Hydrogen

Formula: H₂
Molecular weight: 2.01588
IUPAC Standard InChI: InChI=1S/H2/h1H
IUPAC Standard InChIKey: UFHFLCQGNIYNRP-UHFFFAOYSA-N
CAS Registry Number: 1333-74-0
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.
Isotopologues:
Other names: Dihydrogen; o-Hydrogen; p-Hydrogen; Molecular hydrogen; H2; UN 1049; UN 1966
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Gas phase thermochemistry data

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

Quantity	Value	Units	Method	Reference	Comment
S°_{gas,1 bar}	31.2333 ± 0.0007	cal/mol*K	Review	Cox, Wagman, et al., 1984	CODATA Review value
S°_{gas,1 bar}	31.233	cal/mol*K	Review	Chase, 1998	Data last reviewed in March, 1977

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 1000.	1000. to 2500.	2500. to 6000.
A	7.903006	4.436683	10.376090
B	-2.715922	2.929578	-1.026071
C	2.732508	-0.683505	0.304117
D	-0.662733	0.064110	-0.023154
E	-0.037896	0.472751	-4.907711
F	-2.385468	-0.274244	-9.205344
G	41.278196	37.353760	38.738373
H	0.0	0.0	0.0
Reference	Chase, 1998	Chase, 1998	Chase, 1998
Comment	Data last reviewed in March, 1977; New parameter fit October 2001	Data last reviewed in March, 1977; New parameter fit October 2001	Data last reviewed in March, 1977; New parameter fit October 2001

Reaction thermochemistry data

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

Data compiled as indicated in comments:
MS - José A. Martinho Simões
M - Michael M. Meot-Ner (Mautner) and Sharon G. Lias
ALS - Hussein Y. Afeefy, Joel F. Liebman, and Stephen E. Stein
B - 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.

Reactions 1 to 50

(solution) + Hydrogen (solution) = 2 (solution)

By formula: C₈Co₂O₈ (solution) + H₂ (solution) = 2C₄HCoO₄ (solution)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	4.7 ± 0.2	kcal/mol	EqS	Rathke, Klingler, et al., 1992	solvent: Supercritical carbon dioxide; Temperature range: 333-453 K. The results corrected for 1 atm pressure of H2 are 3.99 kcal/mol and -17.6 J/(mol K) Rathke, Klingler, et al., 1992; MS
Δ_rH°	3.1 ± 0.2	kcal/mol	EqS	Bor, 1986	solvent: n-Hexane; Temperature range: ca. 300-420 K; MS
Δ_rH°	6.31	kcal/mol	KinS	Alemdaroglu, Penninger, et al., 1976	solvent: n-Heptane; The reaction enthalpy relies on the experimental values for the forward and reverse activation enthalpies, 72.4 and 11.0 kcal/mol, respectively Alemdaroglu, Penninger, et al., 1976. A rather different value has, however, been reported for the activation enthalpy of the forward reaction, 25.00 kcal/mol Ungváry, 1972; MS
Δ_rH°	6.60	kcal/mol	EqS	Alemdaroglu, Penninger, et al., 1976	solvent: n-Heptane; Temperature range: 353-428 K; MS
Δ_rH°	3.20	kcal/mol	EqS	Ungváry, 1972	solvent: n-Heptane; Temperature range: 307-428 K. The results corrected for 1 atm pressure of H2 are 4.30 kcal/mol and -10.9 J/(mol K) Rathke, Klingler, et al., 1992; MS

H₃⁺ + Hydrogen = (H₃⁺ • )

By formula: H₃⁺ + H₂ = (H₃⁺ • H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	6.9 ± 0.4	kcal/mol	AVG	N/A	Average of 4 out of 11 values; Individual data points
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	17.4 to 17.4	cal/mol*K	RNG	N/A	Range of 6 values; Individual data points

C₁₁H₂O₁₁Os (solution) + (solution) = Hydrogen (g) + (solution)

By formula: C₁₁H₂O₁₁Os (solution) + CO (solution) = H₂ (g) + C₁₂O₁₂Os₃ (solution)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-9.0 ± 2.3	kcal/mol	ES/KS	Poë, Sampson, et al., 1993	solvent: Decalin; Calculated from equilibrium and kinetic data Poë, Sampson, et al., 1993.; MS
Δ_rH°	-18.5 ± 2.3	kcal/mol	N/A	Poë, Sampson, et al., 1993	solvent: Decalin; Calculated from data for the reactions Os3(CO)10(H)2(solution) + CO(solution) = Os3(CO)11(H)2(solution) (hrxn [kJ/mol]=-39.7±1.3, srxn [J/(mol K)]=-80.3±3.8) and Os3(CO)11(H)2(solution) + CO(solution) = Os3(CO)12(solution) + H2(g) (hrxn [kJ/mol]=-37.7±9.6, srxn [J/(mol K)]=-32.6±27.6) Poë, Sampson, et al., 1993.; MS

+ Hydrogen =

By formula: C₆H₁₀ + H₂ = C₆H₁₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-28. ± 1.	kcal/mol	AVG	N/A	Average of 8 values; Individual data points

(cr) + Hydrogen (g) = 2C₈H₆CrO₃ (cr)

