 |
Thioether
Totally Explained
|
|  |
|
NEW! |
All the latest news in the worlds of
computer gaming,
entertainment,
the environment,
finance,
health,
politics,
science,
stocks & shares,
technology
and much,
much,
more.
|
Everything about Thioether totally explainedA thioether (similar to sulfide) is a functional group in organic chemistry that has the structure R 1-S-R 2 as shown on right. Like many other sulfur-containing compounds, volatile thioethers characteristically have foul odors.
A thioether is similar to an ether except that it contains a sulfur atom in place of the oxygen. Because oxygen and sulfur belong to the chalcogens group in the periodic table, the chemical properties of ethers and thioethers share some commonalities. This functional group is important in biology, most notably in the amino acid methionine and the cofactor biotin.
Preparation
- Thioethers are typically prepared by the alkylation of thiols: » R-Br + HS-R' → R-S-R' + HBr
Such reactions are accelerated in the presence of base, which converts the thiol into the more nucleophilic thiolate.
- An alternative method of synthesis includes the addition of a thiol to an alkene, typically catalysed by free radicals: » R-CH=CH2 + HS-R' → R-CH2-CH2-S-R'
- Thioethers can also be prepared via the Pummerer rearrangement.
Reactions
While ethers are generally stable, thioethers (R-S-R) are easily oxidized to the sulfoxides (R-S(=O)-R), which can themselves be further oxidized to sulfones (R-S(=O)2-R). For example, dimethyl sulfide can be oxidized as follows: » S(CH3)2 + O → OS(CH3)2
OS(CH3)2 + O → O2S(CH3)2
Typical oxidants include peroxides.
The sulfur-sulfur bond in disulfides is susceptible to cleavage by nucleophiles, and reaction with a carbon nucleophile produces a thioether: » R3C- + R1S-SR2 → R3CSR1 + R2S-
Trialkysulfonium salts react with nucleophiles with a dialkyl sulfide as a leaving group: » Nu- + R3S+ → Nu-R + R-S-R
This reaction is exploited in biological systems as a means of transferring an alkyl group. For example, S-adenosylmethionine acts as a methylating agent in biological SN2 reactions.
Ethers can be alkylated at oxygen only with difficulty to give highly reactive trialkyloxonium salts. In contrast, thioethers are readily alkylated to give stable sulfonium salts, such as trimethylsulfonium: » S(CH3)2 + CH3I → [S(CH3)3]+I-
Thiophenes
The heterocyclic compound thiophene is formally a thioether. Because of the aromatic character of this heterocycle, the nonbonding electrons on sulfur, normally responsible for the nucleophilicity so characteristic of thioethers, are delocalized into the π-system. Consequently thiophene exhibits few properties expected for a thioether - thiophene is non-nucleophilic at sulfur and, in fact, is sweet-smelling. Upon hydrogenation, thiophene gives tetrahydrothiophene, C4H8S, which indeed does behave as a typical thioether.
Further Information
Get more info on 'Thioether'.
|
External Link Exchanges
Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:
<a href="http://thioether.totallyexplained.com">Thioether Totally Explained</a>
Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned. |
|
|
