# Thiol

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Any organic compound having a sulfanyl group (–SH)

Thiol with a   blue highlighted sulfhydryl group.

In [organic chemistry](/source/Organic_chemistry), a **thiol** ([/ˈθaɪɒl/](https://en.wikipedia.org/wiki/Help:IPA/English);[1] from [Ancient Greek](/source/Ancient_Greek_language) θεῖον*(theion)* '[sulfur](/source/Sulfur)'[2]), or **thiol derivative**, is any [organosulfur compound](/source/Organosulfur_compound) of the form R−SH, where R represents an [alkyl](/source/Alkyl) or other organic [substituent](/source/Substituent). The −SH [functional group](/source/Functional_group) itself is referred to as either a **thiol group** or a **sulfhydryl group**, or a **sulfanyl group**. Thiols are the sulfur analogue of [alcohols](/source/Alcohol_(chemistry)) (that is, sulfur takes the place of [oxygen](/source/Oxygen) in the [hydroxyl](/source/Hydroxyl) (−OH) group of an alcohol), and the word is a blend of "*thio-*" with "alcohol".

Many thiols have strong odors resembling that of [garlic](/source/Garlic), [cabbage](/source/Cabbage) or rotten eggs. Thiols are used as [odorants](/source/Odorants) to assist in the detection of [natural gas](/source/Natural_gas) (which in pure form is odorless). The smell of natural gas is due to the addition of thiol.

## Nomenclature

Thiols are sometimes referred to as **mercaptans** ([/mərˈkæptænz/](https://en.wikipedia.org/wiki/Help:IPA/English))[3] or **mercapto compounds**,[4][5][6] a term introduced in 1832 by [William Christopher Zeise](/source/William_Christopher_Zeise) and is derived from the [Latin](/source/Latin) *mercurio captāns* ('capturing mercury')[7] because the **thiolate** group (RS−) bonds very strongly with [mercury](/source/Mercury_(element)) compounds.[8]

There are several ways to name the alkylthiols:[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*]

- The suffix *-thiol* is added to the name of the alkane. This method is nearly identical to [naming an alcohol](/source/Alcohol_(chemistry)) and is used by the [IUPAC](/source/IUPAC), e.g. CH3SH would be *[methanethiol](/source/Methanethiol)*.

- The word *mercaptan* replaces *alcohol* in the name of the equivalent alcohol compound. Example: CH3SH would be methyl mercaptan, just as CH3OH is called methyl alcohol.

- The term *sulfhydryl-* or *mercapto-* is used as a prefix, e.g. [mercaptopurine](/source/Mercaptopurine).

## Physical properties

### Odor

Many thiols have strong [odors](/source/Odor) resembling that of [garlic](/source/Garlic). The odors of thiols, particularly those of low molecular weight, are often strong and repulsive. The spray of [skunks](/source/Skunk) consists mainly of low-molecular-weight thiols and derivatives.[9][10][11][12][13] These compounds are detectable by the human nose at concentrations of only 10 parts per billion.[14] Human [sweat](/source/Sweat) contains (*R*)/(*S*)-3-methyl-3-sulfanylhexan-1-ol (3M3SH), detectable at 2 parts per billion and having an onion-like (S enantiomer) and fruity, grapefruit-like odor (R enantiomer).[15] (Methylthio)methanethiol (MeSCH2SH; MTMT) is a strong-smelling volatile thiol, also detectable at parts per billion levels, found in male [mouse](/source/Mouse) urine. [Lawrence C. Katz](/source/Lawrence_C._Katz) and co-workers showed that MTMT functioned as a [semiochemical](/source/Semiochemical), activating certain mouse olfactory sensory neurons, and attracting female [mice](/source/Mouse).[16] [Copper](/source/Copper) has been shown to be required by a specific mouse olfactory receptor, MOR244-3, which is highly responsive to MTMT as well as to various other thiols and related compounds.[17] A human olfactory receptor, [OR2T11](/source/OR2T11), has been identified which, in the presence of copper, is highly responsive to the gas odorants (see below) [ethanethiol](/source/Ethanethiol) and [*t*-butyl mercaptan](/source/Tert-Butylthiol) as well as other low molecular weight thiols, including [allyl mercaptan](/source/Allyl_mercaptan) found in human [garlic](/source/Garlic) breath, and the strong-smelling cyclic sulfide [thietane](/source/Thietane).[18]

Thiols are also responsible for a class of [wine faults](/source/Wine_fault) caused by an unintended reaction between sulfur and [yeast](/source/Yeast_(wine)), as well as the "skunky" odor of beer that has been exposed to ultraviolet light.

Not all thiols have unpleasant odors. For example, [furan-2-ylmethanethiol](/source/Furan-2-ylmethanethiol) contributes to the aroma of roasted [coffee](/source/Coffee), whereas [grapefruit mercaptan](/source/Grapefruit_mercaptan), a [monoterpenoid](/source/Terpene) thiol, is responsible for the characteristic scent of [grapefruit](/source/Grapefruit). The effect of the latter compound is present only at low concentrations. Concentrated samples have an unpleasant odor.