By formula: C₁₆H₁₀Cr₂O₆ (cr) + H₂ (g) = 2C₈H₆CrO₃ (cr)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-3.32 ± 0.96	kcal/mol	RSC	Landrum and Hoff, 1985	The reaction enthalpy was obtained from the value for the reaction 2Cr(Cp)(CO)3(H)(cr) + 1,3-cy-C6H8(solution) = [Cr(Cp)(CO)3]2(cr) + cy-C6H10(solution), -23.5 ± 0.91 kcal/mol Landrum and Hoff, 1985, together with the calculated enthalpy for 1,3-cy-C6H8(l) + H2(g) = cy-C6H10(l), -112.2±1.3 Pedley, 1994. It was assumed that 1,3-cy-C6H8 and cy-C6H10 have similar solution enthalpies in heptane; MS
Δ_rH°	-3.6 ± 1.0	kcal/mol	DSC	Landrum and Hoff, 1985	The reaction enthalpy was obtained from the value for the reaction 2Cr(Cp)(CO)3(H)(cr) + 1,3-cy-C6H8(solution) = [Cr(Cp)(CO)3]2(cr) + cy-C6H10(solution), -23.5 ± 0.91 kcal/mol Landrum and Hoff, 1985, together with the calculated enthalpy for 1,3-cy-C6H8(l) + H2(g) = cy-C6H10(l), -112.2±1.3 Pedley, 1994. It was assumed that 1,3-cy-C6H8 and cy-C6H10 have similar solution enthalpies in heptane; MS

Hydrogen + =

By formula: H₂ + C₆H₁₂ = C₆H₁₄

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-30.0 ± 0.6	kcal/mol	AVG	N/A	Average of 8 values; Individual data points

(H₃⁺ • Hydrogen ) + = (H₃⁺ • 2)

By formula: (H₃⁺ • H₂) + H₂ = (H₃⁺ • 2H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.3 ± 0.2	kcal/mol	PHPMS	Hiraoka, 1987	gas phase; M
Δ_rH°	3.1	kcal/mol	HPMS	Beuhler, Ehrenson, et al., 1983	gas phase; M
Δ_rH°	3.4	kcal/mol	HPMS	Beuhler, Ehrenson, et al., 1983	gas phase; deuterated; M
Δ_rH°	4.1	kcal/mol	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
Δ_rH°	1.8	kcal/mol	HPMS	Bennett and Field, 1972	gas phase; Entropy change is questionable; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	17.4	cal/mol*K	PHPMS	Hiraoka, 1987	gas phase; M
Δ_rS°	16.9	cal/mol*K	HPMS	Beuhler, Ehrenson, et al., 1983	gas phase; M
Δ_rS°	16.1	cal/mol*K	HPMS	Beuhler, Ehrenson, et al., 1983	gas phase; deuterated; M
Δ_rS°	19.8	cal/mol*K	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
Δ_rS°	10.8	cal/mol*K	HPMS	Bennett and Field, 1972	gas phase; Entropy change is questionable; M

Hydrogen + =

By formula: H₂ + C₇H₁₄ = C₇H₁₆

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-29.8 ± 0.5	kcal/mol	AVG	N/A	Average of 6 values; Individual data points

+ Hydrogen =

By formula: C₈H₁₆ + H₂ = C₈H₁₈

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-30. ± 2.	kcal/mol	AVG	N/A	Average of 7 values; Individual data points

+ = Hydrogen

By formula: H^- + H⁺ = H₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	400.40	kcal/mol	N/A	Shiell, Hu, et al., 2000	gas phase; Given: 139714.8±1 cm-1 at 0K, or 399.465±0.003 kcal/mol; B
Δ_rH°	400.40	kcal/mol	N/A	Pratt, McCormack, et al., 1992	gas phase; 399.46±0.01 kcal/mol at 0K; 0.94 correction, Gurvich, Veyts, et al.; B
Δ_rH°	400.40	kcal/mol	D-EA	Lykke, Murray, et al., 1991	gas phase; Reported: 6082.99±0.15 cm-1, or 0.754195(18) eV; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	394.20 ± 0.10	kcal/mol	H-TS	Shiell, Hu, et al., 2000	gas phase; Given: 139714.8±1 cm-1 at 0K, or 399.465±0.003 kcal/mol; B
Δ_rG°	394.20	kcal/mol	H-TS	Lykke, Murray, et al., 1991	gas phase; Reported: 6082.99±0.15 cm-1, or 0.754195(18) eV; B

Hydrogen + =

By formula: H₂ + C₅H₈ = C₅H₁₀

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-26.94 ± 0.13	kcal/mol	Chyd	Allinger, Dodziuk, et al., 1982	liquid phase; solvent: Hexane; ALS
Δ_rH°	-26.8 ± 0.2	kcal/mol	Chyd	Roth and Lennartz, 1980	liquid phase; solvent: Cyclohexane; ALS
Δ_rH°	-26.04 ± 0.44	kcal/mol	Chyd	Turner, Jarrett, et al., 1973	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-26.2 ± 0.2	kcal/mol	Chyd	Rogers and McLafferty, 1971	liquid phase; solvent: Hydrocarbon; ALS
Δ_rH°	-26.67 ± 0.06	kcal/mol	Chyd	Dolliver, Gresham, et al., 1937	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -26.92 ± 0.06 kcal/mol; At 355 °K; ALS

