Benzyl potassium explained

Benzylpotassium is an organopotassium compound with the formula C₆H₅CH₂K, an orange powder. Like organo-alkali metal reagents in general, benzyl potassium is highly reactive, so much so that it reacts with most solvents. It is highly air sensitive.

Synthesis

One early synthesis proceeds by two-step transmetallation reaction by p-tolylpotassium:^[1]

(CH₃C₆H₄)₂Hg + 2 K → 2 CH₃C₆H₄K + Hg

CH₃C₆H₄K → KCH₂C₆H₅A modern synthesis involves the reaction of butyllithium, potassium tert-butoxide, and toluene.^[2] Although potassium hydride can also be used as a strong base for preparing potassium salts, benzyl potassium has the advantage of being molecular and hence more fast-acting.

References

1. 10.1021/ja01863a054. Benzylalkali Compounds1. Journal of the American Chemical Society. 62. 6. 1514. 1940. Gilman. Henry. Pacevitz. Henry A. Baine. Ogden.
2. 10.1016/0022-328X(87)80117-1. Lithium-potassium exchange in alkyllithium/potassium t-pentoxide systems. Journal of Organometallic Chemistry. 326. 1. 1987. Lochmann. L. Trekoval. J.