Rodanic acid

Rodanic acid
Rodanic acid
	Rodovodorodnaya acid, Thiocyanic acid.png
Are common
Traditional names	thiocyanic acid, rhodium hydrogen
Chem. formula	HNCS
Physical properties
Molar mass	59.0917 g / mol
Thermal properties
T. melt.	−110 ° C
T.	−90 ° C
Mol heat capacity	48.16 J / (mol · K)
Education enthalpy	104.6 kJ / mol
Chemical properties
Water solubility	dissolves
Classification
Reg. CAS number	463-56-9
Pubchem
Reg. EINECS number
SMILES
Inchi
CHEBI
Chemspider

Rodovodorodnaya (thiocyanic) acid - a yellowish, oily, sharp-smelling liquid . Chemical formula HNCS ^[1] .

Content

Build

Earlier, it was widely believed that thiocyanic acid is a mixture of two tautomers:

{\mathsf {H{-}S{-}C\equiv N\rightleftarrows H{-}N{=}C{\text{=}}S}}

{\ displaystyle {\ mathsf {H {-} S {-} C \ equiv N \ rightleftarrows H {-} N {=} C {\ text {=}} S}}}

but later it turned out that the acid has the structure of HNCS. The alkali metal and ammonium thiocyanates have the formula Me ⁺ NCS ^- , the formula Me (SCN) _x is possible for other thiocyanates.

Physical and chemical properties

Hydrogenic acid is stable only at low temperatures (about –90 ° C) or in dilute aqueous solutions (less than 5%). It is a strong acid - its solutions are almost completely dissociated. It is well soluble in water and a number of organic solvents ( ethanol , diethyl ether , benzene ).

In the range from –90 ° C to –85 ° C, it polymerizes to a colorless crystalline mass. With weak heating in vacuum , rhodanuric acid (HNCS) _{3 is formed} , which passes back to HNCS at 3-5 ° C. Density = 2.04 g / cm ³ .

Aqueous solutions are stable up to 5% concentration, in more concentrated solutions decomposes, turning into so-called. Xanthogen hydrogen and a number of other products.

Reacts with alkali metals . It is reduced by zinc in hydrochloric acid to methylamine and 1,3,5-trithiane ( thioformaldehyde trimer).

{\mathsf {10Zn+20HCl+8HNCS\rightarrow 3(HCSH)_{3}+2CH_{3}NH_{2}+10ZnCl_{2}}}

{\ displaystyle {\ mathsf {10Zn + 20HCl + 8HNCS \ rightarrow 3 (HCSH) _ {3} + 2CH_ {3} NH_ {2} + 10ZnCl_ {2}}}}

It is oxidized with potassium permanganate to sulfuric acid, hydrogen peroxide to hydrocyanic acid , bromine to bromine cyanide .

{\mathsf {2HNCS+2KMnO_{4}\rightarrow H_{2}SO_{4}+2MnO_{2}\downarrow +2KCNO+S\downarrow }}

{\ displaystyle {\ mathsf {2HNCS + 2KMnO_ {4} \ rightarrow H_ {2} SO_ {4} + 2MnO_ {2} \ downarrow + 2KCNO + S \ downarrow}}}

{\mathsf {2HNCS+2KMnO_{4}\rightarrow H_{2}SO_{4}+2MnO_{2}\downarrow +2KCN+SO_{2}\uparrow }}

{\ displaystyle {\ mathsf {2HNCS + 2KMnO_ {4} \ rightarrow H_ {2} SO_ {4} + 2MnO_ {2} \ downarrow + 2KCN + SO_ {2} \ uparrow}}}

{\mathsf {2HSCN+Br_{2}\rightarrow 2BrCN+H_{2}S_{2}\uparrow }}

{\ displaystyle {\ mathsf {2HSCN + Br_ {2} \ rightarrow 2BrCN + H_ {2} S_ {2} \ uparrow}}}

Slow oxidation leads to rodan (SCN) ₂ . Hydrogen sulfide decomposes to carbon disulfide and ammonia . Attaches to unsaturated compounds. Salts of this acid are called thiocyanates .

{\mathsf {H_{2}S+HNCS\rightarrow CS_{2}\uparrow +NH_{3}\uparrow }}

{\ displaystyle {\ mathsf {H_ {2} S + HNCS \ rightarrow CS_ {2} \ uparrow + NH_ {3} \ uparrow}}}

The formation of blood-red thiocyanate-ion complexes with the Fe ³⁺ ion is one of the qualitative reactions to iron.

Application

Practical use is found only for the salts of hydrocyanic acid, as well as its esters , used as insecticides and fungicides .

Notes

↑ Chemical encyclopedia / Redcol .: Knunyants I.L. et al. - M .: Soviet Encyclopedia, 1995. - Vol. 4 (Paul-Three). - 639 s. - ISBN 5-82270-092-4 .

Literature

Chemical Encyclopedia / Redkol .: Knunyants I.L. et al. - M .: Soviet Encyclopedia, 1995. - Vol. 4 (Paul-Three). - 639 s. - ISBN 5-82270-092-4 .

[1] Chemical encyclopedia / Redcol .: Knunyants I.L. et al. - M .: Soviet Encyclopedia, 1995. - Vol. 4 (Paul-Three). - 639 s. - ISBN 5-82270-092-4 .