A-H bond dissociation energies: Trends across the periodic table and halogen substituent effects

PHYS 524

Willem-Jan van Zeist, vzeist@few.vu.nl, Department of Theoretical Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, Amsterdam, NL-1081 HV, Netherlands, Marcel Swart, Institut de Química Computacional and ICREA, Universitat de Girona, Campus de Montilivi, 17071 Girona, Spain, and F. Matthias Bickelhaupt, fm.bickelhaupt@few.vu.nl, Department of Theoretical Chemistry and Amsterdam Center for Multiscale Modeling, Vrije Universiteit Amsterdam, De Boelelaan 1083, NL-1081 HV, Amsterdam, Netherlands.
Using DFT we present a complete description of the BDEs of all A-H bonds occurring in archetypal maingroup-element hydrides AHn of groups 14 - 17 and periods 2 - 6. This gives a clear overview of the behavior of BDEs across both groups and periods in the periodic table. Furthermore, we have studied the influence of step-wise halogenation of carbon and silicon on the A-H bond in species XmAH4-m (X = F, Cl, Br and I; A = C, Si; m = 0, 1, 2, 3). Via a thermocyclic decomposition of the bond energy we assess the stabilizing/destabilizing effects of the substituents. Our method shows the importance of taking stabilizing effects into account on both sides of the bond breaking reaction (i.e., on both the resulting radical and the parent molecule). For example we show that along CH4, CClH3, CCl2H2, CCl3H the C-H BDE decreases because the resulting radical is destabilized less by the chloride substituents than the corresponding parent molecule.

 

PHYS Poster Session - General Theory
7:30 PM-10:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Hall A, Poster

Division of Physical Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008