The substituent effect on the single and double hydrogen atom transfer reactions in para-substituted benzoic acid isobutyl esters

✍ Scribed by Seiji Tobita; Susumu Tajima; Toshikazu Tsuchiya

• Publisher: John Wiley and Sons
• Year: 1984
• Tongue: English
• Weight: 363 KB
• Volume: 19
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/oms.1210190707

✦ Synopsis

The substituent effect on the single and double hydrogen atom transfer reactions in para-substituted benzoic acid isobutyl esters has been investigated by electron impact mass spectrometry. Electron-donahg substituents favour formation of the [M-C4&]+' ion generated by single hydrogen atom transfer reaction (McLafferty rearrangement), whereas electron-withdrawing substituents favour formation of the [M-C&]+ ion generated by double hydrogen atom transfer reaction. In the case of the latter compounds, the m/z% ([C&]+.) ion, which is generated by single hydrogen atom transfer reaction with charge migration, is very intense, while in the former compounds, the m/z 56 ion is very weak. These observations can be reasonably explained on thermochemid grounds based on the sum of the standard heats of formation of the fragments.