Diphosgene

<h2 id="production-and-uses">Production and uses</h2>
<p>Diphosgene is prepared by <a href="/facts/Radical_(chemistry)/qFymuVoT">radical</a> chlorination of <a href="/facts/Methyl_chloroformate/8BDLGmlQ">methyl chloroformate</a> under <a href="/facts/Ultraviolet/kncBUqn5">UV light</a>:<a class="footnote-ref" id="fnref:1" href="#fn:1"><sup>1</sup></a>
</p>
Cl-CO-OCH3 + 3 Cl2 —(hv)→ Cl-CO-OCCl3 + 3 HCl
<p>Another method is the radical chlorination of methyl formate:<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>
</p>
H-CO-OCH3 + 4 Cl2 —(hv)→ Cl-CO-OCCl3 + 4 HCl
<p>Diphosgene converts to phosgene upon heating or upon <a href="/facts/Catalysis/LPBS7TQC">catalysis</a> with <a href="/facts/Charcoal/tpYGBHTn">charcoal</a>. It is thus useful for reactions traditionally relying on phosgene. For example, it convert <a href="/facts/Amine/JvfYJfP6">amines</a> into <a href="/facts/Isocyanate/YYDoDBgp">isocyanates</a>, secondary amines into <a href="/facts/Carbamoyl/pNQWDyam">carbamoyl</a> chlorides, <a href="/facts/Carboxylic_acid/U4xuMosy">carboxylic acids</a> into <a href="/facts/Acid_chloride/R4ppUXre">acid chlorides</a>, and <a href="/facts/Formamide/IP7mDEFF">formamides</a> into <a href="/facts/Isocyanide/VmkIBMKR">isocyanides</a>. Diphosgene serves as a source of two equivalents of phosgene:
</p>
2 RNH2 + ClCO2CCl3 → 2 RNCO + 4 HCl
<p>With α-<a href="/facts/Amino_acid/WDxYwBny">amino acids</a> diphosgene gives the acid chloride-isocyanates, OCNCHRCOCl, or <i>N</i>-carboxy-amino acid anhydrides depending on the conditions.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a>
</p><p>It hydrolyzes to release HCl in humid air.
</p><p>Diphosgene is used in some laboratory preparations because it is easier to handle than phosgene.
</p>
<h2 id="role-in-warfare">Role in warfare</h2>
<p>Diphosgene was originally developed as a <a href="/facts/Pulmonary_agent/Efes5SXS">pulmonary agent</a> for <a href="/facts/Chemical_warfare/zT4t2DGk">chemical warfare</a>, a few months after the first use of phosgene. It was used as a poison gas in <a href="/facts/Artillery/GLpMYG9o">artillery</a> shells by <a href="/facts/Germany/paluuWBX">Germany</a> during <a href="/facts/World_War_I/vITTUanQ">World War I</a>. The first recorded battlefield use was in May 1916.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> Diphosgene was developed because the vapors could destroy the filters of the <a href="/facts/WWI_gas_mask/1I8Y1wSs">gas masks</a> in use at the time.
</p>
<h2 id="safety">Safety</h2>
<p>Diphosgene has a relatively high <a href="/facts/Vapor_pressure/whrEr96T">vapor pressure</a> of 10 mm Hg (1.3 kPa) at 20 °C and decomposes to <a href="/facts/Phosgene/Adeazsck">phosgene</a> around 300 °C. Exposure to diphosgene is similar in hazard to phosgene.
</p>
<h2 id="see-also">See also</h2>
<ul><li><a href="/facts/Phosgene/Adeazsck">Phosgene</a></li>
<li><a href="/facts/Triphosgene/Qo6Krohd">Triphosgene</a></li>
<li><a href="/facts/Carbonyldiimidazole/UhPyRR1c">Carbonyldiimidazole</a></li></ul>

<h2 id="external-links">External links</h2>
<ul><li><a href="http://author.emedicine.com/EMERG/topic906.htm">medical care guide</a>.</li>
<li><a href="https://web.archive.org/web/20031103141039/http://www.nbc-med.org/SiteContent/MedRef/OnlineRef/FieldManuals/fm8_285/PART_I/chapter5.htm">NATO guide</a>, includes treatment advice</li>
<li><a href="http://www.boc.com/gases/pdf/msds/G067.pdf">material safety data sheet</a> (PDF, for phosgene and diphosgene treated as one).</li>
<li><a href="http://www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=US&language=en&productNumber=23261&brand=ALDRICH&PageToGoToURL=http%3A%2F%2Fwww.sigmaaldrich.com%2Fcatalog%2Fsearch%3Finterface%3DAll%26term%3Ddiphosgene%26lang%3Den%26region%3DUS%26focus%3Dproduct%26N%3D0%2B220003048%2B219853269%2B219853286%26mode%3Dmatch%2520partialmax">MSDS for diphosgene specifically</a></li></ul>

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Keisuke Kurita and Yoshio Iwakura (1979). "Trichloromethyl Chloroformate as a Phosgene Equivalent: 3-Isocyanatopropanoyl Chloride". Organic Syntheses. 59: 195; Collected Volumes, vol. 6, p. 715.
 <a href="http://www.orgsyn.org/demo.aspx?prep=cv6p0715" target="_blank">http://www.orgsyn.org/demo.aspx?prep=cv6p0715</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Lohs, K. H.: Synthetische Gifte; Berlin (east), 1974 (German). <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Encyclopedia of Reagents for Organic Synthesis, 2001, doi:10.1002/047084289X, hdl:10261/236866, ISBN 978-0-471-93623-7 <a href="978-0-471-93623-7" target="_blank">978-0-471-93623-7</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Jones, Simon; Hook, Richard (2007). World War I Gas Warfare Tactics and Equipment. Osprey Publishing. ISBN 978-1-84603-151-9. <a href="978-1-84603-151-9" target="_blank">978-1-84603-151-9</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
</ol>

Diphosgene open-in-new

Diphosgene