Unsaturated groups infrared spectroscopy

Infrared Spectroscopy. The following bands are seen in the ir spectrum of PPG 2970, 2940, 2880 cm-1 (C—H stretch, m) 1460,1375 cm-1 (C—H bend, m) 1100,1015 cm-1 (C—O stretch, m) of which the 2940 and 1015 band are specific. The latter are also present in copolymers of EO and PO. Absorptions due to unsaturated end groups are found at 1650 cm-1 (allyl ether) and 1672 cm-1 (1-propenyl ether). The O—H stretching band at 3470 cm-1 shows the greatest variation for different hydroxyl number polyols and has been used to estimate the hydroxyl number (169). 

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). 

Conventional Raman spectroscopy cannot be applied directly to aqueous extracts of sediments and soils, although it is occasionally used to provide information on organic solvent extracts of such samples. Fourier transform Raman spectroscopy, on the other hand, can be directly applied to water samples. The technique complements infrared spectroscopy in that some functional groups, eg unsaturation, give a much stronger response in the infrared. Several manufacturers (Perkin-Elmer, Digilab, Broker) now supply Fourier transform infrared spectrometers. 

The polymerisation of DVF was first investigated by two independent research groups (2-7) who reported that soluble polymers could readily be obtained using free radical and cationic initiators. These authors proposed that cyclopolymerisation had occurred with the formation of linear polymers having three-carbon bridged ferrocene units (I), and some acyclic units (II), in the chain. Evidence for structure (I) as the predominant unit in the polymer chain was provided by the low level of vinyl unsaturation detectable by NMR or infrared spectroscopy and the observation that bands attributable to a bridged ferrocene (8) were to be found in the infrared spectra of these polymers. 

Poly butadiene rapidly becomes crosslinked when irradiated in vacuo at 253.7 nm [54]. A decrease amounting to 80% of the original unsaturation is observed by infrared spectroscopy. Since no new unsaturation has been detected this decrease has been accounted for by cyclization. However, the absence of absorption at 1020 cm-1 implies that formation of cyclopropyl groups does not occur. Formation of a ladder polymer is also unlikely since all attempts to accomplish the free radical post-polymerization of 1,2-poly butadiene have been unsuccessful namely,... 

The presence of methyl groups and unsaturated bonds in polymer, confirmed by the infrared spectroscopy demonstrates the ability of such a course of reaction. 

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