Raman analysis of formaldehyde aqueous solutions as a function of concentration

Abstract

AbstractRaman spectra of aqueous solutions containing up to 40 mol% of formaldehyde were recorded in the 120–4000 cm−1 spectral range. The water vibrational modes are not too heavily modified by the presence of the polymerized species in the aqueous solutions. The intensity of the bands corresponding to the C–O and C–H vibrational modes depends on the water content. Two bands are found for the C–O symmetric and antisymmetric stretching modes. The first is related to the C–O–C groups formed within the oligomer chains as the condensation increases and the second to the C–OH groups located at the end of the oligomer chains. A change in the intensity evolution of the bands corresponding to the stretching modes of the C–O–C groups occurs above 15 mol% formaldehyde concentration, corresponding to the formation of the HO(CH2O)nH oligomers with n≥3. The intensity of the stretching modes due to the C–OH groups varies linearly with concentration. A linear variation of the band intensity of the CH modes as a function of formaldehyde content is also observed. Copyright © 2003 John Wiley & Sons, Ltd.