Thioether
| Thioether |
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| R 1 and R 2 are organyl groups . The functional group is marked in blue . |
Thioethers are organic sulfides , i.e. in chemistry a group of substances with the general structure R 1 −S − R 2 , where R 1 and R 2 are organic radicals . They are the sulfur analogues of ethers . The thioethers derived from alkanes are also known as dialkyl sulfides . Compounds with several sulfur atoms (n> 1) in series, R 1 -S n −R 2 , are called di-, tri- etc. sulfides , e.g. B. Disulfides R 1 −S − S − R 2 . In symmetrical thioethers (R 1 −S − R 1 ) the two organic radicals are the same, in unsymmetrical thioethers (R 1 −S − R 2 ) they are different. In dialkyl sulfides the two organic radicals are alkyl groups , in diaryl sulfides they are aryl groups and in alkyl aryl sulfides, R 1 is an alkyl group and R 2 is an aryl group.
presentation
Thioethers can be synthesized by reacting alkyl halides with (alkali) thiolates , by reducing sulfoxides or sulfones, or by double alkylation of sulfur dichloride . The Asinger reaction can be used to produce heterocyclic sulfides with a sulfur atom and a reactive C = N double bond in the ring.
properties
Chemical properties
Thioethers form salt -like addition compounds with halogens , haloalkanes or metal salts . Their oxidation products are sulfoxides , R 1 -SO-R 2 , and sulfones , R 1 -SO 2 -R 2 .
Physical Properties
Volatile thioethers usually have a very unpleasant odor. The simplest representative of this class of compounds is the highly volatile dimethyl sulfide (boiling point 37 ° C). They are mostly insoluble in water.
Occurrence
The proteinogenic amino acid methionine is a thioether. The dimer of the amino acid cysteine , cystine , contains a disulfide bridge . These bridges are important for the formation of the secondary and tertiary structures of proteins , e.g. B. in keratin .
Dimethyl sulfide is formed e.g. B. in the decomposition of sulfur-containing proteins and is one of the causes of the resulting odor. The gross odor of the stinkhorn , Phallus impudicus , is mainly caused by dimethyl disulfide and trisulfide. The latter two are also important for the smell and taste of various truffles , especially the white truffle , Tuber magnatum . Its most important component in sensory terms, bis (methylthio) methane, CH 2 (SCH 3 ) 2 , can also be referred to as thioether, but should be understood more as a thioacetal of formaldehyde .
The chemical warfare agent mustard gas , bis (2-chloroethyl) sulfide, is also a thioether.
literature
- A simple synthesis of racemic cysteine by Jürgen Martens , Heribert Offermanns and Paul Scherberich: Angewandte Chemie 93, 680 (1981) doi : 10.1002 / ange.19810930808 ; Angewandte Chemie International Edition 20, 668 (1981) doi : 10.1002 / anie.198106681 .
- D- Penicillamin - Production and Properties by Wolfgang M. Weigert, Heribert Offermanns and Paul Scherberich, Angewandte Chemie International Edition 14, 330-336 (1975) doi : 10.1002 / anie.197503301 .
- Amino acids - production and extraction by Bernd Hoppe and Jürgen Martens, Chemie in our time 18, 73−86 (1984) doi : 10.1002 / ciuz.19840180302 .