In the United States, distributors are required to add thiols, originally [ethanethiol](/source/Ethanethiol), to natural gas (which is naturally odorless) after the deadly [New London School explosion](/source/New_London_School_explosion) in [New London, Texas](/source/New_London%2C_Texas), in 1937, although many distributors were odorizing gas prior to this event. Most currently-used gas odorants contain mixtures of mercaptans and sulfides, with [*t*-butyl mercaptan](/source/Tert-Butylthiol) as the main odor constituent in natural gas and [ethanethiol](/source/Ethanethiol) in [liquefied petroleum gas](/source/Liquefied_petroleum_gas) (LPG, propane).[19] In situations where thiols are used in commercial industry, such as liquid petroleum gas tankers and bulk handling systems, an oxidizing [catalyst](/source/Catalysis) is used to destroy the odor. A copper-based oxidation catalyst neutralizes the volatile thiols and transforms them into inert products.

### Boiling points and solubility

Thiols show little association by [hydrogen bonding](/source/Hydrogen_bond), both with water molecules and among themselves. Hence, they have lower [boiling points](/source/Boiling_point) and are less [soluble](/source/Soluble) in water and other [polar solvents](/source/Solvent#Polarity,_solubility,_and_miscibility) than alcohols of similar molecular weight. For this reason also, thiols and their corresponding sulfide functional group [isomers](/source/Structural_isomer) have similar solubility characteristics and boiling points, whereas the same is not true of alcohols and their corresponding isomeric ethers.

## Structure and bonding

Thiols having the structure R−S−H, in which an [alkyl](/source/Alkyl) group (R) is attached to a [sulfhydryl](/source/Sulfhydryl) group (SH), are referred to as *alkanethiols* or *alkyl thiols*.[20] Thiols and alcohols have similar connectivity. Because sulfur atoms are larger than oxygen atoms, C−S [bond lengths](/source/Bond_length)—typically around 180 [picometres](/source/Picometre)—are about 40 picometers longer than typical C−O bonds. C−S−H angles approach 90°, whereas the angle for the C−O−H group is more obtuse. In solids and liquids, the [hydrogen-bonding](/source/Hydrogen-bonding) between individual thiol groups is weak, and thus thiols are more volatile than the corresponding alcohols. The main cohesive forces for thiols involves [Van der Waals interactions](/source/Van_der_Waals_interaction) between the highly polarizable divalent sulfur centers.

The S−H bond is much weaker than the O−H bond as reflected in their respective [bond dissociation energies](/source/Bond_dissociation_energy) (BDE). For CH3S−H, the BDE is 366 kJ/mol (87 kcal/mol), while for CH3O−H, the BDE is 440 kJ/mol (110 kcal/mol).[21] Hydrogen-atom abstraction from a thiol gives a [thiyl radical](/source/Thiyl_radical) with the formula RS•, where R = alkyl or aryl.

## Characterization

Volatile thiols are easily and almost unerringly detected by their distinctive odor. Sulfur-specific analyzers for [gas chromatographs](/source/Gas_chromatograph) are useful. Spectroscopic indicators are the [D2O](/source/Heavy_water)-exchangeable S**H** signal in the [1H NMR spectrum](/source/Proton_NMR) ([33S](/source/Sulfur-33) is [NMR](/source/NMR)-active but signals for divalent sulfur are very broad and of little utility[22]). The *ν*SH band appears near 2400 cm−1 in the [IR spectrum](/source/IR_spectrum).[4] In the [nitroprusside reaction](/source/Nitroprusside_reaction), free thiol groups react with [sodium nitroprusside](/source/Sodium_nitroprusside) and [ammonium hydroxide](/source/Ammonium_hydroxide) to give a red colour.

## Preparation

In industry, methanethiol is prepared by the reaction of [hydrogen sulfide](/source/Hydrogen_sulfide) with [methanol](/source/Methanol). This method is employed for the industrial synthesis of [methanethiol](/source/Methanethiol):

- CH3OH + H2S → CH3SH + H2O

Such reactions are conducted in the presence of acidic catalysts. The other principal route to thiols involves the addition of hydrogen sulfide to [alkenes](/source/Alkene). Such reactions are usually conducted in the presence of an acid catalyst or UV light. [Halide](/source/Halogen) displacement, using the suitable organic halide and sodium hydrogen sulfide has also been used.[23]

Another method entails the alkylation of [sodium hydrosulfide](/source/Sodium_hydrosulfide).

- RX + NaSH → RSH + NaX (X = Cl, Br, I)

This method is used for the production of [thioglycolic acid](/source/Thioglycolic_acid) from [chloroacetic acid](/source/Chloroacetic_acid).

### Laboratory methods

In general, on the typical laboratory scale, the direct reaction of a [haloalkane](/source/Halogenoalkane) with sodium hydrosulfide is *in*efficient owing to the competing formation of [sulfides](/source/Thioether) (overalkylation). Instead, alkyl halides are converted to thiols via an *S*-alkylation of [thiourea](/source/Thiourea). This multistep, one-pot process proceeds via the intermediacy of the [isothiouronium salt](/source/Isothiouronium_salt), which is hydrolyzed in a separate step:[24][25]

- CH3CH2Br + SC(NH2)2 → [CH3CH2SC(NH2)2]Br

- [CH3CH2SC(NH2)2]Br + NaOH → CH3CH2SH + OC(NH2)2 + NaBr

The thiourea route works well with primary halides, especially activated ones. Secondary and tertiary thiols are less easily prepared. Secondary thiols can be prepared from the ketone via the corresponding [dithioketals](/source/Thioketal).[26] A related two-step process involves alkylation of thiosulfate to give the thiosulfonate ("[Bunte salt](/source/Bunte_salt)"), followed by hydrolysis. The method is illustrated by one synthesis of [thioglycolic acid](/source/Thioglycolic_acid):

