Polynomial Dependence for the Calculation of Vaporization Enthalpies of Organophosphorus Compounds

Abstract

Enthalpies of vaporization of organic phosphorus compounds are related to the normal-pressure boiling points through a polynomial dependence. Each class of organophosphorus compounds is characterized by its own specific parameters of the general dependence. The polynomial dependences may be used for the calculation of vaporization enthalpies of organophosphorus compounds with different modes of phosphorus coordination.Most of the known experimental enthalpies of vaporization of organic three-and four-coordinate phosphorus compounds were determined by two methods. The first of these is based on the Clapeyron-Clausius equation [1]:where p is the vapor pressure; H vap is the enthalpy of vaporization (kJ/mol), R is the universal gas constant, T is the absolute temperature, and C is the integration constant.The second method is based on the Solomonov equation [2,3]:where H dis is the enthalpy of dissolution of a substance (kJ/mol), and MR D is its molecular refraction. However, both these procedures for experimental determination of H°v ap of organophosphorus compounds are not free from a number of disadvantages which could appreciably restrict the scope of their application in practice. For example, the use of the Clapeyron-Clausius equation is limited due to high boiling points of organic phosphorus compounds which therefore tend to decompose on heating. Determination of the enthalpies of dissolution of organophosphorus compounds in inert organic solvents, which are necessary for the calculation of vaporization enthalpies by the Solomonov equation, is not always possible due to insufficient stability of these compounds to oxidation on exposure to atmospheric oxygen and to hydrolysis in the presence of traces of water. Taking into account the above stated, theoretical methods for the calculation of vaporization enthalpies of organophosphorus compounds become more important. In particular, the additivity scheme involving group contributions [4] can be used for this purpose:Here, m i is the number of similar fragments in a molecule, and X i is an increment characterizing the group contribution of an ith fragment. However, the calculation of standard enthalpies of vaporization of organic phosphorus compounds according to the additivity scheme may be difficult, for there are very limited published data on the contributions of phosphorus-containing groups to H°v ap . The relevant data have been reported in a few articles [5,6]. Moreover, the possibility for calculating contributions of phosphorus-containing groups to the enthalpy of vaporization of organophosphorus compounds is limited due to shortage of experimental data and, in some cases, large errors in experimental determination.In the recent time, attempts were made [7-10] to calculate enthalpies of vaporization of three-coordinate

Synthesis of β-Aminophosphonates and Study of Their Acid-Base Properties and Phase Distribution in Water-Organic Solvent Systems

“…In this case, introduction of an additional methylene unit between the phosphorus and nitrogen atoms increases the hydrophilicity due to enhanced strength of H-comcomplexes with water molecules as a result of increase in the electron density on the basic centers (nitrogen and phosphoryl oxygen atoms), for their mutual acceptor effect becomes weaker. Clearly pronounced protonacceptor properties of aminophosphonates follow, e.g., from the results of our previous calorimetric studies on reactions of -aminophosphonates with proton-donor regents [15]. Unfortunately, the limited set of data for -aminophosphoryl compounds, as compared to much more extensively studied -homologs, does not allow us to draw more profound generalizations.…”

Calculation of Fundamental Thermochemical Parameters of Phosphoranes by the Additivity Scheme

“…In continuation of our studies [4][5][6][7] on thermochemistry of organophosphorus compounds, in the present work we analyzed the available experimental enthalpies of vaporization and formation of alkoxyphosphoranes on the basis of the additivity scheme using group contributions and made an attempt to develop an approach to calculation of fundamental thermochemical parameters of these compounds. All experimental thermochemical data that we succeeded in finding in the literature for five-coordinate phosphorus derivatives are collected in Table 1.…”