Raman Spectroscopic Studies of Temperature Dependent Conformational Changes in Fatty Acids P R Vijayakumar a , Siva Umapathy* a B Vishwanathan b , S Ramamurthi b and V Krishnan* b a Dept. of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore – 560012, India b ITC Research & Development Center, Peenya Industrial Area, Phase I, Bangalore-560058, India * umapathy@ipc.iisc.ernet.in and venkat.krishnan@itc.in Vibrational spectroscopy is a powerful tool for understanding the temperature dependent conformational change in structure of salts of fatty acids [CH 3 (CH 2 ) n COO - M] (n=10, 12, 14 & 16; M=Na + or Ca 2+ ). There are considerable number of reports in the literature dealing with temperature induced structural changes on hydrocarbon chain using XRD, FT-IR & DSC 1-4 , however, studies on even numbered fatty acids by Raman Spectroscopy are scant 5-10 . With this aim, the experimental method was applied to salts of fatty acid consisting a long hydrocarbon chain with a carboxylic acid group at one end which has ionic bonded metal ion (sodium or calcium). The hydrocarbon end is non-polar and is soluble in non-polar solvents, and the ionic end is soluble in water. FIGURE 1. Temperature dependence of Raman spectra for Sodium stearate (a) Range 400 – 1800 cm -1 ; (b) range 2750 - 3050cm -1 .