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Encyclopedia > Thiol
Sulphydryl
Sulphydryl

Contents

In organic chemistry, a thiol is a compound that contains the functional group composed of a sulfur atom and a hydrogen atom (-SH). Being the sulfur analogue of an alcohol group (-OH), this functional group is referred to either as a thiol group or a sulfhydryl group. More traditionally, thiols are often referred to as mercaptans. Image File history File links Thiol-group. ... Image File history File links Thiol-group. ... Organic chemistry is a specific discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of chemical compounds consisting of primarily carbon and hydrogen, which may contain any number of other elements, including nitrogen, oxygen, halogens as well... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Standard atomic weight 32. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Functional group of an alcohol molecule. ...


Nomenclature

When a thiol group is a substituent on an alkane, there are several ways of naming the resulting thiol: In organic chemistry, a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon. ... Chemical structure of methane, the simplest alkane Alkanes are chemical compounds that consists only of the elements carbon (C) and hydrogen (H) (i. ...

  • The preferred method (used by the IUPAC) is to add the suffix -thiol to the name of the alkane. The method is nearly identical to naming an alcohol. Example: CH3SH would be methanethiol.
  • An older method, the word mercaptan replaces alcohol in the name of the equivalent alcohol compound. Example: CH3SH would be methyl mercaptan. (CH3OH would be methanol)
  • As a prefix, the term mercapto- is used. Example: mercaptopurine.

The International Union of Pure and Applied Chemistry (IUPAC) is an international non-governmental organization devoted to the advancement of chemistry. ... Functional group of an alcohol molecule. ... Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naptha or wood spirits, is a chemical compound with chemical formula CH3OH. It is the simplest alcohol, and is a light, volatile, colourless, flammable, poisonous liquid with a distinctive odor that is somewhat milder and sweeter than ethanol (ethyl alcohol). ... Mercaptopurine: chemical structure Mercaptopurine (also called 6-MP or by its brand name Purinethol®) is an immunosuppressive drug used to treat leukemia. ...

Etymology

The term mercaptan comes from the Latin mercurius captans, meaning 'laying hold of mercury,' because the –SH group binds tightly to the element mercury. Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... General Name, Symbol, Number mercury, Hg, 80 Chemical series transition metals Group, Period, Block 12, 6, d Appearance silvery Atomic mass 200. ...


Physical Properties

Odour

Many thiols are colorless liquids having an odor resembling that of garlic. The odor of thiols is often strong and repulsive, particularly for those of low molecular weight. Thiols bind strongly to skin proteins, and are responsible for the intolerable, persistent odor produced by feces, rotting flesh and the spraying of skunks. Natural gas distributors began adding various forms of pungent thiols, usually ethanethiol, to natural gas, which is naturally odorless, after the deadly 1937 New London School explosion in New London, Texas. Thiols are also responsible for a class of wine faults caused by an unintended reaction between sulfur and yeast. However, not all thiols have unpleasant odors. For example, grapefruit mercaptan, a monoterpenoid thiol, is responsible for the characteristic scent of grapefruit. A liquid will usually assume the shape of its container A liquid is one of the main states of matter. ... Odor receptors on the antennae of a Luna moth An odor or odour (see spelling differences) is a chemical dissolved in air, generally at a very low concentration, which we perceive by the sense of olfaction. ... Binomial name Allium sativum L. Allium sativum L., commonly known as garlic, is a species in the onion family Alliaceae. ... In zootomy and dermatology, skin is the largest organ of the integumentary system made up of multiple layers of epithelial tissues that guard underlying muscles and organs. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Feces, faeces, or fæces (see spelling differences) In humans, defecation may occur (depending on the individual and the circumstances) from once every two or three days to several times a day. ... Genera Conepatus Mydaus Mephitis Spilogale Skunks are mammals, usually with black-and-white fur, belonging to the family Mephitidae and to the order Carnivora. ... Natural gas is a gaseous fossil fuel consisting primarily of methane but including significant quantities of ethane, butane, propane, carbon dioxide, nitrogen, helium and hydrogen sulfide. ... Ethanethiol, also known as ethyl mercaptan, is an organic compound used as an odorant in propane. ... Natural gas is a gaseous fossil fuel consisting primarily of methane but including significant quantities of ethane, butane, propane, carbon dioxide, nitrogen, helium and hydrogen sulfide. ... 1937 (MCMXXXVII) was a common year starting on Friday (link will take you to calendar). ... The New London School explosion occurred on March 18, 1937, when a natural gas leak caused an explosion, destroying the New London School of the city of New London, Texas. ... New London is a city located in Rusk County, Texas. ... A wine fault or defect is an unpleasant characteristic of a wine often resulting from poor wine making practices or storage conditions, and leading to wine spoilage. ... Typical divisions Ascomycota (sac fungi) Saccharomycotina (true yeasts) Taphrinomycotina Schizosaccharomycetes (fission yeasts) Basidiomycota (club fungi) Urediniomycetes Sporidiales Yeasts are a growth form of eukaryotic microorganisms classified in the kingdom Fungi. ... Grapefruit mercaptan is the common name for a natural organic compound found in grapefruit. ... Many terpenes are derived from conifer resins, here a pine. ... Binomial name Citrus paradisi Macfad. ...


