4- Bromoacetophenone

Bromoacetophenone was obtained by Emmerling and Engler by the reaction of bromine on acetophenone. 

In the laboratory it is usually prepared by Mohlau s modification of Emmerling s original method, that is, by the action of bromine on acetophenone. 

acetophenone and 125 gm. acetic acid are placed in a flask through whose stopper passes a reflux condenser, a tap-funnel and a delivery-tube for carbon dioxide. While agitating the contents of the flask, 30 gm. bromine are added little by little from the tap-funnel, meanwhile passing a current of carbon dioxide through the liquid to remove the hydrobromic acid formed in the reaction. When all the bromine has been added, the current of carbon dioxide is continued for 5-10 minutes and then the whole allowed to stand for about i hour before heating on the water-bath to remove the carbon dioxide completely. When the liquid in the flask is colourless it is poured into much water. The bromoacetophenone separates for the most part as a yellow oil which forms a crystalline mass on cooling. The crystals are collected and purified by alcohol. 

Bromoacetophenone forms white rhombic prisms which become greenish on exposure to light, owing to incipient decomposition. It melts at 50° C. and boils at ordinary pressure at 260° C. with decomposition, and at 12 mm. mercury pressure at 133° to 135° C. with partial decomposition. It is insoluble in water, but soluble in the common organic solvents (alcohol, ether, benzene, etc.). 

Treated in the cold with alcoholic ammonia, it forms iso-indole. The reaction with aniline is more vigorous than in the case of chloroacetophenone.  

In a 1-litre three-necked flask, equipped as in Section IV,137, place 78-5 g. (52-5 ml.) of dry bromobenzene (Section IV,18), 200 ml. of dry 

These are all prepared in the same manner, viz., 0 5 mol of the derivative of the aromatic hydrocarbon, 150 g. of finely-powdered anhydrous aluminium chloride and 0-5 mol of the acid anhydride. Thus — 

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Nuclear halogenation of acetophenone depends on formation of the aluminum chloride complex. If less than one equivalent of aluminum chloride is used, side-chain halogenation occurs. 3-Bromoacetophenone has been prepared from 3-aminoaceto-phenone by the Sandmeyer reaction. The synthesis described here has been taken from work of the submitters, who have used it to prepare many 3-bromo- and 3-chloroacetophenones and benzaldehydes, as well as more highly halogenated ones (Notes 7 and 8). 

Bromine, reaction with furan in methanol to yield 2,5-dimethoxy-2,5-dihydrofuran, 40, 29 3-Bromoacetophenone, 40, 7... 

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