Hydrogen iodide

Formula: HI
Molecular weight: 127.91241
IUPAC Standard InChI: InChI=1S/HI/h1H
IUPAC Standard InChIKey: XMBWDFGMSWQBCA-UHFFFAOYSA-N
CAS Registry Number: 10034-85-2
Chemical structure:
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Gas phase thermochemistry data

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Quantity	Value	Units	Method	Reference	Comment
Δ_fH°_gas	6.334 ± 0.024	kcal/mol	Review	Cox, Wagman, et al., 1984	CODATA Review value
Δ_fH°_gas	6.300	kcal/mol	Review	Chase, 1998	Data last reviewed in September, 1961
Quantity	Value	Units	Method	Reference	Comment
S°_{gas,1 bar}	49.376	cal/mol*K	Review	Chase, 1998	Data last reviewed in September, 1961

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 1400.	1400. to 6000.
A	6.225000	8.471219
B	1.120860	0.338123
C	1.173941	-0.043520
D	-0.634416	0.002813
E	0.029020	-0.969063
F	4.482551	1.892711
G	56.69259	57.38760
H	6.299960	6.299960
Reference	Chase, 1998	Chase, 1998
Comment	Data last reviewed in September, 1961	Data last reviewed in September, 1961

Phase change data

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

Quantity	Value	Units	Method	Reference	Comment
T_fus	222.15	K	N/A	Beckmann and Waentig, 1910	Uncertainty assigned by TRC = 1.5 K; TRC

Enthalpy of vaporization

Δ_vapH (kcal/mol)	Temperature (K)	Method	Reference	Comment
4.73	238.	C	Giauque and Wiebe, 1929	AC

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
149.8 to 238.1	4.26283	939.994	-18.012	Stull, 1947	Coefficents calculated by NIST from author's data.

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:

Reaction thermochemistry data

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

Note: Please consider using the reaction search for this species. This page allows searching of all reactions involving this species. A general reaction search form is also available. Future versions of this site may rely on reaction search pages in place of the enumerated reaction displays seen below.

Individual Reactions

+ Hydrogen iodide = ( • )

By formula: I^- + HI = (I^- • HI)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	17.0 ± 2.0	kcal/mol	TDEq	Caldwell and Kebarle, 1985	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	24.4	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; switching reaction(I-)SO2; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	9.7 ± 2.6	kcal/mol	TDEq	Caldwell and Kebarle, 1985	gas phase; B

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
9.7	300.	PHPMS	Caldwell and Kebarle, 1985	gas phase; switching reaction(I-)SO2; M

+ = Hydrogen iodide

By formula: I^- + H⁺ = HI

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	314.350 ± 0.020	kcal/mol	D-EA	Pelaez, Blondel, et al., 2009	gas phase; Given: 3.0590463(38) eV; B
Δ_rH°	313.60	kcal/mol	N/A	Check, Faust, et al., 2001	gas phase; Fe(CO)2-(q); ; ΔS(EA)=5.0; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	309.280 ± 0.060	kcal/mol	H-TS	Pelaez, Blondel, et al., 2009	gas phase; Given: 3.0590463(38) eV; B
Δ_rG°	308.50	kcal/mol	N/A	Check, Faust, et al., 2001	gas phase; Fe(CO)2-(q); ; ΔS(EA)=5.0; B

Hydrogen iodide + = +

By formula: HI + C₃H₅I = C₃H₆ + I₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-7.96 ± 0.33	kcal/mol	Eqk	Rodgers, Golden, et al., 1966	gas phase; ALS
Δ_rH°	-9.5 ± 1.0	kcal/mol	Eqk	Rodgers, Golden, et al., 1966	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -8.33 ± 0.23 kcal/mol; At 527 K; ALS

