XI Simpósio Brasileiro de Química Teórica
Caxambu, 18 a 21 Novembro de 2001
 
 
 
 

P227

ON PHYSICO-CHEMICAL PROPERTIES OF PAHs

Márcia M. C. Ferreira (PQ) and Rudolf Kiralj (PQ), Instituto de Química, Universidade
Estadual de Campinas, Campinas, SP, 13083-970, Brazil. marcia@iqm.unicamp.br
 

Many benzenoid polycyclic aromatic hydrocarbons (PAHs) are characterized by number
of physical, chemical, biochemical and environmental properties.   Some PAHs are toxic
and even mutagens and cancerogens,  while all of them are  air,  soil,  water  and  food
pollutants with tendency to accumulate  in  all media  including living organisms.   PAHs
undergo chemical changes,   especially  if  mediated  by  UV  light;   this  can  go  up  to
enzymatic oxydation via  mechanism  of  free  radicals  where  PAHs  turn  into reactive
epoxydes  and  polydiols,^1,2   which   then  easily  bind   to  DNA  and   other   biological
macromolecules.   There  are  various  studies  on  PAHs  in environmental  science  at
QSPR/SPR or even QSAR/SAR level. This work continues a recent study on 48 PAHs³
on   several   physico-chemical   properties   like   boiling   point,   retention   index,   n-
octanol/water coefficient, solubility,  n-octanol/air coefficient,  soli sorption,  Henry's law
constant and bioconcentration factor. Various types of molecular descriptors were used
as  quantum-mechanical  (semi-empirical  ESP-PM3 charges,  dipole moments),  shape
descriptors   (number  of  rings,   Connolly  volumes  and  surfaces),   aromaticity  (PM3
resonance energy)  and intermolecular interaction descriptors  (crystal packing  energy,
water-PAH interaction energy). All physico-chemical properties showed high correlation
with molecular descriptors.  The full description of the properties is carried out by using
Principal Component Analysis  and  the high-level prediction  by  Partial Least Squares
Regression  (r > 0.9).  The detailed analysis of all the data will be discussed.
1 A. F. Lehner, J. Horn, J. W. Flesher, J. Mol. Struct. (Theochem), 366 (1996) 203-217.
2 J. Jacob, Pure Appl. Chem., 68 (1996) 301-308.
3 M. M. C. Ferreira, Chemosphere, 44 (2001) 125-146.

(FAPESP