- ClCH2CO2H + Na2S2O3 → Na[O3S2CH2CO2H] + NaCl

- Na[O3S2CH2CO2H] + H2O → HSCH2CO2H + NaHSO4

[Organolithium compounds](/source/Organolithium_compound) and [Grignard reagents](/source/Grignard_reagent) react with sulfur to give the thiolates, which are readily hydrolyzed:[27]

- RLi + S → RSLi

- RSLi + HCl → RSH + LiCl

Phenols can be converted to the thiophenols via [rearrangement](/source/Newman-Kwart_rearrangment) of their *O*-aryl dialkylthiocarbamates.[28]

Thiols are prepared by reductive dealkylation of sulfides, especially benzyl derivatives and thioacetals.[29]

Thiophenols are produced by *S*-arylation or the replacement of diazonium leaving group with sulfhydryl anion (SH−):[30][31]

- ArN+ 2 + SH− → ArSH + N2

## Classes of thiols

### Alkyl and aryl thiols

Alkyl thiols are the simplest thiols. [Methanethiol](/source/Methanethiol) (CH3SH, methyl mercaptan), [ethanethiol](/source/Ethanethiol) (C2H5SH, ethyl mercaptan), [propanethiol](/source/Propanethiol) (C3H7SH), [butanethiols](/source/Butanethiol) (C4H9SH, *n*-butyl mercaptan and [*tert*-Butyl mercaptan](/source/Tert-Butyl_mercaptan), are common reagents. While these thiols have the characteristic unpleasant odors, some thiols are responsible for the flavor and fragrance of foods, e.g. [furan-2-ylmethanethiol](/source/Furan-2-ylmethanethiol). [1-Hexadecanethiol](/source/1-Hexadecanethiol) is a lipophilic alkylthiol.

Aryl thiols include the parent [thiophenol](/source/Thiophenol) (C6H5SH). [Pentachlorobenzenethiol](/source/Pentachlorobenzenethiol) has pesticidal properties.

### Dithiols

[1,3-Propanedithiol](/source/1%2C3-Propanedithiol) and [1,2-ethanedithiol](/source/1%2C2-Ethanedithiol) are reagents in organic chemistry. [Dimercaptosuccinic acid](/source/Dimercaptosuccinic_acid) is a chelating agent. [Lipoic acid](/source/Lipoic_acid), a naturally occurring modification of 1,3-propanedithiol, is a [cofactor](/source/Cofactor_(biochemistry)) for many enzymes. [Dithiothreitol](/source/Dithiothreitol) is a reagent in [biochemistry](/source/Biochemistry).

### Unsaturated thiols

Vinyl thiols are rare, but other unsaturated thiols are numerous. A textbook unsaturated thiol is [grapefruit mercaptan](/source/Grapefruit_mercaptan), which exists as two enantiomers, each with distinct odors. The main component of skunk spray is a butenylthiol.[32]

### Thioalcohols

[2-Mercaptoethanol](/source/2-Mercaptoethanol) is a reagent in biochemistry. [3-Mercaptopropane-1,2-diol](/source/3-Mercaptopropane-1%2C2-diol) is a medicine. These compounds have high solubility in water owing to the presence of OH substituent(s).

### Thiol-carboxylic acids

[Cysteine](/source/Cysteine) and [penicillamine](/source/Penicillamine) have the formula HSCR2CH(NH2)CO2H, where R = H and CH3, respectively. Cysteine is common [amino acid](/source/Amino_acid), and penicillamine has medicinal properties. [Coenzyme A](/source/Coenzyme_A) and [glutathione](/source/Glutathione) are more complicated thiol-containing derivatives. Cysteine-rich proteins called [metallothionein](/source/Metallothionein) have high affinity for heavy metals. [Thiocarboxylic acids](/source/Thiocarboxylic_acid), with the formula HS(O)CR, can be considered thiols also. [Thioacetic acid](/source/Thioacetic_acid) is one example.

### Aminothiols

Cysteine and penicillamine also are classified as an aminothiols. One variation is [cysteamine](/source/Cysteamine) (HSCH2CH2NH2.

## Reactions

Thiols form [sulfides](/source/Organic_sulfide), [thioacetals](/source/Thioacetal), and [thioesters](/source/Thioester), which are analogous to [ethers](/source/Ethers), [acetals](/source/Acetal), and [esters](/source/Esters), respectively.

### Acidity

Thiols are easily deprotonated.[33] Relative to the alcohols, thiols are more acidic. The conjugate base of a thiol is called a **thiolate**. Butanethiol has a [p*K*a](/source/PKa) of 10.5 vs 15 for butanol. Thiophenol has a [p*K*a](/source/PKa) of 6, versus 10 for [phenol](/source/Phenol). A highly acidic thiol is [pentafluorothiophenol](/source/Pentafluorothiophenol) (C6F5SH) with a p*K*a of 2.68. Thus, thiolates can be obtained from thiols by treatment with alkali metal hydroxides.

