Selected ATcT [1, 2] enthalpy of formation based on version 1.172 of the Thermochemical Network [3]

This version of ATcT results[3] was generated by additional expansion of version 1.156 to include species relevant to a study of photodissociation of formamide[4].

Diiodine

Formula: I2 (g)

CAS RN: 7553-56-2

ATcT ID: 7553-56-2*0

SMILES: II

InChI: InChI=1S/I2/c1-2

InChIKey: PNDPGZBMCMUPRI-UHFFFAOYSA-N

Hills Formula: I2

2D Image:

Aliases: I2; Diiodine; Iodine molecule; Iodine; Molecular iodine; Diatomic iodine

Relative Molecular Mass: 253.808940 ± 0.000060

Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units
65.497	62.417	± 0.0041	kJ/mol

3D Image of I2 (g)

spin ON spin OFF

Top contributors to the provenance of Δ_fH° of I2 (g)

The 5 contributors listed below account for 93.3% of the provenance of Δ_fH° of I2 (g).

Please note: The list is limited to 20 most important contributors or, if less, a number sufficient to account for 90% of the provenance. The Reference acts as a further link to the relevant references and notes for the measurement. The Measured Quantity is normaly given in the original units; in cases where we have reinterpreted the original measurement, the listed value may differ from that given by the authors. The quoted uncertainty is the a priori uncertainty used as input when constructing the initial Thermochemical Network, and corresponds either to the value proposed by the original authors or to our estimate; if an additional multiplier is given in parentheses immediately after the prior uncertainty, it corresponds to the factor by which the prior uncertainty needed to be multiplied during the ATcT analysis in order to make that particular measurement consistent with the prevailing knowledge contained in the Thermochemical Network.

Contribution (%)	TN ID	Reaction	Measured Quantity	Reference
21.8	1271.2	I2 (cr,l) → I2 (g)	Δ_rG°(298.15 K) = 4.616 ± 0.002 kcal/mol	Giauque 1931, Baxter 1915, Baxter 1907, 3rd Law, est unc
21.8	1271.4	I2 (cr,l) → I2 (g)	Δ_rG°(298.15 K) = 4.618 ± 0.002 kcal/mol	Gerry 1932, Giauque 1931, 3rd Law, est unc
21.8	1276.6	I2 (cr,l) → I2 (g)	Δ_rH°(298.15 K) = 14.919 ± 0.002 kcal/mol	Shirley 1959, Baxter 1907, Baxter 1915, 2nd Law
21.8	1276.8	I2 (cr,l) → I2 (g)	Δ_rH°(325.8 K) = 14.799 ± 0.002 kcal/mol	Shirley 1959, Baxter 1907, Baxter 1915, 2nd Law
5.9	1270.8	I2 (cr,l) → I2 (g)	Δ_rG°(298.15 K) = 4.614 ± 0.002 (×1.915) kcal/mol	Baxter 1915, Baxter 1907, 3rd Law

Top 10 species with enthalpies of formation correlated to the Δ_fH° of I2 (g)

Please note: The correlation coefficients are obtained by renormalizing the off-diagonal elements of the covariance matrix by the corresponding variances.
The correlation coefficient is a number from -1 to 1, with 1 representing perfectly correlated species, -1 representing perfectly anti-correlated species, and 0 representing perfectly uncorrelated species.

