Potassium tert-butoxide
- Potassium tert-butoxide
- Potassium tert-butoxide
- KO -t-butyl
- KTB
White to pale yellow odorless solid
Fixed
256-258 ° C
- Violent decomposition in water
- Poorly in hexane, toluene, and diethyl ether
- Well in tert -butanol and THF
Risk
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Potassium tert- butoxide is the Alkoholatsalz of tert -butanol and potassium. It is a strong non-nucleophilic base, which is commercially available both in solution and as a solid.
Representation
The preparation of potassium tert- butoxide is carried out according to the usual procedure for preparing alcoholates. It can be produced in the absence of water in an inert gas by reaction of elemental potassium to tert -butanol according to the following equation:
The resulting solution of potassium tert- butoxide in tert -butanol can be used either directly or to remove the solvent.
Since potassium tert- butoxide faster aging (indicated by a yellowish discoloration ), is recommended for older batches to clean it before use. This is done by sublimation at 220 ° C and a pressure of 1.3 hPa
Properties
Potassium tert- butoxide, is a white solid which reacts violently with water. It has an ignition temperature of 360 ° C and is already inflamed by brief exposure to flame. The flammability increases with a finer distribution of the substance.
The base can sometimes react violently with short-chain alcohols and ketones, esters, diethyl sulfate and air.
Potassium tert- butoxide has a higher basicity than the homologous alcoholates of 1- butanol, 2 -butanol and isobutanol. This is due to the higher I effect of the tert- Butylrests.
Use
In organic synthesis, potassium tert- butoxide is used as the strong, non - nucleophilic base. The low nucleophilicity is a consequence of high steric hindrance of the alkoxide with the bulky tert- butyl. On the other hand, it is suitable for deprotonation C, H -acidic compounds and dehydrohalogenation.
In solution of potassium tert- butoxide complex structures is formed, which leads to a reduction in their reactivity. These structures can be broken up by the addition of DMSO.
In mixture with lithium alkyls is potassium tert- butoxide called Schlosser base, whereby the basicity is increased.