Kinetic Study of Thermal 1,3-Dipolar Cycloaddition of Azomethine Ylides by Using Differential Scanning Calorimetry

Authors

  • Juan Mancebo-Aracil,

    1. Departamento de Química Orgánica e Instituto de Síntesis Orgánica (ISO), Universidad de Alicante, 03080 Alicante (Spain), Fax: (+34) 965903549
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  • Dr. María J. Muñoz-Guillena,

    1. Servicios Técnicos de Investigación, Universidad de Alicante, 03080 Alicante (Spain)
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  • Ion Such-Basáñez,

    1. Servicios Técnicos de Investigación, Universidad de Alicante, 03080 Alicante (Spain)
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  • Dr. José M. Sansano-Gil

    Corresponding author
    1. Departamento de Química Orgánica e Instituto de Síntesis Orgánica (ISO), Universidad de Alicante, 03080 Alicante (Spain), Fax: (+34) 965903549
    • Departamento de Química Orgánica e Instituto de Síntesis Orgánica (ISO), Universidad de Alicante, 03080 Alicante (Spain), Fax: (+34) 965903549
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Abstract

The kinetics of 1,3-dipolar cycloaddition involving azomethine ylides, generated from thermal 1,2-prototropy of the corresponding imino ester, employing differential scanning calorimetry (DSC), is surveyed. Glycine and phenylalanine derived imino esters have different behavior. The first one prefers reacting with itself at 75 °C, rather than with the dipolarophile. However, the α-substituted imino ester gives the cycloadduct at higher temperatures. Thermal dynamic analysis, by using 1H NMR spectroscopy, of the neat reaction mixture of the glycine derivative reveals the presence of signals corresponding to the dipole in small abundance. The non-isothermal and isothermal DSC curves of the cycloaddition of phenylalaninate and diisobutyl fumarate are obtained from freshly prepared samples. The application of known kinetic models and mathematical multiple non-linear regressions (NLR) allow the determintion and comparison of Ea, lnA, reaction orders, and reaction enthalpy values. Finally a rate equation for each different temperature studied can be established for this particular thermal cycloaddition.

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