Correlation Coefficent (%)	Species Name	Formula	Δ_fH°(0 K)	Δ_fH°(298.15 K)	Uncertainty	Units	Relative Molecular Mass	ATcT ID
99.9	Iodine	I (g, 2P3/2)	107.157	106.757	± 0.0021	kJ/mol	126.904470 ± 0.000030	14362-44-8*1
99.9	Iodine	I (g, 2P1/2)	198.109	197.709	± 0.0021	kJ/mol	126.904470 ± 0.000030	14362-44-8*2
99.9	Iodine	I (g)	107.157	106.757	± 0.0021	kJ/mol	126.904470 ± 0.000030	14362-44-8*0
98.5	Iodide	I- (g)	-187.996	-188.396	± 0.0021	kJ/mol	126.905019 ± 0.000030	20461-54-5*0
31.1	Iodine cation	I+ (g)	1115.549	1115.149	± 0.0062	kJ/mol	126.903921 ± 0.000030	22541-93-1*0
22.5	Diiodine cation	[I2]+ (g)	963.523	960.408	± 0.018	kJ/mol	253.808391 ± 0.000060	28712-14-3*0
16.1	Iodine monochloride	ICl (g)	19.024	17.391	± 0.013	kJ/mol	162.35717 ± 0.00090	7790-99-0*0
5.5	Hydrogen iodide	HI (g)	28.645	26.470	± 0.036	kJ/mol	127.912410 ± 0.000076	10034-85-2*0
4.7	Diiodine	I2 (aq, undissoc)		23.243	± 0.082	kJ/mol	253.808940 ± 0.000060	7553-56-2*1000
3.1	Iodine monochloride	ICl (cr)	-36.511	-35.537	± 0.063	kJ/mol	162.35717 ± 0.00090	7790-99-0*510

Most Influential reactions involving I2 (g)

Please note: The list, which is based on a hat (projection) matrix analysis, is limited to no more than 20 largest influences.

Influence Coefficient	TN ID	Reaction	Measured Quantity	Reference
0.958	1280.1	[I2]- (g) → I2 (g)	Δ_rH°(0 K) = 2.524 ± 0.005 eV	Zanni 1997
0.924	6313.1	CF3Br (g) + I2 (g) → CF3I (g) + IBr (g)	Δ_rH°(298.15 K) = 9.55 ± 0.06 kcal/mol	Lord 1967, as quoted by Cox 1970
0.780	1297.1	2 HI (g) → H2 (g) + I2 (g)	Δ_rG°(721.5 K) = 23.625 ± 0.080 kJ/mol	Taylor 1941, 3rd Law
0.671	1277.1	I2 (g) → I2 (aq, undissoc)	Δ_rG°(298.15 K) = -2.727 ± 0.10 kJ/mol	Sanemasa 1984
0.598	7564.1	CHICHI (g, cis) → HCCH (g) + I2 (g)	Δ_rG°(600 K) = 0.60 ± 0.10 kcal/mol	Furuyama 1968
0.598	7565.1	CHICHI (g, trans) → HCCH (g) + I2 (g)	Δ_rG°(600 K) = 1.26 ± 0.10 kcal/mol	Furuyama 1968
0.498	1279.2	I2 (g) → [I2]+ (g)	Δ_rH°(0 K) = 75069 ± 2 cm-1	Cockett 1996
0.498	1279.1	I2 (g) → [I2]+ (g)	Δ_rH°(0 K) = 75069 ± 2 cm-1	Cockett 1995
0.446	1290.9	I2 (g) → I (g, 2P3/2) + I (g, 2P1/2)	Δ_rH°(0 K) = 20043.176 ± 0.016 cm-1	Gerstenkorn 1983
0.317	1352.1	[I3]- (g) → I2 (g) + I- (g)	Δ_rH°(0 K) = 126 ± 6 kJ/mol	Do 1997
0.316	1290.11	I2 (g) → I (g, 2P3/2) + I (g, 2P1/2)	Δ_rH°(0 K) = 20043.159 ± 0.019 cm-1	Tromp 1983
0.239	1351.1	[I3]+ (g) → I2 (g) + I+ (g)	Δ_rH°(298.15 K) = 56.8 ± 2 kcal/mol	Thanthiriwatte 2014, est unc
0.218	1271.4	I2 (cr,l) → I2 (g)	Δ_rG°(298.15 K) = 4.618 ± 0.002 kcal/mol	Gerry 1932, Giauque 1931, 3rd Law, est unc
0.218	1271.2	I2 (cr,l) → I2 (g)	Δ_rG°(298.15 K) = 4.616 ± 0.002 kcal/mol	Giauque 1931, Baxter 1915, Baxter 1907, 3rd Law, est unc
0.218	1276.8	I2 (cr,l) → I2 (g)	Δ_rH°(325.8 K) = 14.799 ± 0.002 kcal/mol	Shirley 1959, Baxter 1907, Baxter 1915, 2nd Law
0.218	1276.6	I2 (cr,l) → I2 (g)	Δ_rH°(298.15 K) = 14.919 ± 0.002 kcal/mol	Shirley 1959, Baxter 1907, Baxter 1915, 2nd Law
0.163	1352.2	[I3]- (g) → I2 (g) + I- (g)	Δ_rH°(298.15 K) = 32.0 ± 2 kcal/mol	Thanthiriwatte 2014, est unc
0.130	6311.1	CHF3 (g) + I2 (g) → CF3I (g) + HI (g)	Δ_rH°(298.15 K) = 17.10 ± 0.34 kcal/mol	Goy 1967, as quoted by Cox 1970
0.113	1298.1	HI (g) → 1/2 H2 (g) + 1/2 I2 (g)	Δ_rG°(704 K) = 11.571 ± 0.028 (×3.748) kJ/mol	Rittenberg 1934, note HI, 3rd Law
0.107	1277.5	I2 (g) → I2 (aq, undissoc)	Δ_rG°(298.15 K) = -2.699 ± 0.25 kJ/mol	Palmer 1985, Sander 2023, NIST WebBook, est unc

