 200 molecules in Handbook of HeI Photoelectron Spectra of Fundamental Organic Compounds, Japan Scientific Soc. Press, Tokyo, 1981. [all data]

Bieri, Burger, et al., 1977
Bieri, G.; Burger, F.; Heilbronner, E.; Maier, J.P., Valence ionization enrgies of hydrocarbons, Helv. Chim. Acta, 1977, 60, 2213. [all data]

Schmidt and Wilkins, 1972
Schmidt, W.; Wilkins, B.T., Das "Equivalent Orbital" (EO)-verfahren zur interpretation von photoelektronen(PE)-spektren: Neopentan, Angew. Chem., 1972, 84, 168. [all data]

Murrell and Schmidt, 1972
Murrell, J.N.; Schmidt, W., Photoelectron spectroscopic correlation of the molecular orbitals of methane, ethane, propane, isobutane and neopentane, J. Chem. Soc. Faraday Trans. 2, 1972, 68, 1709. [all data]

Olmsted, Street, et al., 1964
Olmsted, J., III; Street, K., Jr.; Newton, A.S., Excess-kinetic-energy ions in organic mass spectra, J. Chem. Phys., 1964, 40, 2114. [all data]

Lampe and Field, 1959
Lampe, F.W.; Field, F.H., The decomposition of neopentane under electron impact, J. Am. Chem. Soc., 1959, 81, 3238. [all data]

Steiner, Giese, et al., 1961
Steiner, B.; Giese, C.F.; Inghram, M.G., Photoionization of alkanes. Dissociation of excited molecular ions, J. Chem. Phys., 1961, 34, 189. [all data]

Chesnavich, Su, et al., 1978
Chesnavich, W.J.; Su, T.; Bowers, M.T., Reactions of vibrationally excited ions. A theoretical and experimental analysis of the reaction (C₄H₉⁺) + NH₃ Ü NH₄⁺ + C₄H₈, J. Am. Chem. Soc., 1978, 100, 4362. [all data]

Lossing and Semeluk, 1970
Lossing, F.P.; Semeluk, G.P., Free radicals by mass spectrometry. XLII.Ionization potentials and ionic heats of formation for C₁-C₄ alkyl radicals, Can. J. Chem., 1970, 48, 955. [all data]

DePuy, Gronert, et al., 1989
DePuy, C.H.; Gronert, S.; Barlow, S.E.; Bierbaum, V.M.; Damrauer, R., The Gas Phase Acidities of the Alkanes, J. Am. Chem. Soc., 1989, 111, 6, 1968, https://doi.org/10.1021/ja00188a003 . [all data]

Graul and Squires, 1990
Graul, S.T.; Squires, R.R., Gas-Phase Acidities Derived from Threshold Energies for Activated Reactions, J. Am. Chem. Soc., 1990, 112, 7, 2517, https://doi.org/10.1021/ja00163a007 . [all data]

Notes

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

Symbols used in this document:

AE	Appearance energy
C_p,gas	Constant pressure heat capacity of gas
C_p,liquid	Constant pressure heat capacity of liquid
IE (evaluated)	Recommended ionization energy
S°_liquid	Entropy of liquid at standard conditions
Δ_cH°_gas	Enthalpy of combustion of gas at standard conditions
Δ_cH°_liquid	Enthalpy of combustion of liquid at standard conditions
Δ_fH°_gas	Enthalpy of formation of gas 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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