Hydrogen iodide + = +

By formula: HI + CH₃I = CH₄ + I₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-12.56 ± 0.13	kcal/mol	Eqk	Golden, Walsh, et al., 1965	gas phase; ALS
Δ_rH°	-12.67 ± 0.05	kcal/mol	Eqk	Goy and Pritchard, 1965	gas phase; ALS
Δ_rH°	-11.0 ± 1.3	kcal/mol	Cm	Nichol and Ubbelohde, 1952	gas phase; ALS

(l) + (cr) = Hydrogen iodide (g) + (cr)

By formula: C₅HMnO₅ (l) + I₂ (cr) = HI (g) + C₅IMnO₅ (cr)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-26. ± 2.	kcal/mol	RSC	Connor, Zafarani-Moattar, et al., 1982	The reaction enthalpy relies on -6. ± 1. kcal/mol for the enthalpy of solution of HI(g) in benzene Connor, Zafarani-Moattar, et al., 1982.; MS

+ = Hydrogen iodide +

By formula: C₂H₃IO + H₂O = HI + C₂H₄O₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-22.46	kcal/mol	Cm	Devore and O'Neal, 1969	liquid phase; Heat of hydrolysis; ALS
Δ_rH°	-21.59	kcal/mol	Cm	Carson and Skinner, 1949	liquid phase; Heat of hydrolysis; ALS

= Hydrogen iodide +

By formula: C₄H₉I = HI + C₄H₈

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-19.4 ± 0.5	kcal/mol	Eqk	Benson and Amano, 1962	gas phase; ALS
Δ_rH°	-19.2 ± 1.0	kcal/mol	Eqk	Jones and Ogg, 1937	gas phase; At 408-464 K; ALS

Hydrogen iodide + = +

By formula: HI + C₆H₁₁I = C₆H₁₂ + I₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-7.8 ± 2.0	kcal/mol	Cm	Brennan and Ubbelohde, 1956	gas phase; Reanalyzed by Cox and Pilcher, 1970, Original value = -6.8 ± 1.0 kcal/mol; ALS

+ = Hydrogen iodide +

By formula: C₂H₃F₃ + I₂ = HI + C₂H₂F₃I

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-15.3 ± 0.5	kcal/mol	Eqk	Wu and Rodgers, 1974	gas phase; Heat of formation Unpublished results by B.J. Zwolinski; ALS

+ = Hydrogen iodide +

By formula: C₇H₉NO + C₇H₅IO = HI + C₁₄H₁₃NO₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-44.1 ± 0.5	kcal/mol	Cac	Kiselev, Khuzyasheva, et al., 1979	liquid phase; solvent: Benzene; ALS

+ = Hydrogen iodide +

By formula: C₇H₉N + C₇H₅IO = HI + C₁₄H₁₃NO

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-40.2 ± 0.4	kcal/mol	Cac	Kiselev, Khuzyasheva, et al., 1979	liquid phase; solvent: Benzene; ALS

+ = Hydrogen iodide +

By formula: C₇H₅IO + C₆H₇N = HI + C₁₃H₁₁NO

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-39.7 ± 0.5	kcal/mol	Cac	Kiselev, Khuzyasheva, et al., 1979	liquid phase; solvent: Benzene; ALS

(cr) + (solution) = Hydrogen iodide (solution) + C₈H₅IO₃W (solution)

By formula: C₈H₆O₃W (cr) + I₂ (solution) = HI (solution) + C₈H₅IO₃W (solution)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-16.1 ± 0.91	kcal/mol	RSC	Landrum and Hoff, 1985	solvent: Dichloromethane; MS

C₈H₆MoO₃ (cr) + (solution) = C₈H₅IMoO₃ (solution) + Hydrogen iodide (solution)

By formula: C₈H₆MoO₃ (cr) + I₂ (solution) = C₈H₅IMoO₃ (solution) + HI (solution)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-18.0 ± 0.60	kcal/mol	RSC	Landrum and Hoff, 1985	solvent: Dichloromethane; MS

2 + = 2 Hydrogen iodide +

By formula: 2C₃H₈S + I₂ = 2HI + C₆H₁₄S₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-29.85	kcal/mol	Cm	Sunner, 1955	liquid phase; solvent: Ethanol/water(90/10); ALS

