Cyclopentane, 1,1-dimethyl-

Formula: C₇H₁₄
Molecular weight: 98.1861
IUPAC Standard InChI: InChI=1S/C7H14/c1-7(2)5-3-4-6-7/h3-6H2,1-2H3
IUPAC Standard InChIKey: QWHNJUXXYKPLQM-UHFFFAOYSA-N
CAS Registry Number: 1638-26-2
Chemical structure:
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Other names: Gem-Dimethylcyclopentane; 1,1-Dimethylcyclopentane
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Gas phase thermochemistry data

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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	-33.05 ± 0.28	kcal/mol	Cm	Johnson, Prosen, et al., 1949	ALS
Quantity	Value	Units	Method	Reference	Comment
S°_gas	85.870	cal/mol*K	N/A	Stull D.R., 1969	This value was obtained using low temperature data of [ Gross M.E., 1953].; GT

Constant pressure heat capacity of gas

C_p,gas (cal/mol*K)	Temperature (K)	Reference	Comment
10.60	50.	Thermodynamics Research Center, 1997	p=1 bar. Recommended values are in close agreement with those calculated by a method of increments [ Epstein M.B., 1949] at low temperatures. Discrepancies increase up to 2-4 J/mol*K at T=1500 K.; GT
13.63	100.
17.51	150.
21.67	200.
29.04	273.15
31.86	298.15
32.07	300.
43.55	400.
53.85	500.
62.45	600.
69.62	700.
75.62	800.
80.74	900.
85.11	1000.
88.84	1100.
92.07	1200.
94.84	1300.
97.25	1400.
99.33	1500.
103.4	1750.
106.4	2000.
108.6	2250.
110.3	2500.
111.5	2750.
112.5	3000.

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	-41.14 ± 0.27	kcal/mol	Cm	Johnson, Prosen, et al., 1949	ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_liquid	-1095.44 ± 0.25	kcal/mol	Cm	Johnson, Prosen, et al., 1949	Corresponding Δ_fHº_liquid = -41.12 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS
Quantity	Value	Units	Method	Reference	Comment
S°_liquid	63.339	cal/mol*K	N/A	Gross, Oliver, et al., 1953	DH

Constant pressure heat capacity of liquid

C_p,liquid (cal/mol*K)	Temperature (K)	Reference	Comment
44.780	299.81	Gross, Oliver, et al., 1953	T = 13 to 300 K. Unsmoothed experimental datum.; DH

Gas phase ion energetics data

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Data compiled by: Sharon G. Lias and Joel F. Liebman

Ionization energy determinations

IE (eV)	Method	Reference
9.46 ± 0.05	EI	Holmes and Lossing, 1991

References

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Johnson, Prosen, et al., 1949
Johnson, W.H.; Prosen, E.J.; Rossini, F.D., Heats of combustion and isomerization of the six C₇H₁₄ alkylcyclopentanes, J. Res. NBS, 1949, 42, 251-255. [all data]

Stull D.R., 1969
Stull D.R., Jr., The Chemical Thermodynamics of Organic Compounds. Wiley, New York, 1969. [all data]

Gross M.E., 1953
Gross M.E., Low-temperature thermal data for some C7H14 alkylcyclopentanes, J. Am. Chem. Soc., 1953, 75, 2801-2804. [all data]

Thermodynamics Research Center, 1997
Thermodynamics Research Center, Selected Values of Properties of Chemical Compounds., Thermodynamics Research Center, Texas A&M University, College Station, Texas, 1997. [all data]

Epstein M.B., 1949
Epstein M.B., Heats, equilibrium constants, and free energies of formation of the dimethylcyclopentanes, J. Res. Nat. Bur. Stand., 1949, 43, 245-250. [all data]

Gross, Oliver, et al., 1953
Gross, M.E.; Oliver, G.D.; Huffman, H.M., Low-temperature thermal data for some C₇H₁₄ alkylcyclopentanes, J. Am. Chem. Soc., 1953, 75, 2801-2804. [all data]

Holmes and Lossing, 1991
Holmes, J.L.; Lossing, F.P., Ionization energies of homologous organic compounds and correlation with molecular size, Org. Mass Spectrom., 1991, 26, 537. [all data]

Notes

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Symbols used in this document:

C_p,gas	Constant pressure heat capacity of gas
C_p,liquid	Constant pressure heat capacity of liquid
S°_gas	Entropy of gas at standard conditions
S°_liquid	Entropy of liquid 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

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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