Methane

Formula: CH₄
Molecular weight: 16.0425
IUPAC Standard InChI: InChI=1S/CH4/h1H4
IUPAC Standard InChIKey: VNWKTOKETHGBQD-UHFFFAOYSA-N
CAS Registry Number: 74-82-8
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: Marsh gas; Methyl hydride; CH4; Fire Damp; R 50; Biogas; R 50 (refrigerant)
Permanent link for this species. Use this link for bookmarking this species for future reference.
Information on this page:
Other data available:
- Reaction thermochemistry data: reactions 1 to 50, reactions 51 to 100, reactions 101 to 112
- IR Spectrum
- Mass spectrum (electron ionization)
- Vibrational and/or electronic energy levels
- Fluid Properties
Data at other public NIST sites:
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Gas phase thermochemistry data

Go To: Top, Phase change data, Henry's Law data, Gas phase ion energetics data, Ion clustering data, References, Notes

Data compiled as indicated in comments:
DRB - Donald R. Burgess, Jr.
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	-17.89	kcal/mol	Review	Chase, 1998	Data last reviewed in March, 1961
Δ_fH°_gas	-17.8 ± 0.07	kcal/mol	Review	Manion, 2002	adopted recommendation of Gurvich, Veyts, et al., 1991; DRB
Δ_fH°_gas	-17.8 ± 0.1	kcal/mol	Ccb	Pittam and Pilcher, 1972	ALS
Δ_fH°_gas	-17.889 ± 0.075	kcal/mol	Ccb	Prosen and Rossini, 1945	Hf derived from Heat of Hydrogenation; ALS
Δ_fH°_gas	-17.54 ± 0.26	kcal/mol	Ccb	Roth and Banse, 1932	Reanalyzed by Cox and Pilcher, 1970, Original value = -17.97 kcal/mol; ALS
Quantity	Value	Units	Method	Reference	Comment
Δ_cH°_gas	-212.88 ± 0.09	kcal/mol	Ccb	Pittam and Pilcher, 1972	Corresponding Δ_fHº_gas = -17.80 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS
Δ_cH°_gas	-212.798 ± 0.072	kcal/mol	Ccb	Prosen and Rossini, 1945	Hf derived from Heat of Hydrogenation; Corresponding Δ_fHº_gas = -17.883 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS
Δ_cH°_gas	-213.14 ± 0.26	kcal/mol	Ccb	Roth and Banse, 1932	Reanalyzed by Cox and Pilcher, 1970, Original value = -212.07 ± 0.25 kcal/mol; Corresponding Δ_fHº_gas = -17.54 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS
Δ_cH°_gas	-212.753 ± 0.072	kcal/mol	Cm	Rossini, 1931	Corresponding Δ_fHº_gas = -17.928 kcal/mol (simple calculation by NIST; no Washburn corrections); ALS
Quantity	Value	Units	Method	Reference	Comment
S°_gas	45.09 ± 0.10	cal/mol*K	N/A	Colwell J.H., 1963	The calorimetric value is significantly higher than the statistically calculated entropy, 186.26 J/molK, which remains the best value for use in thermodynamic calculations [ Vogt G.J., 1976, Friend D.G., 1989, Gurvich, Veyts, et al., 1989]. Earlier the value of 185.3 J/molK was calculated from experimental data [ Giauque W.F., 1931]. The value of S(298.15 K)=185.94 J/mol*K was obtained by high accuracy ab initio calculation [ East A.L.L., 1997].; GT
Quantity	Value	Units	Method	Reference	Comment
S°_{gas,1 bar}	44.515	cal/mol*K	Review	Chase, 1998	Data last reviewed in March, 1961

Constant pressure heat capacity of gas

C_p,gas (cal/mol*K)	Temperature (K)	Reference	Comment
8.346 ± 0.060	279.	Halford J.O., 1957	GT

Constant pressure heat capacity of gas

C_p,gas (cal/mol*K)	Temperature (K)	Reference	Comment
7.954	100.	Gurvich, Veyts, et al., 1989	p=1 bar. Because of more precise method of calculation, the recommended values are more accurate, especially at high temperatures, than those obtained by [ McDowell R.S., 1963] and often regarded as reference data [ Friend D.G., 1989].; GT
8.009	200.
8.530	298.15
8.547	300.
9.711	400.
11.14	500.
12.61	600.
14.01	700.
15.32	800.
16.52	900.
17.63	1000.
18.62	1100.
19.52	1200.
20.33	1300.
21.06	1400.
21.72	1500.
22.31	1600.
22.84	1700.
23.33	1800.
23.78	1900.
24.197	2000.
24.577	2100.
24.931	2200.
25.263	2300.
25.574	2400.
25.868	2500.
26.145	2600.
26.410	2700.
26.663	2800.
26.905	2900.
27.139	3000.

Gas Phase Heat Capacity (Shomate Equation)

C_p° = A + B*t + C*t² + D*t³ + E/t²
H° − H°_298.15= A*t + B*t²/2 + C*t³/3 + D*t⁴/4 − E/t + F − H
S° = A*ln(t) + B*t + C*t²/2 + D*t³/3 − E/(2*t²) + G
C_p = heat capacity (cal/mol*K)
H° = standard enthalpy (kcal/mol)
S° = standard entropy (cal/mol*K)
t = temperature (K) / 1000.

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View table.

