Infrared spectra fatty acids

Extracts of these fat samples were treated with sodium sulfate-concentrated sulfuric acid mixture and fuming acid by the method described by Schechter et al. 5) in order to separate the organic-chlorine compound from the fatty materials. An infrared spectrum from 7 to 15 microns on carbon disulfide solutions of the residues from the fat qualitatively identified the organic-chlorine compound as toxaphene. All the bands of toxaphene in this spectral region were plainly seen in the treated steer extract, whereas none of the absorption bands were visible in the untreated steer extract. 

Infrared. The C=0 absorption region of the infrared spectrum is of interest so far as the acid-soaps are concerned. Un-ionized fatty acids have a C=0 absorption band at 5.9 microns (.—1700 cm.1). For soaps there is a strong absorption band at 6.4 microns ( 1560 cm.-1) (I). 

The existence of a substance in two or more forms, which are significantly different in physical or chemical properties, is known as polymorphism. The difference between the forms arises firom different modes of molecular packing in the crystal structure of certain triglycerides. Certain pure or mixed fatty acid triglycerides may show as many as five different melting points. Each crystal system has a characteristic melting point, x-ray diffraction pattern, and infrared spectrum. For example, tristearin can exist in three polymorphic forms with melting points of 54.7, 63.2, and 73.5°C. 

The ether layer is washed successively with 5% hydrochloric acid, 5% sodium carbonate aqueous solution and water, and then dried over sodium sulfate. Upon evaporation of ether, the residue is subjected to fractional distillation in vacuo, thereby to yield 8.9 g. of N-methyl linseed oil fatty acid amide, B.P. 178-190° C./0.03 mm. Hg, I.R. 1,650 cm.-l. (I.R. means wave number of the infrared absorption spectrum.)... 

Infrared results obtained for adsorbed surfactant layers on certain minerals show that fatty acids and sulfonates can adsorb also through covalent bonding (Robert et al., 1954 Peck and Wards worth, 1965). However identification of a bonding type on infrared spectrum does not necessarily suggest the existence of such bonding on minerals in surfactant solutions because of the possible alterations in the chemical state of the adsorbed surfac-... 

As described in Section 3.1, Baier et al. (1974) have used a machined germanium prism to sample surface organic monolayers in the manner developed earlier by Blodgett (1934,1935) for fatty acid films. The basis of their analytical method, infrared spectroscopy by the technique of internal reflections inside the machined prisms, is only qualitative but serves very well to examine the chemical nature of the surface organics. It is well known that when an internal reflection prism made of a material with a sufficiently high index of refiraction such as germanium is used, the internal reflection IR spectrum obtained suffers no band distortion or band shift when compared to conventional transmission spectra of the same substance (Barr and Flournoy, 1969). 

Golmohammadi (1966) has investigated the effect on the infrared spectrum of the increase in the number of selenium atoms incorporated in a fatty acid chain. The intensity of the bands near 1250 cm was selenium dependent. A progressive increase in the intensity of the bands in this region together with a displacement of the bands toward lower frequency was observed when the number of selenium atoms in the chain was increased progressively from one to three. 

Eremin et al. (1965) have precipitated carbohydrate material with ethanol after alkaline hydrolysis of cultures of Whitmore s bacillus Pseudomonas pseudomailer), Pasteurella pestis, and Vibrio comma, and have subjected these polyoses to infrared spectroscopy. All spectra had strong absorption at 1660 and 1550 cm the former was related to double-bond vibrations and the latter was associated with stretching vibrations of C—N. The latter absorption was almost completely absent in the spectrum of a complex from V. comma. Absorption at 970 cm (the C=C double bond in the trans position) and traces of absorption at 790 cm characteristic of the 1 — 3 bond were always present. A polysaccharide from the cell wall of P. pestis had a wide band at 1170-1000 cm the low intensity bands at 1190 and 1160cm indicated the presence of P—O—Me and P—O—Et groups. The spectrum of a complex from Whitmore s bacillus differed from the others by the presence of a band at 1735 cm due to esters of fatty acids. 

Analyze the infrared spectrum by identifying the principal absorption bands. Look for peaks in the spectrum that may indicate possible contamination from methanol, glycerol, or free fatty acids. Indicate any impurities found in your biodiesel bases on the infrared spectrum. 

Figure 10.10 shows the spectrum of a typical fatty acid. Figure 10.11 the spectrum of a fatty acid salt. Clearly infrared is an excellent method for revealing whether the acid has been neutralised or not. 

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