the production of thymoquinone from thymol and carvacrol

Figure 7.4 (cont.)
The IR spectra of the encapsulated complexes were essentially similar to that of
the free complexes; this was observed from Figure 7.4. However, some IR bands of
encapsulated complexes and free ligand showed some differences from each other. For
example free ligand (H2salpn) exhibited (C=N) stretch at 1580 1/cm. In complexes,
this band shifted to lower frequency. As seen in Table 7.2, this band appeared in the
range 1523-1570 1/cm. This shift was the indication of the coordination of azomethine
nitrogen to the metal. Our results showed good agreement with the results reported in
the literature earlier (Maurya et al. 2002a; Maurya et al. 2003). According to the FTIR
results, there was no significant expansion of the zeolite cavities, dealumination or
structural changes during the encapsulation process. IR spectra of NaY zeolite, metal-
exchanged zeolites and catalysts were shown in Figure 7.3. This indicated that, the
structure of metal complexes fitted nicely within the cavity of the zeolite. The presence
of several bands of low intensity in 2700–2900 1/cm regions indicated the existence of
ethylene group of the amine residue of the ligand.
45