In organic chemistry, a sulfide (British English sulphide) or thioether is an organosulfur functional group with the connectivity R−S−R' as shown on right. Like many other sulfur-containing compounds, volatile sulfides have foul odors.[1] A sulfide is similar to an ether except that it contains a sulfur atom in place of the oxygen. The grouping of oxygen and sulfur in the periodic table suggests that the chemical properties of ethers and sulfides are somewhat similar, though the extent to which this is true in practice varies depending on the application.
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Alcohols | Alcohols, ethers, epoxides, sulfides | Organic chemistry | Khan Academy
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Thiol and Sulfide Nomenclature
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Sulfide nomenclature
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Naming Thiols ie Sulfur Alcohols
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Sulfide, Sulfite, Sulfate Ions (Difference and Formulas)
Transcription
We've already seen alcohols in many of these videos, but I thought it was about time that I actually made a video on alcohols. Now, alcohols is the general term for any molecule that fits the pattern some type of functional group or chain of carbons OH. And they use the letter R. And I've used it before. R stands for radical. And I don't want you to confuse this R with free radical. It means completely different things. R in this form really just means a functional group or a chain of carbons here. It doesn't mean a free radical. This just means it could be just something attached to this OH right there. Now another point of clarification, do not think that anything that fits this pattern is drinkable. Do not associate it with the traditional alcohol that you may or may not have been exposed to. Traditional drinking alcohol is actually ethanol. Alcohol is actually-- let me write out the molecular formula. CH3, CH2, and then OH. This is what is inside of wine and beer and hard liquor, or whatever you might want. You do not want to drink and maybe you might not actually want to drink this either, but you definitely do not want to drink something like methanol. It might kill you. So you do not want to do something like this. You do not want to ingest that. Might kill or blind you. This might do it in a more indirect way. So I want to get that out of the way and just so that we get kind of a little bit more comfortable with alcohols, and we've seen them involved in other reactions. We've seen hydroxides act as nucleophiles and Sn2 substitution reactions create alcohols. But I want to do is just learn to get comfortable and really make sure we know how to name these things. So let's just name these molecules that I drew right before I pressed record right over here. So over here, like everything else, we always want to define the longest carbon chain. We have 1, 2, 3, 4, 5 carbons. So it's going to be pent. And there's no double bonds. So it's a pentane. So I'll just write pentane right then. And we're not going to just write a pentane because actually, the fact that makes it an alcohol, that takes precedence over the fact that it is an alkane. So it actually, the suffix of the word will involve the alcohol part. So it is pentanol. That tells us that's an alcohol. And to know where the OH is grouped, we'll start numbering closest to the OH. So 1, 2, 3, 4, 5. Sometimes it'll be called 2-pentanol. And this is pretty clear because we only have one group here, only one OH. So we know that that is what the 2 applies to. But a lot of times, if people want to be a little bit more particular, they might write pentan-2-ol. And this way is more useful, especially if you have multiple functional groups. So you know exactly where they sit. This one is harder to say. 2-pentanol is pretty straightforward. Now let's try the name this beast right over here. So we have a couple of things going on. This is an alkyne. We have a triple bond. It's an alkyne. We have two bromo groups here. And it's also an alcohol. And alcohol takes precedence on all of them. So we want to start numbering closest to the alcohol. So we want to start numbering from this end of the carbon chain. And we have 1, 2, 3, 4, 5, 6, 7, 8 carbons. We want to call it an octyne. But because we have an alcohol there, we want to call this an octyne-- let me make it very clear. So oct tells us that we have 8 carbons. Now we have to specify where that triple bond is. The triple bond is on the 5 carbon. You always specify the lower number of the carbons on that triple bond. So it is oct-5-yn. That tells us that's where the triple bond is. And then we have the OH on the 4 carbon. So 4-al. And now we have these two bromo groups here on the 7 carbon. So it's 7,7-dibromo oct-5-yn-4-al. And this would all be one word. Let me make sure that you realize that this should be connected. I just ran out of space. So that's probably about as messy of a thing you'll have to name, but just showing you that these things can be named. Now let's think about this one over here in green. So we have 1, 2, 3, 4, 5, 6 carbons. So it's going to be a hex. And they're all single bonds, so it's a hexane. It's a cyclohexane. But then of course, the hydroxide or the hydroxy group I should call it, takes dominance. It's a hexanol. So this is a cyclohexanol. And once again, that comes from the OH right there. And you don't have to number it. Because no matter what carbon it's on, it's on the same one. If you had more than one of these OH groups, then we would have to worry about numbering them. Let's just do this one right over here. So once again, what is our carbon chain? We have 1, 2, 3 carbons. And we have the hydroxy group attached to the 1 and the 3 carbon. Prop is our prefix. It is an alkane. So we would call this-- and there's a couple of ways to do this. We could call this 1 comma 3 propanediol. Actually, I don't have to put a dash their. Propanediol. And over here, we would add the E because we have the D right there. So it's propanediol. If it wasn't diol, it would be propanal. You wouldn't have the E, D and the I there. So this would specify we're at the 1 and the 3 carbons. We have the hydroxy group. Or this could also be written as propane- 1, 3- diol. And once again, the di is telling us that we have two of the hydroxy groups attached to this thing. But either of these things are ways that you would see this molecule named.
