Grignard dried

Evidently, the types of compound compatible with this mixture are not many, but it has been used successfully for various 1,3-dioxacycloalkanes and hydrocarbons. It must not be used with halogen compounds although chloro- and bromo-alkanes can be dried safely over sodium films, provided that they are initially at least Grignard dry and free of oxygen. In the author s laboratory specimens of CHjClj and MeBr which had been over sodium films under vacuum for several years were analysed and found to contain only traces of the Wurtz-condensation products. 

For some purposes in the Grignard reaction) solid carbon dioxide, narketed as Dry Ice or Drikold, may be employed. 

Commercial magnesium turnings for the Grignard reaction should be washed with sodium-dried ether to remove any surface grease which may be present, dried at 100°, and allowed to cool in a desiccator. 

Alternatively, add a solution of 4 5 g. of p-toluidine in dry ether to the Grignard reagent prejjared from 1 0 g. of magnesium as detailed above. Then introduce 1 0 g. (or 0 02 mol) of the ester and proceed as described lOr anihdes. 

Method 2. Equip a 1 htre thre necked flask with a double surface reflux condenser, a mechanical stirrer and a separatory funnel, and place 12 -2 g. of dry magnesium turnings, a crystal of iodine, 50 ml. of sodium-dried ether and 7-5 g. (5 ml.) of a-bromonaphthalene (Section IV,20) in the flask. If the reaction does not start immediately, reflux gently on a water bath until it does remove the water bath. Stir the mixture, and add a solution of 96 g. (65 ml.) of a-bromonaphthalene in 250 ml. of anhydrous ether from the separatory funnel at such a rate that the reaction is vmder control (1 -5-2 hours). Place a water bath under the flask and continue the stirring and refluxing for a further 30 minutes. The Grignard reagent collects as a heavy oil in the bottom of the flask ... 

Alternatively, the solution of the Grignard reagent may be poured on to solid carbon dioxide (Dry Ice)—for experimental details, see under n-Valeric Acid, Section 111,84. 

In an alternative method of preparation, benzophenone is used. Prepare the Grignard reagent from 13 -5 g. of magnesium turnings as above, cool in cold water, and add a solution of 91 g. of benzophenone (Section IV,139) in 200 ml. of dry benzene at such a rate that the mixture refluxes gently. Reflux the mixture for 60 minutes, and isolate the triphenylcarbinol in the manner described above. The yield is of the same order. 

The receiving flask contents should contain a very pure product. There is no need to clean up any further. For the next stage however they wilt need to be dried over sodium sulphate. This can either be done now or later. Now is better, dry your product before you weigh it and place it in a screw capped bottle ready for the Grignard reaction. 

Safrole from the Grignard reagent Keeping the apparatus from the above reaction, pour 60g of allylbromide into the sep funnel. As with the ingredients of the last procedure the allylbromide must be dried over sodium sulphate. This stuff is really nasty, use a mask at least or a fume cupboard if you can get access to one or fill the sep funnel outdoors. The fumes are invisible and pretty lethal -please be warned. 

After the air in the flask had been replaced completely with nitrogen, 100 ml of dry diethyl ether, 0.20 mol of the cumulenic ether (see Chapter V, Exps. 7, 8 and 11) and 1 g (note 1) of copper(l) bromide were placed in it. A solution of the Grignard-reagent, prepared from 0.50 mol of the chloride (see Chapter II,... 

Solvent Preparation. The most critical aspect of the solvent is that it must be dry (less than 0.02 wt % of H2O) and free of O2. If the H2O content is above 0.02 wt %, then the reaction of Mg and RX does not initiate, except for an extremely reactive RX species, such as benzyl bromide. Although adventitious O2 does not retard the initiation process, the O2 reacts with the Grignard reagent to form a RMg02X species. Furthermore, upon hydrolysis, the oxidized Grignard reagent forms a ROH species that may cause purification problems. 

D. a-Allyl- -bromoelhyl ethyl ether. The same apparatus is used as in the preparation of allylmagnesium bromide. The flask is charged with an amount of the Grignard solution (part C) equivalent to 2.78 moles of allylmagnesium bromide (or chloride) and cooled in an ice bath. A solution of 580 g. (2.5 moles) of o , 3-dibromoethyl ethyl ether (part B) in an equal volume of anhydrous ether is added slowly with stirring over a period of 3-4 hours. The mixture is allowed to stand overnight and is then hydrolyzed with 75 ml. of 20% acetic acid followed by 500 ml. of water. The ether layer is separated, washed with four 100-ml. portions of 10% aqueous sodium bicarbonate solution followed by four 100-ml. portions of saturated aqueous sodium chloride solution, dried over 100 g. of anhydrous calcimn sulfate, and distilled under reduced pressure. The yield of colorless a-allyl-/3-bromoethyl ethyl ether is 370-396 g. (77-82% based on the a, 3-dibromoethyl ethyl ether), b.p. 72-75°/21 mm., 1.4600-1.4606. 

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