Synthesis of thiophenolate from thiophenol

### *S*-Based nucleophilicity

The conjugate base of thiols are potent nucleophiles. They alkylate to give sulfides:

- RSH + R′Br + B → RSR′ + [HB]Br (B = base)

Many electrophiles participate in this reaction. [α,β-Unsaturated carbonyl compounds](/source/%CE%91%2C%CE%B2-Unsaturated_carbonyl_compound) add thiols, especially in the presence of base catalysts. Thiolates react with [carbon disulfide](/source/Carbon_disulfide) to give [thioxanthate](/source/Thioxanthate) (RSCS− 2).

### Redox

Thiols, especially in the presence of base, are readily [oxidized](/source/Redox) by reagents such as [bromine](/source/Bromine) and [iodine](/source/Iodine) to give an organic [disulfide](/source/Disulfide) (R−S−S−R).

- 2 R−SH + Br2 → R−S−S−R + 2 HBr

Oxidation by more powerful reagents such as [sodium hypochlorite](/source/Sodium_hypochlorite) or [hydrogen peroxide](/source/Hydrogen_peroxide) can also yield [sulfonic acids](/source/Sulfonic_acid) (RSO3H).

- R−SH + 3 H2O2 → RSO3H + 3 H2O

Oxidation can also be effected by oxygen in the presence of catalysts:[34]

- 2 R–SH + 1⁄2 O2 → RS−SR + H2O

Thiols participate in thiol-disulfide exchange:

- RS−SR + 2 R′SH → 2 RSH + R′S−SR′

This reaction is important in nature.

### Metal ion complexation

With metal ions, thiolates behave as ligands to form [transition metal thiolate complexes](/source/Transition_metal_thiolate_complex). The term *mercaptan* is derived from the [Latin](/source/Latin) *mercurium captans* (capturing mercury)[7] because the thiolate group bonds so strongly with [mercury](/source/Mercury_(element)) compounds. According to [hard/soft acid/base (HSAB) theory](/source/HSAB_theory), sulfur is a relatively soft (polarizable) atom. This explains the tendency of thiols to bind to soft elements and ions such as mercury, lead, or cadmium. The stability of metal thiolates parallels that of the corresponding sulfide minerals. [Sodium aurothiolate](https://en.wikipedia.org/w/index.php?title=Sodium_aurothiolate&action=edit&redlink=1) is an [antiarthritic](https://en.wikipedia.org/w/index.php?title=Antiarthritic&action=edit&redlink=1) drug.[35]

## Thiyl radicals

Main article: [Thiyl radical](/source/Thiyl_radical)

[Free radicals](/source/Free_radical) derived from mercaptans, called [thiyl radicals](/source/Thiyl_radical), are commonly invoked to explain reactions in [organic chemistry](/source/Organic_chemistry) and [biochemistry](/source/Biochemistry). They have the formula RS• where R is an organic substituent such as [alkyl](/source/Alkyl) or [aryl](/source/Aryl).[6] They arise from or can be generated by a number of routes, but the principal method is H-atom abstraction from thiols. Another method involves [homolysis](/source/Homolysis_(chemistry)) of organic disulfides.[36] In biology thiyl radicals are responsible for the formation of the deoxyribonucleic acids, building blocks for [DNA](/source/DNA). This conversion is catalysed by [ribonucleotide reductase](/source/Ribonucleotide_reductase) (see figure).[37] Thiyl intermediates also are produced by the oxidation of [glutathione](/source/Glutathione), an antioxidant in biology. Thiyl radicals (sulfur-centred) can transform to carbon-centred radicals via [hydrogen](/source/Hydrogen) atom exchange [equilibria](/source/Chemical_equilibrium). The formation of [carbon](/source/Carbon)-centred radicals could lead to protein damage via the formation of [C](/source/Carbon)−C bonds or backbone fragmentation.[38]

Because of the weakness of the S−H bond, thiols can function as [scavengers](/source/Scavenger_(chemistry)) of [free radicals](/source/Free_radical).[39]

## Biological importance

The catalytic cycle for [ribonucleotide reductase](/source/Ribonucleotide_reductase), demonstrating the role of thiyl radicals in producing the genetic machinery of life.

### Cysteine and cystine

As the functional group of the [proteinogenic amino acid](/source/Proteinogenic_amino_acid) [cysteine](/source/Cysteine), the thiol group plays a very important role in biology. When the thiol groups of two cysteine residues (as in monomers or constituent units) are brought near each other in the course of [protein](/source/Protein) folding, an [oxidation reaction](/source/Oxidation) can generate a [cystine](/source/Cystine) unit with a [disulfide bond](/source/Disulfide_bond) (−S−S−). Disulfide bonds can contribute to a protein's [tertiary structure](/source/Tertiary_structure) if the cysteines are part of the same [peptide](/source/Peptide) chain, or contribute to the [quaternary structure](/source/Quaternary_structure) of multi-unit proteins by forming fairly strong covalent bonds between different peptide chains. A physical manifestation of cysteine-cystine equilibrium is provided by [hair straightening](/source/Hair_straightening) technologies.[40]

Sulfhydryl groups in the [active site](/source/Active_site) of an [enzyme](/source/Enzyme) can form [noncovalent bonds](/source/Noncovalent_bond) with the enzyme's [substrate](/source/Substrate_(biochemistry)) as well, contributing to covalent [catalytic activity](/source/Catalysis) in [catalytic triads](/source/Catalytic_triad). Active site cysteine residues are the functional unit in [cysteine protease](/source/Cysteine_protease) [catalytic triads](/source/Catalytic_triad). Cysteine residues may also react with heavy metal ions (Zn2+, Cd2+, Pb2+, Hg2+, Ag+) because of the high affinity between the soft sulfide and the soft metal (see [hard and soft acids and bases](/source/Hard_and_soft_acids_and_bases)). This can deform and inactivate the protein, and is one mechanism of [heavy metal poisoning](/source/Heavy_metal_poisoning).

