Molecular structure and association of diphenylguanidine in solution

Abstract

An experimental and theoretical study of the structure and aggregation of diphenylguanidine (DPhG) in nonpolar and low-polarity solvents (CCI,, c6H6, C2HCI, and CHCIJ was performed. Dipole moments, IR spectra and average molecular weight measurements as a function of concentration demonstrate that DPhG is strongly associated in the solvents studied. The dimerization constant in CCI, is 192 i 7 dm'mol-I. Experimental results and a theoretical discussion on the basis of MNDO-PM3 and -AM1 methods show that in low-polarity solvents DPhG exists in the form of an asymmetric tautomer, the same as was found in the solid-state structure. INTRODUCTIONThe structure, thermodynamic and spectroscopic characteristics of hydrogen-bonded complexes, formed by molecules possessing a few functional atoms or atomic groups able to enter into intermolecular interaction, are defined by the peculiarities of their electronic and molecular structures. It has been demonstrated that compounds such as pyrazoles, aiazenes and amidinesl-' form open associates with the linear H-bond and also cyclic structures with several H-bonds, where the NH group plays a role of a proton donor and the basic nitrogen atom is a proton acceptor.

Rapid Determination of Uranium in Water Samples by Adsorptive Cathodic Stripping Voltammetry Using a Tin-Bismuth Alloy Electrode

“…Previous studies have determined the pKa of diphenylguanidine to be $10.12. Under the acidic acetate buffering conditions, a proportional C==NH group of the diphenylguanidine is protonated and present in a cationic form [54]. Therefore, during the negative voltammetric scan, diphenylguanidine cations probably prefer to be adsorbed on the surface of the working electrode, which can cause the surface charge change of the electrode, and then results in the change of the electrode/solution electrical double layer structure.…”

Self‐assembly of molecules containing the 2‐aminopyridine unit in non‐polar solvents

“…where D and M are the dipole moments of the dimer and monomer, respectively; X M ¼ C M =ðC M þ C D Þ and X D ¼ 1 À X M are the mole fractions of solute in monomer and dimer form, respectively. In our experience, 11 the most objective data on X D and X M can be obtained from the association constant provided by spectroscopic (IR) measurements. The values of M and D in CCl 4 determined according to the above procedure are presented in Table 1.…”

“…A combined experimental approach for the study in solutions was undertaken, involving measurements of IR spectra, dipole moments and average molecular weights. Such a combination of experimental techniques was previously successfully applied to the aggregation of 2oxoindolines 11 and diphenylguanidine 12 in solution. A strong decrease of dipole moment with concentration was evidence of cyclic dimer formation.…”