2 + = 2 Hydrogen iodide +

By formula: 2C₅H₁₂S + I₂ = 2HI + C₁₀H₂₂S₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-29.85	kcal/mol	Cm	Sunner, 1955	liquid phase; solvent: Ethanol/water(90/10); ALS

+ = 2 Hydrogen iodide +

By formula: C₄H₁₀S₂ + I₂ = 2HI + C₄H₈S₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-29.45	kcal/mol	Cm	Sunner, 1955	liquid phase; solvent: Ethanol/water(90/10); ALS

+ = 2 Hydrogen iodide +

By formula: C₈H₁₆O₂S₂ + I₂ = 2HI + C₈H₁₄O₂S₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-26.20	kcal/mol	Cm	Sunner, 1955	liquid phase; solvent: Ethanol/water(90/10); ALS

+ = 2 Hydrogen iodide +

By formula: C₃H₈S₂ + I₂ = 2HI + C₃H₆S₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-25.75	kcal/mol	Cm	Sunner, 1955	liquid phase; solvent: Ethanol/water(90/10); ALS

Hydrogen iodide + = +

By formula: HI + C₇H₇I = C₇H₈ + I₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-7.8 ± 1.1	kcal/mol	Cm	Graham, Nichol, et al., 1955	liquid phase; solvent: p-Xylene; ALS

+ = Hydrogen iodide +

By formula: C₃H₅I + H₂O = HI + C₃H₆O

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-2.10	kcal/mol	Cm	Gellner and Skinner, 1949	liquid phase; Heat of hydrolysis; ALS

+ = Hydrogen iodide +

By formula: C₇H₇I + H₂O = HI + C₇H₈O

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-3.00	kcal/mol	Cm	Gellner and Skinner, 1949	liquid phase; Heat of hydrolysis; ALS

+ = Hydrogen iodide +

By formula: C₇H₅IO + H₂O = HI + C₇H₆O₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-24.47	kcal/mol	Cm	Carson, Pritchard, et al., 1950	liquid phase; Heat of hydrolysis; ALS

C₃H₉ISn (l) + (l) = ( Hydrogen iodide • 55) (solution) + C₃H₁₀OSn (cr)

By formula: C₃H₉ISn (l) + H₂O (l) = (HI • 55H₂O) (solution) + C₃H₁₀OSn (cr)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-4.21 ± 0.1	kcal/mol	RSC	Baldwin, Lappert, et al., 1972	MS

Hydrogen iodide + = +

By formula: HI + CH₃IS = CH₄S + I₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-2.88 ± 0.54	kcal/mol	Eqk	Shum and Benson, 1983	gas phase; ALS

+ = Hydrogen iodide +

By formula: C₃H₆O + I₂ = HI + C₃H₅IO

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	12.1 ± 1.2	kcal/mol	Eqk	Solly, Golden, et al., 1970	gas phase; ALS

+ = Hydrogen iodide +

By formula: C₂H₄O + I₂ = HI + C₂H₃IO

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	0.7 ± 0.5	kcal/mol	Eqk	Walsh and Benson, 1966	gas phase; ALS

Hydrogen iodide + = +

By formula: HI + C₇H₇IO = C₇H₈O + I₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-6.9 ± 1.2	kcal/mol	Cm	Brennan and Ubbelohde, 1956	gas phase; ALS

Hydrogen iodide + = +

By formula: HI + C₂H₅IS = C₂H₆S + I₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-6.6 ± 1.1	kcal/mol	Kin	Shum and Benson, 1985	gas phase; ALS

C₁₀H₁₂W (cr) + 2 (cr) = C₁₀H₁₀I₂W (cr) + 2 Hydrogen iodide (g)

By formula: C₁₀H₁₂W (cr) + 2I₂ (cr) = C₁₀H₁₀I₂W (cr) + 2HI (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-24.9 ± 1.3	kcal/mol	RSC	Calado, Dias, et al., 1979	MS

