Editing Mustard gas (section)

===Mechanism of cellular toxicity===
[[File:Mustard-dna.svg|thumb|upright=1.8|Mustard gas alkylating an amino group via conversion to a sulfonium ion (2-chloroethylthiiranium)]]
Sulfur mustards readily eliminate [[chloride]] ions by intramolecular [[nucleophilic substitution]] to form cyclic [[sulfonium]] ions. These very reactive intermediates tend to permanently [[alkylation|alkylate]] [[nucleotide]]s in [[DNA]] strands, which can prevent cellular division, leading to [[apoptosis|programmed cell death]].<ref name="opcw.org">[http://www.opcw.org/about-chemical-weapons/types-of-chemical-agent/mustard-agents/ Mustard agents: description, physical and chemical properties, mechanism of action, symptoms, antidotes and methods of treatment]. Organisation for the Prohibition of Chemical Weapons. Accessed June 8, 2010.</ref> Alternatively, if cell death is not immediate, the damaged DNA can lead to the development of cancer.<ref name="opcw.org" /> [[Oxidative stress]] is another pathology involved in mustard gas toxicity.<ref>{{Cite journal |last=Ghabili |first=Kamyar |last2=Agutter |first2=Paul S. |last3=Ghanei |first3=Mostafa |last4=Ansarin |first4=Khalil |last5=Shoja |first5=Mohammadali M. |date=October 2010 |title=Mustard gas toxicity: the acute and chronic pathological effects |url=https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/jat.1581 |journal=Journal of Applied Toxicology |language=en |volume=30 |issue=7 |pages=627–643 |doi=10.1002/jat.1581 |issn=0260-437X}}</ref>

Various compounds with the structural subgroup BC<sub>2</sub>H<sub>4</sub>X, where X is any [[leaving group]] and B is a [[Lewis base]], have a common name of mustard. Such compounds can form cyclic [[onium ion|"onium" ions]] (sulfonium, [[ammonium]], etc.) that are good [[alkylating agent]]s. These compoudsn include bis(2-haloethyl)ethers ([[Bis(chloroethyl) ether|oxygen mustards]]), the (2-haloethyl)amines ([[nitrogen mustard]]s), and [[sesquimustard]], which has two α-chloroethyl thioether groups (ClC<sub>2</sub>H<sub>4</sub>S−) connected by an ethylene bridge (−C<sub>2</sub>H<sub>4</sub>−). These compounds have a similar ability to alkylate DNA, but their physical properties vary.