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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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