Hydrogen iodide + = +

By formula: HI + C₇H₅IO = C₇H₆O + I₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-3.0 ± 1.0	kcal/mol	Eqk	Solly and Benson, 1971	gas phase; ALS

C₁₀H₁₁ClZr (cr) + (cr) = C₁₀H₁₀ClIZr (cr) + Hydrogen iodide (g)

By formula: C₁₀H₁₁ClZr (cr) + I₂ (cr) = C₁₀H₁₀ClIZr (cr) + HI (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-18.7 ± 0.57	kcal/mol	RSC	Diogo, Simoni, et al., 1993	MS

C₁₀H₁₂Mo (cr) + 2 (cr) = C₁₀H₁₀I₂Mo (cr) + 2 Hydrogen iodide (g)

By formula: C₁₀H₁₂Mo (cr) + 2I₂ (cr) = C₁₀H₁₀I₂Mo (cr) + 2HI (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-21.0 ± 1.2	kcal/mol	RSC	Calado, Dias, et al., 1979	MS

+ = Hydrogen iodide +

By formula: C₂H₄F₂ + I₂ = HI + C₂H₃BrF₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	12.2 ± 0.2	kcal/mol	Eqk	Pickard and Rodgers, 1977	gas phase; ALS

+ = Hydrogen iodide +

By formula: C₇H₆O + I₂ = HI + C₇H₅IO

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	3.0 ± 1.0	kcal/mol	Eqk	Solly and Benson, 1971	gas phase; ALS

Hydrogen iodide + = +

By formula: HI + C₆H₅I = C₆H₆ + I₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-5.2 ± 1.4	kcal/mol	Cm	Graham, Nichol, et al., 1955	gas phase; ALS

C₁₀H₁₁IW (cr) + (cr) = C₁₀H₁₀I₂W (cr) + Hydrogen iodide (g)

By formula: C₁₀H₁₁IW (cr) + I₂ (cr) = C₁₀H₁₀I₂W (cr) + HI (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-20.2 ± 0.98	kcal/mol	RSC	Calhorda, Dias, et al., 1987	MS

(g) + (g) = Hydrogen iodide (g) + (g)

By formula: I (g) + H₄Ge (g) = HI (g) + H₃Ge (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	11.2 ± 0.98	kcal/mol	KinG	Noble and Walsh, 1983	MS

+ = 2 Hydrogen iodide +

By formula: C₅H₁₀ + I₂ = 2HI + C₅H₈

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	24.40	kcal/mol	Eqk	Furuyama, Golden, et al., 1970	gas phase; ALS

Hydrogen iodide + = +

By formula: HI + C₄H₇IO = I₂ + C₄H₈O

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-10.2	kcal/mol	Kin	Solly, Golden, et al., 1970, 2	gas phase; ALS

2 Hydrogen iodide + = +

By formula: 2HI + C₅H₆ = C₅H₈ + I₂

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-21.4	kcal/mol	Eqk	Furuyama, Golden, et al., 1970	gas phase; ALS

Hydrogen iodide + =

By formula: HI + C₃H₆ = C₃H₇I

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	-20.62	kcal/mol	Eqk	Furuyama, Golden, et al., 1969	gas phase; ALS

(g) + C₃H₁₀Ge (g) = C₃H₉Ge (g) + Hydrogen iodide (g)

By formula: I (g) + C₃H₁₀Ge (g) = C₃H₉Ge (g) + HI (g)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	10.0 ± 0.43	kcal/mol	KinG	Doncaster and Walsh, 1979	MS

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
2.5×10⁺⁹/K_A	9800.	T	N/A	For strong acids, the solubility is often expressed as k_H = ([H⁺] * [A^-]) / p(HA). To obtain the physical solubility of HA, the value has to be divided by the acidity constant K_A. missing citation corrects erroneous data from missing citation.
2.2×10⁺⁹/K_A	9800.	T	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
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 HI⁺ (ion structure unspecified)