Temperature (K)	298. to 1300.	1300. to 6000.
A	-0.168028	20.50960
B	25.92670	2.692321
C	-10.16290	-0.505293
D	1.401240	0.033028
E	0.162181	-6.315060
F	-18.36610	-36.69520
G	37.93411	53.63631
H	-17.89510	-17.89510
Reference	Chase, 1998	Chase, 1998
Comment	Data last reviewed in March, 1961	Data last reviewed in March, 1961

Phase change data

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Data compiled as indicated in comments:
TRC - Thermodynamics Research Center, NIST Boulder Laboratories, Chris Muzny director
DH - Eugene S. Domalski and Elizabeth D. Hearing
AC - William E. Acree, Jr., James S. Chickos

Quantity	Value	Units	Method	Reference	Comment
T_boil	111. ± 2.	K	AVG	N/A	Average of 13 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
T_fus	85.7	K	N/A	Streng, 1971	Uncertainty assigned by TRC = 0.2 K; TRC
T_fus	90.6	K	N/A	Van't Zelfde, Omar, et al., 1968	Uncertainty assigned by TRC = 0.3 K; TRC
T_fus	91.2	K	N/A	Timmermans, 1935	Uncertainty assigned by TRC = 2. K; TRC
T_fus	90.6	K	N/A	Clusius, 1929	Uncertainty assigned by TRC = 0.2 K; TRC
T_fus	90.5	K	N/A	Eucken and Karwat, 1924	Uncertainty assigned by TRC = 0.2 K; TRC
Quantity	Value	Units	Method	Reference	Comment
T_triple	90.67 ± 0.03	K	AVG	N/A	Average of 25 out of 32 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
P_triple	0.1154 ± 0.0006	atm	AVG	N/A	Average of 20 out of 23 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
T_c	190.6 ± 0.3	K	AVG	N/A	Average of 19 out of 23 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
P_c	45.5 ± 0.3	atm	AVG	N/A	Average of 16 out of 21 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
V_c	0.09860	l/mol	N/A	Ambrose and Tsonopoulos, 1995
V_c	0.09852	l/mol	N/A	Younglove and Ely, 1987	TRC
V_c	0.100	l/mol	N/A	Terry, Lynch, et al., 1969	Uncertainty assigned by TRC = 0.001 l/mol; TRC
Quantity	Value	Units	Method	Reference	Comment
ρ_c	10.1 ± 0.2	mol/l	AVG	N/A	Average of 16 out of 17 values; Individual data points

Enthalpy of vaporization

Δ_vapH (kcal/mol)	Temperature (K)	Method	Reference	Comment
2.036	99.54	N/A	Vogt and Pitzer, 1976	P = 2.81 kPa Data from Frank and Clusius, 1937 and 39FRA/CLU.; DH
2.1	101.	N/A	Stock, Henning, et al., 2006	Based on data from 92. to 110. K. See also Boublik, Fried, et al., 1984.; AC
2.1	105.	A	Stephenson and Malanowski, 1987	Based on data from 90. to 120. K.; AC
2.0	134.	A	Stephenson and Malanowski, 1987	Based on data from 115. to 149. K.; AC
2.1	174.	A	Stephenson and Malanowski, 1987	Based on data from 148. to 189. K.; AC
1.95	111.7	N/A	Majer and Svoboda, 1985
2.1	112.	N/A	Ott, Goates, et al., 1972	Based on data from 91. to 127. K. See also Boublik, Fried, et al., 1984.; AC
2.0	175.	N/A	Ott, Goates, et al., 1972	Based on data from 91. to 190. K.; AC
1.9	137.	N/A	Reid, 1972	AC
2.1	175.	N/A	Ambrose, Counsell, et al., 1970	Based on data from 100. to 190. K.; AC
2.0	112.	C	Hestermans and White, 1961	AC
1.8	130.	C	Hestermans and White, 1961	AC
1.4	160.	C	Hestermans and White, 1961	AC
0.96	180.	C	Hestermans and White, 1961	AC
2.0	149.	N/A	Hestermans and White, 1961	Based on data from 109. to 189. K.; AC
2.0 ± 0.02	99.	N/A	Frank and Clusius, 1939	AC

Enthalpy of vaporization

Δ_vapH = A exp(-αT_r) (1 − T_r)^β
Δ_vapH = Enthalpy of vaporization (at saturation pressure) (kcal/mol)
T_r = reduced temperature (T / T_c)

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Temperature (K)	112. to 180.
A (kcal/mol)	2.416
α	-0.22
β	0.388
T_c (K)	190.6
Reference	Majer and Svoboda, 1985

Entropy of vaporization

Δ_vapS (cal/mol*K)	Temperature (K)	Reference	Comment
20.45	99.54	Vogt and Pitzer, 1976	P; DH

Antoine Equation Parameters

log₁₀(P) = A − (B / (T + C))
P = vapor pressure (atm)
T = temperature (K)

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Temperature (K)	A	B	C	Reference	Comment
90.99 to 189.99	3.9838	443.028	-0.49	Prydz and Goodwin, 1972	Coefficents calculated by NIST from author's data.
96.89 to 110.19	1.99682	125.819	-48.823	Regnier, 1972	Coefficents calculated by NIST from author's data.
93.04 to 107.84	3.79664	403.106	-5.479	Cutler and Morrison, 1965	Coefficents calculated by NIST from author's data.
110.00 to 190.5	4.21490	516.689	11.223	Hestermans and White, 1961	Coefficents calculated by NIST from author's data.