Boiling points and solubility

Due to the small electronegativity difference between sulfur and hydrogen, an S-H bond is practically nonpolar covalent. Therefore, the S-H bond in the thiols have a lower dipole moment as compared to the alcohol's O-H bond. Thiols show little association by hydrogen bonding, with both water molecules and among themselves. Hence, they have lower boiling points and are less soluble in water and other polar solvents than alcohols of similar molecular weight. Thiols are as soluble and have similar boiling points to isomeric sulphides. Electronegativity is a measure of the ability of an atom or molecule to attract electrons in the context of a chemical bond. ... In chemistry, a nonpolar compound is one that does not have concentrations of positive or negative electric charge. ... Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ... This article is about the electromagnetic phenomenon. ... Snapshot from a simulation of liquid water. ... The boiling point of a substance is the temperature at which it can change its state from a liquid to a gas throughout the bulk of the liquid at a given pressure. ... It has been suggested that this article or section be merged with Solution. ... A solvent is a liquid that dissolves a solid, liquid, or gaseous solute, resulting in a solution. ... In chemistry, a sulfide (sulphide in British and Canadian English) is a combination of sulfur with an oxidation number of -2, with another chemical element or a radical thereof. ...


Chemical Properties

Synthesis

The methods used in making thiols are analogous to those used to make alcohols and ethers. The reactions are quicker and higher yielding because sulphur anions are better nucleophiles than oxygen atoms.


Thiols are formed when a halogenoalkane is heated with a solution of sodium hydrosulphide Haloalkane, halogenoalkanes or alkyl halides are compounds derived from alkanes by substituting one or more hydrogen atoms with halogen atoms. ...

CH3CH2Br + NaSH heated in ethanol(aq) → CH3CH2SH + NaBr

In addition, disulphides can be readily reduced by reducing agents like lithium aluminium hydride in dry ether to form two thiols. In chemistry, a disulfide is an ion formed by sulfur atoms. ...

R-S-S-R' → R-SH + R'-SH

Reactions

The thiol group is the sulfur analog of the hydroxyl group (-OH) found in alcohols. Since sulfur and oxygen belong to the same periodic table group, they share some similar chemical bonding properties. Like alcohol, in general, the deprotonated form RS (called a thiolate) is more chemically reactive than the protonated thiol form RSH Hydroxide is a functional group consisting of oxygen and hydrogen: -O−H It has a charge of 1-. The term hydroxyl group is used when the functional group -OH is counted as a substituent of an organic compound. ... Functional group of an alcohol molecule. ... General Name, Symbol, Number sulfur, S, 16 Chemical series nonmetals Group, Period, Block 16, 3, p Appearance lemon yellow Standard atomic weight 32. ... General Name, Symbol, Number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... A periodic table group is a vertical column in the periodic table of the chemical elements. ... A chemical bond is the physical process responsible for the attractive interactions between atoms and molecules, and that which confers stability to diatomic and polyatomic chemical compounds. ...


