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Thermal degradation mechanism for citalopram and escitalopram

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A Correction to this article was published on 18 May 2018

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Abstract

Citalopram, [(R,S)-1-[3-(dimethylamino)propyl]-1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile] hydrobromide and its S-isomer, escitalopram oxalate, were analyzed regarding thermal degradation by TG/DTG–DTA, DSC, hot-stage microscopy and coupled TG-FTIR techniques. Citalopram presented a decomposition in a single step after melting at 189.3 °C (ΔHfus= 94.4 J g−1), without evidences of crystallization on cooling. Thermal techniques results combined with those from evolved gas analysis suggested decomposition via HBr, dimethylamine and fluorobenzene. Escitalopram presented a thermal degradation that started with the decomposition of the counter ion, after melting at 158.3 °C (ΔHfus= 106.2 J g−1), without evidences of crystallization on cooling followed by the release of dimethylamine and fluorobenzene. GC–MS of the residues confirmed the observations from the thermal analysis, but revealed several intermediates in the degradation of the racemate, probably due to the mixture of isomers. Differences in thermal behavior were attributed to differences in structure and counter ions. A tentative mechanism for their thermal behavior is proposed in both cases.

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  • 18 May 2018

    The structural formulas of the oxalic acid are incorrect in both Figures 1 and 6.

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Acknowledgements

The authors are grateful to agencies FAPESP (Processes: 2014/22142-4 and 2015/09299-4) and CNPq for support.

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Authors and Affiliations

  1. Instituto de Química de São Carlos, Universidade de São Paulo – USP, Avenida do Trabalhador São-carlense, 400, São Carlos, SP, 13565-590, Brazil

    B. V. Pinto, A. P. G. Ferreira & E. T. G. Cavalheiro

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  1. B. V. Pinto
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  2. A. P. G. Ferreira
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  3. E. T. G. Cavalheiro
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Correspondence to E. T. G. Cavalheiro.

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Pinto, B.V., Ferreira, A.P.G. & Cavalheiro, E.T.G. Thermal degradation mechanism for citalopram and escitalopram. J Therm Anal Calorim 133, 1509–1518 (2018). https://doi.org/10.1007/s10973-018-7226-7

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  • DOI: https://doi.org/10.1007/s10973-018-7226-7

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