Thermodynamics of the formation of complexes between aniline derivatives and proton acceptors in solution

• Published in: Journal of molecular liquids 2000-11, Vol.88 (2), p.259-276
• Main Authors: Borisenko, V.E., Kuzmin, D.S., Morev, A.V., Koll, A.
• Format: Article
• Language: English
• Subjects: aniline derivatives; enthalpy of complex formation; hydrogen bonding; spectral characteristics of NH stretching bands; temperature effects
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/S0167-7322(00)00144-6

The M (0),, M (1) and 2(M (2)) 1 2 spectral moments of the v(NH) bands of aniline derivatives as well as their complexes with various proton acceptors in solution were determined in the temperature range 285–330K. Studied compounds were: aniline; 4-metoxytetrafluoraniline; 2,3,5,6-tetrafluoraniline and 4-aminotetrafluorpyridine. The coefficients of linear Y=aT+b regression of the spectral moments M (0),, M (1) and 2( M (2)) 1 2 with temperature were determined for the free amino groups as well as for 1:1 complexes with various proton acceptors in CCl 4 solutions. An analysis of the influence of temperature on the spectral characteristics of monomers and their 1:1 complexes with various proton acceptors was performed. The heat formation (ΔH 1) of the 1:1 complexes with proton acceptors was determined using the dependence of the equilibrium constants on temperature. On the basis of the “rule of intensity”: -Δ H = αΔ B 1 2 , the ΔH 2 for the complexes of 1:2 stoichiometry was calculated, allowing the estimation of the relation ΔH 1/ΔH 2 It was shown that ΔH 1 is larger than ΔH 2 recalculated for a single bond. Comparison of the dynamics characteristics of the N-H bonds in amino groups in complexes of different stoichiometry proves that the hydrogen bonds in 1:1 complexes is stronger than in the complexes of 1:2 stoichoimetry.