Contact ion pairs: a quantitative Raman study of the NaClO 3 –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 3 v symmetry. In the ν 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 37 ClO, 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 NaClO 3 –DMF system is significantly greater than in the NaClO 4 –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 © 2004 John Wiley & Sons, Ltd.