### Cofactors

Many [cofactors](/source/Cofactor_(biochemistry)) (non-protein-based helper molecules) feature thiols. The biosynthesis and degradation of fatty acids and related long-chain hydrocarbons is conducted on a scaffold that anchors the growing chain through a thioester derived from the thiol [coenzyme A](/source/Coenzyme_A). [Dihydrolipoic acid](/source/Dihydrolipoic_acid), a [dithiol](/source/Dithiol), is the reduced form of [lipoic acid](/source/Lipoic_acid), a cofactor in several metabolic processes in mammals. [Methane biosynthesis](/source/Methane_biosynthesis), the principal [hydrocarbon](/source/Hydrocarbon) on Earth, arises from the reaction mediated by [coenzyme M](/source/Coenzyme_M) (2-mercaptoethyl sulfonic acid) and [coenzyme B](/source/Coenzyme_B) (7-mercaptoheptanoylthreoninephosphate). Thiolates, the conjugate bases derived from thiols, form strong complexes with many metal ions, especially those classified as soft. The stability of metal thiolates parallels that of the corresponding sulfide minerals.

### Drugs

Drugs containing thiol group:

- [6-Mercaptopurine](/source/6-Mercaptopurine) (anticancer)

- [Captopril](/source/Captopril) (antihypertensive)

- [D-penicillamine](/source/D-penicillamine) (antiarthritic)

## See also

- [Doctor sweetening process](/source/Doctor_sweetening_process)

- [Odorizer](/source/Odorizer)

- [Persulfide](/source/Persulfide)

- [Saville reaction](/source/Saville_reaction)

- [Thiol-disulfide exchange](/source/Thiol-disulfide_exchange)

## References

1. **[^](#cite_ref-1)** *[Dictionary Reference](/source/Dictionary.com)*: [thiol](http://dictionary.reference.com/browse/thiol) [Archived](https://web.archive.org/web/20130411021707/http://dictionary.reference.com/browse/thiol) 2013-04-11 at the [Wayback Machine](/source/Wayback_Machine)

1. **[^](#cite_ref-2)** [θεῖον](https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dqei%3Don1) [Archived](https://web.archive.org/web/20170510073237/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3Dqei%3Don1) 2017-05-10 at the [Wayback Machine](/source/Wayback_Machine), Henry George Liddell, Robert Scott, *A Greek–English Lexicon*

1. **[^](#cite_ref-3)** *[Dictionary Reference](/source/Dictionary.com)*: [mercaptan](http://dictionary.reference.com/browse/mercaptan) [Archived](https://web.archive.org/web/20121113062439/http://dictionary.reference.com/browse/mercaptan) 2012-11-13 at the [Wayback Machine](/source/Wayback_Machine)

1. ^ [***a***](#cite_ref-Patai_4-0) [***b***](#cite_ref-Patai_4-1) Patai, Saul, ed. (1974). *The Chemistry of the Thiol Group. Part 1*. London: Wiley. [doi](/source/Doi_(identifier)):[10.1002/9780470771310](https://doi.org/10.1002%2F9780470771310). [ISBN](/source/ISBN_(identifier)) [9780470771310](https://en.wikipedia.org/wiki/Special:BookSources/9780470771310).

1. **[^](#cite_ref-5)** Patai, Saul, ed. (1974). *The Chemistry of the Thiol Group. Part 2*. London: Wiley. [doi](/source/Doi_(identifier)):[10.1002/9780470771327](https://doi.org/10.1002%2F9780470771327). [ISBN](/source/ISBN_(identifier)) [9780470771327](https://en.wikipedia.org/wiki/Special:BookSources/9780470771327).

1. ^ [***a***](#cite_ref-CremlynAn_6-0) [***b***](#cite_ref-CremlynAn_6-1) R. J. Cremlyn (1996). *An Introduction to Organosulfur Chemistry*. Chichester: John Wiley and Sons. [ISBN](/source/ISBN_(identifier)) [978-0-471-95512-2](https://en.wikipedia.org/wiki/Special:BookSources/978-0-471-95512-2).

1. ^ [***a***](#cite_ref-ReferenceA_7-0) [***b***](#cite_ref-ReferenceA_7-1) *Oxford American Dictionaries* ([Mac OS X Leopard](/source/Mac_OS_X_Leopard)).

