J. R. B. GOMES ET AL.
o
experimental result published previously, i.e., DfH ðgÞ ¼
6-311 þ G(2d,2p) selected optimized parameters for compounds
1, 3, and 5. Table SM2 with the energies and thermal corrections
(T ¼ 298.15 K) for all species considered in the present work. This
material is available free of charge in Wiley Interscience.
m
ꢂ1 [10]
ꢂ(178.0 ꢀ 4.3) kJ ꢁ mol
.
That for compound 6 differs by
from that previously estimated with another
ꢂ1
ꢃ9 kJ ꢁ mol
ꢂ1 [10]
working reaction, c.f ꢂ(159.2 ꢀ [5.0]) kJ ꢁ mol
.
it is possible to suggest a value for the standard molar enthalpy of
Nevertheless,
dissociation of the second (N—O) in compound 4 using the
o
m
result for compound 6 obtained in this work. The suggested value
experimental DfH ðgÞ result for compound 2 and the estimated
Acknowledgements
Thanks are due to FCT and to FEDER for financial support to the
research project (POCTI/44471/QUI/2002). J.R.B.G. and A.R.M.
thank FCT for the award of their research scholarships. Thanks
are also due to the University of Porto for funding through the
program ‘Investiga c¸ a˜ o Cient ´ı fica na Pr e´ -gradua c¸ a˜ o’ and sup-
ported by Caixa Geral de Dep o´ sitos.
is also reported in Table 5 and it is DH
2
(N—O) ¼ 254 ꢀ [9]
ꢂ1
kJ ꢁ mol . Importantly, the present work clearly shows that the
energy required to cleave the N—O bonds is almost unchanged
[
13]
with R ¼ CH
3 2 3
or CH CH confirming previous assumptions.
Finally, it must be stressed out here that the differences
between calculated and experimental DH (N—O) and DH (N—O)
1
2
ꢂ1
are of about 10 kJ ꢁ mol , almost included in the uncertainties
associated with the experimental results (Table 5). Nevertheless,
these discrepancies have obvious influences on the experimental
or calculated DH2-1 ¼ DH (N—O)ꢂDH (N—O) differences for
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www.interscience.wiley.com/journal/poc
Copyright ß 2008 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2009, 22 17–23