Thioformic acid

{{Chembox

| ImageFile = Thioformic acid.svg

| ImageSize = 120px

| ImageAlt =

| IUPACName = Methanethioic S-acid

| OtherNames = Monothioformic acid

| Section1 = {{Chembox Identifiers

| CASNo = 16890-80-5

| ChemSpiderID = 452997

| PubChem = 519335

| SMILES = C(=O)S

| SMILES1 = S=CO

| InChI = 1S/CH2OS/c2-1-3/h1H,(H,2,3)

| InChIKey = AWIJRPNMLHPLNC-UHFFFAOYSA-N

}}

| Section2 = {{Chembox Properties

| C = 1 | H = 2 | O = 1 | S = 1

| Appearance =

| Density =

| MeltingPt =

| BoilingPtC = 86

| BoilingPt_ref = {{Cite journal | title = Antituberculous sulfur compounds. III. Substituted propylene sulfides | author = Adams, E. P.; Ayad, K. N.; Doyle, F. P.; Holland, D. O.; Hunter, W. H.; Nayler, J. H. C.; Queen, A. | journal = Journal of the Chemical Society | date = 1960 | pages = 2665–2673 | doi = 10.1039/jr9600002665 }}

| Solubility =

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| Section3 = {{Chembox Hazards

| MainHazards =

| FlashPt =

| AutoignitionPt =

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Thioformic acid is a chemical compound with the molecular formula {{chem2|CH2OS}}. As the simplest thiocarboxylic acid,{{cite journal | doi = 10.1021/acs.jpca.2c06860 | title = Formation of Thioformic Acid (HCOSH)─The Simplest Thioacid─in Interstellar Ice Analogues | date = 2022 | last1 = Wang | first1 = Jia | last2 = Marks | first2 = Joshua H. | last3 = Tuli | first3 = Lotefa B. | last4 = Mebel | first4 = Alexander M. | last5 = Azyazov | first5 = Valeriy N. | last6 = Kaiser | first6 = Ralf I. | journal = The Journal of Physical Chemistry A | volume = 126 | issue = 51 | pages = 9699–9708 | pmid = 36534075 | bibcode = 2022JPCA..126.9699W }} it has been the subject of studies on its properties which may be extrapolated to more complex thiocarboxylic acids.{{Cite journal | doi = 10.1016/0022-2860(90)80122-Z | title = Comment on the geometries of cis and trans thioformic and formic acids | date = 1990 | last1 = Williams | first1 = Gwilym A. | last2 = MacDonald | first2 = John N. | last3 = Boggs | first3 = James E. | journal = Journal of Molecular Structure | volume = 220 | issue = 1–2 | pages = 321–326 | bibcode = 1990JMoSt.220..321W }}{{Cite journal | doi = 10.1016/0166-1280(89)87062-9 | title = Ab initio SCF studies on thioformic acid: Basis-set effects | date = 1989 | last1 = Raaska | first1 = T. | journal = Journal of Molecular Structure: Theochem | volume = 201 | issue = 1–2 | pages = 59–67 }}{{Cite journal | doi = 10.1051/0004-6361/202142287 | title = The trans/Cis ratio of formic (HCOOH) and thioformic (HC(O)SH) acids in the interstellar medium | date = 2022 | last1 = García de la Concepción | first1 = J. | last2 = Colzi | first2 = L. | last3 = Jiménez-Serra | first3 = I. | last4 = Molpeceres | first4 = G. | last5 = Corchado | first5 = J. C. | last6 = Rivilla | first6 = V. M. | last7 = Martín-Pintado | first7 = J. | last8 = Beltrán | first8 = M. T. | last9 = Mininni | first9 = C. | journal = Astronomy & Astrophysics | volume = 658 | pages = A150 | arxiv = 2111.10842 | bibcode = 2022A&A...658A.150G }}

Like other thiocarboxylic acids, thioformic acid can occur in either of two tautomers. The ratio of the two is dependent on solvent and other factors.{{Cite journal | doi = 10.1021/jp983298c | title = Thiol−Thione Tautomerism in Thioformic Acid: Importance of Specific Solvent Interactions | date = 1999 | last1 = Delaere | first1 = David | last2 = Raspoet | first2 = Greet | last3 = Nguyen | first3 = Minh Tho | journal = The Journal of Physical Chemistry A | volume = 103 | issue = 1 | pages = 171–177 | bibcode = 1999JPCA..103..171D }}{{Cite journal | doi = 10.1080/00268971003698064 | title = The catalytic effect of water on the keto-enol tautomerisation reaction of thioformic acid | date = 2010 | last1 = Duarte | first1 = Fernanda | last2 = Toro-Labbé | first2 = Alejandro | journal = Molecular Physics | volume = 108 | issue = 10 | pages = 1375–1384 | bibcode = 2010MolPh.108.1375D }}

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Thioformic acid has been detected in the interstellar medium near the giant molecular cloud G+0.693–0.027 and the hot core G31.41+0.31.{{Cite journal | doi = 10.3847/2041-8213/abf7cb | doi-access = free | title = Thiols in the Interstellar Medium: First Detection of HC(O)SH and Confirmation of C₂H₅SH | date = 2021 | last1 = Rodríguez-Almeida | first1 = Lucas F. | last2 = Jiménez-Serra | first2 = Izaskun | last3 = Rivilla | first3 = Víctor M. | last4 = Martín-Pintado | first4 = Jesús | last5 = Zeng | first5 = Shaoshan | last6 = Tercero | first6 = Belén | last7 = De Vicente | first7 = Pablo | last8 = Colzi | first8 = Laura | last9 = Rico-Villas | first9 = Fernando | last10 = Martín | first10 = Sergio | last11 = Requena-Torres | first11 = Miguel A. | journal = The Astrophysical Journal Letters | volume = 912 | issue = 1 | pages = L11 | arxiv = 2104.08036 | bibcode = 2021ApJ...912L..11R }}