Enthalpy of sublimation

Δ_subH (kcal/mol)	Temperature (K)	Method	Reference	Comment
2.3	72.	N/A	Stephenson and Malanowski, 1987	Based on data from 53. to 91. K.; AC
2.2	72.	N/A	Bondi, 1963	Based on data from 54. to 90. K. See also Armstrong, Brickwedde, et al., 1955.; AC
2.39	84.	N/A	Jones, 1960	Based on data from 79. to 89. K.; AC
2.3	63.	A,MS	Tickner and Lossing, 1951	Based on data from 48. to 78. K.; AC
2.30	77.	A	Stull, 1947	Based on data from 67. to 88. K.; AC

Enthalpy of phase transition

ΔH_trs (kcal/mol)	Temperature (K)	Initial Phase	Final Phase	Reference	Comment
0.02236	20.53	crystaline, II	crystaline, I	Vogt and Pitzer, 1976	Lambda transition.; DH
0.2245	90.67	crystaline, I	liquid	Vogt and Pitzer, 1976	DH

Entropy of phase transition

ΔS_trs (cal/mol*K)	Temperature (K)	Initial Phase	Final Phase	Reference	Comment
1.089	20.53	crystaline, II	crystaline, I	Vogt and Pitzer, 1976	Lambda; DH
2.476	90.67	crystaline, I	liquid	Vogt and Pitzer, 1976	DH

In addition to the Thermodynamics Research Center (TRC) data available from this site, much more physical and chemical property data is available from the following TRC products:

Henry's Law data

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Data compiled by: Rolf Sander

Henry's Law constant (water solution)

k_H(T) = k°_H exp(d(ln(k_H))/d(1/T) ((1/T) - 1/(298.15 K)))
k°_H = Henry's law constant for solubility in water at 298.15 K (mol/(kg*bar))
d(ln(k_H))/d(1/T) = Temperature dependence constant (K)

k°_H (mol/(kg*bar))	d(ln(k_H))/d(1/T) (K)	Method	Reference	Comment
0.0014	1600.	L	N/A	The parameterization given by missing citation (parameters A, B, C) doesn't fit the data in the same paper for this substance. Therefore the parameteriztaion of the solubility data (X₁) was recalculated.
0.0013	1900.	Q	N/A	Only the tabulated data between T = 273. K and T = 303. K from missing citation was used to derive k_H and -Δ k_H/R. Above T = 303. K the tabulated data could not be parameterized by equation (reference missing) very well. The partial pressure of water vapor (needed to convert some Henry's law constants) was calculated using the formula given by missing citation. The quantities A and α from missing citation were assumed to be identical.
0.0015		Q	N/A	missing citation give several references for the Henry's law constants but don't assign them to specific species.
0.0013		L	N/A
0.0013	1800.	X	N/A
0.0014	1700.	L	N/A
0.0015		V	N/A
0.00097		C	N/A
0.0014		R	N/A
0.0092		V	N/A

Gas phase ion energetics data

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Data evaluated as indicated in comments:
HL - Edward P. Hunter and Sharon G. Lias
L - Sharon G. Lias

Data compiled as indicated in comments:
B - John E. Bartmess
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 CH₄⁺ (ion structure unspecified)

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	12.61 ± 0.01	eV	N/A	N/A	L
Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	129.9	kcal/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	124.4	kcal/mol	N/A	Hunter and Lias, 1998	HL

Ionization energy determinations

IE (eV)	Method	Reference	Comment
12.61 ± 0.01	PI	Berkowitz, Greene, et al., 1987	LBLHLM
12.6 ± 0.4	EI	Chatham, Hils, et al., 1984	LBLHLM
12.63 ± 0.02	EI	Plessis, Marmet, et al., 1983	LBLHLM
13.6	PE	Kimura, Katsumata, et al., 1981	LLK
12.75 ± 0.02	PE	Bieri, Burger, et al., 1977	LLK
12.82 ± 0.02	EI	Selim and El-Kholy, 1975	LLK
12.6	PE	Debies and Rabalais, 1975	LLK
12.6	PI	Rabalais, Debies, et al., 1974	LLK
12.8	EI	Morrison and Traeger, 1973	LLK
12.64	PE	Potts and Price, 1972	LLK
12.94 ± 0.04	EI	Finney and Harrison, 1972	LLK
12.51	PE	Bergmark, Rabalais, et al., 1972	LLK
~12.51	PE	Rabalais, Bergmark, et al., 1971	LLK
≤12.615 ± 0.010	PI	Chupka and Berkowitz, 1971	LLK
12.78	PE	Pullen, Carlson, et al., 1970	RDSH
12.75	PE	Brundle, Robin, et al., 1970	RDSH
≤12.70	EI	Lossing and Semeluk, 1969	RDSH
12.99 ± 0.05	EI	Williams and Hamill, 1968	RDSH
12.75 ± 0.05	TE	Villarejo, Stockbauer, et al., 1968	RDSH
12.9	CI	Cermak, 1968	RDSH
12.70	PE	Baker, Baker, et al., 1968	RDSH
12.55 ± 0.05	PI	Brehm, 1966	RDSH
12.704 ± 0.008	PI	Nicholson, 1965	RDSH
12.71 ± 0.02	PI	Dibeler, Krauss, et al., 1965	RDSH
13.00 ± 0.02	EI	Melton and Hamill, 1964	RDSH
13.6	PE	Bieri and Asbrink, 1980	Vertical value; LLK
13.6 ± 0.1	PE	Bieri, Burger, et al., 1977	Vertical value; LLK
13.60	EI	Harshbarger, Robin, et al., 1973	Vertical value; LLK

