Contact ion pairs:: a quantitative Raman study of the NaClO3-DMF system

Raman spectra of sodium chlorate in N,N-dimethylformamide (DMF) solution were obtained. The band at 926 cm(-1) that has been previously assigned to the vibrational mode of the associated chlorate with C-s symmetry is, in fact, due to the non-associated chlorate vibration with C-3v symmetry. In the v(2) region of the chlorate anion, a new feature at 600 cm-1 was observed and the results show that it also belongs to the non-associated chlorate. Both bands at 926 and 600 cm(-1) are assigned to the vibrations involving O-Cl-37-O, in full agreement with the results of normal coordinate analysis reported by others workers. Quantitative measurements performed in the range 590-630 cm(-1), allowed the determination of the extent of contact ion pair formation. The results show that the ion association in the NaClO3-DMF system is significantly greater than in the NaClO4-DMF system and this is due the higher charge density and lower symmetry of the chlorate anion. Similar conclusions were reached by others who used different experimental techniques. Copyright (C) 2004 John Wiley Sons, Ltd.