Potassium tert -butanolate

Structural formula
General
Surname	Potassium tert -butanolate
other names	Potassium tert -butoxide; Potassium tert -butoxide; KO- t -butyl; KTB; t -BuOK;
Molecular formula	C 4 H 9 KO
Brief description	white to yellowish odorless solid
External identifiers / databases
EC number	212-740-3
ECHA InfoCard	100,011,583
PubChem	23665647
ChemSpider	63266
Wikidata	Q285903
properties
Molar mass	112.21 g mol −1
Physical state	firmly
Melting point	256-258 ° C
pK s value	19 (in water ); 32.2 (in DMSO );
solubility	violent decomposition in water; poor in hexane , toluene and diethyl ether ; good in tert -butanol and THF ;
safety instructions
H and P phrases	H: 228-252-314
	EUH: 014
	P: 405
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Potassium tert -butanolate is the alcoholate salt made from tert -butanol and potassium . It is a strong, non- nucleophilic base that is commercially available both in solution and as a solid.

presentation

Potassium tert -butanolate is prepared using the usual procedure for the production of alcoholates. It can be produced in the absence of water under protective gas by reacting elemental potassium with tert- butanol according to the following equation:

{\ displaystyle {\ ce {2 (CH3) 3C-OH + 2K -> 2 (CH3) 3C-OK + H2 ^}}}

The resulting solution of potassium tert -butanolate in tert- butanol can either be used directly or the solvent can be removed.

As potassium tert- butanolate ages faster (recognizable by a yellowish discoloration), it is recommended that older batches be cleaned before use. This is done by sublimation at 220 ° C and a pressure of 1.3 h Pa .

properties

Potassium tert -butanolate is a white solid that reacts violently with water. It has an ignition temperature of 360 ° C and can be ignited even by brief exposure to flames. 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 -butanolate 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-butyl radical.

use

In organic synthesis , potassium tert- butoxide is used as a strong, non-nucleophilic base. The low nucleophilicity is a consequence of the high steric hindrance of the alcoholate by the sterically demanding tert-butyl radical . In contrast, it is suitable for deprotonating C, H-acidic compounds and for dehydrohalogenation .

In solution, potassium tert- butoxide forms complex structures, which leads to a reduction in its reactivity. These structures can be broken up by adding DMSO .

In a mixture with lithium alkyls , potassium tert -butanolate is called Schlosser's base , which increases the basicity.

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g Entry on potassium tert-butoxide in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .
↑ Joseph Hornback: Organic Chemistry. Cengage Learning, 2005, ISBN 978-0-534-38951-2 ( limited preview in Google Book Search), p. 131.
^ FG Bordwell: Bordwell pKa Table (Acidity in DMSO) .
↑ ^a ^b ^c ^d ^e ^f ^g D. Caine: Potassium tert -butoxide , in: Encyclopedia of Reagents in Organic Synthesis , John Wiley & Sons, New York, 2006; doi : 10.1002 / 047084289X.rp198.pub2 .

[gestis-1] ↑ ^a ^b ^c ^d ^e ^f ^g Entry on potassium tert-butoxide in the GESTIS substance database of the IFA , accessed on January 10, 2017(JavaScript required) .

[2] Joseph Hornback: Organic Chemistry. Cengage Learning, 2005, ISBN 978-0-534-38951-2 ( limited preview in Google Book Search), p. 131.

[3] FG Bordwell: Bordwell pKa Table (Acidity in DMSO) .

[eros-4] ↑ ^a ^b ^c ^d ^e ^f ^g D. Caine: Potassium tert -butoxide , in: Encyclopedia of Reagents in Organic Synthesis , John Wiley & Sons, New York, 2006; doi : 10.1002 / 047084289X.rp198.pub2 .