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
C⁺	25. ± 2.	?	EI	Chatham, Hils, et al., 1984	LBLHLM
C⁺	19.56 ± 0.20	2H₂	EI	Plessis, Marmet, et al., 1983	LBLHLM
C⁺	≤25.2	?	EI	Morrison and Traeger, 1973	LLK
CH⁺	22.2 ± 0.4	?	EI	Chatham, Hils, et al., 1984	LBLHLM
CH⁺	19.11 ± 0.20	H^-+H₂	EI	Plessis, Marmet, et al., 1983	LBLHLM
CH⁺	19.87 ± 0.20	H+H₂	EI	Plessis, Marmet, et al., 1983	LBLHLM
CH⁺	22.4	H₂+H?	EI	Morrison and Traeger, 1973	LLK
CH₂⁺	15.1 ± 0.4	H₂	EI	Chatham, Hils, et al., 1984	LBLHLM
CH₂⁺	15.06 ± 0.02	H₂	EI	Plessis, Marmet, et al., 1983	LBLHLM
CH₂⁺	15.16 ± 0.02	H₂	PI	McCulloh and Dibeler, 1976	T = 0K; LLK
CH₂⁺	15.3	H₂	EI	Morrison and Traeger, 1973	LLK
CH₂⁺	15.19 ± 0.02	H₂	PI	Chupka, 1968	RDSH
CH₂⁺	15.16 ± 0.04	H₂	PI	Dibeler, Krauss, et al., 1965	RDSH
CH₃⁺	14.3 ± 0.4	H	EI	Chatham, Hils, et al., 1984	LBLHLM
CH₃⁺	13.25 ± 0.08	H^-	EI	Plessis, Marmet, et al., 1983	LBLHLM
CH₃⁺	14.01 ± 0.08	H	EI	Plessis, Marmet, et al., 1983	LBLHLM
CH₃⁺	14.30	H	PIPECO	Stockbauer, 1977	LLK
CH₃⁺	14.324 ± 0.003	H	PI	McCulloh and Dibeler, 1976	T = 0K; LLK
CH₃⁺	14.4	H	EI	Morrison and Traeger, 1973	LLK
CH₃⁺	14.30	H	EI	Lossing and Semeluk, 1970	RDSH
CH₃⁺	14.24 ± 0.05	H	EI	Williams and Hamill, 1968	RDSH
CH₃⁺	13.50 ± 0.05	H^-	PI	Chupka, 1968	RDSH
CH₃⁺	14.320 ± 0.004	H	PI	Chupka, 1968	RDSH
CH₃⁺	14.23 ± 0.05	H	PI	Brehm, 1966	RDSH
CH₃⁺	14.25 ± 0.02	H	PI	Dibeler, Krauss, et al., 1965	RDSH
H⁺	21.3 ± 0.3	CH₃	EI	Locht, Olivier, et al., 1979	LLK
H⁺	24.0 ± 0.5	CH₃	EI	Appell and Kubach, 1971	LLK

De-protonation reactions

CH₃^- + = Methane

By formula: CH₃^- + H⁺ = CH₄

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	416.74 ± 0.70	kcal/mol	D-EA	Ellison, Engelking, et al., 1978	gas phase; B
Δ_rH°	418.0 ± 3.5	kcal/mol	CIDT	Graul and Squires, 1990	gas phase; B
Δ_rH°	>404.18 ± 0.10	kcal/mol	G+TS	Bohme, Lee-Ruff, et al., 1972	gas phase; B
Δ_rH°	414.80	kcal/mol	N/A	Check, Faust, et al., 2001	gas phase; FeBr3; ; ΔS(EA)=9.3; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	408.66 ± 0.80	kcal/mol	H-TS	Ellison, Engelking, et al., 1978	gas phase; B
Δ_rG°	409.9 ± 3.6	kcal/mol	H-TS	Graul and Squires, 1990	gas phase; B
Δ_rG°	>396.10	kcal/mol	IMRB	Bohme, Lee-Ruff, et al., 1972	gas phase; B
Δ_rG°	407.30	kcal/mol	N/A	Check, Faust, et al., 2001	gas phase; FeBr3; ; ΔS(EA)=9.3; B

Ion clustering data

Go To: Top, Gas phase thermochemistry data, Phase change data, Henry's Law data, Gas phase ion energetics data, References, Notes

Data compiled as indicated in comments:
B - John E. Bartmess
M - Michael M. Meot-Ner (Mautner) and Sharon G. Lias
RCD - Robert C. Dunbar

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. Searches may be limited to ion clustering reactions. A general reaction search form is also available.

Clustering reactions

+ Methane = CH₄Br^-

By formula: Br^- + CH₄ = CH₄Br^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.10	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-2.27	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

+ Methane = ( • Methane )

By formula: CF₃⁺ + CH₄ = (CF₃⁺ • CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	4.6	kcal/mol	HPMS	Bennet and Field, 1972	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.8	cal/mol*K	HPMS	Bennet and Field, 1972	gas phase; M

CH₄Cl^- + 2 Methane = C₂H₈Cl^-

By formula: CH₄Cl^- + 2CH₄ = C₂H₈Cl^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.50	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-3.06	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

CH₄F^- + 2 Methane = C₂H₈F^-

By formula: CH₄F^- + 2CH₄ = C₂H₈F^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	5.90	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-0.36	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

CH₅⁺ + Methane = (CH₅⁺ • Methane )

By formula: CH₅⁺ + CH₄ = (CH₅⁺ • CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	6.9 ± 0.3	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Δ_rH°	7.4	kcal/mol	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
Δ_rH°	4.1	kcal/mol	HPMS	Field and Beggs, 1971	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.1	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Δ_rS°	20.8	cal/mol*K	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
Δ_rS°	12.4	cal/mol*K	HPMS	Field and Beggs, 1971	gas phase; Entropy change is questionable; M