Hydrogen + =

By formula: H₂ + C₈H₁₄ = C₈H₁₆

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-24.3	kcal/mol	Chyd	Doering, Roth, et al., 1989	liquid phase; ALS
Δ_rH°	-24.5 ± 0.2	kcal/mol	Chyd	Roth and Lennartz, 1980	liquid phase; solvent: Cyclohexane; ALS
Δ_rH°	-23.04 ± 0.17	kcal/mol	Chyd	Rogers, Von Voithenberg, et al., 1978	liquid phase; solvent: Hexane; ALS
Δ_rH°	-23.0 ± 0.1	kcal/mol	Chyd	Turner and Meador, 1957	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-23.28 ± 0.15	kcal/mol	Chyd	Conn, Kistiakowsky, et al., 1939	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -23.53 ± 0.04 kcal/mol; At 355 K; ALS

0.5C₃₆H₈₄Cl₂P₄Rh₂ (solution) + Hydrogen (g) = C₁₈H₄₄ClP₂Rh (solution)

By formula: 0.5C₃₆H₈₄Cl₂P₄Rh₂ (solution) + H₂ (g) = C₁₈H₄₄ClP₂Rh (solution)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-23.6 ± 0.65	kcal/mol	RSC	Wang, Rosini, et al., 1995	solvent: Benzene; The reaction enthalpy was calculated from the enthalpies of the reactions Rh[P(i-Pr)3]2(Cl)(H)2(solution) + t-BuNC(solution) = Rh[P(i-Pr)3]2(Cl)(CN-t-Bu)(solution) + H2(g), -9.89 ± 0.41 kcal/mol, and 0.5{Rh[P(i-Pr)3]2(Cl)}2(solution) + t-BuNC(solution) = Rh[P(i-Pr)3]2(Cl)(CN-t-Bu)(solution), -33.51 ± 0.50 kcal/mol Wang, Rosini, et al., 1995. The enthalpy of solution of {Rh[P(i-Pr)3]2(Cl)}2(cr) was measured as 4.80 ± 0.31 kcal/mol Wang, Rosini, et al., 1995.; MS

Hydrogen + =

By formula: H₂ + C₆H₁₀ = C₆H₁₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-24.09 ± 0.15	kcal/mol	Chyd	Rogers, Crooks, et al., 1987	liquid phase; ALS
Δ_rH°	-24.22 ± 0.12	kcal/mol	Chyd	Allinger, Dodziuk, et al., 1982	liquid phase; solvent: Hexane; ALS
Δ_rH°	-23.01 ± 0.04	kcal/mol	Chyd	Turner and Garner, 1958	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-23.01 ± 0.04	kcal/mol	Chyd	Turner and Garner, 1957	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-23.01 ± 0.04	kcal/mol	Chyd	Turner and Garner, 1957, 2	liquid phase; solvent: Acetic acid; ALS

2 Hydrogen + =

By formula: 2H₂ + C₆H₁₀ = C₆H₁₄

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-60.3 ± 0.4	kcal/mol	Chyd	Fang and Rogers, 1992	liquid phase; solvent: Cyclohexane; ALS
Δ_rH°	-60.69 ± 0.65	kcal/mol	Chyd	Molnar, Rachford, et al., 1984	liquid phase; solvent: Dioxane; ALS
Δ_rH°	-60.17 ± 0.37	kcal/mol	Chyd	Turner, Mallon, et al., 1973	liquid phase; solvent: Glacial acetic acid; ALS
Δ_rH°	-60.03 ± 0.10	kcal/mol	Chyd	Kistiakowsky, Ruhoff, et al., 1936	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -60.53 ± 0.15 kcal/mol; At 355 °K; ALS

Hydrogen + =

By formula: H₂ + C₇H₁₂ = C₇H₁₄

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-24.36 ± 0.15	kcal/mol	Chyd	Allinger, Dodziuk, et al., 1982	liquid phase; solvent: Hexane; ALS
Δ_rH°	-23.5 ± 0.2	kcal/mol	Chyd	Rogers and McLafferty, 1971	liquid phase; solvent: Hydrocarbon; ALS
Δ_rH°	-23.56 ± 0.11	kcal/mol	Chyd	Turner and Garner, 1958	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-23.56 ± 0.11	kcal/mol	Chyd	Turner and Garner, 1957	liquid phase; solvent: Acetic acid; ALS

Hydrogen + =

By formula: H₂ + C₇H₁₂ = C₇H₁₄

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-25.6 ± 0.1	kcal/mol	Chyd	Allinger, Dodziuk, et al., 1982	liquid phase; solvent: Hexane; ALS
Δ_rH°	-24.2 ± 0.2	kcal/mol	Chyd	Rogers and McLafferty, 1971	liquid phase; solvent: Hydrocarbon; ALS
Δ_rH°	-24.88 ± 0.12	kcal/mol	Chyd	Turner and Garner, 1958	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-24.88 ± 0.12	kcal/mol	Chyd	Turner and Garner, 1957	liquid phase; solvent: Acetic acid; ALS

