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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3.3.1. Oxidation State<br />
The transition metals show a formidable number <strong>of</strong> oxidation states. The reason<br />
for exhibiting such a variety <strong>of</strong> oxidation states is <strong>the</strong> closeness <strong>of</strong> 3d <strong>and</strong> 4s energy<br />
states. Table 3.2 summarizes known oxidation numbers <strong>of</strong> <strong>the</strong> first row transition<br />
elements. The most prevalent oxidation numbers are shown in bold. The oxidation<br />
number zero usually assigned to elemental state has been omitted <strong>from</strong> <strong>the</strong> Table.<br />
Table 3.2. Known oxidation numbers <strong>of</strong> first row transition elements.<br />
Sc +3<br />
(Source: Anthony 1999)<br />
Ti +1 +2 +3 +4<br />
V +1 +2 +3 +4 +5<br />
Cr +1 +2 +3 +4 +5 +6<br />
Mn +1 +2 +3 +4 +5 +6 +7<br />
Fe +1 +2 +3 +4 +5 +6<br />
Co +1 +2 +3 +4 +5<br />
Ni +1 +2 +3 +4<br />
Cu +1 +2 +3<br />
Zn +2<br />
There is an increase in <strong>the</strong> number <strong>of</strong> oxidation states <strong>from</strong> Sc to Mn. All seven<br />
oxidation states are exhibited by Mn. The formal oxidation number <strong>of</strong> +7 represents <strong>the</strong><br />
formal loss <strong>of</strong> all seven electrons <strong>from</strong> 3d <strong>and</strong> 4s orbitals. In fact all <strong>of</strong> <strong>the</strong> elements in<br />
<strong>the</strong> series can utilize all <strong>the</strong> electrons in <strong>the</strong>ir 3d <strong>and</strong> 4s orbital. There is a decrease in <strong>the</strong><br />
number <strong>of</strong> oxidation states <strong>from</strong> Mn to Zn. This is because <strong>the</strong> pairing <strong>of</strong> d-electrons<br />
occurs after Mn which in turn decreases <strong>the</strong> number <strong>of</strong> available unpaired electrons <strong>and</strong><br />
hence, <strong>the</strong> number <strong>of</strong> oxidation states.<br />
The stability <strong>of</strong> higher oxidation states decreases in moving <strong>from</strong> Sc to Zn.<br />
Mn(VII) <strong>and</strong> Fe(VI) are powerful oxidizing agents. The relative stability <strong>of</strong> +2 state<br />
with respect to higher oxidation states, particularly +3 state increases in moving <strong>from</strong><br />
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