Carbanion mechanisms XXI. Solution acidity of triphenylsilane

Comparative acidity measurements have been performed between triphenylsilylpotassium and a series of arylmethanes by 1H-NMR in tetrahydrofuran: Metalation of the arylmethane was complete in the case of Ph3CH (pKa 31.4) and Ph2CH2 (pKa 33.4) but with (p-CH3·C6H4)2CH2 (pKa 35.1) ∼50% metalation of the di-p-tolymethane occurred, indicating that the two acids have equal pKa. No reaction occurred with 4-Ph·C6H4·CH3 (pKa 38.7). Thus pKa Ph3SiH≈35.1 in THF. This represents the first solution measurement of the acidity of an organosilane.