Hydrogen iodide

• Formula: HI
• Molecular weight: 127.91241
• IUPAC Standard InChI: InChI=1S/HI/h1H Copy

  
• IUPAC Standard InChIKey: XMBWDFGMSWQBCA-UHFFFAOYSA-N Copy
• CAS Registry Number: 10034-85-2
• 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.
• Permanent link for this species. Use this link for bookmarking this species for future reference.
• Information on this page:
  • Gas phase thermochemistry data
  • Reaction thermochemistry data
  • Gas phase ion energetics data
  • Ion clustering data
  • References
  • Notes
• Other data available:
  • Phase change data
  • Henry's Law data
  • Constants of diatomic molecules
• Data at other public NIST sites:
  • Microwave spectra (on physics lab web site)
  • Gas Phase Kinetics Database
• Options:
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Gas phase thermochemistry data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

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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Reaction thermochemistry data

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Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

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

 +  = ( • )

By formula: I^- + HI = (I^- • HI)

Bond type: Hydrogen bond (negative ion to hydride)

Free energy of reaction

 +  =

By formula: I^- + H⁺ = HI

 +  =  + 

By formula: HI + C₃H₅I = C₃H₆ + I₂

 +  =  + 

By formula: HI + CH₃I = CH₄ + I₂

 (l) +  (cr) =  (g) +  (cr)

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

 +  =  + 

By formula: C₂H₃IO + H₂O = HI + C₂H₄O₂

=  + 

By formula: C₄H₉I = HI + C₄H₈

 +  =  + 

By formula: HI + C₆H₁₁I = C₆H₁₂ + I₂

 +  =  + 

By formula: C₂H₃F₃ + I₂ = HI + C₂H₂F₃I

 +  =  + 

By formula: C₇H₉NO + C₇H₅IO = HI + C₁₄H₁₃NO₂

 +  =  + 

By formula: C₇H₉N + C₇H₅IO = HI + C₁₄H₁₃NO

 +  =  + 

By formula: C₇H₅IO + C₆H₇N = HI + C₁₃H₁₁NO

 (cr) +  (solution) =  (solution) + C₈H₅IO₃W (solution)

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

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

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

2 +  = 2 + 

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

2 +  = 2 + 

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

 +  = 2 + 

By formula: C₄H₁₀S₂ + I₂ = 2HI + C₄H₈S₂

 +  = 2 + 

By formula: C₈H₁₆O₂S₂ + I₂ = 2HI + C₈H₁₄O₂S₂

 +  = 2 + 

By formula: C₃H₈S₂ + I₂ = 2HI + C₃H₆S₂

 +  =  + 

By formula: HI + C₇H₇I = C₇H₈ + I₂

 +  =  + 

By formula: C₃H₅I + H₂O = HI + C₃H₆O

 +  =  + 

By formula: C₇H₇I + H₂O = HI + C₇H₈O

 +  =  + 

By formula: C₇H₅IO + H₂O = HI + C₇H₆O₂

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

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

 +  =  + 

By formula: HI + CH₃IS = CH₄S + I₂

 +  =  + 

By formula: C₃H₆O + I₂ = HI + C₃H₅IO

 +  =  + 

By formula: C₂H₄O + I₂ = HI + C₂H₃IO

 +  =  + 

By formula: HI + C₇H₇IO = C₇H₈O + I₂

 +  =  + 

By formula: HI + C₂H₅IS = C₂H₆S + I₂

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

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

 +  =  + 

By formula: HI + C₇H₅IO = C₇H₆O + I₂

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

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

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

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

 +  =  + 

By formula: C₂H₄F₂ + I₂ = HI + C₂H₃BrF₂

 +  =  + 

By formula: C₇H₆O + I₂ = HI + C₇H₅IO

 +  =  + 

By formula: HI + C₆H₅I = C₆H₆ + I₂

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

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

 (g) +  (g) =  (g) +  (g)