References

1		B. Ruscic, R. E. Pinzon, M. L. Morton, G. von Laszewski, S. Bittner, S. G. Nijsure, K. A. Amin, M. Minkoff, and A. F. Wagner, Introduction to Active Thermochemical Tables: Several "Key" Enthalpies of Formation Revisited. J. Phys. Chem. A 108, 9979-9997 (2004) [DOI: 10.1021/jp047912y]
2		B. Ruscic, R. E. Pinzon, G. von Laszewski, D. Kodeboyina, A. Burcat, D. Leahy, D. Montoya, and A. F. Wagner, Active Thermochemical Tables: Thermochemistry for the 21^st Century. J. Phys. Conf. Ser. 16, 561-570 (2005) [DOI: 10.1088/1742-6596/16/1/078]
3		B. Ruscic and D. H. Bross, Active Thermochemical Tables (ATcT) values based on ver. 1.172 of the Thermochemical Network (2024); available at ATcT.anl.gov
4		K. L. Caster, N. A. Seifert, B. Ruscic, A. W. Jasper, and K. Prozument, Dynamics of HCN, NHC, and HNCO Formation in the 193 nm Photodissociation of Formamide J. Phys. Chem. A (in press) (2024) [DOI: 10.1021/acs.jpca.4c02232]
5		B. Ruscic, Uncertainty Quantification in Thermochemistry, Benchmarking Electronic Structure Computations, and Active Thermochemical Tables. Int. J. Quantum Chem. 114, 1097-1101 (2014) [DOI: 10.1002/qua.24605]
6		B. Ruscic and D. H. Bross, Thermochemistry Computer Aided Chem. Eng. 45, 3-114 (2019) [DOI: 10.1016/B978-0-444-64087-1.00001-2]

Formula

The aggregate state is given in parentheses following the formula, such as: g - gas-phase, cr - crystal, l - liquid, etc.

Uncertainties

The listed uncertainties correspond to estimated 95% confidence limits, as customary in thermochemistry (see, for example, Ruscic [5] and Ruscic and Bross[6]).
Note that an uncertainty of ± 0.000 kJ/mol indicates that the estimated uncertainty is < ± 0.000₅ kJ/mol.

Website Functionality Credits

The reorganization of the website was developed and implemented by David H. Bross (ANL).
The find function is based on the complete Species Dictionary entries for the appropriate version of the ATcT TN.
The molecule images are rendered by Indigo-depict.
The XYZ renderings are based on Jmol: an open-source Java viewer for chemical structures in 3D. http://www.jmol.org/.

Acknowledgement

This work was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences under Contract No. DE-AC02-06CH11357.