Double bond infrared spectroscopy

Infrared IR spectroscopy is quite useful in identifying carboxylic acid derivatives The, carbonyl stretching vibration is very strong and its position is sensitive to the nature of IKT the carbonyl group In general electron donation from the substituent decreases the double bond character of the bond between carbon and oxygen and decreases the stretch mg frequency Two distinct absorptions are observed for the symmetric and antisym metric stretching vibrations of the anhydride function... 

Hydrogenation of polybutadiene converts both cis and trans isomers to the same linear structure and vinyl groups to ethyl branches. A polybutadiene sample of molecular weight 168,000 was found by infrared spectroscopy to contain double bonds consisting of 47.2% cis, 44.9% trans, and 7.9% vinyl. After hydrogenation, what is the average number of backbone carbon atoms between ethyl side chains ... 

Measurement of Unsaturation. The presence of double bonds in a fatty acid side chain can be detected chemically or through use of instmmentation. Iodine value (IV) (74) is a measure of extent of the reaction of iodine with double bonds the higher the IV, the more unsaturated the oil. IV may also be calculated from fatty acid composition. The cis—trans configuration of double bonds may be deterrnined by infrared (59) or nmr spectroscopy. Naturally occurring oils have methylene-intermpted double bonds that do not absorb in the uv however, conjugated dienes maybe deterrnined in an appropriate solvent at 233 nm. 

The ease of sample handling makes Raman spectroscopy increasingly preferred. Like infrared spectroscopy, Raman scattering can be used to identify functional groups commonly found in polymers, including aromaticity, double bonds, and C bond H stretches. More commonly, the Raman spectmm is used to characterize the degree of crystallinity or the orientation of the polymer chains in such stmctures as tubes, fibers (qv), sheets, powders, and films... 

Other spectroscopic methods such as infrared (ir), and nuclear magnetic resonance (nmr), circular dichroism (cd), and mass spectrometry (ms) are invaluable tools for identification and stmcture elucidation. Nmr spectroscopy allows for geometric assignment of the carbon—carbon double bonds, as well as relative stereochemistry of ring substituents. These spectroscopic methods coupled with traditional chemical derivatization techniques provide the framework by which new carotenoids are identified and characterized (16,17). 

The structure of the protonated enamines has been investigated by infrared spectroscopy. On protonation there is a characteristic shift of the band in the double-bond stretching region to higher frequencies by 20 to 50 cm with an increased intensity of absorption (6,13,14a). Protonated enamines also show absorption in the ultraviolet at 220-225 m/x due to the iminium structure (14b). This confirms structure 5 for these protonated enamines, because a compound having structure 4 would be expected to have only end absorption as the electrons on nitrogen would not be available for interaction with the n electrons of the double bond. 

Deprotonation of H2O2 yields OOH , and hydroperoxides of the alkali metals are known in solution. Liquid ammonia can also effect deprotonation and NH4OOH is a white solid, mp 25° infrared spectroscopy shows the presence of NH4+ and OOH ions in the solid phase but the melt appears to contain only the H-bonded species NH3 and H202. " Double deprotonation yields the peroxide ion 02 , and this is a standard route to transition metal peroxides. 

Pseudo-/ -DL-gi Zopyranose triacetate (36) was prepared by hydroxyla-tion of the enetriol triacetate (32) and converted to the corresponding pentol and pentaacetate. The intermediate 32 was obtained by Diels-Alder reaction (200°C., two days) of rans/ rans-l,4-diacetoxy-l,3-buta-diene with allyl acetate. The double bond was surprisingly inert to the usual additive reagents and not detectable by infrared spectroscopy because of near-symmetry, but it did react with tert-butyl hydroxperoxide to give 36 in about 30% yield (27). 

I> = (dc/df)//abs where dc/dr is the rate of disappearance of the olefinic double bonds per unit volume and /abs the rate at which the incident light is absorbed per unit volume of the KBr pellet containing the sample. The rates of disappearance of the olefinic double bonds during oligomerization and polymerization were monitored by infrared (IR) spectroscopy. 

Synthesis. Functionalized monomers (and oligomers) of sebacic acid (SA-Me2) and 1,6 -bis(/ -carboxyphenoxy)hexane (CPH-Me2) were synthesized and subsequently photopolymerized as illustrated in Figure 1. First, the dicarboxylic acid was converted to an anhydride by heating at reflux in methacrylic anhydride for several hours. The dimethacrylated anhydride monomer was subsequently isolated and purified by dissolving in methylene chloride and precipitation with hexane. Infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, and elemental analysis results indicated that both acid groups were converted to the anhydride, and the double bond of the methacrylate group was clearly evident. 

