Phosphorus oxychloride pentachloride

This preparation illustrates the use of phosphorus pentachloride for the preparation of acyl chlorides in this case no difficulty is experienced in separating the 3,5-dinitrobenzoyl chloride from the phosphorus oxychloride formed simultaneously (c/. p. 240), because the former is readily isolated as a crystalline... 

Assemble in a fume-cupboard the apparatus shown in Fig. 67(A). Place 15 g. of 3,5-dinitrobenzoic acid and 17 g. of phosphorus pentachloride in the flask C, and heat the mixture in an oil-bath for hours. Then reverse the condenser as shown in Fig. 67(B), but replace the calcium chloride tube by a tube leading to a water-pump, the neck of the reaction-flask C being closed with a rubber stopper. Now distil off the phosphorus oxychloride under reduced pressure by heating the flask C in an oil-bath initially at 25-30, increasing this temperature ultimately to 110°. Then cool the flask, when the crude 3,5-dinitro-benzoyl chloride will solidify to a brown crystalline mass. Yield, 16 g., i.e,y almost theoretical. Recrystallise from caibon tetrachloride. The chloride is obtained as colourless crystals, m.p. 66-68°, Yield, 13 g Further recrystallisation of small quantities can be performed using petrol (b.p. 40-60°). The chloride is stable almost indefinitely if kept in a calcium chloride desiccator. 

Method 2. Mix 1 0 g. of 3 5-dinitrobenzoic acid with 1 5 g. of phosphorus pentachloride in a small, dry test-tube. Warm the mixture gently over a small smoky fiame to start the reaction when the reaction has subsided (but not before), boil for 1-2 minutes or until the solid matter has dissolved. Pour the mixture while still liquid on a dry watch glass (CAUTION the fumes are irritating to the eyes). When the product has solidified, remove the liquid by-product (phosphorus oxychloride) by transferring the pasty mixture to a pad of several thicknesses of filter paper or to a small piece of porous tile. Spread the material until the liquid has been absorbed and the residual solid is dry. Transfer the 3 5 dinitrobenzoyl chloride to a test-tube, add 0-5-1 ml. of the alcohol, and continue as in Method 1. 

Alternatively a mixture of 90 g. of sodium benzenesulphonate and 60 g. (36 ml.) of phosphorus oxychloride may be used. The experimental procedure is identical with that for phosphorus pentachloride, but the yield is slightly better. 

Place a mixture of 30 g. of 3 5-dinitrobenzoic acid (Section IV,168 and 33 g. of phosphorus pentachloride in a Claisen flask fit a reflux condenser into the short neck and cork the other neck and side arm (compare Fig. Ill, 31, 1). Heat the mixture in an oil bath at 120-130° for 75 minutes. Allow to cool. Remove the phosphorus oxychloride by distillation under reduced pressure (25°/20 mm.) raise the temperature of the bath to 110°. The residual 3 5-dinitrobenzoyl chloride solidifies on cooling to a brown mass the yield is quantitative. Recrystallise from carbon tetrachloride the yield is 25 g., m.p. 67-68° and this is satisfactory for most purposes. Further recrystallisation from a large volume of light petroleum b.p. 40-60°, gives a perfectly pure product, m.p. 69 -6°. 

Chloroquinazoline can be isolated, at best in 40% yield, by boiling 2-hydroxyquinazoline with phosphorus pentachloride in phosphorus oxychloride for 45 min, and attempts to improve this yield have proved fruitless. The yields are much higher when an aryl group is in position 4 w hich suggests an attack of the 3,4-double bond in 2-hydroxy- and 2-chloro-quinazolines by the chlorinating agent. 

Dihydro-l-oxo-3,4-benz-j8-carboline (166) reacted with phosphorus oxychloride and one mole of phosphorus pentachloride at 110° to give l-chloro-3,4-benz-j8-carboline (264). When, however, more than one mole of phosphorus pentachloride was used 265 was obtained, presumably by chlorination of 264. This chlorinating action of phosphorus pentachloride is analogous to that observed when an... 

Chloro-4-Carbethoxy-6-Ethyl-Pyridine 26 grams of the product just obtained are treated with 81 grams of phosphorus pentachloride in 45 cc of phosphorus oxychloride. The phosphorus oxychloride is distiiled off in a vacuum and the residue is treated with absoiute aicohoi. After distillation there are obtained 24 grams of product having a boiling point of 127° to 131°C/8 mm. 

In a 2-1 three-necked flask equipped with a stirrer, a reflux condenser, and a dropping funnel (Note 1) 832 g (4 0 moles) of phosphorus pentachloride is stirred with 250 ml. of phosphorus oxychloride (Note 2) To this is added with stirring 264 g (272 ml, 4 4 moles) of methyl formate (Note 3). During the addition the reaction vessel is cooled in an ice bath to maintain a reaction temperature of 10-20° The addition requires about 1.75 hours When the addition is complete, the solution is stirred at a temperature under 30° until all the phosphorus pentachloride has dissolved (about 1 hour) Then the stirrer is removed, the reflux condenser is replaced by a distilling head, and the reaction... 

Phosphorus oxychloride serves only as a suspension medium for phosphorus pentachloride and makes possible a homogeneous reaction. The phosphorus oxychloride obtained during workup may be recycled in this preparation. 

Dangerous materials may require special equipment. Chlorination with gaseous chlorine requires quite expensive storage facilities. Chlorination with chlorine, thionyl chloride, sulphuryl chloride, phosphorus oxychloride, phosphorus trichloride, or phosphorus pentachloride, all of which are fairly hazardous, requires off-gas treatment. Some of these reactants can be recycled. Pyrophoric solids such as hydrogenation catalysts, anhydrous aluminium trichloride for Friedel-Crafts reactions, or hydrides used as reducing agents should usually be handled using special facilities. Therefore, all of the above proce.sses are usually carried out in dedicated plants. 

The preparation of benzenesulfochloride from sodium ben-zenesulfonate with phosphorus pentachloride or phosphorus oxychloride has already been described in a previous article in this series,1 in which a bibliography of the literature is to be... 

Cyclization of phenacyl derivatives 676 and 678 with phosphorus oxychloride and pentachloride gave 677 and 679, respectively (87KGS533). 

Yoon and co-workers prepared perchlorinated pyridazines via chlorination of pyridazone 164 <00JHC1049>. They reported that the chlorination of 164 using phosphorus oxychloride gave only 165 in 81% yield. However, a solution of phosphorus pentachloride and cyclohexane provided only 166 in 81% yield. Furthermore, other reaction conditions gave a mixture of 165 and 166 in varying ratios depending upon the solvent, temperature, and reaction time. 

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