Hydrogen + =

By formula: H₂ + C₆H₁₀ = C₆H₁₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-27.70 ± 0.23	kcal/mol	Chyd	Allinger, Dodziuk, et al., 1982	liquid phase; solvent: Hexane; ALS
Δ_rH°	-26.88 ± 0.02	kcal/mol	Chyd	Turner and Garner, 1958	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-26.85 ± 0.05	kcal/mol	Chyd	Turner and Garner, 1957	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-26.82 ± 0.08	kcal/mol	Chyd	Turner and Garner, 1957, 2	liquid phase; solvent: Acetic acid; ALS

C₃H₇⁺ + Hydrogen = (C₃H₇⁺ • )

By formula: C₃H₇⁺ + H₂ = (C₃H₇⁺ • H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	2.5	kcal/mol	PHPMS	Hiraoka and Kebarle, 1976	gas phase; Entropy change calculated or estimated, DG<, Δ_rH<; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.	cal/mol*K	N/A	Hiraoka and Kebarle, 1976	gas phase; Entropy change calculated or estimated, DG<, Δ_rH<; M

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
0.9	170.	PHPMS	Hiraoka and Kebarle, 1976	gas phase; Entropy change calculated or estimated, DG<, Δ_rH<; M

+ Hydrogen = ( • )

By formula: Co⁺ + H₂ = (Co⁺ • H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	20. ± 1.	kcal/mol	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(O K)=18.2 kcal/mol, Δ_rS(300 K)=20.6 cal/mol*K; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.0	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(O K)=18.2 kcal/mol, Δ_rS(300 K)=20.6 cal/mol*K; M

Enthalpy of reaction

Δ_rH° (kcal/mol)	T (K)	Method	Reference	Comment
17.5 (+2.3,-0.)		CID	Haynes and Armentrout, 1996	gas phase; guided ion beam CID; M

+ Hydrogen =

By formula: C₅H₁₀ + H₂ = C₅H₁₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-30.27 ± 0.58	kcal/mol	Chyd	Molnar, Rachford, et al., 1984	liquid phase; solvent: Dioxane; ALS
Δ_rH°	-29.87 ± 0.42	kcal/mol	Chyd	Molnar, Rachford, et al., 1984	liquid phase; solvent: Hexane; ALS
Δ_rH°	-29.30 ± 0.57	kcal/mol	Chyd	Rogers and Skanupong, 1974	liquid phase; solvent: Hexane; ALS
Δ_rH°	-28.5 ± 0.3	kcal/mol	Chyd	Rogers and McLafferty, 1971	liquid phase; solvent: Hydrocarbon; ALS

+ Hydrogen =

By formula: C₇H₁₂ + H₂ = C₇H₁₄

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-28.56 ± 0.16	kcal/mol	Chyd	Rogers, Crooks, et al., 1987	liquid phase; ALS
Δ_rH°	-27.75 ± 0.13	kcal/mol	Chyd	Turner and Garner, 1958	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-27.75 ± 0.13	kcal/mol	Eqk	Turner and Garner, 1957	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-28.70 ± 0.07	kcal/mol	Chyd	Turner and Garner, 1957, 2	liquid phase; solvent: Acetic acid; ALS

Hydrogen + =

By formula: H₂ + C₇H₁₂ = C₇H₁₄

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-26.4 ± 0.1	kcal/mol	Chyd	Roth and Lennartz, 1980	liquid phase; solvent: Cyclohexane; ALS
Δ_rH°	-25.85 ± 0.09	kcal/mol	Chyd	Turner, Meador, et al., 1957	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-26.02 ± 0.15	kcal/mol	Chyd	Conn, Kistiakowsky, et al., 1939	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -26.52 ± 0.02 kcal/mol; At 355 K; ALS

3 Hydrogen + =

By formula: 3H₂ + C₇H₈ = C₇H₁₄

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-72.8 ± 0.1	kcal/mol	Chyd	Roth, Klaerner, et al., 1983	liquid phase; solvent: Isooctane; ALS
Δ_rH°	-70.49 ± 0.39	kcal/mol	Chyd	Turner, Meador, et al., 1957	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-72.11 ± 0.30	kcal/mol	Chyd	Conn, Kistiakowsky, et al., 1939	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -72.85 ± 0.01 kcal/mol; at 355 K; ALS

2 Hydrogen + =

By formula: 2H₂ + C₆H₁₀ = C₆H₁₄

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-55.31 ± 0.72	kcal/mol	Chyd	Molnar, Rachford, et al., 1984	liquid phase; solvent: Dioxane; ALS
Δ_rH°	-54.26 ± 0.67	kcal/mol	Chyd	Molnar, Rachford, et al., 1984	liquid phase; solvent: Hexane; ALS
Δ_rH°	-53.39 ± 0.15	kcal/mol	Chyd	Dolliver, Gresham, et al., 1937	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -53.87 ± 0.15 kcal/mol; At 355 °K; ALS

+ 3 Hydrogen =

By formula: C₅H₅N + 3H₂ = C₅H₁₁N

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-46.31 ± 0.18	kcal/mol	Eqk	Hales and Herington, 1957	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -48.32 ± 0.18 kcal/mol; At 400-550 K; ALS
Δ_rH°	-46.12 ± 0.50	kcal/mol	Eqk	Burrows and King, 1935	liquid phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -45.00 kcal/mol; At 423-443 K; ALS

