Organic Molecules Containing Sulfur Functional Groups

Many organic molecules contain sulfur functional groups and have their own importance in chemistry as well as biology. Some of the organic molecules which contain sulfur functional groups and the corresponding sulfur functionality is given below:

  • Thiol-Sulfhydryl group
  • Sulfide (Thioether)-Sulfide group
  • Disulfide-Disulfide group
  • Sulfoxide-Sulfinyl group
  • Sulfinic acid-Sulfino group
  • Sulfonic acid-Sulfo group

Sulfur Functional Groups in Detail


Thiol is a class of organic compounds that contains a functional group consisting of a sulfur atom with a hydrogen atom (-SH). This functional group is known as either a thiol or a sulfur oxide group, as it is the sulfur equivalent of an alcohol group (-OH). Thiols are also addressed to as mercaptans, more generally.


Sulfide commonly corresponds in organic chemistry to the bond C-S-C, though the word thioether is somewhat vague. The thioethyl sulfide, for instance, is CH3-S-CH3. The mathematical formula C6H4S is used for polyphenylene sulfide. Often the term sulfide corresponds to the functional unit -SH ions. For instance, CH3-SH can represent methyl sulfide.

Different sulfur functional groups.


A disulfide linkage is a single covalent bonding formed through the Thiol class pairing. The link is often referred to as an SS or disulfide bridge. Therefore C-S-S-C is the general connection. The bond is technically called a persulfide, although this language is seldom used, analogous to peroxide (R-O-O-R).


Acid molecules that comprise (SOH) groups are classified as following by the number of oxygen atoms present within the group:

RSOH sulfenic acid

RSO2H sulfonic acid

RSO3H sulfonic acid

  • A sulfenic acid has the basic formulation RSOH, a sulfuric complex, and oxoacid. Typically, sulfenic acids are unpredictable. Benzene sulfenic acid, PhSOH, are few examples of sulfenic acid.
  • Sulfinic acids have a formula RSO(OH) and are oxoacids.
  • Sulfonic acid has the equation H-S(=O)2-OH. It is considered a tautomer of sulfuric acid. This compound is irrelevant, but there are some derived ingredients, with R-S(=O)2-OH in different R giving rise to salts or esters, called sulfonates, that can form.
  • Sulfonic esters are a family of generic formula R-SO2-OR .
  • A sulfoxide is a chemical substance with two carbon atoms connected with a sulfinyl functional group. Sulfoxides may be regarded as sulphides oxidized.
  • A sulfone is a chemical substance containing a two-carbon functional sulfonyl component. The core sulfur atom is doubly oxygen-bonded and has two other replacements for hydrocarbons. R-S(=O)(=O)-R is the general structure formula in which R and R' is endogenous. By the intermediary forming of sulfoxides, sulfides are also the beginning resources for sulfones during organic oxidation such as dimethyl sulfide is oxidated to dimethyl sulfoxide and finally converted to dimethyl sulfone.

Mercaptans (Thiols)

In their chemistry, Sulphur seems to be very identical to oxygen and several of the organic Sulphur molecules are like their equivalents in oxygen. It has a chemical formula of R-SH.

Mercaptans (Thio-alcohol) are organic compounds of the form R-SH (R = alkyl group). Mercaptans interact easily with mercuric oxide to create crystalline derivatives of mercury and hence the name. The mercaptans can be made using alkyl halides on an acidic potassium hydrosulfide solution.

Thiols are colorless insoluble liquids with a specific odor. They produce sulfonic acids when oxidized with nitric acid. They interact with aldehydes and ketones with water removal resulting in the formation of mercaptol as well as mercaptals. CH3-SH, a methyl mercaptan, boils at 5.8°C and creates crystalline hydrate after combining with water. C2H5-SH is an ethyl meraptan, a solvent that melts at a temperature of 36.2°C. It is commonly utilized in sulfonal production. The Hg (SC2H5)2 mercury salt precipitates in the plate from alcohol. It breaks down into mercury and ethyldisufide once heated by alcohol to 190°C.

Mercaptans however identical to as well as identical to the alcohols in the name are foul-smelling compounds. Methyl mercaptan, CH3-SH, can be used as a reference.

Biological Role

The thiol group performs a significant component in biological processes as the functional component of amino acid cysteine.

If during the process of protein folding, thiol units of two cysteine molecules such as monomers or compounds are brought together, an oxidation reaction may produce a disulfide-bonded cystine unit (-S-S-).

Disulfide associations may relate to the tertiary protein configuration by establishing very tight covalent links among polypeptide chains, whether the cysteines are components of a common chain, or by contributing to the quaternary arrangement of multi-unit proteins. Strong or light chains of antibodies with disulfide bonds are kept connected. The curly hair twists are also the result of the production of cysteine.

Chemical compounds in hair straightening are reduction products to free cysteine sulphur crossings and chemicals in hair curling are oxidizing cysteine sulfide units to form cystine disulfide bonds. The chemicals employed in hair-stressing are reductive chemicals. In an active site, an enzyme group sulfhydryl may also form noncovalent connections with the surface of the enzyme that contributes to the catalytic action. The functional unit in cysteine proteases consists of functional cysteine residues at the position.

An image showing sulfur functional groups preparation

Sulfonic Acids - Sulfonates

The sulfur compounds analogous to carboxylic acids are sulfonic acids.

Sulfonic Acid

The processing of organic compounds with sulfuric acid produces sulfonic acids. The configuration of carboxylic acids is SO3H instead of -COOH. The sulfonic acid proton is much more acidic than those of the carboxylic acid proton. The classes of sulfonic acids are also used to improve the water solubility of an organic substance because the sulfonate ion predominates at nearly all pH levels.

The H-SO2-OH hypothesized acid is sulfonic acid. This molecule is an HO-S (=O)-OH tautomer which is somewhat stable and can probably be converted very easily if produced. This is the most common compound. Though this compound is irrelevant, several related molecules have R-S (=O)2-OH formulation in different R compounds. These sulfonates can then become salts and ester.


A sulfoxide is a chemical compound that contains a working group of sulfinyl bound to two atoms of carbon. Sulfoxides may be formed by sulfide oxidization.

Nature of the Bond

In general R-S(=O)-R' is the molecular equation of a Sulfoxide. R and R' are organic groups. The relationship among atoms of sulfur or oxygen is not a typical double bond (overlapping p-bonds between the p-orbitals of neighboring atoms), and it is thought that much of the connection lies in the electrostatic attraction around the negative oxygen and its positive sulfur.

Common Mistakes

The most common mistake could be the identification of different sulfur functional groups. It might be confusing so proper identification should be done.

Context and Applications

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for

  • B.Sc. Chemistry, Biotechnology, Biochemistry and Biology
  • M.Sc. Chemistry, Biotechnology, Biochemistry and Biology

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Organic Compounds with Sulphur-containing Functional Groups


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