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

 +  = 2 + 

By formula: C₅H₁₀ + I₂ = 2HI + C₅H₈

 +  =  + 

By formula: HI + C₄H₇IO = I₂ + C₄H₈O

2 +  =  + 

By formula: 2HI + C₅H₆ = C₅H₈ + I₂

 +  =

By formula: HI + C₃H₆ = C₃H₇I

 (g) + C₃H₁₀Ge (g) = C₃H₉Ge (g) +  (g)

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

Gas phase ion energetics data

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

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

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)

Ionization energy determinations

Appearance energy determinations

De-protonation reactions

 +  =

By formula: I^- + H⁺ = HI

Ion clustering data

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

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

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

 +  = ( • )

By formula: I^- + HI = (I^- • HI)

Bond type: Hydrogen bond (negative ion to hydride)

Free energy of reaction

References

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

Data compilation copyright by the U.S. Secretary of Commerce on behalf of the U.S.A. All rights reserved.

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

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

Caldwell and Kebarle, 1985
Caldwell, G.; Kebarle, P., The hydrogen bond energies of the bihalide ions XHX- and YHX-, Can. J. Chem., 1985, 63, 1399. [all data]

Pelaez, Blondel, et al., 2009
Pelaez, R.J.; Blondel, C.; Delsart, C.; Drag, C., Pulsed photodetachment microscopy and the electron affinity of iodine, J. Phys. B: Atom. Mol. Opt. Phys., 2009, 42, 12, 125001, https://doi.org/10.1088/0953-4075/42/12/125001 . [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]

Rodgers, Golden, et al., 1966
Rodgers, A.S.; Golden, D.M.; Benson, S.W., The thermochemistry of the gas phase equilibrium I₂ + C₃H₆ = C₃H₅I + HI, J. Am. Chem. Soc., 1966, 88, 3194-3196. [all data]

Cox and Pilcher, 1970
Cox, J.D.; Pilcher, G., Thermochemistry of Organic and Organometallic Compounds, Academic Press, New York, 1970, 1-636. [all data]

Golden, Walsh, et al., 1965
Golden, D.M.; Walsh, R.; Benson, S.W., The thermochemistry of the gas phase equilibrium I₂ + CH₄ «=» CH₃I + HI and the heat of formation of the methyl radical, J. Am. Chem. Soc., 1965, 87, 4053-4057. [all data]

Goy and Pritchard, 1965
Goy, C.A.; Pritchard, H.O., Kinetics and thermodynamics of the reaction between iodine and methane and the heat of formation of methyl iodide, J. Phys. Chem., 1965, 69, 3040-3041. [all data]

Nichol and Ubbelohde, 1952
Nichol, R.J.; Ubbelohde, A.R., A thermochemical evaluation of bond strengths in some carbon compounds. part II. Bond strengths based on the reaction CH₃I + HI = CH₄ + I₂, J. Am. Chem. Soc., 1952, 415-421. [all data]

Connor, Zafarani-Moattar, et al., 1982
Connor, J.A.; Zafarani-Moattar, M.T.; Bickerton, J.; El-Saied, N.I.; Suradi, S.; Carson, R.; Al Takkhin, G.; Skinner, H.A., Organomet., 1982, 1, 1166. [all data]

Devore and O'Neal, 1969
Devore, J.A.; O'Neal, H.E., Heats of formation of the acetyl halides and of the acetyl radical, J. Phys. Chem., 1969, 73, 2644-2648. [all data]

Carson and Skinner, 1949
Carson, A.S.; Skinner, H.A., 201. Carbon-halogen bond energies in the acetyl halides, J. Chem. Soc., 1949, 936-939. [all data]

Benson and Amano, 1962
Benson, S.W.; Amano, A., Thermodynamic properties of tertiary iodides, J. Chem. Phys., 1962, 37, 197-198. [all data]

Jones and Ogg, 1937
Jones, J.L.; Ogg, R.A., Jr., The equilibrium (CH₃)₃CI = (CH₃)₂C = CH₂ + HI, J. Am. Chem. Soc., 1937, 59, 1943-1945. [all data]

Brennan and Ubbelohde, 1956
Brennan, D.; Ubbelohde, A.R., A thermochemical evaluation of bond strengths in some carbon compounds. Part IV. Bond-strength differences based on the reaction: RI + HI = RH + I₂, where R = p-methoxyphenyl and cyclohexyl, J. Chem. Soc., 1956, 3011-3016. [all data]