Nomenclature
Sulfides are sometimes called thioethers, especially in the old literature. The two organic substituents are indicated by the prefixes. (CH3)2S is called dimethylsulfide. Some sulfides are named by modifying the common name for the corresponding ether. For example, C6H5SCH3 is methyl phenyl sulfide, but is more commonly called thioanisole, since its structure is related to that for anisole, C6H5OCH3.
The modern systematic nomenclature in chemistry for the trival name thioether is sulfane.[2]
Structure and properties
Sulfide is an angular functional group, the C–S–C angle approaching 90° The C–S bonds are about 180 pm. For the prototype, dimethylsulfide, the C-S-C angles is 99°, which is smaller than the C-O-C angle in ether (~110°). The C-S distance in dimethylsulfide is 1.81 Å.[3]
Sulfides are characterized by their strong odors, which are similar to thiol odor. This odor limits the applications of volatile sulfides. In terms of their physical properties they resemble ethers, but are less volatile, higher melting, and less hydrophilic. These properties follow from the polarizability of the divalent sulfur center, which is greater than that for oxygen in ethers.
Thiophenes
Thiophenes are a special class of sulfide-containing heterocyclic compounds. Because of their aromatic character, they are non-nucleophilic. The nonbonding electrons on sulfur are delocalized into the π-system. As a consequence, thiophene exhibits few properties expected for a sulfide – 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 sulfide.
Occurrence and applications
Sulfides are important in biology, notably in the amino acid methionine and the cofactor biotin. Petroleum contains many organosulfur compounds, including sulfides. Polyphenylene sulfide is a useful high temperature plastic. Coenzyme M, CH
3SCH
2CH
2SO−
3, is the precursor to methane (i.e. natural gas) via the process of methanogenesis.
Preparation
Sulfides are typically prepared by alkylation of thiols. Alkylating agents include not only alkyl halides, but also epoxides, aziridines, and Michael acceptors.[4]
- RBr + HSR' → RSR' + HBr
Such reactions are usually conducted in the presence of a base, which converts the thiol into the more nucleophilic thiolate.[5] Analogously, the reaction of disulfides with organolithium reagents produces thioethers:
- R3CLi + R1S-SR2 → R3CSR1 + R2SLi
Analogous reactions are known starting with Grignard reagents.
Alternatively, sulfides can be synthesized by the addition of a thiol to an alkene in the thiol-ene reaction:
- R-CH=CH2 + H-SR' → R-CH2-CH2-S-R'
This reaction is often catalysed by free radicals produced from a photoinitiator.[6]
Sulfides can also be prepared by many other methods, such as the Pummerer rearrangement. Trialkysulfonium salts react with nucleophiles with a dialkyl sulfide as a leaving group:
- Nu− + R3S+ → Nu-R + R2SR1
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.