The chemistry of thiols is thus related to the chemistry of alcohols: thiols form thioethers, thioacetals and thioesters, which are analogous to ethers, acetals, and esters. Furthermore, a thiol group can react with an alkene to create a thioether. (In fact, biochemically, thiol groups may react with vinyl groups to form a thioether linkage.) A thioether (also known as a sulfide) is a functional group in organic chemistry that has the structure R-S-R, where R is any organic group. ... An acetyl group that contains a sulfur atom (see thiol) This page is a candidate to be copied to Wiktionary. ... Thioesters are compounds resulting from the bonding of sulfur with an acyl group (an alkyl group attached to a carbon-oxygen double bond), with the general formula R-S-CO-R. Some biochemists believe that the thioester bond was critical for the origin of life. ... Ethers can refer to: In internet routing, the term associated with hosts In Organic chemistry, the plural of ether This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... An acetal is a functional group or molecule containing the functional group of a carbon bonded to two -OR groups. ... For the Biblical Ester, see Esther. ... The chemical structure of ethylene, the simplest alkene. ... Chemical structure of the vinyl functional group. ... See Thioether. ...


Acidity

The sulfur atom of a thiol is quite nucleophilic, rather more so than the oxygen atom of an alcohol. The thiol group is fairly acidic with a usual pKa around 10 to 11. In the presence of a base, a thiolate anion is formed which is a very powerful nucleophile. The group and its corresponding anion are readily oxidized by reagents such as bromine to give an organic disulfide (R-S-S-R). In chemistry, a nucleophile (literally nucleus lover) is a reagent which is attracted to centres of positive charge. ... In chemistry and biochemistry, acid dissociation constant, the acidity constant, or the acid-ionization constant () is a specific type of equilibrium constant that indicates the extent of dissociation of hydrogen ions from an acid. ... Acids and bases: Acid-base reaction pH Self-ionization of water Buffer solutions Systematic naming Acid-base extraction Acidity function Proton affinity Acids: Strong acids Weak acids Superacids Lewis acids Mineral acids Organic acids Bases: Strong bases Weak bases Superbases Lewis bases Organic bases edit In chemistry, a base is... An anion is an ion with negative charge. ... Illustration of a redox reaction Redox (shorthand for oxidation/reduction reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ... General Name, Symbol, Number bromine, Br, 35 Chemical series halogens Group, Period, Block 17, 4, p Appearance gas/liquid: red-brown solid: metallic luster Atomic mass 79. ... In chemistry, a disulfide is an ion formed by sulfur atoms. ...

2R-SH + Br2 → R-S-S-R + 2HBr

Oxidation by more powerful reagents such as sodium hypochlorite or hydrogen peroxide yield sulfonic acids (RSO3H). Sodium hypochlorite is a chemical compound with the formula NaClO. A solution of sodium hypochlorite is frequently used as a disinfectant and as a bleaching agent; indeed, often it is simply called bleach, though other chemicals are sometimes given that name as well. ... Hydrogen peroxide (H2O2) is a very pale blue liquid which appears colourless in a dilute solution, slightly more viscous than water. ... It has been suggested that Sulfonic acid/Temp be merged into this article or section. ...

