Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Thermodynamic Stability of Fenclorim and Clopyralid

Version 1 : Received: 19 November 2021 / Approved: 22 November 2021 / Online: 22 November 2021 (10:44:06 CET)

How to cite: Almeida, A.R.; Pinheiro, B.D.; Lobo Ferreira, A.I.; Monte, M.J. Thermodynamic Stability of Fenclorim and Clopyralid. Preprints 2021, 2021110375 (doi: 10.20944/preprints202111.0375.v1). Almeida, A.R.; Pinheiro, B.D.; Lobo Ferreira, A.I.; Monte, M.J. Thermodynamic Stability of Fenclorim and Clopyralid. Preprints 2021, 2021110375 (doi: 10.20944/preprints202111.0375.v1).

Abstract

The present work reports an experimental thermodynamic study of two nitrogen heterocyclic organic compounds, fenclorim and clopyralid, that have been used as herbicides. The sublimation vapor pressures of fenclorim (4,6-dichloro-2-phenylpyrimidine) and of clopyralid (3,6-dichloro-2-pyridinecarboxylic acid) were measured, at different temperatures, using a Knudsen mass-loss effusion technique. The vapor pressures of both crystalline and liquid (including supercooled liquid) phases of fenclorim were also determined using a static method based on capacitance diaphragm manometers. The experimental results enabled accurate determination of the standard molar enthalpies, entropies and Gibbs energies of sublimation for both compounds and of vaporization for fenclorim, allowing a phase diagram representation of the (p,T) results, in the neighborhood of the triple point of this compound. The temperatures and molar enthalpies of fusion of the two compounds studied were determined using differential scanning calorimetry. The standard isobaric molar heat capacities of the two crystalline compounds were determined at 298.15 K, using drop calorimetry. The gas phase thermodynamic properties of the two compounds were estimated through ab initio calculations, at the G3(MP2)//B3LYP level, and their thermodynamic stability was evaluated in the gaseous and crystalline phases, considering the calculated values of the standard Gibbs energies of formation, at 298.15 K.

Keywords

Fenclorim; Clopyralid; Vapor pressures; Phase transitions; Heat capacities; Thermodynamic stability

Subject

CHEMISTRY, Physical Chemistry

Comments (0)

We encourage comments and feedback from a broad range of readers. See criteria for comments and our diversity statement.

Leave a public comment
Send a private comment to the author(s)
Views 0
Downloads 0
Comments 0
Metrics 0


×
Alerts
Notify me about updates to this article or when a peer-reviewed version is published.
We use cookies on our website to ensure you get the best experience.
Read more about our cookies here.