the production of thymoquinone from thymol and carvacrol
the production of thymoquinone from thymol and carvacrol
the production of thymoquinone from thymol and carvacrol
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conversion (wt.%)<br />
45<br />
40<br />
35<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
0 100 200 300 400 500<br />
time (min.)<br />
<strong>thymol</strong> oxidation<br />
<strong>carvacrol</strong> oxidation<br />
Figure 7.15. The percentage <strong>of</strong> <strong>thymol</strong> <strong>and</strong> <strong>carvacrol</strong> conversion (reaction conditions:<br />
<strong>thymol</strong> or <strong>carvacrol</strong>/H2O2 molar ratio=1, 0.2 g Cr (salpn)-NaY catalyst,<br />
60ºC)<br />
7.5. Oxidation <strong>of</strong> Thyme Essential Oil<br />
There were several reports in <strong>the</strong> literature about <strong>the</strong> chemical composition <strong>of</strong><br />
essential oil. The summary <strong>of</strong> <strong>the</strong>se studies were also given in Chapter 5. Most reports<br />
indicated that <strong>thymol</strong> or <strong>carvacrol</strong> were <strong>the</strong> major component in <strong>the</strong> essential oil<br />
(Dorman et al. 1995). In this study, essential oil which was purchased <strong>from</strong> Arifo ulları<br />
Company was analyzed in HPLC.<br />
Essentail oil contains many monoterpenes. However, in HPLC analyses only<br />
<strong>carvacrol</strong> <strong>and</strong> <strong>thymoquinone</strong> were observed <strong>and</strong> no o<strong>the</strong>r components were identified<br />
such as <strong>thymol</strong>, p-cymene, α -terpinene for three different wavelengths (254 nm, 280<br />
nm, 295 nm).<br />
In <strong>the</strong> literature for oxidation reactions, large differences have been observed<br />
between GC <strong>and</strong> HPLC analysis results. Using GC for <strong>the</strong> analysis <strong>of</strong> reaction mixtures<br />
in <strong>the</strong> presence <strong>of</strong> residual H2O2, products were oxidized by H2O2 at elevated<br />
temperature in <strong>the</strong> GC system (Ma et al. 2002). Hence, lately HPLC was preferred<br />
technique for <strong>the</strong> oxidation reactions.<br />
As shown in Figure 7.16 <strong>carvacrol</strong> was <strong>the</strong> major component <strong>and</strong> it was<br />
converted to BQ, THQ, TQ (with 33.6% yield), unknown products with 70% conversion<br />
65