Methylarsonic acid

<h2 id="reactions">Reactions</h2>
<p>Near physiological pH, methanearsonic acid converts to its conjugate bases, the methylarsonates.  These include CH3AsO3H− and CH3AsO2−3.
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<h2 id="synthesis-and-biosynthesis">Synthesis and biosynthesis</h2>
<p class="note">Not to be confused with <a href="/facts/Meyer_synthesis/qkz2XScK">Meyer synthesis</a>.</p>
<p>Reaction of <a href="/facts/Arsenous_acid/j6Agkbmb">arsenous acid</a> with <a href="/facts/Methyl_iodide/uUKdue80">methyl iodide</a> gives methylarsonic acid.  This historically significant conversion is called the Meyer reaction:<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>
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As(OH)3 + CH3I  +  NaOH  → CH3AsO(OH)2  + NaI  +  H2O
<p>The then-novel aspect of the reaction was that alkylation occurs at arsenic, leading to oxidation of arsenic from <a href="/facts/Oxidation_state/W53W6s6V">oxidation state</a> +3 to +5.
</p><p>The <a href="/facts/Biomethylation/EvDMWVW5">biomethylation</a> of arsenic compounds is thought to start with the formation of methanearsonates.  Thus, trivalent arsenic compounds are methylated to give methanearsonate. <a href="/facts/S-Adenosylmethionine/oAsJ0SSR"><i>S</i>-Adenosylmethionine</a> is the methyl donor.  The methanearsonates are the precursors to <a href="/facts/Cacodylate/jFVRj127">cacodylates</a>, again by the cycle of reduction (to methylarsonous acid) followed by a second methylation.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a>
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<h2 id="safety">Safety</h2>
<p>Like most arsenic compounds, it is highly toxic.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a>
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<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Grund, S. C.; Hanusch, K.; Wolf, H. U. "Arsenic and Arsenic Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a03_113.pub2. ISBN 978-3-527-30673-2. <a href="978-3-527-30673-2" target="_blank">978-3-527-30673-2</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>G. Meyer (1883). "Ueber einige anomale Reaktionen". Berichte der deutschen chemischen Gesellschaft. 13: 1439–1443. doi:10.1002/cber.188301601316. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
<li id="fn:3"><p>Styblo, M.; Del Razo, L. M.; Vega, L.; Germolec, D. R.; LeCluyse, E. L.; Hamilton, G. A.; Reed, W.; Wang, C.; Cullen, W. R.; Thomas, D. J. (2000). "Comparative toxicity of trivalent and pentavalent inorganic and methylated arsenicals in rat and human cells". Archives of Toxicology. 74: 289–299. doi:10.1007/s002040000134. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li>
<li id="fn:4"><p>Styblo, M.; Del Razo, L. M.; Vega, L.; Germolec, D. R.; LeCluyse, E. L.; Hamilton, G. A.; Reed, W.; Wang, C.; Cullen, W. R.; Thomas, D. J. (2000). "Comparative toxicity of trivalent and pentavalent inorganic and methylated arsenicals in rat and human cells". Archives of Toxicology. 74: 289–299. doi:10.1007/s002040000134. <a href="/wiki/Doi_(identifier)" target="_blank">/wiki/Doi_(identifier)</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li>
</ol>

Methylarsonic acid open-in-new

Methylarsonic acid