An unusual but well tested method for the synthesis of thioethers involves addition of alkenes, especially ethylene across the S-Cl bond of sulfur dichloride. This method has been used in the production of bis(2-chloroethyl)sulfide, a mustard gas:[7]
- SCl2 + 2 C2H4 → (ClC2H4)2S
Reactions
The Lewis basic lone pairs on sulfur dominate the sulfides' reactivity. Sulfides readily alkylate to stable sulfonium salts, such as trimethylsulfonium iodide:[8]
- S(CH3)2 + CH3I → [S(CH3)3]+I−
Sulfides also oxidize easily to sulfoxides (R−S(=O)−R), which can themselves be further oxidized to sulfones (R−S(=O)2−R). Hydrogen peroxide is a typical oxidant—for example, with dimethyl sulfide (S(CH3)2):[9]
- S(CH3)2 + H2O2 → OS(CH3)2 + H2O
- OS(CH3)2 + H2O2 → O2S(CH3)2 + H2O
In analogy to their easy alkylation, sulfides bind to metals to form thioether complexes. Consequently Lewis acids do not decompose thioethers as they do ethers.[10] Sulfides are soft ligands, but their affinity for metals is lower than typical phosphines. Chelating thioethers are known, such as 1,4,7-trithiacyclononane.
Sulfides undergo hydrogenolysis in the presence of certain metals:
- R-S-R' + 2 H2 → RH + R'H + H2S
Raney nickel is useful for stoichiometric reactions in organic synthesis[11] whereas molybdenum-based catalysts are used to "sweeten" petroleum fractions, in the process called hydrodesulfurization.
Unlike ethers, thioethers are stable in the presence of Grignard reagents.[12] The protons adjacent to the sulfur atom are labile, and can be deprotonated with strong bases.[13]
References
- ^ Cremlyn, R. J. (1996). An Introduction to Organosulfur Chemistry. Chichester: John Wiley and Sons. ISBN 0-471-95512-4.
- ^ Hellwinkel, Dieter (2012-12-06). Systematic Nomenclature of Organic Chemistry: A Directory to Comprehension and Application of its Basic Principles (1 ed.). Springer Science & Business Media. p. 131. ISBN 978-3-64256765-0. p. 131:
Individual species of the genus thioether can again most uniformly be named as ...sulfane and ...sulfanyl derivatives, respectively (formerly: ...sulfides and ...thio derivatives, respectively). [...] Cyclic sulfides (thioethers) are treated as heterocycles, in the same way as their ether counterparts. Polysulfides substituted at both ends are named substitutively as ...polysulfanes (formerly: ...polysulfides).
(230 pages) - ^ Iijima, T.; Tsuchiy, S.; Kimura, M. (1977). "The Molecular Structure of Dimethyl Sulfide". Bull. Chem. Soc. Jpn. 50 (10): 2564. doi:10.1246/bcsj.50.2564.
- ^ Chauhan, Pankaj; Mahajan, Suruchi; Enders, Dieter (2014). "Organocatalytic Carbon–Sulfur Bond-Forming Reactions". Chemical Reviews. 114 (18): 8807–8864. doi:10.1021/cr500235v.
- ^ D. Landini; F. Rolla (1978). "Sulfide Synthesis In Preparation Of Dialkyl And Alkyl Aryl Sulfides: Neopentyl Phenyl Sulfide". Org. Synth. 58: 143. doi:10.15227/orgsyn.058.0143.
- ^ Hoyle, Charles E.; Bowman, Christopher N. (2010-02-22). "Thiol-Ene Click Chemistry". Angewandte Chemie International Edition. 49 (9): 1540–1573. doi:10.1002/anie.200903924. PMID 20166107.
- ^ Stewart, Charles D. (2006). Weapons of mass casualties and terrorism response handbook. Boston: Jones and Bartlett. p. 47. ISBN 0-7637-2425-4.
- ^ Brendsma & Arens 1967, p. 596.
- ^ Brendsma & Arens 1967, p. 601.
- ^ Brendsma & Arens 1967, p. 587.
- ^ Brendsma & Arens 1967, pp. 576–578.
- ^ Brendsma & Arens 1967, p. 581.
- ^ Brendsma & Arens 1967, pp. 555–559.
- Brendsma, L.; Arens, J. F. (1967). "The chemistry of thioethers; differences and analogies with ethers". In Patai, Saul (ed.). The Chemistry of the Ether Linkage. The Chemistry of Functional Groups. London: Interscience / William Clowes and Sons. pp. 555–559. LCCN 66-30401.
This page was last edited on 27 April 2024, at 00:46