Polymerization Behavior. Both Fourier-transform infrared spectroscopy (FTIR) and differential scanning photocalorimetry (DPC) were used to characterize the polymerization behavior, curing time, and maximum double bond conversion in these systems. 

However, full structural analysis of a lipid will often necessitate further analysis of the collected column effluent for a single GLC peak. Infrared and NMR spectroscopy and mass spectrometry are all useful techniques which will give information for identification purposes, including the position and configuration of any double bonds. 

The differences in selection rules between Raman and infrared spectroscopy define the ideal situations for each. Raman spectroscopy performs well on compounds with double or triple bonds, different isomers, sulfur-containing and symmetric species. The Raman spectrum of water is extremely weak so direct measurements of aqueous systems are easy to do. Polar solvents also typically have weak Raman spectra, enabling direct measurement of samples in these solvents. Some rough rules to predict the relative strength of Raman intensity from certain vibrations are [7] ... 

An unknown substance, X, was isolated from rabbit muscle. Its structure was determined from the following observations and experiments. Qualitative analysis showed that X was composed entirely of C, H, and 0. A weighed sample of X was completely oxidized, and the H20 and C02 produced were measured this quantitative analysis revealed that X contained 40.00% C, 6.71% H, and 53.29% O by weight. The molecular mass of X, determined by mass spectrometry, was 90.00 u (atomic mass units see Box 1-1). Infrared spectroscopy showed that X contained one double bond. X dissolved readily in water to give an acidic solution the solution demonstrated optical activity when tested in a polarimeter. 

One may perform radical graft copolymerizations onto the butadiene region of copolymers of styrene and butadiene without any reaction occurring at the styrene portions of the copolymer. If the monomer is reactive, reaction of the monomer at an allylic site occurs while for less reactive monomers, the polymeric radical is formed and this adds to the double bond of the polymer. Proof of the site of grafting comes from information about the relative efficiency of different initiators but the most important information is obtained from infrared spectroscopy. One can observe differences in the spectra which can be related to the mode of addition. 

The double bonds of an alkene with no alkenic hydrogens are difficult to detect by infrared spectroscopy and in such cases Raman spectroscopy is helpful (see Section 9-8). 

Investigations by Trifiro et al. (54-57) using infrared spectroscopy have led to the identification of a covalent metal-oxygen double bond which is present in a great majority of the selective oxidation catalysts. On the other hand, this bond is systematically absent from total oxidation catalysts such as the oxides of iron, nickel, and cobalt (55, 56). Trifiro et al. (57) and Akimoto and Echigoya (58) have also reported that there is a direct interaction between adsorbed propylene or acrolein and this... 

The best way to elucidate the reaction path is to follow the evolution of as many independent species and functional groups as possible. For example, analysis of the epoxy-amine reaction following the simultaneous evolution of epoxy and primary amine groups by near infrared spectroscopy (NIR) simultaneous determination of the conversion of double bonds belonging to unsaturated polyester (UP) and styrene (S) using FTIR, as shown in Fig. 5.13 (Yang and Lee, 1988) determination of the evolution of the concentration of free radicals using ESR, as shown in Fig. 5.14 (Tollens and Lee, 1993). 

Surface modification of LDPE film can also be brought about by chemical treatment [118] with an aqueous solution of ammoniacal ammonium persulphate in the presence of Ni+2 ions under variable reaction conditions. The investigation of treated surface showed the presence of polar groups (viz. carbonyl and hydroxyl) in the infrared (IR) spectroscopy, with characteristic bands at 1700, 1622 and 3450 cm-1. It is known that the persulphate ion attacks the double-bond-producing epoxy or diol group. However, the destructive oxidation of saturated hydrocarbons does not occur with persulphate alone, but requires the presence of the nickel (II) ion. The authors have proposed the following mechanism of chemical treatment ... 

Whereas infrared spectroscopy classifies the surface hydroxyls according to their bond strength (free and bridged silanols), 29 Si NMR spectroscopy distinguishes single (either isolated or vicinal) from double (geminal) silanols. This technique can thus be regarded upon as complementary to infrared spectroscopy. 

---