Benson group additivity values of phosphines and phosphine oxides: Fast and accurate computational thermochemistry of organophosphorus species

Abstract

Composite quantum chemical methods W1X‐1 and CBS‐QB3 are used to calculate the gas phase standard enthalpy of formation, entropy, and heat capacity of 38 phosphines and phosphine oxides for which reliable experimental thermochemical information is limited or simply nonexistent. For alkyl phosphines and phosphine oxides, the W1X‐1, and CBS‐QB3 results are mutually consistent and in excellent agreement with available G3X values and empirical data. In the case of aryl‐substituted species, different computational methods show more variation, with G3X enthalpies being furthest from experimental values. The calculated thermochemical data are subsequently used to determine Benson group additivity contributions for 24 Benson groups and group pairs involving phosphorus, thereby allowing fast and accurate estimations of thermochemical data of many organophosphorus compounds of any complexity. Such data are indispensable, for example, in chemical process design or estimating potential hazards of new chemical compounds. © 2018 Wiley Periodicals, Inc.

High-Level Ab Initio Predictions of Thermochemical Properties of Organosilicon Species: Critical Evaluation of Experimental Data and a Reliable Benchmark Database for Extending Group Additivity Approaches

“…Consequently, systematic differences between W1X-1 and CBS-QB3 can be attributed to inadequate treatment of electron correlation effects in the latter that become more prominent with increasing molecular size. This is in stark contrast to our previous study on phosphines and phosphine oxides, 31 in which case W1X-1 and CBS-QB3 showed much more uniform performance, albeit for a more limited set of compounds with less variety in the employed substituents. W1X-1 enthalpies are, therefore, considered superior to CBS-QB3 results and used exclusively in the remaining parts of the analysis and discussion.…”

“…While this convention has been adopted by some authors, including Benson in his later works, 15 we chose to report group pair contributions following the practice adopted in our previous work. 31 …”

“…While this convention has been adopted by some authors, including Benson in his later works, 15 we chose to report group pair contributions following the practice adopted in our previous work. 31 As discussed earlier, Becerra and Walsh have derived group contributions for silicon-based Benson groups and used them extensively in their work. Comparison of our W1X-1 data in Table 3 respectively).…”

“…Following our previous work, the composite method W1X-1 was used for the calculation of standard gas-phase enthalpies of formation (Δ f H 298K ° , kJ mol –1 ), entropies ( S 298K ° , J K –1 mol –1 ), and heat capacities ( C p , J K –1 mol –1 ) for 159 organosilicon compounds (Chart ), which include 42 monosilanes ( 1 – 42 , group I ), 7 polysilanes ( 43 – 49 , groups II – V ), 31 silanols and alkoxysilanes ( 50 – 80 , groups VI – IX ), 70 acylic siloxanes ( 81 – 150 , groups X – XII ), 8 cyclic siloxanes ( 151 – 158 , groups XIII and XIV ), and 1 silylamine ( 159 , group XV ) with alkyl (Me = methyl, Et = ethyl, i Pr = isopropyl, s Bu = sec -butyl, and 3-Pe = 3-pentyl), alkenyl (Vi = vinyl), aryl (Ph = phenyl), and/or fluorine substituents. The size of the investigated systems was limited by the computational cost of the W1X-1 method that became prohibitive for molecules with more than ca.…”

Computational thermochemistry: extension of Benson group additivity approach to organoboron compounds and reliable predictions of their thermochemical properties

“…In some instances, such as with organosilicon compounds, 31 inconsistencies in the reference data have completely prevented the determination of an internally consistent set of group contributions by experimental means. As shown by us 32,33 and by others, 103107 a simple fix to the problem is offered by theoretical approaches and high-level composite methods in particular. In the following, we follow this avenue and determine Benson group contributions for boron using the highlevel W1X-1 data in Table 1.…”