1. **[^](#cite_ref-8)** See: - Zeise, William Christopher (1834). ["Mercaptanet, med bemaerkninger over nogle andre nye producter af svovelvinsyresaltene, som og af den tunge vinolie, ved sulfureter"](https://babel.hathitrust.org/cgi/pt?id=umn.31951d00004546r&view=1up&seq=131) [Mercaptan, with remarks on some other new products of salts of ethyl hydrogen sulfate as well as of heavy oil of wine, by means of hydrogen sulfide]. *Kongelige Danske Videnskabers Selskabs Skrifter*. 4th series (in Danish). **6**: 1–70. On p. 13 the word "mercaptan" is coined. - German translation: Zeise, W. C. (1834). ["Das Mercaptan, nebst Bermerkungen über einige neue Producte aus der Einwirkung der Sulfurete auf weinschwefelsaure Salze und auf das Weinöl"](https://babel.hathitrust.org/cgi/pt?id=wu.89048351654&view=1up&seq=383) [Mercaptan together with comments on some new products from the effect of hydrogen sulfide on salts of ethyl sulfate ((C2H5)HSO4) and heavy oil of wine (a mixture of diethyl sulfate, diethyl sulfite, and polymerized ethylene)]. *Annalen der Physik und Chemie*. 2nd series (in German). **31** (24): 369–431. From p. 378: *" … nenne ich den vom Quecksilber aufgenommenen Stoff*Mercaptum*(von:*Corpus mercurio captum*) … "* ( … I name the substance [that is] absorbed by mercury "mercaptum" (from: the body (substance) [that] has been absorbed by mercury) … ) - German translation is reprinted in:Zeise, W. C. (1834). ["Das Mercaptan, nebst Bemerkungen über einige andere neue Erzeugnisse der Wirkung schwefelweinsaurer Salze, wie auch des schweren Weinöls auf Sulphurete"](https://babel.hathitrust.org/cgi/pt?id=uiug.30112063582438;view=1up;seq=267). *Journal für Praktische Chemie*. **1** (1): 257–268, 345–356, 396–413, 457–475. [doi](/source/Doi_(identifier)):[10.1002/prac.18340010154](https://doi.org/10.1002%2Fprac.18340010154). - Summarized in: Zeise, W. C. (1834). ["Ueber das Mercaptan"](https://books.google.com/books?id=dmgTAAAAQAAJ&pg=PA1) [On mercaptan]. *Annalen der Pharmacie*. **11** (1): 1–10. [doi](/source/Doi_(identifier)):[10.1002/jlac.18340110102](https://doi.org/10.1002%2Fjlac.18340110102). [Archived](https://web.archive.org/web/20150320202059/http://books.google.com/books?id=dmgTAAAAQAAJ&pg=PA1) from the original on 2015-03-20. - Zeise, William Christopher (1834). ["Sur le mercaptan; avec des observations sur d'autres produits resultant de l'action des sulfovinates ainsi que de l'huile de vin, sur des sulfures metalliques"](https://books.google.com/books?id=1Jc5AAAAcAAJ&pg=PA87) [On mercaptan; with observations on other products resulting from the action of sulfovinates [typically, ethyl hydrogen sulfate] as well as oil of wine [a mixture of diethylsulfate and ethylene polymers] on metal sulfides]. *Annales de Chimie et de Physique*. **56**: 87–97. [Archived](https://web.archive.org/web/20150320194543/http://books.google.com/books?id=1Jc5AAAAcAAJ&pg=PA87) from the original on 2015-03-20. "Mercaptan" (ethyl thiol) was discovered in 1834 by the Danish professor of chemistry [William Christopher Zeise](/source/William_Christopher_Zeise) (1789–1847). He called it "mercaptan", a contraction of "corpus mercurio captans" (mercury-capturing substance) [p. 88], because it reacted violently with mercury(II) oxide ("deutoxide de mercure") [p. 92]. - The article in *Annales de Chimie et de Physique* (1834) was translated from the German article: Zeise, W. C. (1834). ["Das Mercaptan, nebst Bemerkungen über einige neue Producte aus der Einwirkung der Sulfurete auf weinschwefelsaure Salze und auf das Weinöl"](https://books.google.com/books?id=wCUAAAAAMAAJ&pg=PA369). *Annalen der Physik und Chemie*. **107** (27): 369–431. [Bibcode](/source/Bibcode_(identifier)):[1834AnP...107..369Z](https://ui.adsabs.harvard.edu/abs/1834AnP...107..369Z). [doi](/source/Doi_(identifier)):[10.1002/andp.18341072402](https://doi.org/10.1002%2Fandp.18341072402). [Archived](https://web.archive.org/web/20150320201943/http://books.google.com/books?id=wCUAAAAAMAAJ&pg=PA369) from the original on 2015-03-20.

1. **[^](#cite_ref-9)** Andersen K. K.; Bernstein D. T. (1978). "Some Chemical Constituents of the Scent of the Striped Skunk (*Mephitis mephitis*)". *Journal of Chemical Ecology*. **1** (4): 493–499. [doi](/source/Doi_(identifier)):[10.1007/BF00988589](https://doi.org/10.1007%2FBF00988589).

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1. **[^](#cite_ref-14)** Aldrich, T.B. (1896). ["A Chemical Study of the Secretion of the Anal Glands of *Mephitis mephitiga* (Common Skunk), with Remarks on the Physiological Properties of This Secretion"](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2117909). *J. Exp. Med*. **1** (2): 323–340. [doi](/source/Doi_(identifier)):[10.1084/jem.1.2.323](https://doi.org/10.1084%2Fjem.1.2.323). [PMC](/source/PMC_(identifier)) [2117909](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2117909). [PMID](/source/PMID_(identifier)) [19866801](https://pubmed.ncbi.nlm.nih.gov/19866801).

