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Title: Protonation effect on chemical shifts of some piperidones — unusual influence by anions
Authors: Manimekalai, A
Jayabharathi, J
Keywords: NMR data
anion influence
Issue Date: Jul-2006
Publisher: CSIR
Series/Report no.: <b>Int.Cl.<sup>8 </sup>C07D</b><b></b>
Abstract: <sup>1</sup>H and <sup>13</sup>C NMR spectra are recorded for twelve picrate derivatives <b>4-15</b> derived from some 3-alkyl-2,6-diarylpiperidin-4-ones and 3,5-dimethyl-2,6-diarylpiperidin-4-ones. The difference in the chemical shift of equatorial methylene proton and axial methylene proton at C(5) [<img src='/image/spc_char/delta.gif' border=0> = <img src='/image/spc_char/delta1.gif' border=0><sub>eq </sub> - <img src='/image/spc_char/delta1.gif' border=0><sub>ax</sub>] is highly negative in <b>4-13</b> which is in contrast to the value observed in the corresponding parent piperidin-4-ones and this is attributed to the <i>syn </i>1,3-diaxial interaction between the axial N-H bond and axial hydrogen at C-5. The effect of protonation on the chemical shifts was studied in detail. The chemical shifts of the heterocyclic ring protons are influenced by the picrate anion.
Description: 1686-1691
ISSN: 0975-0983(Online); 0376-4699(Print)
Appears in Collections:IJC-B Vol.45B(07) [July 2006]

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