(CH₅⁺ • Methane ) + Methane = (CH₅⁺ • 2 Methane )

By formula: (CH₅⁺ • CH₄) + CH₄ = (CH₅⁺ • 2CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	5.3 ± 0.3	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Δ_rH°	5.9	kcal/mol	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
Δ_rH°	1.5	kcal/mol	HPMS	Field and Beggs, 1971	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	24.9	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Δ_rS°	24.4	cal/mol*K	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
Δ_rS°	7.2	cal/mol*K	HPMS	Field and Beggs, 1971	gas phase; Entropy change is questionable; M

(CH₅⁺ • 2 Methane ) + Methane = (CH₅⁺ • 3 Methane )

By formula: (CH₅⁺ • 2CH₄) + CH₄ = (CH₅⁺ • 3CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.1 ± 0.2	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Δ_rH°	4.1	kcal/mol	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.4	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Δ_rS°	26.1	cal/mol*K	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M

(CH₅⁺ • 3 Methane ) + Methane = (CH₅⁺ • 4 Methane )

By formula: (CH₅⁺ • 3CH₄) + CH₄ = (CH₅⁺ • 4CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.0 ± 0.2	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Δ_rH°	3.9	kcal/mol	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	23.7	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Δ_rS°	26.6	cal/mol*K	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M

(CH₅⁺ • 4 Methane ) + Methane = (CH₅⁺ • 5 Methane )

By formula: (CH₅⁺ • 4CH₄) + CH₄ = (CH₅⁺ • 5CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.8 ± 0.2	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	24.8	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(CH₅⁺ • 5 Methane ) + Methane = (CH₅⁺ • 6 Methane )

By formula: (CH₅⁺ • 5CH₄) + CH₄ = (CH₅⁺ • 6CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.7 ± 0.2	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	25.3	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(CH₅⁺ • 6 Methane ) + Methane = (CH₅⁺ • 7 Methane )

By formula: (CH₅⁺ • 6CH₄) + CH₄ = (CH₅⁺ • 7CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.7 ± 0.2	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	26.5	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(CH₅⁺ • 7 Methane ) + Methane = (CH₅⁺ • 8 Methane )

By formula: (CH₅⁺ • 7CH₄) + CH₄ = (CH₅⁺ • 8CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.0 ± 0.2	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.6	cal/mol*K	PHPMS	Hiraoka and Mori, 1989	gas phase; M

(CH₅⁺ • 8 Methane ) + Methane = (CH₅⁺ • 9 Methane )

By formula: (CH₅⁺ • 8CH₄) + CH₄ = (CH₅⁺ • 9CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.54	kcal/mol	PHPMS	Hiraoka and Mori, 1989	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.	cal/mol*K	N/A	Hiraoka and Mori, 1989	gas phase; Entropy change calculated or estimated; M

C₂H₅⁺ + Methane = (C₂H₅⁺ • Methane )

By formula: C₂H₅⁺ + CH₄ = (C₂H₅⁺ • CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	5.50	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Δ_rH°	6.6	kcal/mol	PHPMS	Hiroka and Kebarle, 1975	gas phase; M
Δ_rH°	2.4	kcal/mol	HPMS	Field and Beggs, 1971	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.2	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Δ_rS°	23.4	cal/mol*K	PHPMS	Hiroka and Kebarle, 1975	gas phase; M
Δ_rS°	8.6	cal/mol*K	HPMS	Field and Beggs, 1971	gas phase; Entropy change is questionable; M

(C₂H₅⁺ • Methane ) + Methane = (C₂H₅⁺ • 2 Methane )

By formula: (C₂H₅⁺ • CH₄) + CH₄ = (C₂H₅⁺ • 2CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.37	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	16.1	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺ • 2 Methane ) + Methane = (C₂H₅⁺ • 3 Methane )

By formula: (C₂H₅⁺ • 2CH₄) + CH₄ = (C₂H₅⁺ • 3CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.28	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	17.9	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺ • 3 Methane ) + Methane = (C₂H₅⁺ • 4 Methane )

By formula: (C₂H₅⁺ • 3CH₄) + CH₄ = (C₂H₅⁺ • 4CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.26	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.4	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺ • 4 Methane ) + Methane = (C₂H₅⁺ • 5 Methane )

By formula: (C₂H₅⁺ • 4CH₄) + CH₄ = (C₂H₅⁺ • 5CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.22	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.9	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺ • 5 Methane ) + Methane = (C₂H₅⁺ • 6 Methane )

By formula: (C₂H₅⁺ • 5CH₄) + CH₄ = (C₂H₅⁺ • 6CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.21	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.4	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺ • 6 Methane ) + Methane = (C₂H₅⁺ • 7 Methane )

By formula: (C₂H₅⁺ • 6CH₄) + CH₄ = (C₂H₅⁺ • 7CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.13	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.7	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺ • 7 Methane ) + Methane = (C₂H₅⁺ • 8 Methane )

By formula: (C₂H₅⁺ • 7CH₄) + CH₄ = (C₂H₅⁺ • 8CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.10	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.0	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺ • 8 Methane ) + Methane = (C₂H₅⁺ • 9 Methane )

By formula: (C₂H₅⁺ • 8CH₄) + CH₄ = (C₂H₅⁺ • 9CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.08	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.8	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₂H₅⁺ • 9 Methane ) + Methane = (C₂H₅⁺ • 10 Methane )

