Gallate Diesters

The products from the acid catalyzed Fischer esterification of gallic acid with isopropanol (see “Fantastic Fischer” April 25, 2009) was chromatographed to purify isopropyl gallate. In addition to isopropyl gallate, another gallic_esters_structchromatographic peak was observed. This peak was collected and the NMR performed. Interestingly, this spectrum displayed three aromatic hydrogen signals at 7.207 (d), 7.153 (d) and 7.092 (s). Isopropyl gallate gives a singlet at 7.05 ppm. It also had four distinct septets at 5.130, 5.115 (overlapped), 4.692, and 4.562. Isopropyl gallate gives a septet at 5.129 ppm. The total integration for the aromatic hydrogens and the septets is about equal. I think what I am looking at is a mixture of two compounds created by the esterification of isopropyl gallate at the C3 and C4 hydroxy groups.
gallate_esters

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