Quantity	Value	Units	Method	Reference	Comment
IE (evaluated)	10.386 ± 0.001	eV	N/A	N/A	L
Quantity	Value	Units	Method	Reference	Comment
Proton affinity (review)	150.0	kcal/mol	N/A	Hunter and Lias, 1998	HL
Quantity	Value	Units	Method	Reference	Comment
Gas basicity	143.7	kcal/mol	N/A	Hunter and Lias, 1998	HL

Ionization energy determinations

IE (eV)	Method	Reference	Comment
10.38	PE	Kimura, Katsumata, et al., 1981	LLK
10.386 ± 0.001	S	Eland and Berkowitz, 1977	LLK
10.38 ± 0.01	PE	Lempka, Passmore, et al., 1968	RDSH
10.42 ± 0.01	PE	Frost, McDowell, et al., 1967	RDSH
10.38 ± 0.02	PI	Watanabe, 1957	RDSH
10.3 ± 0.1	EI	Friedman, 1955	RDSH
~10.39	S	Price, 1938	RDSH

Appearance energy determinations

Ion	AE (eV)	Other Products	Method	Reference	Comment
I⁺	13.49 ± 0.13	?	PI	Eland and Berkowitz, 1977	LLK

De-protonation reactions

+ = Hydrogen iodide

By formula: I^- + H⁺ = HI

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	314.350 ± 0.020	kcal/mol	D-EA	Pelaez, Blondel, et al., 2009	gas phase; Given: 3.0590463(38) eV; B
Δ_rH°	313.60	kcal/mol	N/A	Check, Faust, et al., 2001	gas phase; Fe(CO)2-(q); ; ΔS(EA)=5.0; B
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	309.280 ± 0.060	kcal/mol	H-TS	Pelaez, Blondel, et al., 2009	gas phase; Given: 3.0590463(38) eV; B
Δ_rG°	308.50	kcal/mol	N/A	Check, Faust, et al., 2001	gas phase; Fe(CO)2-(q); ; ΔS(EA)=5.0; B

Ion clustering data

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

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

+ Hydrogen iodide = ( • )

By formula: I^- + HI = (I^- • HI)

Bond type: Hydrogen bond (negative ion to hydride)

Quantity	Value	Units	Method	Reference	Comment
Δ_rH°	17.0 ± 2.0	kcal/mol	TDEq	Caldwell and Kebarle, 1985	gas phase; B,M
Quantity	Value	Units	Method	Reference	Comment
Δ_rS°	24.4	cal/mol*K	PHPMS	Caldwell and Kebarle, 1985	gas phase; switching reaction(I-)SO2; M
Quantity	Value	Units	Method	Reference	Comment
Δ_rG°	9.7 ± 2.6	kcal/mol	TDEq	Caldwell and Kebarle, 1985	gas phase; B

Free energy of reaction

Δ_rG° (kcal/mol)	T (K)	Method	Reference	Comment
9.7	300.	PHPMS	Caldwell and Kebarle, 1985	gas phase; switching reaction(I-)SO2; M

Constants of diatomic molecules

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Data compiled by: Klaus P. Huber and Gerhard H. Herzberg

Data collected through September, 1976

Symbols used in the table of constants
Symbol	Meaning
State	electronic state and / or symmetry symbol
T_e	minimum electronic energy (cm^-1)
ω_e	vibrational constant – first term (cm^-1)
ω_ex_e	vibrational constant – second term (cm^-1)
ω_ey_e	vibrational constant – third term (cm^-1)
B_e	rotational constant in equilibrium position (cm^-1)
α_e	rotational constant – first term (cm^-1)
γ_e	rotation-vibration interaction constant (cm^-1)
D_e	centrifugal distortion constant (cm^-1)
β_e	rotational constant – first term, centrifugal force (cm^-1)
r_e	internuclear distance (Å)
Trans.	observed transition(s) corresponding to electronic state
ν₀₀	position of 0-0 band (units noted in table)

