24-May-2013
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Indian Journal of Chemistry -Section A (IJC-A) >
IJC-A Vol.50A [2011] >
IJC-A Vol.50A(02) [February 2011] >
| Title: | Heteroatom effect on intramolecular double proton transfer of 3,6-diiminocyclohexa-1,4-diene-1,4-diamine: A theoretical study |
| Authors: | Tahermansouri, Hasan
Moradi, Shahram
Sayyadi, Robabeh |
| Keywords: | Theoretical chemistry
Proton transfer
Heteroatom effect
Charge distribution
Chemical shift |
| Issue Date: | Feb-2011 |
| Publisher: | NISCAIR-CSIR, India |
| Abstract: | The process of intramolecular proton transfer in
3,6-diiminocyclohexa-1,4-diene-1,4-diamine
and some hetero derivatives has been investigated at HF and DFT (B3LYP)
levels of theory in two states, concerted and stepwise. In
3,6-diiminocyclohexa-1,4-diene-1,4-diamine, the energy barrier
for the proton transfer through concerted and stepwise
mechanism is found to be ~ 27 and 17 kcal/mol, respectively. When replacing two
CH groups by two boron atoms in
the ring (3,6-dihydro-3,6-diimino-1,4-diborinine-2,5-diamine), the obtained
energy barriers are ~ 48 and 26 kcal/mol,
respectively. The values obtained on replacing the CH groups
by two atoms of nitrogen, silicon and phosphor are ~30 and
18 kcal/mol (3,6-dihydro-3,6-diiminopyrazine-2,5-diamine),
86 and 45 kcal/mol (3,6-dihydro-3,6-diimino-1,4-disiline-2,5-diamine) and 84
and 45 kcal/mol (3,6-dihydro-3,6-iimino-1,4-diphosphinine-2,5-iamine)
respectively. The displacement pathway and the resonance forms that are
produced in the
conversion processes have been investigated. The nucleus-independent chemical
shift methodology has been applied
to study the charge distributions in the ring. |
| Page(s): | 180-184 |
| CC License: |  CC Attribution-Noncommercial-No Derivative Works 2.5 India |
| ISSN: | 0975-0975(Online); 0376-4710(Print) |
| Source: | IJC-A Vol.50A(02) [February 2011]
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