+ Hydrogen =

By formula: C₈H₁₆ + H₂ = C₈H₁₈

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-25.5	kcal/mol	Chyd	Turner, Nettleton, et al., 1958	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-26.99 ± 0.06	kcal/mol	Chyd	Dolliver, Gresham, et al., 1937	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -27.24 ± 0.06 kcal/mol; At 355 °K; ALS
Δ_rH°	-28.58 ± 0.80	kcal/mol	Chyd	Crawford and Parks, 1936	liquid phase; ALS

+ Hydrogen =

By formula: C₃H₆ + H₂ = C₃H₈

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-29.5 ± 1.2	kcal/mol	Chyd	Kistiakowsky and Nickle, 1951	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -29.85 ± 0.50 kcal/mol; ALS
Δ_rH°	-29.87 ± 0.10	kcal/mol	Chyd	Kistiakowsky, Ruhoff, et al., 1935	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -30.115 ± 0.013 kcal/mol; At 355 °K; ALS

( • ) + Hydrogen = ( • • )

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

Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.9	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993, 2	gas phase; switching reaction(Co+).2H2, Δ_rS(440 K); Kemper, Bushnell, et al., 1993; M

Enthalpy of reaction

Δ_rH° (kcal/mol)	T (K)	Method	Reference	Comment
17.4 (+0.8,-0.)		SIDT	Kemper, Bushnell, et al., 1993, 2	gas phase; switching reaction(Co+).2H2, Δ_rS(440 K); Kemper, Bushnell, et al., 1993; M

Hydrogen + =

By formula: H₂ + C₃H₆O = C₃H₈O

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-16.43 ± 0.10	kcal/mol	Cm	Wiberg, Crocker, et al., 1991	liquid phase; ALS
Δ_rH°	-13.20	kcal/mol	Eqk	Buckley and Herington, 1965	gas phase; ALS
Δ_rH°	-13.24 ± 0.10	kcal/mol	Chyd	Dolliver, Gresham, et al., 1938	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -13.4 ± 0.1 kcal/mol; At 355 °K; ALS

( • Hydrogen ) + = ( • • )

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, 2	gas phase; switching reaction(Co+)2H2, Δ_rS(440 K); Kemper, Bushnell, et al., 1993; M

Enthalpy of reaction

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

+ Hydrogen =

By formula: C₈H₁₄ + H₂ = C₈H₁₆

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-26.2 ± 0.3	kcal/mol	Chyd	Rogers and McLafferty, 1971	liquid phase; solvent: Hydrocarbon; ALS
Δ_rH°	-26.32 ± 0.04	kcal/mol	Chyd	Turner and Garner, 1958	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-26.32 ± 0.04	kcal/mol	Chyd	Turner and Garner, 1957	liquid phase; solvent: Acetic acid; ALS

Hydrogen + =

By formula: H₂ + C₈H₁₄ = C₈H₁₆

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-34.5 ± 0.1	kcal/mol	Chyd	Roth, Adamczak, et al., 1991	liquid phase; see Doering, Roth, et al., 1989; ALS
Δ_rH°	-34.41 ± 0.43	kcal/mol	Chyd	Rogers, Von Voithenberg, et al., 1978	liquid phase; solvent: Hexane; ALS
Δ_rH°	-32.24 ± 0.21	kcal/mol	Chyd	Turner and Meador, 1957	liquid phase; solvent: Acetic acid; ALS

( • Hydrogen ) + = ( • 2)

By formula: (Co⁺ • H₂) + H₂ = (Co⁺ • 2H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	18.0 ± 0.6	kcal/mol	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(0 K)=17.0 kcal/mol, Δ_rS(300 K)=24.5 cal/mol*K; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	24.5	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(0 K)=17.0 kcal/mol, Δ_rS(300 K)=24.5 cal/mol*K; M

( • 2 Hydrogen ) + = ( • 3)

By formula: (Co⁺ • 2H₂) + H₂ = (Co⁺ • 3H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	10.6 ± 0.4	kcal/mol	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(0 K)=9.6 kcal/mol, Δ_rS(300 K)=20.5 cal/mol*K; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	20.5	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(0 K)=9.6 kcal/mol, Δ_rS(300 K)=20.5 cal/mol*K; M

( • 3 Hydrogen ) + = ( • 4)

By formula: (Co⁺ • 3H₂) + H₂ = (Co⁺ • 4H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	10.4 ± 0.6	kcal/mol	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(0 K)=9.6 kcal/mol, Δ_rS(300 K)=25.2 cal/mol*K; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	24.2	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(0 K)=9.6 kcal/mol, Δ_rS(300 K)=25.2 cal/mol*K; M

( • 4 Hydrogen ) + = ( • 5)

By formula: (Co⁺ • 4H₂) + H₂ = (Co⁺ • 5H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	5.2 ± 0.6	kcal/mol	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(0 K)=4.3 kcal/mol, Δ_rS(300 K)=21.9 cal/mol*K; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	22.5	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(0 K)=4.3 kcal/mol, Δ_rS(300 K)=21.9 cal/mol*K; M

