Consequences of proton transfer in guanidine

Abstract

Consequences of proton‐transfer reactions in guanidine in the solid state, solution and gas phase are discussed. Y‐delocalization, resonance and symmetry strongly influence the basicity of guanidine in the gas phase. These effects are, however, insufficient to explain the basicity of guanidine which in aqueous solution is stronger than that of trisubstituted alkylamines and proton sponge (DMAN). The intrinsic (gas‐phase) basicity of guanidine is close to that of triethylamine. The large difference between the basicities of amines and guanidine in solution is attributed to the important role played by effects such as polarizability and internal and external solvation. Copyright © 2003 John Wiley & Sons, Ltd.

Derivatives of the Triaminoguanidinium Ion, 2. Prototropic Tautomerism, Crystal and Molecular Structure of N,N´,N´´-Tris(propan- 2-iminyl)guanidine [1, 2]

“…Prototropic tautomerism of guanidines has often been discussed in the literature [18,19], but it seems that detailed investigations on the mechanism of the …”

“…Similarly, in N,N ,Ntris(benzylamino)guanidinium salts, the C-N bond lengths are in the range 1.321(3) -1.333(3)Å [1]. In contrast, the C=N and the C-N bond lengths in several substituted guanidines are distinctly different [18] [25]. Unresolved superposition of prototropic tautomers has also been suggested to explain the experimentally observed equalized C-N bond lengths of N-cyanoguanidine as compared to the data of the individual tautomers obtained from quantum chemical calculations [21].…”

Synthesis, characterization and crystal structure of novel mononuclear peroxotungsten(VI) complexes. Insulinomimetic activity of W(VI) and Nb(V) peroxo complexes

“…In addition, the remarkable thermodynamic and biological stability of guanidinium ion (CN 3 H þ 6 , noted as gu + ) led us to the synthesis of a peroxo-quinaldate complex with this cation. It is also demonstrated that guanidine, guanidinium ion and their derivatives have antibacterial, antiviral, cytotoxic, antifungal and anti-inflammatory properties [25].…”

Interactions of guanidinium with benzene-sulphonic, -phosphonic and -arsonic acids and several of their nitro-derivatives

“…1c. Most of the biological properties of the guanidium cation are related to its strong basicity in aqueous media, and the richness of its intermolecular interactions [2]. The guanidinium cation has a complementary geometry and is able to interact with these anions, and many others [2], through donor (D)-acceptor (A) (N-HÁ Á ÁO) hydrogen-bonding, and if all three anions are present, it is reasonable to expect that they will compete for binding to CðNH 2 Þ þ 3 .…”

“…Most of the biological properties of the guanidium cation are related to its strong basicity in aqueous media, and the richness of its intermolecular interactions [2]. The guanidinium cation has a complementary geometry and is able to interact with these anions, and many others [2], through donor (D)-acceptor (A) (N-HÁ Á ÁO) hydrogen-bonding, and if all three anions are present, it is reasonable to expect that they will compete for binding to CðNH 2 Þ þ 3 . However, whilst the interaction of sulphonic acids with guanidinium cation has attracted much activity in recent years [3][4][5][6], supramolecular interactions of organic phosphonate groups have been overshadowed by the greater interest in metal phosphonates [7][8][9][10][11][12], with the exception of one study by Weakley [13], and there are no reports in the literature of the interaction of guanidinium cation with arsonates.…”