By formula: (C₂H₅⁺ • 9CH₄) + CH₄ = (C₂H₅⁺ • 10CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.91	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.	cal/mol*K	N/A	Hiraoka, Mori, et al., 1993	gas phase; Entropy change calculated or estimated; M

C₂H₈F^- + 3 Methane = C₃H₁₂F^-

By formula: C₂H₈F^- + 3CH₄ = C₃H₁₂F^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	5.50	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-1.36	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

C₃H₇⁺ + Methane = (C₃H₇⁺ • Methane )

By formula: C₃H₇⁺ + CH₄ = (C₃H₇⁺ • CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.59	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Δ_rH°	3.4	kcal/mol	PHPMS	Hiraoka and Kebarle, 1976	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	17.4	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Δ_rS°	20.	cal/mol*K	PHPMS	Hiraoka and Kebarle, 1976	gas phase; M

(C₃H₇⁺ • Methane ) + Methane = (C₃H₇⁺ • 2 Methane )

By formula: (C₃H₇⁺ • CH₄) + CH₄ = (C₃H₇⁺ • 2CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.45	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.0	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₃H₇⁺ • 2 Methane ) + Methane = (C₃H₇⁺ • 3 Methane )

By formula: (C₃H₇⁺ • 2CH₄) + CH₄ = (C₃H₇⁺ • 3CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.26	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.4	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₃H₇⁺ • 3 Methane ) + Methane = (C₃H₇⁺ • 4 Methane )

By formula: (C₃H₇⁺ • 3CH₄) + CH₄ = (C₃H₇⁺ • 4CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.20	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.0	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₃H₇⁺ • 4 Methane ) + Methane = (C₃H₇⁺ • 5 Methane )

By formula: (C₃H₇⁺ • 4CH₄) + CH₄ = (C₃H₇⁺ • 5CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.20	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.9	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₃H₇⁺ • 5 Methane ) + Methane = (C₃H₇⁺ • 6 Methane )

By formula: (C₃H₇⁺ • 5CH₄) + CH₄ = (C₃H₇⁺ • 6CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.19	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.0	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₃H₇⁺ • 6 Methane ) + Methane = (C₃H₇⁺ • 7 Methane )

By formula: (C₃H₇⁺ • 6CH₄) + CH₄ = (C₃H₇⁺ • 7CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.16	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.8	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₃H₇⁺ • 7 Methane ) + Methane = (C₃H₇⁺ • 8 Methane )

By formula: (C₃H₇⁺ • 7CH₄) + CH₄ = (C₃H₇⁺ • 8CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.98	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.	cal/mol*K	N/A	Hiraoka, Mori, et al., 1993	gas phase; Entropy change calculated or estimated; M

C₃H₁₂F^- + 4 Methane = C₄H₁₆F^-

By formula: C₃H₁₂F^- + 4CH₄ = C₄H₁₆F^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	5.00	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-2.16	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

C₄H₉⁺ + Methane = (C₄H₉⁺ • Methane )

By formula: C₄H₉⁺ + CH₄ = (C₄H₉⁺ • CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.48	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.5	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺ • Methane ) + Methane = (C₄H₉⁺ • 2 Methane )

By formula: (C₄H₉⁺ • CH₄) + CH₄ = (C₄H₉⁺ • 2CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.39	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.4	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺ • 2 Methane ) + Methane = (C₄H₉⁺ • 3 Methane )

By formula: (C₄H₉⁺ • 2CH₄) + CH₄ = (C₄H₉⁺ • 3CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.37	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.7	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺ • 3 Methane ) + Methane = (C₄H₉⁺ • 4 Methane )

By formula: (C₄H₉⁺ • 3CH₄) + CH₄ = (C₄H₉⁺ • 4CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.36	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.0	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺ • 4 Methane ) + Methane = (C₄H₉⁺ • 5 Methane )

By formula: (C₄H₉⁺ • 4CH₄) + CH₄ = (C₄H₉⁺ • 5CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.21	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.4	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺ • 5 Methane ) + Methane = (C₄H₉⁺ • 6 Methane )

By formula: (C₄H₉⁺ • 5CH₄) + CH₄ = (C₄H₉⁺ • 6CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.09	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.3	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺ • 6 Methane ) + Methane = (C₄H₉⁺ • 7 Methane )

By formula: (C₄H₉⁺ • 6CH₄) + CH₄ = (C₄H₉⁺ • 7CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.05	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.7	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺ • 7 Methane ) + Methane = (C₄H₉⁺ • 8 Methane )

By formula: (C₄H₉⁺ • 7CH₄) + CH₄ = (C₄H₉⁺ • 8CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.99	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.1	cal/mol*K	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; M

(C₄H₉⁺ • 8 Methane ) + Methane = (C₄H₉⁺ • 9 Methane )

By formula: (C₄H₉⁺ • 8CH₄) + CH₄ = (C₄H₉⁺ • 9CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.86	kcal/mol	PHPMS	Hiraoka, Mori, et al., 1993	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.	cal/mol*K	N/A	Hiraoka, Mori, et al., 1993	gas phase; Entropy change calculated or estimated; M

C₄H₁₆F^- + 5 Methane = C₅H₂₀F^-

By formula: C₄H₁₆F^- + 5CH₄ = C₅H₂₀F^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	4.50	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-2.95	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

C₅H₂₀F^- + 6 Methane = C₆H₂₄F^-

By formula: C₅H₂₀F^- + 6CH₄ = C₆H₂₄F^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	4.20	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-3.25	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

C₅MnO₅⁺ + Methane = (C₅MnO₅⁺ • Methane )