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1. **[^](#cite_ref-18)** ["Copper key to our sensitivity to rotten eggs' foul smell"](https://www.chemistryworld.com/news/copper-key-to-our-sensitivity-to-rotten-eggs-foul-smell/1017492.article). *chemistryworld.com*. [Archived](https://web.archive.org/web/20170510113946/https://www.chemistryworld.com/news/copper-key-to-our-sensitivity-to-rotten-eggs-foul-smell/1017492.article) from the original on 10 May 2017. Retrieved 3 May 2018.

1. **[^](#cite_ref-Roberts_19-0)** Roberts, J. S., ed. (1997). *Kirk-Othmer Encyclopedia of Chemical Technology*. Weinheim: Wiley-VCH.[*[page needed](https://en.wikipedia.org/wiki/Wikipedia:Citing_sources)*]

1. **[^](#cite_ref-20)** ["Alkanethiols"](https://www.rsc.org/publishing/journals/prospect/ontology.asp?id=CHEBI:47908&MSID=c000442a). [Royal Society of Chemistry](/source/Royal_Society_of_Chemistry). Retrieved 4 September 2019.

1. **[^](#cite_ref-21)** Luo, Y.-R.; Cheng, J.-P. (2017). "Bond Dissociation Energies". In J. R. Rumble (ed.). *Handbook of Chemistry and Physics*. CRC Press.

1. **[^](#cite_ref-22)** Man, Pascal P. ["Sulfur-33 NMR references"](http://www.pascal-man.com/periodic-table/sulfur.shtml). *www.pascal-man.com*. [Archived](https://web.archive.org/web/20170823184753/http://www.pascal-man.com/periodic-table/sulfur.shtml) from the original on 23 August 2017. Retrieved 3 May 2018.

1. **[^](#cite_ref-23)** John S Roberts, "Thiols", in *Kirk-Othmer Encyclopedia of Chemical Technology*, 1997, Wiley-VCH, Weinheim. [doi](/source/Doi_(identifier)):[10.1002/0471238961.2008091518150205.a01](https://doi.org/10.1002%2F0471238961.2008091518150205.a01)

1. **[^](#cite_ref-24)** Speziale, A. J. (1963). ["Ethanedithiol"](https://www.orgsyn.org/demo.aspx?prep=cv4p0401). *[Organic Syntheses](/source/Organic_Syntheses)*; *Collected Volumes*, vol. 4, p. 401..

1. **[^](#cite_ref-25)** Urquhart, G. G.; Gates, J. W. Jr.; Connor, Ralph (1941). "*n*-Dodecyl Mercaptan". *Org. Synth*. **21**: 36. [doi](/source/Doi_(identifier)):[10.15227/orgsyn.021.0036](https://doi.org/10.15227%2Forgsyn.021.0036).

1. **[^](#cite_ref-26)** S. R. Wilson, G. M. Georgiadis (1990). ["Mecaptans from Thioketals: Cyclododecyl Mercaptan"](https://www.orgsyn.org/demo.aspx?prep=cv7p0124). *[Organic Syntheses](/source/Organic_Syntheses)*; *Collected Volumes*, vol. 7, p. 124..

1. **[^](#cite_ref-27)** E. Jones and I. M. Moodie (1990). ["2-Thiophenethiol"](https://www.orgsyn.org/demo.aspx?prep=cv6p0979). *[Organic Syntheses](/source/Organic_Syntheses)*; *Collected Volumes*, vol. 6, p. 979..

1. **[^](#cite_ref-28)** Melvin S. Newman and Frederick W. Hetzel (1990). ["Thiophenols from Phenols: 2-Naphthalenethiol"](https://www.orgsyn.org/demo.aspx?prep=cv6p0824). *[Organic Syntheses](/source/Organic_Syntheses)*; *Collected Volumes*, vol. 6, p. 824..

1. **[^](#cite_ref-29)** Eliel, Ernest L.; Lynch, Joseph E.; Kume, Fumitaka; Frye, Stephen V. (1993). ["Chiral 1,3-oxathiane from (+)-Pulegone: Hexahydro-4,4,7-trimethyl-4*H*-1,3-benzoxathiin"](https://www.orgsyn.org/demo.aspx?prep=cv8p0302). *[Organic Syntheses](/source/Organic_Syntheses)*; *Collected Volumes*, vol. 8, p. 302.

1. **[^](#cite_ref-30)** Kazem-Rostami, Masoud; Khazaei, Ardeshir; Moosavi-Zare, Ahmad; Bayat, Mohammad; Saednia, Shahnaz (2012). "Novel One-Pot Synthesis of Thiophenols from Related Triazenes under Mild Conditions". *Synlett*. **23** (13): 1893–1896. [doi](/source/Doi_(identifier)):[10.1055/s-0032-1316557](https://doi.org/10.1055%2Fs-0032-1316557).

1. **[^](#cite_ref-31)** Leuckart, Rudolf (1890). ["Eine neue Methode zur Darstellung aromatischer Mercaptane"](https://books.google.com/books?id=KxlLAAAAYAAJ&pg=PA179) [A new method for the preparation of aromatic mercaptans]. *Journal für Praktische Chemie*. 2nd series (in German). **41**: 179–224. [doi](/source/Doi_(identifier)):[10.1002/prac.18900410114](https://doi.org/10.1002%2Fprac.18900410114).

