Issue 6, 2001

The proton affinity of some extended π-systems involving guanidine and cyclopropenimine subunits

Abstract

The proton affinity (PA) of some extended π-electron systems with guanidine and cyclopropenimine structural motifs is explored by theoretical MP2 and HFSC models. It is shown that some of the studied molecules should exhibit higher gas-phase basicity than the Schwesinger proton sponge II, which is considered to be one of the most powerful organic superbases. The origin of the increased basicity is traced to a dramatic resonance effect triggered by the protonation. It is interesting to note that the examined compounds possess higher PAs than their polyguanide counterparts. The reason behind this is the well-established fact that three-membered rings undergo aromatization in the conjugate acids form. The important role of substituents in determining high inherent basicities is underscored.

Graphical abstract: The proton affinity of some extended π-systems involving guanidine and cyclopropenimine subunits

Article information

Article type
Paper
Submitted
06 Feb 2001
Accepted
20 Apr 2001
First published
17 May 2001

J. Chem. Soc., Perkin Trans. 2, 2001, 886-891

The proton affinity of some extended π-systems involving guanidine and cyclopropenimine subunits

B. Kovačević, Z. B. Maksić and R. Vianello, J. Chem. Soc., Perkin Trans. 2, 2001, 886 DOI: 10.1039/B101213O

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