( • 5 Hydrogen ) + = ( • 6)

By formula: (Co⁺ • 5H₂) + H₂ = (Co⁺ • 6H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	4.7 ± 0.6	kcal/mol	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(0 K)=4.0 kcal/mol, Δ_rS(300 K)=23.8 cal/mol*K; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	23.7	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(0 K)=4.0 kcal/mol, Δ_rS(300 K)=23.8 cal/mol*K; M

( • 6 Hydrogen ) + = ( • 7)

By formula: (Co⁺ • 6H₂) + H₂ = (Co⁺ • 7H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.5 ± 0.7	kcal/mol	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(0 K)=0.8 kcal/mol; Δ_rS(300 K)=18.0 cal/mol*K; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.0	cal/mol*K	SIDT	Kemper, Bushnell, et al., 1993	gas phase; Δ_rH(0 K)=0.8 kcal/mol; Δ_rS(300 K)=18.0 cal/mol*K; M

(H₃⁺ • 3 Hydrogen ) + = (H₃⁺ • 4)

By formula: (H₃⁺ • 3H₂) + H₂ = (H₃⁺ • 4H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	1.7 ± 0.1	kcal/mol	PHPMS	Hiraoka, 1987	gas phase; M
Δ_rH°	2.4	kcal/mol	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	17.9	cal/mol*K	PHPMS	Hiraoka, 1987	gas phase; M
Δ_rS°	19.3	cal/mol*K	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M

(H₃⁺ • 2 Hydrogen ) + = (H₃⁺ • 3)

By formula: (H₃⁺ • 2H₂) + H₂ = (H₃⁺ • 3H₂)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.2 ± 0.1	kcal/mol	PHPMS	Hiraoka, 1987	gas phase; M
Δ_rH°	3.8	kcal/mol	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	18.5	cal/mol*K	PHPMS	Hiraoka, 1987	gas phase; M
Δ_rS°	20.2	cal/mol*K	PHPMS	Hiraoka and Kebarle, 1975	gas phase; M

Hydrogen + =

By formula: H₂ + C₈H₁₆ = C₈H₁₈

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-28.25 ± 0.1	kcal/mol	Chyd	Rogers, Dejroongruang, et al., 1992	liquid phase; solvent: Cyclohexane; ALS
Δ_rH°	-28.62 ± 0.52	kcal/mol	Chyd	Rogers and Siddiqui, 1975	liquid phase; solvent: n-Hexane; ALS
Δ_rH°	-27.39 ± 0.14	kcal/mol	Chyd	Turner, Jarrett, et al., 1973	liquid phase; solvent: Acetic acid; ALS

2 Hydrogen + =

By formula: 2H₂ + C₈H₁₄ = C₈H₁₈

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-64.22 ± 0.26	kcal/mol	Chyd	Rogers, Dagdagan, et al., 1979	liquid phase; solvent: Hexane; ALS
Δ_rH°	-62.80 ± 0.16	kcal/mol	Chyd	Turner, Jarrett, et al., 1973	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-62.8	kcal/mol	Chyd	Sicher, Svoboda, et al., 1966	liquid phase; solvent: Acetic acid; ALS

Hydrogen + =

By formula: H₂ + C₈H₁₄O = C₈H₁₆O

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-13.32	kcal/mol	Chyd	Wiberg, Crocker, et al., 1991	liquid phase; ALS
Δ_rH°	-12.70	kcal/mol	Chyd	Wiberg, Crocker, et al., 1991	solid phase; ALS
Δ_rH°	-9.31	kcal/mol	Chyd	Wiberg, Crocker, et al., 1991	gas phase; ALS
Δ_rH°	-12.70 ± 0.14	kcal/mol	Cm	Wiberg, Crocker, et al., 1991	solid phase; ALS

Hydrogen + =

By formula: H₂ + C₇H₁₂ = C₇H₁₄

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-26.63 ± 0.088	kcal/mol	Chyd	Rogers, Crooks, et al., 1987	liquid phase; ALS
Δ_rH°	-25.41 ± 0.11	kcal/mol	Chyd	Turner and Garner, 1958	liquid phase; solvent: Acetic acid; ALS
Δ_rH°	-25.41 ± 0.11	kcal/mol	Chyd	Turner and Garner, 1957	liquid phase; solvent: Acetic acid; ALS

2 Hydrogen + =

By formula: 2H₂ + C₇H₁₀ = C₇H₁₄

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-49.92 ± 0.08	kcal/mol	Chyd	Turner, Mallon, et al., 1973	liquid phase; solvent: Glacial acetic acid; ALS
Δ_rH°	-50.77 ± 0.15	kcal/mol	Chyd	Conn, Kistiakowsky, et al., 1939	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -51.26 ± 0.05 kcal/mol; At 355 K; ALS

Hydrogen + =

By formula: H₂ + C₇H₁₀ = C₇H₁₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-32.8 ± 0.1	kcal/mol	Chyd	Doering, Roth, et al., 1988	gas phase; ALS
Δ_rH°	-33.82 ± 0.28	kcal/mol	Chyd	Rogers, Choi, et al., 1980	liquid phase; solvent: Hexane; Author was aware that data differs from previously reported values; ALS
Δ_rH°	-33.13 ± 0.21	kcal/mol	Chyd	Turner, Meador, et al., 1957	liquid phase; solvent: Acetic acid; ALS