Wu and Rodgers, 1974
Wu, E.; Rodgers, A.S., Thermochemistry of gas-phase equilibrium CF₃CH₃ + I₂ = CF₃CH₂I + HI. The carbon-hydrogen bond dissociation energy in 1,1,1-trifluoroethane and the heat of formation of the 2,2,2-trifluoroethyl radical, J. Phys. Chem., 1974, 78, 2315-2317. [all data]

Kiselev, Khuzyasheva, et al., 1979
Kiselev, V.D.; Khuzyasheva, d.G.; Konovalov, A.I., Thermochemical study of the acylation of para-substituted anilines, J. Gen. Chem. USSR, 1979, 49, 2273-2276. [all data]

Landrum and Hoff, 1985
Landrum, J.T.; Hoff, C.D., J. Organometal. Chem., 1985, 282, 215. [all data]

Sunner, 1955
Sunner, S., Strain in 6,8-thioctic acid, Nature (London), 1955, 176, 217. [all data]

Graham, Nichol, et al., 1955
Graham, W.S.; Nichol, R.J.; Ubbelohde, A.R., A thermochemical evaluation of bond strengths in some carbon compounds. Part III. Bond strengths based on the reactions: (a) Ph·CH₂I + HI=Ph·CH₃ + I₂ and (b) PhI + HI=PhH + I₂, J. Chem. Soc., 1955, 115-121. [all data]

Gellner and Skinner, 1949
Gellner, O.H.; Skinner, H.A., Dissociation energies of carbon-halogen bonds. The bond strengths allyl-X and benzyl-X, J. Chem. Soc., 1949, 1145-1148. [all data]

Carson, Pritchard, et al., 1950
Carson, A.S.; Pritchard, H.O.; Skinner, H.A., The heats of hydrolysis of the benzoyl halides, J. Chem. Soc., 1950, 656-659. [all data]

Baldwin, Lappert, et al., 1972
Baldwin, J.C.; Lappert, M.F.; Pedley, J.B.; Poland, J.S., J. Chem. Soc., Dalton Trans., 1972, 1943.. [all data]

Shum and Benson, 1983
Shum, L.G.S.; Benson, S.W., Thermochemnistry and kinetics of the reaction of methyl mercaptan with iodine, Int. J. Chem. Kinet., 1983, 15, 433-453. [all data]

Solly, Golden, et al., 1970
Solly, R.K.; Golden, D.M.; Benson, S.W., Thermochemical properties of iodoacetone. Intramolecular electrostatic interactions in polar molecules, J. Am. Chem. Soc., 1970, 92, 4653-4656. [all data]

Walsh and Benson, 1966
Walsh, R.; Benson, S.W., The heats of formation of acetyl iodide and the acetyl radical, J. Phys. Chem., 1966, 70, 3751-3753. [all data]

Shum and Benson, 1985
Shum, L.G.S.; Benson, S.W., Iodine catalyzed pyrolysis of dimethyl sulfide. Heats of formaton of CH₃SCH₂I, the CH₃SCH₂ radical, and the pibond energy in CH₂S, Int. J. Chem. Kinet., 1985, 17, 277-292. [all data]

Calado, Dias, et al., 1979
Calado, J.C.G.; Dias, A.R.; Martinho Simões, J.A.; Ribeiro da Silva, M.A.V., Rev. Port. Quím., 1979, 21, 129. [all data]

Solly and Benson, 1971
Solly, R.K.; Benson, S.W., Thermochemistry of the reaction of benzaldehyde with iodine. The enthalpy of formation of benzaldehyde and benzoyl iodide, J. Chem. Thermodyn., 1971, 3, 203-209. [all data]

Diogo, Simoni, et al., 1993
Diogo, H.P.; Simoni, J.A.; Minas da Piedade, M.E.; Dias, A.R.; Martinho Simões, J.A., J. Am. Chem. Soc., 1993, 115, 2764. [all data]

