{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,15]],"date-time":"2026-07-15T23:10:53Z","timestamp":1784157053596,"version":"3.55.0"},"reference-count":24,"publisher":"Wiley","issue":"10","license":[{"start":{"date-parts":[[2025,2,25]],"date-time":"2025-02-25T00:00:00Z","timestamp":1740441600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":["analyticalsciencejournals.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Rapid Comm Mass Spectrometry"],"published-print":{"date-parts":[[2025,5,30]]},"abstract":"<jats:title>ABSTRACT<\/jats:title>\n                  <jats:sec>\n                    <jats:title>Rationale<\/jats:title>\n                    <jats:p>This study compares the EI fragmentation mechanisms for the regioisomeric 2\u2010, 3\u2010, and 4\u2010ethoxy and methoxymethyl substituted methyl benzoates. These compounds represent isomerism in disubstituted aromatic ring and position of oxygen in the ether substituent. These esters are required synthetic intermediates for the design and synthesis of phenethylamine analogs as potential new drug substances. Regioisomerism of substituents and heteroatoms position often plays a significant role in drug action, potency, and MS fragmentations.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      The ethoxy substituted isomers were obtained from commercial source. The methoxymethyl substituted isomers were prepared from 2\u2010, 3\u2010, and 4\u2010(chloromethyl)benzoyl chloride by methoxide displacement using Na\/methanol. The D\n                      <jats:sub>3<\/jats:sub>\n                      \u2010methyl esters were prepared by acid\u2010catalyzed ester exchange using methanol\u2010D\n                      <jats:sub>4<\/jats:sub>\n                      and ethyl esters as substrates. The compounds were evaluated using GC, stable isotope, EI, and MS\/MS studies.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      The major EI\u2010MS fragments for methyl ethoxybenzoates are\n                      <jats:italic>m\/z<\/jats:italic>\n                      152, 149, and a base peak (3\u2010 and 4\u2010substituted isomers) at\n                      <jats:italic>m\/z<\/jats:italic>\n                      121 from the loss of ethene, methoxy radical, and carbomethoxy radical, respectively. The\n                      <jats:italic>ortho<\/jats:italic>\n                      effect in methyl 2\u2010ethoxybenzoate yields a base peak at\n                      <jats:italic>m\/z<\/jats:italic>\n                      120 and other unique cations at\n                      <jats:italic>m\/z<\/jats:italic>\n                      133, 147, and 165 due to the interaction of\n                      <jats:italic>ortho\u2010<\/jats:italic>\n                      side chains. The major\n                      <jats:italic>ortho<\/jats:italic>\n                      effect in methyl 2\u2010methoxymethylbenzoate arises from the ease of formation of the hydrogen rearrangement product yielding the\n                      <jats:italic>m\/z<\/jats:italic>\n                      133 base peak and inhibiting the formation of\n                      <jats:italic>m\/z<\/jats:italic>\n                      121 and 179 ions observed in 3\u2010 and 4\u2010substituted isomers.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>\n                      The methoxymethyl substituted isomers yield more fragments than the ethoxy isomers. Thus, the alkyl ether is a more active participant in the fragmentation processes than the aromatic\/phenolic ether for the ethoxy series. The major\n                      <jats:italic>ortho<\/jats:italic>\n                      effect in this series favors the distonic molecular radical cation formation yielding the\n                      <jats:italic>m\/z<\/jats:italic>\n                      133 base peak for the 2\u2010substituted isomer and inhibiting the formation of\n                      <jats:italic>m\/z<\/jats:italic>\n                      121 and 179 species.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1002\/rcm.10013","type":"journal-article","created":{"date-parts":[[2025,3,10]],"date-time":"2025-03-10T07:04:04Z","timestamp":1741590244000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":2,"title":["Comparison of Electron Ionization Fragmentation Pathways for Regioisomeric Ethoxy and Methoxymethyl Substituted Benzoate Esters"],"prefix":"10.1002","volume":"39","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-4063-605X","authenticated-orcid":false,"given":"C.\u00a0Randall","family":"Clark","sequence":"first","affiliation":[{"name":"Department of Drug Discovery and Development, Harrison College of Pharmacy Auburn University  Auburn Alabama USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2694-7561","authenticated-orcid":false,"given":"Younis","family":"Abiedalla","sequence":"additional","affiliation":[{"name":"Department of Drug Discovery and Development, Harrison College of Pharmacy Auburn University  Auburn Alabama USA"},{"name":"Department of Medicinal Chemistry, Faculty of Pharmacy Omar Al\u2010Mukhtar University  Al Bayda Libya"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2025,2,25]]},"reference":[{"key":"e_1_2_7_2_1","doi-asserted-by":"publisher","DOI":"10.1002\/rcm.9654"},{"key":"e_1_2_7_3_1","doi-asserted-by":"publisher","DOI":"10.1002\/rcm.8593"},{"key":"e_1_2_7_4_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.talanta.2017.04.067"},{"key":"e_1_2_7_5_1","doi-asserted-by":"publisher","DOI":"10.1021\/ac500316x"},{"key":"e_1_2_7_6_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.forc.2021.100314"},{"key":"e_1_2_7_7_1","doi-asserted-by":"publisher","DOI":"10.1255\/ejms.1185"},{"key":"e_1_2_7_8_1","doi-asserted-by":"publisher","DOI":"10.1007\/s11419-015-0270-0"},{"key":"e_1_2_7_9_1","volume-title":"PiHKAL: A Chemical Love Story","author":"Shulgin A.","year":"1991"},{"key":"e_1_2_7_10_1","doi-asserted-by":"publisher","DOI":"10.1016\/S0091-3057(97)00323-7"},{"key":"e_1_2_7_11_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.forc.2019.100164"},{"key":"e_1_2_7_12_1","doi-asserted-by":"publisher","DOI":"10.1093\/chromsci\/bms031"},{"key":"e_1_2_7_13_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.forsciint.2010.03.033"},{"key":"e_1_2_7_14_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.forsciint.2008.12.003"},{"key":"e_1_2_7_15_1","doi-asserted-by":"publisher","DOI":"10.1093\/chromsci\/46.8.671"},{"key":"e_1_2_7_16_1","volume-title":"NIST Chemistry WebBook, NIST Standard Reference Database Number 69","author":"Linstrom P. 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