TETRABROMO-0-XYLENE

B. o-Phthalaldehyde. The a,a,a, a -tetrabromo-0-xylene (344-370 g.) obtained as described above, part A, is placed in a 5-1. round-bottomed flask with 4 1. of 50% (by volume) ethanol and 275 g. of potassium oxalate. The mixture is heated under reflux for 50 hours (a clear yellow solution is formed after 25-30 hours). About 1750 ml. of the ethanol is then removed by distillation (which is stopped before the product begins to steam-distil), and 700 g. of disodium monohydrogen phosphate dodecahydrate (Na2HP04-12H20) is added to the aqueous residue. The mixture is steam-distilled rapidly (Note 4), using an efficient condenser, until 10-12 1. of distillate is collected and the distillate no longer gives a black color test for o-phthalaldehyde 8 when a portion is treated with concentrated ammonium hydroxide fol-... 

The o-quinodimethanes are very reactive, unstable dienes, which are usually prepared in situ. The cycloaddition under high pressure of the dibromo-o-quinodimethane 91, generated in situ from a,a,a, a -tetrabromo-o-xylene. 

Another surprising feature appears in the reactions of certain alkyl-benzenes with tetrabromo- and tetraiodo-benzyne generated by the aprotic diazotisation of the corresponding anthranilic acids S9K While only one product (41, X = Br or I, R = H or Me) was obtained in the reactions with benzene or -xylene, three products, (42, X = Br or I, R = Me, Pr1, or But), (43, X = Br or I, R = Me, Pr1, or But) and a naphthalene derivative a> were obtained in reactions with toluene, cumene (isopropylbenzene), and f-butylbenzene. 

Accumulation in Fish. The accumulation coefficient and excretion half-life of tri- and tetrabromo-benzenes, dibromo-toluene and xylene, are within a range expected on the basis of similar experiments Q ), and are summarized in Table II. 

Sulfonation (66JOC565) or nitration (74JOC1157) of the acridizinium (benzo[Z ]quin-olizinium) ion (3) occurs at position 10 (Scheme 31). When acridizinium bromide is dissolved in liquid bromine and allowed to stand for 15 h the perbromide salt of 7,8,9,10-tetrabromo-7,8,9,10-tetrahydroacridizinium ion is formed and this is easily converted to the simple bromide by the action of acetone. If the tetrabromo salt is refluxed in xylene, it is reconverted to acridizinium bromide (3) in good yield. Treatment of the tetrabromide with sodium acetate gives 10-bromoacridinium bromide (Scheme 32). 

A. a,a,ot, a -Tetrabromo-o-xylene. In a 2-1. three-necked flask equipped with an oil-lubricated Trubore stirrer, a dropping funnel, a thermometer extending nearly to the bottom of the flask, and a reflux condenser (Note 1) attached to a gas absorption trap 2 is placed 117 g. (1.1 moles) of dry o-xylene (Note 2). An ultraviolet lamp such as a General Electric R.S. Reflector Type 275-watt sun lamp is placed about 1 cm. from the flask so as to admit the maximum amount of light. The stirrer is started, and the o-xylene is heated to 120° with an electric heating mantle. A total of 700 g. (4.4 moles) of bromine (n.f. grade) is added in portions from the dropping funnel to the reaction flask at such a rate that the bromine color is removed as fast as it is added. 

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