Diatomic constants for H¹²⁷I
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
L	[100640] 1										L ← X	99500
L	↳Terwilliger and Smith, 1975
H (1)	[75435] 2										H ← X	74290
H (1)	↳missing citation; missing citation
F ¹Δ	[71372.8]				[6.33₅] 3			[2.₃E-4] 3		[1.631]	F ← X R	70228.2 Z
F ¹Δ	↳missing citation
f₁ ³Δ₁	[70831.5]				[6.01₅] 4					[1.674]	f₁ ← X R	69686.9 Z
f₁ ³Δ₁	↳missing citation
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
D ¹Π	[70389.0]				[6.198] 5			[2.1E-4] 5		[1.649]	D ← X R	69244.4 Z
D ¹Π	↳missing citation
d₀ ³Π₀	[70302.4]				[6.117] 6			[2.1E-4] 6		[1.660]	d₀ ← X R	69157.8 6 Z
	↳missing citation
	7
	↳Ginter, Tilford, et al., 1975
G 1	[70136.4]				[6.406] 8			[3.2E-4] 8		[1.622]	G ← X R	68991.8 Z
G 1	↳missing citation; missing citation
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
V ¹Σ⁺					[2.84] 9			[2.0E-4] 9		[2.44] 9	V ← X R	68004.4 9 Z
V ¹Σ⁺	↳missing citation
E ¹Σ⁺	(66326)	[1681.8] Z			[6.110]	10		[2.5E-4] 10		[1.661₁]	E ← X R	66022.6 Z
E ¹Σ⁺	↳missing citation; missing citation
f₂ ³Δ₂	[65838.6]				[6.757] 11			[12.₃E-4] 11		[1.580]	f₂ ← X V	64694.0 Z
f₂ ³Δ₂	↳missing citation
f₃ ³Δ₃	[65717.5]				[5.706] 12			[-8.3E-4] 12		[1.719]	f₃ ← X R	64572.9 Z
f₃ ³Δ₃	↳missing citation
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
e ³Σ⁺	[65345] 13										e ← X	64200
e ³Σ⁺	↳missing citation
d₁ ³Π₁	[65028] 14										d₁ ← X	63883 H^Q
d₁ ³Π₁	↳missing citation
d₂ ³Π₂	(63922)	[2154.4] Z			[6.065]	15		1.7E-4		[1.667₃]	d₂ ← X R	63854.9 Z
d₂ ³Π₂	↳missing citation
C ¹Π	(62378)	[2183] H^Q 16									C ← X	62325 H^Q
C ¹Π	↳Price, 1938; Tilford, Ginter, et al., 1970
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
b₀ ³Π₀₊	60858.7	2314.7 17 Z	54.3 17		6.493 17	0.118 17				1.611₄	b₀ ← X	60857.9 Z
b₀ ³Π₀₊	↳missing citation; missing citation
b₀ ³Π_0-	(60840) 18	2314.7 17 Z	54.3 17		6.493 17	0.118 17				1.611₄	b₀ ← X	60839 H^Q
b₀ ³Π_0-	↳missing citation
b₁ ³Π₁	(56783)	[2200]			[6.427] 19					[1.619₆]	b₁ ← X	56738.3 Z
b₁ ³Π₁	↳Price, 1938; Tilford, Ginter, et al., 1970
b₂ ³Π₂	(55874)	[2207.4] Z			6.436	0.175				1.618₅	b₂ ← X	55833.1 Z
b₂ ³Π₂	↳missing citation
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
A (¹Π)	20										A ← X 21
	↳Goodeve and Taylor, 1936; Datta and Kundu, 1941; Romand, 1949; Huebert and Martin, 1968; Ogilvie, 1971
	20										a ← X 21
	↳Goodeve and Taylor, 1936; Datta and Kundu, 1941; Romand, 1949; Huebert and Martin, 1968; Ogilvie, 1971
(³Π₀₊)	20										A ← X 21
(³Π₀₊)	↳Goodeve and Taylor, 1936; Datta and Kundu, 1941; Romand, 1949; Huebert and Martin, 1968; Ogilvie, 1971
(³Π₁)	20										a ← X 21
(³Π₁)	↳Goodeve and Taylor, 1936; Datta and Kundu, 1941; Romand, 1949; Huebert and Martin, 1968; Ogilvie, 1971
State	T_e	ω_e	ω_ex_e	ω_ey_e	B_e	α_e	γ_e	D_e	β_e	r_e	Trans.	ν₀₀
X ¹Σ⁺	0	2309.01₄ Z	39.643₅ 22	-0.0200	[6.4263650] 23 24	0.1688₆ 25	-0.00095	[2.069E-4] 23		1.60916 26
	↳Boyd and Thompson, 1952; Haeusler, Meyer, et al., 1964; Hurlock, Alexander, et al., 1971; Bernage, Niay, et al., 1974
										27
	↳Czerny, 1927; Palik, 1955; Cowan and Gordy, 1956; De Lucia, Helminger, et al., 1971
										28
	↳Cherlow, Hyatt, et al., 1975