+ Hydrogen =

By formula: C₃H₆O + H₂ = C₃H₈O

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-20.14 ± 0.09	kcal/mol	Cm	Wiberg, Crocker, et al., 1991	liquid phase; solvent: Triglyme; Heat of hydrogenation; ALS
Δ_rH°	-16.62 ± 0.18	kcal/mol	Eqk	Connett, 1972	gas phase; At 473-524 K; ALS
Δ_rH°	-15.72 ± 0.16	kcal/mol	Chyd	Buckley and Cox, 1967	gas phase; ALS

2 Hydrogen + =

By formula: 2H₂ + C₆H₈ = C₆H₁₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-53.64 ± 0.29	kcal/mol	Chyd	Turner, Mallon, et al., 1973	liquid phase; solvent: Glacial acetic acid; ALS
Δ_rH°	-54.88 ± 0.10	kcal/mol	Chyd	Kistiakowsky, Ruhoff, et al., 1936	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -55.4 ± 0.1 kcal/mol; At 355 °K; ALS

(solution) + Hydrogen (solution) = 2 (solution)

By formula: C₁₀Mn₂O₁₀ (solution) + H₂ (solution) = 2C₅HMnO₅ (solution)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	8.70 ± 0.31	kcal/mol	EqS	Klingler R.J. and Rathke, 1992	solvent: Supercritical carbon dioxide; Temperature range: 373-463 K; MS

Gas phase ion energetics data

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

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
LL - Sharon G. Lias and Joel F. Liebman
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 H₂⁺ (ion structure unspecified)

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	15.42593 ± 0.00005	eV	N/A	N/A	L
Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	100.9	kcal/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	94.34	kcal/mol	N/A	Hunter and Lias, 1998	HL

Ionization energy determinations

IE (eV)	Method	Reference	Comment
15.425927	EVAL	Shiner, Gilligan, et al., 1993	T = 0K; LL
15.425930	EVAL	Shiner, Gilligan, et al., 1993	T = 0K; LL
15.425932 ± 0.000002	S	McCormack, Gilligan, et al., 1989	T = 0K; LL
15.429558 ± 0.00001	LS	Glab and Hessler, 1987	T = 0K; LBLHLM
15.433174 ± 0.00001	LS	Glab and Hessler, 1987	T = 0K; LBLHLM
15.425942 ± 0.00001	LS	Glab and Hessler, 1987	T = 0K; LBLHLM
15.425932	S	Eyler, Short, et al., 1986	T = 0K; LBLHLM
15.425929	S	Eyler, Short, et al., 1986	T = 0K; LBLHLM
15.425930 ± 0.000027	N/A	Eyler, Short, et al., 1986	LBLHLM
15.5 ± 1.0	S	Farber, Srivastava, et al., 1982	LBLHLM
15.98	PE	Kimura, Katsumata, et al., 1981	LLK
15.43	PE	Bieri, Schmelzer, et al., 1980	LLK
15.42589	EVAL	Huber and Herzberg, 1979	LLK
16. ± 1.	EI	Farber and Srivastava, 1977	LLK
15.4	PI	Rabalais, Debies, et al., 1974	LLK
15.43	PE	Lee and Rabalais, 1974	LLK
15.42589 ± 0.00005	S	Herzberg and Jungen, 1972	LLK
15.4256 ± 0.0001	S	Takezawa, 1970	RDSH
15.38186 ± 0.00031	PE	Asbrink, 1970	RDSH
15.44 ± 0.01	EI	Lossing and Semeluk, 1969	RDSH
15.4256	S	Herzberg, 1969	RDSH
15.431 ± 0.022	TE	Villarejo, 1968	RDSH
15.439 ± 0.015	PE	Collin and Natalis, 1968	RDSH
15.43	CI	Cermak, 1968	RDSH
15.37 ± 0.05	EI	Kerwin, Marmet, et al., 1963	RDSH
15.4269 ± 0.0016	S	Beutler and Junger, 1936	RDSH

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
H⁺	18.078 ± 0.003	H	PIPECO	Weitzel, Mahnert, et al., 1994	T = 0K; LL
H⁺	18.0 ± 0.2	H	EI	Crowe and McConkey, 1973	LLK
H⁺	17.28 ± 0.16	H^-	EI	Locht and Momigny, 1971	LLK
H⁺	17.3	H^-	EI	Curran, Laboratories	RDSH

De-protonation reactions

+ = Hydrogen

By formula: H^- + H⁺ = H₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	400.40	kcal/mol	N/A	Shiell, Hu, et al., 2000	gas phase; Given: 139714.8±1 cm-1 at 0K, or 399.465±0.003 kcal/mol; B
Δ_rH°	400.40	kcal/mol	N/A	Pratt, McCormack, et al., 1992	gas phase; 399.46±0.01 kcal/mol at 0K; 0.94 correction, Gurvich, Veyts, et al.; B
Δ_rH°	400.40	kcal/mol	D-EA	Lykke, Murray, et al., 1991	gas phase; Reported: 6082.99±0.15 cm-1, or 0.754195(18) eV; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	394.20 ± 0.10	kcal/mol	H-TS	Shiell, Hu, et al., 2000	gas phase; Given: 139714.8±1 cm-1 at 0K, or 399.465±0.003 kcal/mol; B
Δ_rG°	394.20	kcal/mol	H-TS	Lykke, Murray, et al., 1991	gas phase; Reported: 6082.99±0.15 cm-1, or 0.754195(18) eV; B

