Ketyl

As ketyl radicals - also ketyls or Metallketyle - is referred to in organic chemistry radical anions derived from ketones and occur in several resonance structures:

Ketyls are not very stable and usually occur as very reactive intermediates. They are formed by single-electron transfer (SET = single electron transfer ) of alkali metals to carbonyl groups. For example, one uses the reduction of benzophenone by sodium to the intensely blue colored ketyl in solvents to prove that they are absolutely free of water.

Ketyls are intermediates in the pinacol coupling, the acyloin condensation and the McMurry reaction.

In the laboratory, the ketyl radical of benzophenone is used as an indicator for the dehydration of solvents with sodium application. The absence of water and oxygen is indicated by the deep blue color of the ketyl radical.

In practice to the absolutierende solvent, e.g. toluene, is heated under inert gas to elemental sodium and a small amount of benzophenone as long (hours to days ) at reflux, until the blue color is apparent. Since the added excess sodium with the (possibly) present in the solvent, water, sodium hydroxide and sodium reacts with the oxygen to ( per) oxide, an electron transfer from the sodium benzophenone according to the completion of the reaction, and the formed colored ketyl radical. Under certain circumstances and depending on the nature of the further soiling the solution in absolutierten state does not necessarily have a blue color, since other colors can come about through a side reaction.

Are called " ketyliert " and refers to the device structure shown on the right side as " ketyls " In this way absolutierte solvent. In many laboratories, there are specially furnished rooms or specific deductions, where Ketylen run continuously, in order to continually have absolutierte solvent available, and to prevent by avoiding constant drain and rebuild whole apparatus that extended by humidity of the cleaning process or already absolutiertes solvent resumes water and oxygen.