By formula: C₅MnO₅⁺ + CH₄ = (C₅MnO₅⁺ • CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	7.2	kcal/mol	ICRCD	Hop and McMahon, 1991	gas phase; Ar collision gas, Δ_rH<; M

C₆H₂₄F^- + 7 Methane = C₇H₂₈F^-

By formula: C₆H₂₄F^- + 7CH₄ = C₇H₂₈F^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.30	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-2.96	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

C₇H₂₈F^- + 8 Methane = C₈H₃₂F^-

By formula: C₇H₂₈F^- + 8CH₄ = C₈H₃₂F^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.90	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-3.66	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

C₈H₃₂F^- + 9 Methane = C₉H₃₆F^-

By formula: C₈H₃₂F^- + 9CH₄ = C₉H₃₆F^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.30	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-3.96	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

C₉H₃₆F^- + 10 Methane = C₁₀H₄₀F^-

By formula: C₉H₃₆F^- + 10CH₄ = C₁₀H₄₀F^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.80	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-4.16	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

+ Methane = CH₄Cl^-

By formula: Cl^- + CH₄ = CH₄Cl^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.80	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-2.16	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

+ Methane = ( • Methane )

By formula: Co⁺ + CH₄ = (Co⁺ • CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	19.8	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rS(530 K); M

Enthalpy of reaction

Δ_rH° (kcal/mol)	Method	Reference	Comment
21.5 (+1.6,-0.)	CID	Haynes and Armentrout, 1996	gas phase; guided ion beam CID; M
21.5 (+1.4,-0.)	CID	Armentrout and Kickel, 1994	gas phase; guided ion beam CID; M
22.5 (+0.5,-0.)	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rS(530 K); M

( • Methane ) + Methane = ( • 2 Methane )

By formula: (Co⁺ • CH₄) + CH₄ = (Co⁺ • 2CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	26.1	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rS(500 K); M

Enthalpy of reaction

Δ_rH° (kcal/mol)	T (K)	Method	Reference	Comment
22.9 (+1.2,-0.)		CID	Armentrout and Kickel, 1994	gas phase; guided ion beam CID; M
24.8 (+1.0,-0.)		SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rS(500 K); M

( • 2 Methane ) + Methane = ( • 3 Methane )

By formula: (Co⁺ • 2CH₄) + CH₄ = (Co⁺ • 3CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	11.	kcal/mol	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Entropy change calculated or estimated; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.	cal/mol*K	N/A	Kemper, Bushnell, et al., 1993	gas phase; Entropy change calculated or estimated; M

Enthalpy of reaction

Δ_rH° (kcal/mol)	T (K)	Method	Reference	Comment
9.8 (+1.2,-0.)		CID	Armentrout and Kickel, 1994	gas phase; guided ion beam CID; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
0.7	477.	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Entropy change calculated or estimated; M

( • 3 Methane ) + Methane = ( • 4 Methane )

By formula: (Co⁺ • 3CH₄) + CH₄ = (Co⁺ • 4CH₄)

Enthalpy of reaction

Δ_rH° (kcal/mol)	T (K)	Method	Reference	Comment
16.2 (+1.4,-0.)		CID	Armentrout and Kickel, 1994	gas phase; guided ion beam CID; M

( • ) + Methane = ( • Methane • )

By formula: (Co⁺ • C₂H₆) + CH₄ = (Co⁺ • CH₄ • C₂H₆)

Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	26.4	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rS(490 K); M

Enthalpy of reaction

Δ_rH° (kcal/mol)	T (K)	Method	Reference	Comment
24.4 (+1.1,-0.)		SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rS(490 K); M

( • ) + Methane = ( • Methane • )

By formula: (Co⁺ • H₂O) + CH₄ = (Co⁺ • CH₄ • H₂O)

Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	27.0	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rS(525 K); M

Enthalpy of reaction

Δ_rH° (kcal/mol)	T (K)	Method	Reference	Comment
25.9 (+0.7,-0.)		SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rS(525 K); M

( • ) + Methane = ( • Methane • )

By formula: (Co⁺ • H₂) + CH₄ = (Co⁺ • CH₄ • H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	21.8	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; switching reaction(Co+)2H2, Δ_rS(440 K); Kemper, Bushnell, et al., 1993, 2; M

Enthalpy of reaction

Δ_rH° (kcal/mol)	T (K)	Method	Reference	Comment
22.6 (+1.2,-0.)		SIDT	Kemper, Bushnell, et al., 1993	gas phase; switching reaction(Co+)2H2, Δ_rS(440 K); Kemper, Bushnell, et al., 1993, 2; M

+ Methane = CH₄F^-

By formula: F^- + CH₄ = CH₄F^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	6.70	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	1.63	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

+ Methane = ( • Methane )

By formula: Fe⁺ + CH₄ = (Fe⁺ • CH₄)

Enthalpy of reaction

Δ_rH° (kcal/mol)	T (K)	Method	Reference	Comment
13.6 (+0.7,-0.)		CID	Armentrout and Kickel, 1994	gas phase; guided ion beam CID; M

( • Methane ) + Methane = ( • 2 Methane )

By formula: (Fe⁺ • CH₄) + CH₄ = (Fe⁺ • 2CH₄)

Enthalpy of reaction

Δ_rH° (kcal/mol)	T (K)	Method	Reference	Comment
23.2 (+1.0,-0.)		CID	Armentrout and Kickel, 1994	gas phase; guided ion beam CID; M

( • 2 Methane ) + Methane = ( • 3 Methane )