Pickard and Rodgers, 1977
Pickard, J.M.; Rodgers, A.S., The kinetics and thermochemistry of the reaction of 1,1-difluoroethane with iodine. The difluoromethylene-hydrogen bond dissociation energy in 1,1-difluoroethane and the heat of formation of 1,1-difluoroethyl, J. Am. Chem. Soc., 1977, 99, 691-694. [all data]

Calhorda, Dias, et al., 1987
Calhorda, M.J.; Dias, A.R.; Minas da Piedade M.E.; Salema, M.S.; Martinho Simões J.A., Organometallics, 1987, 6, 734. [all data]

Noble and Walsh, 1983
Noble, P.N.; Walsh, R., Kinetics of the gas phase reaction between iodine and monogermane and the bond dissociation energy D(H₃Ge-H), Int. J. Chem. Kinet., 1983, 15, 547. [all data]

Furuyama, Golden, et al., 1970
Furuyama, S.; Golden, D.M.; Benson, S.W., Thermochemistry of cyclopentene and cyclopentadiene from studies of gas-phase equilibria, J. Chem. Thermodyn., 1970, 2, 161-169. [all data]

Solly, Golden, et al., 1970, 2
Solly, R.K.; Golden, D.M.; Benson, S.W., Kinetics and thermochemistry of the gas phase reaction of methyl ethyl ketone with iodine. II. The heat of formation and unimolecular decomposition of 2-iodo-3-butanone, Int. J. Chem. Kinet., 1970, 2, 393-407. [all data]

Furuyama, Golden, et al., 1969
Furuyama, S.; Golden, D.M.; Benson, S.W., Thermochemistry of the gas phase equilibria i-C₃H₇I = C₃H₆ + HI, n-C₃H₇I = i-C₃H₇I, and C₃H₆ + 2HI = C₃H₈ + I₂, J. Chem. Thermodyn., 1969, 1, 363-375. [all data]

Doncaster and Walsh, 1979
Doncaster, A.M.; Walsh, R., J. Phys. Chem., 1979, 83, 578. [all data]

Hunter and Lias, 1998
Hunter, E.P.; Lias, S.G., Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update, J. Phys. Chem. Ref. Data, 1998, 27, 3, 413-656, https://doi.org/10.1063/1.556018 . [all data]

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

Eland and Berkowitz, 1977
Eland, J.H.D.; Berkowitz, J., Photoionization mass spectrometry of HI and DI at high resolution, J. Chem. Phys., 1977, 67, 5034. [all data]

Lempka, Passmore, et al., 1968
Lempka, H.J.; Passmore, T.R.; Price, W.C., The photoelectron spectra and ionized states of the halogen acids, Proc. Roy. Soc. (London), 1968, A304, 53. [all data]

Frost, McDowell, et al., 1967
Frost, D.C.; McDowell, C.A.; Vroom, D.A., Photoelectron spectra of the halogens and the hydrogen halides, J. Chem. Phys., 1967, 46, 4255. [all data]

Watanabe, 1957
Watanabe, K., Ionization potentials of some molecules, J. Chem. Phys., 1957, 26, 542. [all data]

Friedman, 1955
Friedman, L., Mass spectrum of lithium iodide, J. Chem. Phys., 1955, 23, 477. [all data]

Price, 1938
Price, W.C., The absorption spectra of the halogen acids in the vacuum ultra-violet, Proc. Roy. Soc. (London), 1938, A167, 216. [all data]

Notes

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

• 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
  ΔfH°gas	Enthalpy of formation of gas at standard conditions
  ΔrG°	Free energy of reaction at standard conditions
  ΔrH°	Enthalpy of reaction at standard conditions
  ΔrS°	Entropy of reaction at standard conditions

• Data from NIST Standard Reference Database 69: NIST Chemistry WebBook
• The National Institute of Standards and Technology (NIST) uses its best efforts to deliver a high quality copy of the Database and to verify that the data contained therein have been selected on the basis of sound scientific judgment. However, NIST makes no warranties to that effect, and NIST shall not be liable for any damage that may result from errors or omissions in the Database.
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