1. **[^](#cite_ref-32)** Wood, William F. (1999). "The History of Skunk Defensive Secretion Research". *The Chemical Educator*. **4** (2): 44–50. [doi](/source/Doi_(identifier)):[10.1007/s00897990286a](https://doi.org/10.1007%2Fs00897990286a).

1. **[^](#cite_ref-33)** M. E. Alonso; H. Aragona (1978). "Sulfide Synthesis in Preparation of Unsymmetrical Dialkyl Disulfides: Sec-butyl Isopropyl Disulfide". *Org. Synth*. **58**: 147. [doi](/source/Doi_(identifier)):[10.15227/orgsyn.058.0147](https://doi.org/10.15227%2Forgsyn.058.0147).

1. **[^](#cite_ref-34)** Akhmadullina, A. G.; Kizhaev, B. V.; Nurgalieva, G. M.; Khrushcheva, I. K.; Shabaeva, A. S.; Tugushi, S. O.; Bednov, B. V. (March 1993). "Heterogeneous catalytic demercaptization of light hydrocarbon feedstock". *Chemistry and Technology of Fuels and Oils*. **29** (3): 108–109. [Bibcode](/source/Bibcode_(identifier)):[1993CTFO...29..108A](https://ui.adsabs.harvard.edu/abs/1993CTFO...29..108A). [doi](/source/Doi_(identifier)):[10.1007/bf00728009](https://doi.org/10.1007%2Fbf00728009).

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## External links

- [Mercaptans (or Thiols)](http://www.periodicvideos.com/videos/mv_smelly.htm) at *[The Periodic Table of Videos](/source/The_Periodic_Table_of_Videos)* (University of Nottingham)

- [Applications, Properties, and Synthesis of ω-Functionalized n-Alkanethiols and Disulfides – the Building Blocks of Self-Assembled Monolayers](https://web.archive.org/web/20061010191459/http://dysa.northwestern.edu/CurrOrgChem.pdf) by D. Witt, R. Klajn, P. Barski, B.A. Grzybowski at Northwestern University.

- [Mercaptan](http://www.factmonster.com/ce6/sci/A0832739.html), by *[The Columbia Electronic Encyclopedia](/source/The_Columbia_Electronic_Encyclopedia)*

- [What is Mercaptan?](http://www.columbiagaspamd.com/community_outreach/mercaptan.htm) [Archived](https://web.archive.org/web/20081220153149/http://www.columbiagaspamd.com/community_outreach/mercaptan.htm) 2008-12-20 at the [Wayback Machine](/source/Wayback_Machine), by Columbia Gas of Pennsylvania and Maryland.

- [What Is the Worst Smelling Chemical?](http://chemistry.about.com/od/chemistryfaqs/f/blsmell.htm) [Archived](https://web.archive.org/web/20110606080415/http://chemistry.about.com/od/chemistryfaqs/f/blsmell.htm) 2011-06-06 at the [Wayback Machine](/source/Wayback_Machine), by About Chemistry.

v t e Functional groups Hydrocarbons (only C and H) Alkyl Methyl Ethyl Propyl Cyclopropyl Butyl Pentyl Methylene Bridge Methine Alkene Vinyl Allyl 1-Propenyl Crotyl Allene Cumulene Aryl Phenyl Benzyl Alkyne Carbene Only carbon, hydrogen, and oxygen (only C, H and O) R-O-R Acetal Alcohol Alkoxy Methoxy Ether Enol ether Epoxide Peroxy Hydroperoxy Dioxiranes Ethylenedioxy Methylenedioxy carbonyl Acyl Acetyl Acryloyl Benzoyl Aldehyde Ketene Ketone Ynone Reductone carboxy Carboxyl Acetoxy Anhydride Ester Orthoester Only one element, not being carbon, hydrogen, or oxygen (one element, not C, H or O) Nitrogen Amine Enamine Ammonium Hydrazo Nitrene Imine Oxime Hydrazone Azo Amide Imidate Amidine Carbamate Imide Nitrile Isonitrile Cyanate Isocyanate Nitrate Nitrite Nitro Nitroso NONOate Triazole Tetrazole Silicon Silane Hydrosilane Chlorosilane Silene Silanol Siloxide Siloxane Silanone Silether Silole Silatrane Silicate Phosphorus Phosphate Phosphodiester Phosphonate Phosphite Phosphonous Phosphinate Phosphine oxide Phosphine Phosphonium Phosphaalkene Phosphaalkyne Phosphaallene Arsenic Arsinic acid Arsonic acid Arsole Sulfur Thiol Thioether Sulfonium Thia-crown ether Persulfide Disulfide Sulfenic acid Thiosulfinate Sulfoxide Thiosulfonate Sulfinic acid Sulfone Sulfonic acid Thioketone Thial Thioester Thionoester Thioxanthate Xanthate Boron Boronic acid Borinic acid Selenium Selenol Selenonic acid Seleninic acid Selenenic acid Selone Selenoether Tellurium Tellurol Telluroketone telluroether Polonium Polonol Polonoether Halo Haloalkane Fluoroethyl Trifluoromethyl Trichloromethyl Trifluoromethoxy Hypervalent iodine Vinyl halide Iodide Acyl halide Chloride Perchlorate Other Isothiocyanate Phosphoramides Sulfenyl chloride Sulfonamide Thiocyanate Sulfinylamines See also chemical classification chemical nomenclature inorganic organic

Authority control databases International GND National United States Japan Czech Republic Israel Other Yale LUX

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