Organic Sulfites

Organic sulfites are organosulfur compounds , sulfuric acid esters with the general formula ROS (O) OR ', where R, R' are hydrocarbon radicals.

Content

Nomenclature

Organic sulfites can be symmetric (RO) ₂ SO, asymmetric ROS (O) OR ', cyclic. Their name is determined by the names of the corresponding hydrocarbon radicals and the term “-sulfite”:

${\mathsf {(CH_{3}O)_{2}SO}}$ ${\ displaystyle {\ mathsf {(CH_ {3} O) _ {2} SO}}}$ - dimethyl sulfite
${\mathsf {CH_{3}OS(O)OC_{2}H_{5}}}$ ${\ displaystyle {\ mathsf {CH_ {3} OS (O) OC_ {2} H_ {5}}}}$ - methyl ethyl sulfite

Cyclic sulfites are called on a carbon chain in a cycle:

- ethylene sulfite

- phenylene sulfite

Physical and chemical properties

Lower organic sulfites are liquids with a pungent odor and tear effect. Higher sulfites are viscous oily liquids, cyclic sulfites are solid fusible substances.

The sulfite group has a tetrahedral structure, the sulfur atom is located at one of the vertices of the tetrahedron. In the IR spectra of sulfites, a characteristic absorption band is found in the region of 1200 and 1245 cm ^-1 , which is related to stretching vibrations of the S = O bond.

Organic sulfites are hydrolyzed under the action of acids and bases with the breaking of the SO bond, while cyclic and aromatic sulfites hydrolyze faster.

During the oxidation of sulfites, the corresponding sulfates are formed:

{\mathsf {(CH_{3}O)_{2}SO{\xrightarrow[{}]{KMnO_{4}}}(CH_{3}O)_{2}SO_{2}}}

{\ displaystyle {\ mathsf {(CH_ {3} O) _ {2} SO {\ xrightarrow [{}] {KMnO_ {4}}} (CH_ {3} O) _ {2} SO_ {2}}} }

When interacting with halogens ( chlorine , bromine ), sulfites break the SO bond with the formation of an alkyl halide and an alkyl halosulfonate:

{\mathsf {(CH_{3}O)_{2}SO+Cl_{2}\rightarrow CH_{3}OSO_{2}Cl+CH_{3}Cl}}

{\ displaystyle {\ mathsf {(CH_ {3} O) _ {2} SO + Cl_ {2} \ rightarrow CH_ {3} OSO_ {2} Cl + CH_ {3} Cl}}}

Under the action of primary and secondary alcohols (but not tertiary) in the presence of acids or bases, organic sulfites are capable of transesterification:

{\mathsf {(CH_{3}O)_{2}SO+2C_{2}H_{5}OH\rightarrow (C_{2}H_{5}O)_{S}O+2CH_{3}OH}}

{\ displaystyle {\ mathsf {(CH_ {3} O) _ {2} SO + 2C_ {2} H_ {5} OH \ rightarrow (C_ {2} H_ {5} O) _ {S} O + 2CH_ { 3} OH}}}

Sulfites act as alkylating agents:

{\mathsf {(CH_{3})_{3}COH+(CH_{3}O)_{2}SO\rightarrow (CH_{3})_{3}COCH_{3}+CH_{3}OH+SO_{2}}}

{\ displaystyle {\ mathsf {(CH_ {3}) _ {3} COH + (CH_ {3} O) _ {2} SO \ rightarrow (CH_ {3}) _ {3} COCH_ {3} + CH_ {3 } OH + SO_ {2}}}}

The interaction of dialkyl sulfites with selenium dioxide leads to dialkyl selenites:

{\mathsf {(RO)_{2}SO+SeO_{2}\rightarrow (RO)_{2}SeO+SO_{2}}}

{\ displaystyle {\ mathsf {(RO) _ {2} SO + SeO_ {2} \ rightarrow (RO) _ {2} SeO + SO_ {2}}}}

Receiving and applying

The synthesis of organic sulfites is carried out by the reaction of alcohols with thionyl chloride in a pyridine medium:

{\mathsf {ROH{\xrightarrow[{C_{6}H_{5}N}]{+SOCl_{2},-HCl}}ROSOCl{\xrightarrow[{C_{6}H_{5}N}]{+SOCl_{2},-HCl}}(RO)_{2}SO}}

{\ displaystyle {\ mathsf {ROH {\ xrightarrow [{C_ {6} H_ {5} N}] {+ SOCl_ {2}, - HCl}} ROSOCl {\ xrightarrow [{C_ {6} H_ {5} N }] {+ SOCl_ {2}, - HCl}} (RO) _ {2} SO}}}

Instead of thionyl chloride, a solution of sulfur dioxide in pyridine in the presence of bromine or iodine can be used. Methylalkyl sulfites can be prepared by reacting diazomethane with a solution of sulfur dioxide in the corresponding alcohol. A number of organic sulfites are synthesized by transesterification reaction.

Alkyl and aryl sulfites are used as insecticides and biocides .

Literature

Chemical Encyclopedia / Editorial Board: Knunyants I.L. et al. - M .: Soviet Encyclopedia, 1995. - T. 4 (Half-Three). - 639 p. - ISBN 5-82270-092-4 .