Preparation of cyclohexylmagnesium iodide
1-liter three-necked flask is fitted with air tight stirrer, a 500 ml dropping funnel and a reflux condenser to the upper end of which a drying tube with anhydrous calcium iodide is attached. All parts of the glass apparatus must be dry. The flask is partially immersed in a bath of water and charged with 26.7 grams of magnesium turnings (the turnings are prepared by washing with a little absolute ether to remove surface grease, drying at 100-120° C, and allowing to cool in a desiccator) and a crystal of iodine in the flask. Separately in a dry vessel 129.3 ml (or 210 grams) of cyclohexyl iodide (iodocyclohexane) and 450 ml of absolute ether are mixed and introduced about 100 ml of the ether and 15 ml of the cyclohexyl iodide into the reaction flask. The water bath is slowly heated so that the ether refluxes gently in order to start the reaction. When the reaction has commenced the water bath is removed and sufficient amount of absolute ether is introduced with constant stirring to cover the magnesium. Then the remainder amount of the cyclohexyl iodide dissolved in the residual ether is introduced during 30-45 minutes. If the reaction becomes too vigorous, the flask is cooled in ice water. When all cyclohexyl iodide has been added the refluxing and stirring is continued for 15-20 minutes in order to complete the formation of the Grignard reagent – cyclohexylmagnesium iodide.
A text book of practical organic chemistry, by A. I. Vogel, 252, 1974