Notes

Broad absorption peak (width ~4500 cm^-1). 31

First member of a Rydberg series converging to X ² Π_1/2 (v=0) of HI⁺ (I.P. = 11.05 eV); fragments of additional series. 32

Average B and D, B(2⁺) - B(2^-)= -0.05.

Average of B value, B(1⁺) - B(1^-) = +0.240.

Refers to the 1⁺ component; B(1^-) ~ 6.25.

Constants refer to the 0⁺ component; for 0^- B₀ = 6.091, v₀₀ = 69149.5.

Additional unclassified absorption bands between 68100 and 69000 cm^-1.

missing note

Vibrational numbering uncertain; the numbers given refer to the lowest level observed in absorption for which v is probably fairly high. Several higher vibrational levels have been found; strong perturbations.

B₁ = 5.62, D₁= 28E-4, perturbed at high J.

Average B and D, B(2⁺) - B(2^-) = -0.040.

Average B and D, B(3⁺) - B(3^-) = +0.018.

Very diffuse feature.

Diffuse feature.

B₁(³Π₂)= -5.92₃.

Diffuse, no rotational structure.

From v=0, 1, 3 only; γr_e = -0.031₇.

Diffuse Q head only.

(v=1 diffuse Q head)

Continuous absorption starting at ~28000 with maximum at ~46000 cm^-1.

Photofragment spectroscopy at 37550 cm^-1 Clear, Riley, et al., 1975 shows that the continuum is of composite nature; 36% of the absorption is due to ³Π₀₊ yielding H + I(²P_1/2). Clear, Riley, et al., 1975 have analyzed the continuum in terms of three overlapping transitions ¹Π, ³Π₀₊, ³Π₁ ← X. A very weak continuum with maximum at 23500 cm^-1 was reported by Datta and Kundu, 1941.

w_ez_e = +0.01621, from the 1-0,...,4-0 vibrational-rotational bands Hurlock, Alexander, et al., 1971; very slightly different constants are given by Bernage, Niay, et al., 1974 who have measured the 5-0 and 6-0 bands.

Microwave value De Lucia, Helminger, et al., 1971.

Dunham potential coefficients Ogilvie and Koo, 1976.

γ_e from Hurlock, Alexander, et al., 1971, see 22.

Rot.-vib. sp. 34

Rotation sp. 35 36

Raman sp. 37

From D₀⁰(H₂), D₀⁰(I₂), and ΔH_f0(HI, from gaseous H₂,I₂).

From photoionization studies by Watanabe, Nakayama, et al., 1962; refers to X ²Π_3/2 of HI⁺. Lempka, Passmore, et al., 1968 give the same value, Frost, McDowell, et al., 1967 give 10.42 eV from the photoelectron spectrum.

Diffuse on account of predissociation and preionization; presumably first member of a Rydberg series converging to A ²Σ⁺ of HI⁺ Terwilliger and Smith, 1975.

