resumo
Spectroscopic evidence for C-H center dot center dot center dot O hydrogen bonding in chloroform center dot center dot center dot acetone [Cl3CH center dot center dot center dot O=C(CH3)(2)] mixtures was obtained from vibrational inelastic neutron scattering (INS) spectra. Comparison between the INS spectra of pure samples and their binary mixtures reveals the presence of new bands at about 82, 130 and 170 cm(-1). Assignment of the 82 cm(-1) band to the vO center dot center dot center dot H anti-translational mode is considered and discussed. In addition, the beta C-H mode of CHCl3 at 1242 cm(-1) is split in the spectra of the mixtures, and the high-wavenumber component is assigned to the hydrogen-bonded complex. The plot of the integrated intensity of this component shows a maximum for x=0.5, in agreement with the 1:1 stoichiometry of the chloroform center dot center dot center dot acetone complex, with a calculated complexation constant of 0.15 dm(3)mol(-1). Results also show that the complex behaves as an independent entity, that is, despite being weak, such interactions play a key role in supramolecular chemistry.
palavras-chave
PROTON MAGNETIC RESONANCE; SPECTROSCOPIC BEHAVIOR; COMPLEX-FORMATION; LIQUID-PHASE; RED-SHIFT; AB-INITIO; MIXTURES; RAMAN; 2-PROPANONE; ORBITALS
categoria
Chemistry
autores
Vaz, PD; Nolasco, MM; Gil, FPSC; Ribeiro-Claro, PJA; Tomikinson, J
nossos autores
Mariela Martins Nolasco
Investigador Auxiliar
Paulo Ribeiro-Claro
Professor Associado com Agregaçãoagradecimentos
The authors thank to the Portuguese Foundation for the Science and Technology, FCT, co-financed by the European Community Fund FEDER and the