By formula: (Fe⁺ • 2CH₄) + CH₄ = (Fe⁺ • 3CH₄)

Enthalpy of reaction

Δ_rH° (kcal/mol)	T (K)	Method	Reference	Comment
23.7 (+1.4,-0.)		CID	Armentrout and Kickel, 1994	gas phase; guided ion beam CID; M

( • 3 Methane ) + Methane = ( • 4 Methane )

By formula: (Fe⁺ • 3CH₄) + CH₄ = (Fe⁺ • 4CH₄)

Enthalpy of reaction

Δ_rH° (kcal/mol)	T (K)	Method	Reference	Comment
17.7 (+1.4,-0.)		CID	Armentrout and Kickel, 1994	gas phase; guided ion beam CID; M

+ Methane = ( • Methane )

By formula: H₃O⁺ + CH₄ = (H₃O⁺ • CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	8.0	kcal/mol	HPMS	Bennet and Field, 1972, 2	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.4	cal/mol*K	HPMS	Bennet and Field, 1972, 2	gas phase; M

( • Methane ) + Methane = ( • 2 Methane )

By formula: (H₃O⁺ • CH₄) + CH₄ = (H₃O⁺ • 2CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.4	kcal/mol	HPMS	Bennet and Field, 1972, 2	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	8.1	cal/mol*K	HPMS	Bennet and Field, 1972, 2	gas phase; Entropy change is questionable; M

H₃S⁺ + Methane = (H₃S⁺ • Methane )

By formula: H₃S⁺ + CH₄ = (H₃S⁺ • CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.9	kcal/mol	HPMS	Bennet and Field, 1972	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.1	cal/mol*K	HPMS	Bennet and Field, 1972	gas phase; M

+ Methane = ( • Methane )

By formula: H₄N⁺ + CH₄ = (H₄N⁺ • CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.6	kcal/mol	HPMS	Bennet and Field, 1972	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	15.5	cal/mol*K	HPMS	Bennet and Field, 1972	gas phase; Entropy change is questionable; M

+ Methane = CH₄I^-

By formula: I^- + CH₄ = CH₄I^-

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.60	kcal/mol	N/A	Hiraoka, Mizuno, et al., 2001	gas phase; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	-2.77	kcal/mol	TDAs	Hiraoka, Mizuno, et al., 2001	gas phase; B

+ Methane = ( • Methane )

By formula: Mg⁺ + CH₄ = (Mg⁺ • CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	6.7 ± 1.6	kcal/mol	CIDT	Andersen, Muntean, et al., 2000	RCD

( • Methane ) + Methane = ( • 2 Methane )

By formula: (Mg⁺ • CH₄) + CH₄ = (Mg⁺ • 2CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.5 ± 1.6	kcal/mol	CIDT	Andersen, Muntean, et al., 2000	RCD

+ Methane = ( • Methane )

By formula: Na⁺ + CH₄ = (Na⁺ • CH₄)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	7.2	kcal/mol	HPMS	Castleman, Peterson, et al., 1983	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	14.1	cal/mol*K	HPMS	Castleman, Peterson, et al., 1983	gas phase; M

References

Go To: Top, Gas phase thermochemistry data, Phase change data, Henry's Law data, Gas phase ion energetics data, Ion clustering data, Notes

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Bohme, Lee-Ruff, et al., 1972
Bohme, D.K.; Lee-Ruff, E.; Young, L.B., Acidity order of selected bronsted acids in the gas phase at 300K, J. Am. Chem. Soc., 1972, 94, 5153. [all data]

Check, Faust, et al., 2001
Check, C.E.; Faust, T.O.; Bailey, J.M.; Wright, B.J.; Gilbert, T.M.; Sunderlin, L.S., Addition of Polarization and Diffuse Functions to the LANL2DZ Basis Set for P-Block Elements, J. Phys. Chem. A,, 2001, 105, 34, 8111, https://doi.org/10.1021/jp011945l . [all data]

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Bennet and Field, 1972
Bennet, S.L.; Field, F.H., Reversible Reactions of Gaseous Ions. VI. The NH3 - CH4, H2S - CH4 and CF4 - CH4 Systems at Low Temperatures, J. Am. Chem. Soc., 1972, 94, 18, 6305, https://doi.org/10.1021/ja00773a009 . [all data]

Hiraoka and Mori, 1989
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Notes

Go To: Top, Gas phase thermochemistry data, Phase change data, Henry's Law data, Gas phase ion energetics data, Ion clustering data, References

Symbols used in this document:

AE	Appearance energy
C_p,gas	Constant pressure heat capacity of gas
IE (evaluated)	Recommended ionization energy
P_c	Critical pressure
P_triple	Triple point pressure
S°_gas	Entropy of gas at standard conditions
S°_{gas,1 bar}	Entropy of gas at standard conditions (1 bar)
T	Temperature
T_boil	Boiling point
T_c	Critical temperature
T_fus	Fusion (melting) point
T_triple	Triple point temperature
V_c	Critical volume
d(ln(k_H))/d(1/T)	Temperature dependence parameter for Henry's Law constant
k°_H	Henry's Law constant at 298.15K
ΔH_trs	Enthalpy of phase transition
ΔS_trs	Entropy of phase transition
Δ_cH°_gas	Enthalpy of combustion of gas at standard conditions
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
Δ_rS°	Entropy of reaction at standard conditions
Δ_subH	Enthalpy of sublimation
Δ_vapH	Enthalpy of vaporization
Δ_vapS	Entropy of vaporization
ρ_c	Critical density

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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