Above the first ionization limit (X ²Π_3/2) the members of the series are subject to preionization and are seen as photoionization peaks Tsai and Baer, 1974.

Average B and D, B(1⁺) - B(1^-) = +0.107.

The 1-0,...,6-0 bands have been observed in absorption. Absolute intensities, dipole moment function Ameer and Beneschi, 1962, Benesch, 1963, Meyer, Haeusler, et al., 1965, Jacobi, 1967, Tipping and Forbes, 1971. The R branch of the fundamental is much stronger than the P branch on account of rotation-vibration interaction; for the overtones this effect is very small Benesch, 1963, Meyer, Haeusler, et al., 1965. The overall intensities decrease rather slowly in the series 1-0, 2-0, 3-0 Benesch, 1963, Meyer, Haeusler, et al., 1965. Line width, pressure broadening studied by Ameer and Beneschi, 1962, Meyer, Haeusler, et al., 1965.

From the hfs of the microwave spectrum Van Dijk and Dymanus, 1968 derive nuclear quadrupole (I) and other hyperfine coupling constants; see also De Lucia, Helminger, et al., 1971. From the Stark effect in the hfs of the 1-0 transition van Dijk and Dymanus, 1970 obtain μ_el(v=0) = 0.4477.

Absolute intensities Chamberlain and Gebbie, 1965.

Vibrational Raman cross sections.

References

Go To: Top, Gas phase thermochemistry data, Phase change data, Reaction thermochemistry data, Henry's Law data, Gas phase ion energetics data, Ion clustering data, Constants of diatomic molecules, NIST Free Links, NIST Subscription Links, Notes

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Watanabe, Nakayama, et al., 1962
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Tsai and Baer, 1974
Tsai, B.P.; Baer, T., Analysis of autoionizing Rydberg states in HI and CH₃I. Comments on Rydberg electron wavefunctions, J. Chem. Phys., 1974, 61, 2047. [all data]

Ameer and Beneschi, 1962
Ameer, G.; Beneschi, W., Line strengths and widths in hydrogen iodide, J. Chem. Phys., 1962, 37, 2699. [all data]

Benesch, 1963
Benesch, W., Simultaneous measurement of HI fundamental and overtone lines, J. Chem. Phys., 1963, 39, 1048. [all data]

Meyer, Haeusler, et al., 1965
Meyer, C.; Haeusler, C.; Barchewitz, P., Intensites et largeurs des raies de vibration-rotation de molecules diatomiques, J. Phys. (Paris), 1965, 26, 305. [all data]

Jacobi, 1967
Jacobi, N., Electrical anharmonicities of diatomic molecules, J. Mol. Spectrosc., 1967, 22, 76. [all data]

Tipping and Forbes, 1971
Tipping, R.H.; Forbes, A., Dipole moment function of HI, J. Mol. Spectrosc., 1971, 39, 65. [all data]

Van Dijk and Dymanus, 1968
Van Dijk, F.A.; Dymanus, A., Hyperfine structure of the rotational spectrum of HI in the submillimeter region, Chem. Phys. Lett., 1968, 2, 235. [all data]

van Dijk and Dymanus, 1970
van Dijk, F.A.; Dymanus, A., The electric dipole moment of HI and HBr, Chem. Phys. Lett., 1970, 5, 387. [all data]

Chamberlain and Gebbie, 1965
Chamberlain, J.E.; Gebbie, H.A., Sub-millimetre dispersion and rotational line strengths of the hydrogen halides, Nature (London), 1965, 208, 480. [all data]

Notes

Symbols used in this document:

AE	Appearance energy
IE (evaluated)	Recommended ionization energy
S°_gas	Entropy of gas at standard conditions
S°_{gas,1 bar}	Entropy of gas at standard conditions (1 bar)
T	Temperature
T_fus	Fusion (melting) point
d(ln(k_H))/d(1/T)	Temperature dependence parameter for Henry's Law constant
k°_H	Henry's Law constant at 298.15K
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_vapH	Enthalpy of vaporization

Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
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