Heat Capacity and Enthalpy of Formation of Trimethyl Phosphite, 2-Chloromethylbenzonitrile, and 2-Dimethylphosphonomethylbenzonitrile

Abstract

The heat capacities, C p , of trimethyl phosphite, 2-dimethylphosphonomethylbenzonitrile, and 2-chloromethylbenzonitrile are measured with an adiabatic calorimeter, and the standard enthalpies of formation, ∆ f H o (298.15 K) (l or cr), for the three substances are determined. For this purpose, C p (T) values of trimethyl phosphite and 2-dimethylphosphonomethylbenzonitrile are measured in the temperature range from (298.15 to 350.32) K, and the C p (T) curves of 2-chloromethylbenzonitrile are also obtained for the crystal (300.35 to 329.00 K) and the liquid (337.26 to 372.45 K), respectively. The deviation of experimental heat capacities from the corresponding smoothed values lies within ( 1.5 %. A fusion transition phenomenon is found from the C p (T) curves of 2-chloromethylbenzonitrile, and the enthalpy of fusion is measured with a differential scanning calorimeter (DSC). The gas-phase standard enthalpies of formation, ∆ f H o (g, 298.15 K), of the three compounds are evaluated by the Benson group additive method. The critical temperature T c , critical pressure P c , and enthalpy of vaporization ∆ vap H o of the compounds are also calculated by different group additive methods. On the basis of the above data, the values of ∆ f H o (l, 298.15 K) of trimethyl phosphate and 2-dimethylphosphonomethylbenzonitrile and of ∆ f H o -(cr, 298.15 K) of 2-chloromethylbenzonitrile are estimated. A thermochemical cycle including a chemical reaction is designed to examine the reliability of the values by measuring the heat of reaction. The result shows that the enthalpies of formation, ∆ f H o (298.15 K) (l or cr), for the three substances are acceptable.

Heat Capacity, Density, Vapor Pressure, and Enthalpy of Vaporization of Propyl Cinnamate

“…8 Heat capacity values are characteristic data related to the structure of substances, and can be widely applied to chemical engineering, energy, and material engineering. 9 For instance, standard Gibbs energy change of a reaction can be calculated by heat capacity, enthalpy, and entropy. 10−12 Therefore, it is necessary to make efforts to carry out extensive research concerning these fundamental physicochemical properties.…”

“…Among them, density is an important characteristic of substances which can monitor product quality and is also essential in the calculation of chemical processes. , Vapor pressure, a fundamental physicochemical property of substances, is also indispensable in plenty of significant applications, such as the distillation process and two-phase reactions. − Furthermore, the vaporization enthalpy, being able to obtain from vapor pressure data, is one of the important thermodynamic data required for the calculation, analysis, and design of chemical processes . Heat capacity values are characteristic data related to the structure of substances, and can be widely applied to chemical engineering, energy, and material engineering . For instance, standard Gibbs energy change of a reaction can be calculated by heat capacity, enthalpy, and entropy. − Therefore, it is necessary to make efforts to carry out extensive research concerning these fundamental physicochemical properties.…”

Heat Capacity, Density, Vapor Pressure, and Enthalpy of Vaporization of Isoamyl dl-Lactate

“…Heat capacity of a pure substance is an important thermodynamic property, and it can be used to calculate the changes of enthalpy and entropy over different temperature ranges. − As an essential part of p – V – T data, liquid density plays an important role in chemical thermodynamics and engineering design. It is indispensable in the calculation of chemical processes such as fluid mechanics, heat transfer, and mass transfer. − In addition, vapor pressure and vaporization enthalpy data are essential to optimize industrial synthesis and separation technologies. − …”

Vapour pressure and vapourisation enthalpy of pyridine N‐oxide

“…The fusion temperature ( T fus ) of pyridine N ‐oxide was reported to be 339.15 K (Tolstikov et al, 1971), where it was measured to be 338.05 K by DSC (DSC200F3, Netzsch, Freistaat Bayern, German). The procedure has been described in more detail in the literature (Xu et al, 2007). Hereinafter, we take 339.15 K as the fusion temperature of pyridine N ‐oxide.…”

“…In this work, the heat capacity of solid, C p (s), was measured by adiabatic calorimeter. The apparatus and experimental procedures used here are similar to those described in the literature (Xu et al, 2007). See Figure 5, the heat capacity of pyridine N ‐oxide was measured in the temperature range from 295.23 to 335.13 K, a polynomial function was used to correlate the experimental values of C p (s) with temperature by the method of least‐squares …”