References

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

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Cox, J.D.; Wagman, D.D.; Medvedev, V.A., CODATA Key Values for Thermodynamics, Hemisphere Publishing Corp., New York, 1984, 1. [all data]

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Chase, M.W., Jr., NIST-JANAF Themochemical Tables, Fourth Edition, J. Phys. Chem. Ref. Data, Monograph 9, 1998, 1-1951. [all data]

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Hiraoka, K., A Determination of the Stabilities of H3+(H2)n with n=1-9 from Measurements of the gas-Phase Ion Equilibria H3+(H2)n-1 + H2 = H3+(H2)n, J. Chem. Phys., 1987, 87, 7, 4048, https://doi.org/10.1063/1.452909 . [all data]

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Hiraoka, K.; Kebarle, P., A Determination of the Stabilities of H5+, H7+, H9+, and H11+ from Measurement of the Gas Phase Ion Equilibria Hn+ + H2 = H(n + 2)+ (n = 3, 5, 7, 9), J. Chem. Phys., 1975, 62, 6, 2267, https://doi.org/10.1063/1.430751 . [all data]

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Pratt, McCormack, et al., 1992
Pratt, S.T.; McCormack, E.F.; Dehmer, J.L.; Dehmer, P.M., Field-Induced Ion-Pair Formation in Molecular Hydrogen, Phys. Rev. Lett., 1992, 68, 5, 584, https://doi.org/10.1103/PhysRevLett.68.584 . [all data]

Gurvich, Veyts, et al.
Gurvich, L.V.; Veyts, I.V.; Alcock, C.B., Hemisphere Publishing, NY, 1989, V. 1 2, Thermodynamic Properties of Individual Substances, 4th Ed. [all data]

Lykke, Murray, et al., 1991
Lykke, K.R.; Murray, K.K.; Lineberger, W.C., Threshold Photodetachment of H-, Phys. Rev. A, 1991, 43, 11, 6104, https://doi.org/10.1103/PhysRevA.43.6104 . [all data]

Allinger, Dodziuk, et al., 1982
Allinger, N.L.; Dodziuk, H.; Rogers, D.W.; Naik, S.N., Heats of hydrogenation and formation of some 5-membered ring compounds by molecular mechanics calculations and direct measurements, Tetrahedron, 1982, 38, 1593-1597. [all data]

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Roth, W.R.; Lennartz, H.W., Heats of hydrogenation. I. Determination of heats of hydrogenation with an isothermal titration calorimeter, Chem. Ber., 1980, 113, 1806-1817. [all data]

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Turner, R.B.; Jarrett, A.D.; Goebel, P.; Mallon, B.J., Heats of hydrogenation. 9. Cyclic acetylenes and some miscellaneous olefins, J. Am. Chem. Soc., 1973, 95, 790-792. [all data]

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Rogers, D.W.; McLafferty, F.J., A new hydrogen calorimeter. Heats of hydrogenation of allyl and vinyl unsaturation adjacent to a ring, Tetrahedron, 1971, 27, 3765-3775. [all data]

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Doering, W.E.; Roth, W.R.; Bauer, F.; Breuckmann, R.; Ebbrecht, T.; Herbold, M.; Schmidt, R.; Lennartz, H-W.; Lenoir, D.; Boese, R., Rotational barriers of strained olefines, Chem. Ber., 1989, 122, 1263-1266. [all data]

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Conn, J.B.; Kistiakowsky, G.B.; Smith, E.A., Heats of organic reactions. VIII. Some further hydrogenations, including those of some acetylenes, J. Am. Chem. Soc., 1939, 61, 1868-1876. [all data]

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Rogers, D.W.; Crooks, E.; Dejroongruang, K., Enthalpies of hydrogenation of the hexenes, J. Chem. Thermodyn., 1987, 19, 1209-1215. [all data]

Turner and Garner, 1958
Turner, R.B.; Garner, R.H., Heats of hydrogenation. V. Relative stabilities in certain exocyclic-endocyclic olefin pairs, J. Am. Chem. Soc., 1958, 80, 1424-1430. [all data]

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Turner, R.B.; Garner, R.H., The stability relationship of 1-methyl-cyclopentene and methylenecyclopentane, J. Am. Chem. Soc., 1957, 79, 253. [all data]

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Fang, W.; Rogers, D.W., Enthalpy of hydrogenation of the hexadienes and cis- and trans-1,3,5-hexatriene, J. Org. Chem., 1992, 57, 2294-2297. [all data]

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Notes

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Symbols used in this document:

AE	Appearance energy
IE (evaluated)	Recommended ionization energy
S°_{gas,1 bar}	Entropy of gas at standard conditions (1 bar)
T	Temperature
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

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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