{"id":38,"date":"2005-08-27T19:32:56","date_gmt":"2005-08-28T00:32:56","guid":{"rendered":"http:\/\/www.nomad.priv.at\/researchblog\/?p=38"},"modified":"2005-08-27T19:32:56","modified_gmt":"2005-08-28T00:32:56","slug":"first-nmr-problem-solved","status":"publish","type":"post","link":"http:\/\/www.nomad.priv.at\/researchblog\/?p=38","title":{"rendered":"First NMR problem &#8230; solved"},"content":{"rendered":"<p>Well, right during one of my training sessions, the first measurement problem surfaced. I want to monitor malonic acid degradation in aqeous solution and therefore I have prepared a couple of standards in D<sub>2<\/sub>O. Strangely, the singlet at 45 ppm always showed up as a quintett, pointing towards coupling with some other species other than H (the decoupler was working fine and the <sup>1<\/sup>H spectrum was good too. All other <sup>13<\/sup>C spectra that I recorded were fine too. The only other NMR active species present was deuterium, so I speculated that some exchange reactions must be going on, replacing the H in the molecule with D. The most acidic H was the one on the carboxylic acid group, but after discussion with the NMR facilities manager, we ruled out this process, because it takes place too quickly.<\/p>\n<p>So the only other possibility was the C<sub>2<\/sub> and its 2 (less) acidic H atoms. And this was indeed the case. Assuming this exchange, the resulting quintet makes sense and in diluted D<sub>2<\/sub>O (only 10%, with the rest being H<sub>2<\/sub>O, this rather weak effect was not observed. During the day of measurements, I have also posted the issue on sci.chem and got my thoughts and experimental results confirmed. Nice!<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Well, right during one of my training sessions, the first measurement problem surfaced. I want to monitor malonic acid degradation in aqeous solution and therefore I have prepared a couple of standards in D2O. Strangely, the singlet at 45 ppm always showed up as a quintett, pointing towards coupling with some other species other than &hellip; <a href=\"http:\/\/www.nomad.priv.at\/researchblog\/?p=38\" class=\"more-link\">Continue reading <span class=\"screen-reader-text\">First NMR problem &#8230; solved<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-38","post","type-post","status-publish","format-standard","hentry","category-research"],"_links":{"self":[{"href":"http:\/\/www.nomad.priv.at\/researchblog\/index.php?rest_route=\/wp\/v2\/posts\/38","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.nomad.priv.at\/researchblog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.nomad.priv.at\/researchblog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.nomad.priv.at\/researchblog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.nomad.priv.at\/researchblog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=38"}],"version-history":[{"count":0,"href":"http:\/\/www.nomad.priv.at\/researchblog\/index.php?rest_route=\/wp\/v2\/posts\/38\/revisions"}],"wp:attachment":[{"href":"http:\/\/www.nomad.priv.at\/researchblog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=38"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.nomad.priv.at\/researchblog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=38"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.nomad.priv.at\/researchblog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=38"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}