Hydroxyl groups primary-secondary, identification

Identification. The retention times on the HPLC system and the Rf-values on silica gel TLC of compounds 1 to and 1 2 to 2A agreed with those of the known carotenoids from Anacystis nidulans and Chromatium vinosum, respectively. Spectroscopic properties, molecular weights and number of hydroxyl groups, all of which are primary and/or secondary, are shown in TABLE 1. Assignments of H-NMR spectra of 2 "to 6 and 8 to 11 were made by comparison with the data of typical carotenoids. The CD spectra indicated that the absolute configuration of the hydroxyl groups at C-2 and C-3 were 2R and 3R, respectively. The position of the aldehyde group in IjO was analyzed with the EI-MS spectrum [3,4] ... 

The use of NO and sulphur tetrafluoride (SF4) gas treatments allows more precise identification and quantification of hydroxyl (OH) and hydroperoxy (OOH) groups (as nitrites and nitrates, respectively, after NO reaction) and carboxylic acids (after SF4 treatment to produce acid fluorides) (cf. section 10.17.1.5) and ketones (after removal of the overlapping acid absorptions and hydrogen-bonding effects with —OH groups by SF4 reactions) [362]. The NO reaction products are particularly informative because of their intense absorptions (up to 4-7 times stronger than those of the original OH species) and because primary, secondary and tertiary products have different IR absorptions [362]. 

Heatley [36] provided very valuable NMR spectroscopic information on polyethers. The NMR spectra of the copolyethers after trifluorination allowed the determination of the oxyethylene-to-oxypropylene unit ratio in the chain and the concentrations of primary (triplet at 4.42 ppm) and secondary (sextet at 5.16 ppm) hydroxyl groups. Their NMR spectra were compared to those of a,o -dihydroxy-polyaxyethylene and a,cn-dihydroxy-polyoxypropylene, which confirmed the NMR data and permitted the identification of each configuration in the chain. 

Figure 2.8, is generated, presenting peaks correspondent to functional groups, such as epoxide, primary and secondary amines, and hydroxyl. The values of the absorption bands for these groups can be found in the papers referenced earlier. The basic principle of all these methods is the comparison between the spectrum of reference substances and spectra of the reactants and products of a curing reaction subjected to radiation. A qualitative and quantitative identification of the components is then possible. 

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