Theoretical thermochemistry: entropies and heat capacities for series of organosilicon compounds. Part II

• Published in: Thermochimica acta 1991-01, Vol.176, p.259-265
• Main Authors: Guan-Zhi, Ju, Wen-Sheng, Bian
• Format: Article
• Language: English
• ISSN: 0040-6031; 1872-762X
• DOI: 10.1016/0040-6031(91)80281-M

Ab initio molecular orbital theory was used to compute entropies and heat capacities for HSiCH 3, HSiSiH 3, CH 3SiCH 3, FSiSiH 3, CH 3HSi=CH 2 and FHSi=SiH 2 in the temperature range 300–1500 K. For this series of organosilicon compounds, the members of which are often considered to be reactive intermediates and are all unstable, there is currently almost no information available about entropies or heat capacities. On the basis of the calculated heat capacities for the compounds involved, we have fitted the temperature-dependent functions for heat capacities to functions of the form ( a + bT + cT 2) and ( a' + b'T + c'T −2) over the range 300–1500 K. It was found that the first form is superior to the latter for all species considered. Finally, 1 e.u. is suggested to be the upper limit of the deviation for calculations of entropies and heat capacities over the temperature range concerned, and 2 JK −1 mol −1 the deviation limit for our fittings of heat capacities.