Other Ester Bands

Most aliphatic esters have bands in the regions 645-585 cm (15.50-17.09pm) and 350-300cm (28.57-33.33 pm). 

All acetates absorb strongly at 665-635cm (15.04-15.75pm) due to the bending of the O-C-O group and at 615-580cm (16.29-17.24pm) 

For the I group, a medium intensity band is observed near 

M-Propyl esters have a band near 1390 cm (7.19 pm) and bands of variable intensities at 605—585cm (16.53-17.09pm), near 495cm (20.20pm) and at 350-340cm (28.57-29.41 pm). The band near 600 cm is not present for the formate. Isopropyl esters have bands of variable intensity at 605-585 cm (16.53-17.09 pm) and 505-480cm (19.80-20.83 pm) and strong bands near 435 cm (22.99 pm) and at 

425-410cm (23.53-24.39pm), but isopropyl formate exhibits only the band near 435 cm .  

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The monocarboxylic esters were separated from other acid esters by thin-layer chromatography (TLC) on silica GF254 (Merck) by development in n-heptane-diethyl ether-methanol (80 20 2, v/v/v). TLC plates were visualized under ultraviolet light after spraying with 2,7-dichlorofluorescein, and the mono carboxylic ester band (R = 0.52) was removed and extracted with chloroform. 

An application of Fourier transform infrared spectroscopy (FTIR) to maleated polypropylene-treated wood liber has indicated that esterification reaction between hydroxyl groups of lignilied liber (unbleached thermomechanical pulp, TPM) and the coupling agent does not occur [5], The FTIR spectra did not indicate the presence of any distinct absorption bands near 1730 cm, which may be associated to other ester links besides those already present in wood fiber. However, tensile and flexural strength and impact resistance of the WPC in the presence of the maleated polypropylenes increased significantly (up to 280%) (Tables 5.9 and 5.10). 

The IR spectrum of PVOCCl quantitatively modified by glycine ethylester displays a large carbonyl band at 1725 cm" which corresponds to the superposition of the two carbonyl bands of the carbamate and of the ester groups. The C-Cl band of PVOCCl at 680 cm"l has completely disappeared. The other characteristic bands are at 3360 cm (vs) and 1530 cm"l (s), v(NH) 1210 cm" (s), v(0-C ester) 1280 cm" (s), v(0-C carbamate) and 1370 cm"l (m), v(CH3). The NMR spectrum of this polymer recorded at 15.1 MHz in CD2CI2 at 20 C affords a confirmation of the structure. The results of Table 3 show that the methine carbon of the chain is not stereosensitive, contrary to that of PVOCCl for which a triplet was observed on a spectrum recorded under similar conditions. 

The bands of acetates are always narrower than those of other esters [12] which suggests that rotational isomerism involving two forms is taking place as in the ketones. 

The alcohol from which the ester is made may be characterized in some cases.Some of these bands are seen in Fig. 5.8, where a methyl ester has an asymmetric CH3 stretch near 2960 cm" , and a symmetric CH3 deformation band near 1440 cm S and other weaker bands (shown in Fig. 5.8). 

Figure 5 shows the spectrum of isobutyl methyl ketone. The position of the carbonyl, while suiting a ketone, is also consistent with conjugated ester and carboxylic acid, but other characteristic bands from these two groups are not present. 

In Table IV some physical data and spectral characteristics of 6,7-secoberbines are listed. Only methyl corydalate (55) is optically active. Formula 55 presents the spatial structure of this compound, deduced by Nonaka et al. (65) and confirmed by Cushman et al. by both correlation with (+)-mesotetrahydrocorysamine (72) (<5S) and total synthesis (69). It is difficult to find common characteristic features in both the mass and H-NMR spectra of these alkaloids because they differ significantly from each other in their structures. On one hand, corydalic acid methyl ester (55) incorporates a saturated nitrogen heterocycle, while the three aromatic bases (56-58) differ in the character of the side chain nitrogen. For example, in mass fragmentation, ions of the following structures may be ascribed to the most intensive bands in the spectrum of 55 ... 

The new absorption band at 435 ran in the C60 spectrum has been attributed to the 1,2 addition to the fullerene cage to the fatty acid chains either across to the double bonds by a Diels-Alder addition or, more simply, by radical addition (Cataldo and Braun, 2007). Thus, fatty acid esters are able to not only dissolve C60, but also react with this molecule causing the addition of the fatty chain to the fullerene cage. In fact, the bands at 435 ran shown in Fig. 13.3 appear only when C60 is stirred at 75°C for a couple of hours in the esters of fatty acids. Only for olive oil the new band appears much weaker than in the other cases and displaced at 450 ran (Fig. 13.3B). Since this oil contains chlorophyll, the displacement may be probably due also to a charge-transfer interaction between C60 and chlorophyll or with other impurities. 

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