Studies on the Grignard Reaction IV. The Quantitative Determination of Grignard Reagent Concentration

It is shown that the methods used to evaluate Grignard reagent concentration (acidimetry, argentometry, iodometry) give to high results. Two new methods are proposed, one based on the estimation of unreacted excess acetone (with hydroxylamine) and one upon a photometric determination of benzophenone excess. The latter only gives good results with aliphatic non‐tertiary derivatives. The methods can be extended to dialkyl magnesium compounds when enough magnesium bromide is added.