Dichloro-p-xylene

Thus, p- xylene yielded 2,5-dichloro-p-xylene. The principal reaction with anisole was also chlorination and with phenol nitration when nitration temperature was low (-80°C) both o- and p- nitrophenols were formed. At room temperature chlorination also occurred yielding 2,4-dichloro-6-nitrophenol and 3,6-dichloro-2-nitro-phenol. 

Improved solubility was achieved by preparing polymer 186 through use of co-monomer mixtures of 1,3,5-triethynylbenzene and 2,5-diethynyl-p-xylene in various molar ratios (1 10, 1 50, 1 100) with /r/ //j--dichloro(tri-/ -butylphosphine)platinum. The high degree of cross-linking for the 1 10 mixture resulted in an insoluble material, whereas soluble co-polymers were obtained for the other two mixtures with 4/ = 58,000 and 27,000 (by GPG relative to PS) for the 1 50 and 1 100 molar ratio, respectively." ... 

W.J. Swatos and B. Gordon, III, Polymerization of 2,2-di- -hexyloxy-a,a -dichloro-p-xylene with potassium tert-butoxide a novel route to poly(2,5-di- -hexyloxy-p-phenylene vinylene), Polym. Prepr., 31(1) 505-506, 1990. 

Perhalomethylbenzenes can be chlorinated by treatment with a mixture of excess chlorosulfonic acid, iodine and chlorine. For instance, hexachloro-p-xylene 69 reacts with chlorosulfonic acid (240 parts), iodine (2 parts) and chlorine (30 parts) at 5-10 °C (4 hours) to give a very high yield (96%) of the 2,5-dichloro derivative. However, when hexachloro- -xylene 69 was warmed with chlorosulfonic acid (30 °C, 10 hours) in the presence of excess chlorine and iodine catalyst, the product was tetrachloroterephthaloyl chloride (85%) 70 (Equation 21). 

The presence of iodine is known to catalyse the chlorination of organic compounds by chlorosulfonic acid, enabling the reaction to proceed under comparatively mild conditions. So chlorination is a feature of the attempted sulfonation of aromatic iodo compounds with chlorosulfonic acid (see Chapter 2, p 19) for instance, reaction of />-diiodobenzene with excess reagent (five equivalents) at 50 C yields tetrachlorodiiodobenzene (82%), (Chapter 6, ref. 13). The chlorination is catalysed by traces of iodine and the reaction under these conditions probably involves both homolytic and heterolytic steps (see Chapter 4, p 49). Hexachloro-/7-xylene, by treatment with a mixture of chlorosulfonic acid, iodine and chlorine afforded either the 2,5-dichloro derivative or tetrachloro-terephthaloyl chloride depending on the experimental conditions (see Chapter 4, p 51). 

Deactivation (weak) from the adjoining ring does not prevent facile disubstitution of 4-methyl- and 4-phenyl-2,7-dichloro-1,8-naphthyridines wdth alkoxides (65°, 30 min), p-phenetidine (ca. 200°, 2 hr), hydrazine hydrate (100°, 8 hr), or diethylaminoethylmer-captide (in xylene, 145°, 24 hr) mono-substitution has not been reported. Nor does stronger deactivation prevent easy 2-oxonation of 5,7-dimethoxy-l-methylnaphthyridinium iodide wdth alkaline ferricyanide via hydroxide ion attack adjacent to the positive charge and loss of hydride ion by oxidation. 

Dichloro-2-diazo-p-xylene Salts (Ref, p 508) Tribromide, C3H7Cl2.N2.Br3 lt-yel ndls... 

Adams platinum oxide catalyst is readily prepared from chloroplatinio acid or from ammonium chloroplatinate, and is employed for catalytio hydrogenation at pressures of one atmosphere to several atmospheres and from room temperature to about 90°. Reduction is usually carried out with rectified spirit or absolute alcohol as solvents. In some cases (e.g., the reduction of benzene, toluene, xylene, mesitylene, cymene and diphenyl ), the addition to the absolute alcohol solution of 2-5 per cent, of the volume of rectified spirit which has been saturated with hydrogen chloride increases the effectiveness of the catalyst under these conditions chlorobenzene, bromobenzene, o-, m- and p-bromotoluenes, p-dichloro- and p-dibromo-benzene are reduced completely but the halogens are simultaneously eliminated. Other solvents which are occasionally employed include glacial acetic acid, ethyl acetate, ethyl acetate with 17 per cent, acetic acid or 8 per cent, of alcohol. In the actual hydrogenation the platinum oxide Pt02,H20 is first reduced to an active form of finely-divided platinum, which is the real catalyst allowance must be made for the consumption of hydrogen in the process. 

Several dehydrogenations forming double bonds conjugated with aromatic rings are achieved by heating with quinones. Acenaphthene gives a 75% yield of acenaphthylene when refluxed with chloranil for 16 h in xylene at 140 °C [967], and p,p -dimethoxybibenzyl affords an 83-85% yield of p,p -dimethoxystilbene when refluxed with 2,3-dichloro-5,6-dicy-ano-p-benzoquinone in dioxane at 105 °C [968]. 

When pressure (1.5 GPa) is applied at room temperature on the reaction of [Pt2(p-S)2(dppp)] (189) with an excess of a-a -dichloro-o-xylene (190) a product mixture is obtained from which 3,8-dibenzo-l,6-dithiacyclodecane 192 (35%) has been isolated. Apart from its pharmacological value, it could be used in molecular sensors and conductive polymers. The one-pot formation of 192 at... 

The dinitrile precursors for p-tetra- and p-octatrifluoromethylphlhalocyanines [MPcP(CF3)4] and [MPci (CF3)g] (Scheme 24) were obtained [69] starting from the mono(bis)trifluoromethyl substituted acetylenes 88a,b and 2,3-dimetylbutadiene 89 which easily give the Diels-Alder products 90a,b. These adducts were converted quantitatively upon dehydrogenation with 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) to o-xylene derivatives 91a,b. Their oxidation Cr03 in a mixture of acetic and sulfuric acids affords the phthalic acids 91a,b (yield ca. 80 %) which were converted to dinitriles 96a,b and diiminoimides 97a,b in a common way through intermediate anhydrides 93a,b, imides 94a,b, diamides 95a,b. 

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