Ab initio studies on the structures and thermodynamic functions of phenanthrene and anthracene

✍ Scribed by Xue-Dong Gong; He-Ming Xiao

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 67 KB
• Volume: 12
• Category: Article
• ISSN: 0894-3230
• DOI: 10.1002/(sici)1099-1395(199906)12:6<441::aid-poc145>3.0.co;2-j

✦ Synopsis

The molecular geometries and electronic structures of phenanthrene and anthracene in the gas phase were studied by using an ab initio molecular orbital method at the HF and MP2 levels with the 6-31G* basis set. Normal-mode vibrational analyses were performed at the HF/6-31G* level. The standard thermodynamic functions were calculated using the frequencies scaled by a factor 0.899, and were in good agreement with the experimental results. The equilibrium mole fractions of the title compounds in an equilibrium mixture were derived from the thermodynamic functions. It is shown that, compared with those of anthracene, the molecular total energy of phenanthrene is lower, the conjugation effect in phenanthrene is stronger and the equilibrium mole fraction of phenanthrene is larger, all showing that phenanthrene is more stable than anthracene. The mole fraction of phenanthrene calculated at room temperature is 0.686, and it decreases slightly as the temperature rises.