Benzyl magnesium chloride can be prepared from Benzyl chloride in diethyl ether with a small iodine crystal. Grignard reaction on Acetaldehyde Methylamine yields Methamphetamine. Acetaldehyde Methylimine is prone to polymerization, so it must be used quickly. Grignard reaction on Acetone Methylimine yields Mephentermine. Acetone imine isn't prone to polymerization.