Kinetic analysis and mechanism of the hydrolytic degradation of squaramides and squaramic Acids

Show simple item record Ximenis Campins, Marta Bustelo, Emilio Algarra, Andrés G. Vega Reynés, Manuel Rotger Pons, María del Carmen Basallote, Manuel G. Costa Torres, Antonio 2018-12-11T11:50:51Z 2018-12-11T11:50:51Z
dc.description.abstract [eng] The hydrolytic degradation of squaramides and squaramic acids, the product of partial hydrolysis of squaramides, has been evaluated by UV spectroscopy at 37 °C in the pH range 3−10. Under these conditions, the compounds are kinetically stable over long time periods (>100 days). At pH >10, the hydrolysis of the squaramate anions shows first-order dependence on both squaramate and OH−. At the same temperature and [OH−], the hydrolysis of squaramides usually displays biphasic spectral changes (A → B → C kinetic model) with formation of squaramates as detectable reaction intermediates. The measured rates for the first step (k1 ≈ 10−4 M−1 s−1) are 2−3 orders of magnitude faster than those for the second step (k2 ≈ 10−6 M−1 s−1). Experiments at different temperatures provide activation parameters with values of ΔH⧧ ≈ 9−18 kcal mol−1 and ΔS⧧ ≈ −5 to −30 cal K−1 mol−1. DFT calculations show that the mechanism for the alkaline hydrolysis of squaramic acids is quite similar to that of amides.
dc.format application/pdf
dc.relation.isformatof Versió postprint del document publicat a:
dc.relation.ispartof Journal of Organic Chemistry, 2017, vol. 82, p. 2160-2170
dc.rights (c) American Chemical Society , 2017
dc.subject.classification 54 - Química
dc.subject.other 54 - Chemistry. Crystallography. Mineralogy
dc.title Kinetic analysis and mechanism of the hydrolytic degradation of squaramides and squaramic Acids
dc.type info:eu-repo/semantics/article
dc.type info:eu-repo/semantics/acceptedVersion 2018-12-11T11:50:52Z
dc.rights.accessRights info:eu-repo/semantics/openAccess

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