2R-SH + 2H2O2 → RSO3H + 2H2O

Biological importance

As the functional group of the amino acid cysteine, the thiol group plays an important role in biological systems. When the thiol groups of two cysteine residues (as in monomers or constituent units) are brought near each other in the course of protein folding, an oxidation reaction can create a cystine unit with a disulfide bond (-S-S-). Disulfide bonds can contribute to a protein's tertiary structure if the cysteines are part of the same peptide chain, or contribute to the quaternary structure of multi-unit proteins by forming fairly strong covalent bonds between different peptide chains. The heavy and light chains of antibodies are held together by disulfide bridges. Also, the kinks in curly hair are a product of cystine formation. Permanents take advantage of the oxidizability of cysteine residues. The chemicals used in hair straightening are reductants that reduce cystine disulfide bridges to free cysteine sulfhydryl groups, while chemicals used in hair curling are oxidants that oxidize cysteine sulfhydryl groups to form cystine disulfide bridges. Sulfhydryl groups in the active site of an enzyme can form noncovalent bonds with the enzyme's substrate as well, contributing to catalytic activity. Active site cysteine residues are the functional unit in cysteine proteases. Phenylalanine is one of the standard amino acids. ... Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... The most fundamental reactions in chemistry are the redox processes. ... Chemical structure of cystine formed from L-cysteine (under biological conditions) 3D representation of cystine with the disulfide bond shown in yellow Cystine is a conditionally non-essential crystalline, sulfur-containing amino acid. ... In chemistry, a disulfide bond is a single covalent bond derived from the coupling of thiol groups. ... In biochemistry, the tertiary structure of a protein is its overall shape. ... Peptides (from the Greek πεπτος, digestible), are the family of short molecules formed from the linking, in a defined order, of various α-amino acids. ... In biochemistry, many proteins are actually assemblies of more than one protein (polypeptide) molecule, which in the context of the larger assemblage are known as protein subunits. ... Schematic diagram of an typical antibody showing two Ig heavy chains (blue) linked by disulphide bonds to two Ig light chains (green). ... Wikipedia does not yet have an article with this exact name. ... A strand of human hair under magnification Hair is also the name of a musical, see respective articles for the stage production and the movie. ... Electrochemistry is the science of the reactions that can take place at the interface of an electronic conductor (the electrode, which can be a metal or a semiconductor including graphite) and an ionic conductor (the electrolyte). ... An oxidizing agent is a substance that oxidizes another substance in electrochemistry or redox chemical reactions in general. ... The active site of an enzyme is the binding site where catalysis occurs. ... Ribbon diagram of the enzyme TIM, surrounded by the space-filling model of the protein. ... Noncovalent bonding refers to a variety of interactions, that are not covalent in nature, between molecules or parts of molecules that provide force to hold the molecules or parts of molecules together usually in a specific orientation or conformation. ... In biochemistry, a substrate is a molecule upon which an enzyme acts. ... In chemistry and biology, catalysis is the acceleration (increase in rate) of a chemical reaction by means of a substance, called a catalyst, that is itself not consumed by the overall reaction. ... Proteases are enzymes that degrade polypeptides. ...


Examples of thiols

Methanethiol (also known as methyl mercaptan) is a colorless gas with a smell like rotten cabbage. ... Ethanethiol, also known as ethyl mercaptan, is an organic compound used as an odorant in propane. ... Coenzyme A (CoA, CoASH, or HSCoA) is a coenzyme, notable for its role in the synthesis and oxidization of fatty acids, and the oxidation of pyruvate in the citric acid cycle. ... Lipoamide is a trivial name for 6,8-dithiooctanoic amide. ... Skeletal formula of glutathione 3D model of glutathione Glutathione (GSH), whose IUPAC name is 2-amino-5-{[2-[(carboxymethyl)amino]- 1-(mercaptomethyl)-2-oxoethyl]amino}-5-oxopentanoic acid, is γ-glutamylcysteinylglycine, a tripeptide. ... Cysteine is a naturally occurring, sulfur-containing amino acid that is found in most proteins, although only in small quantities. ... Dithiothreitol is the common name for the reagent also known as DTT, 1,4-Dicaptomercapto-2,3-butanediol, Clelands reagent or (as a solid catalyst) Reductacryl. ... Oxidized form of dithioerythritol (DTE) In chemistry, dithioerythritol (DTE) is an epimer of dithiothreitol (DTT). ... In chemistry, an epimer is a stereoisomer that has a different configuration at only one of several stereogenic centers. ... 2-Mercaptoindole is a bicyclic heterocycle containing a thiol group. ...

See also

Chemical structure of a thial. ... In chemistry, a disulfide bond is a single covalent bond derived from the coupling of thiol groups. ... Thiol-disulfide exchange is a chemical reaction in which a thiolate group attacks a sulfur atom of a disulfide bond -S-S-. The original disulfide bond is broken, and its other sulfur atom (green atom in Figure 1) is released as a new thiolate, carrying away the negative charge. ...

External links

  • Applications, Properties, and Synthesis of w-Functionalized n-Alkanethiols and Disulfides — the Building Blocks of Self-Assembled Monolayers by D. Witt, R. Klajn, P. Barski, B.A. Grzybowski at Northwestern University.
  • Mercaptan, by The Columbia Electronic Encyclopedia
  • What is Mercaptan?, by Columbia Gas of Pennsylvania and Maryland
  • What Is the Worst Smelling Chemical?, by About Chemistry

  Results from FactBites:
 
Thiol - Wikipedia, the free encyclopedia (810 words)
The thiol group is the sulfur analog of the hydroxyl group (-OH) found in alcohols.
Thiols bind strongly to skin proteins, and are responsible for the intolerable, persistent odor produced by feces, rotting flesh and the spraying of skunks.
Thiols are also responsible for a class of wine faults caused by an unintended reaction between sulfur and yeast.
  More results at FactBites »

 
 

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