Polyhalogeno - compounds

The first reported initiators were polyhalogeno-compounds (e.g. CC14, CHC13, CCl3CH2OH, CCl3Br). Trichloromcthanc derivatives and tctrachloromethanc appear effective initiators. Mono- and dichloromethane derivatives are inefficient initiators. Tetrachloromethane may act as a difunctional initiator. 

Pyrrole and its simple alkyl derivatives are polymerized by many of the typical acidic electrophiles. Nitration with acetyl nitrate (Scheme 4.31) under mild conditions gives the 2-nitro compound, together with small amounts of 3-nitropyrrole. Halogenation is rapid but it gives a complex mixture of polyhalogeno compounds. 

The halogenopyrazines are liquids but the polyhalogeno compounds are usually low melting solids (Table V.3 contains representative literature values). 2-Chloro-pyrazine is a strong smelling liquid and 2-chloromethylpyrazine a lacrimatory oil (679). 

Heteroaromatic Polyhalogeno-compounds.—Rate constants for the reactions of various polyfluoro- and chloropolyfluoro-pyridines with ammonia in dioxan-water have enabled the separate effects of fluorine and chlorine atoms that are ortho, meta, and para to the reaction centre to be determined. In each case the order is ortho > meta > para for fluorine, 31 23 0.26 and for chlorine, 86 24 6.9, both sequences being relative to a hydrogen atom at the same position. Both pentafluoro- and pentachloro-pyridine undergo Arbusov reactions at C-4 with (EtO)3P, the chloro-compound also giving the 2,4-bis(diethoxyphosphinyl) derivative. 3-Chloro-2,4,5,6-tetrafluoro- and 3,5-dichloro-2,4,6-trifluoro-pyridines are readily converted into the corresponding 4-iodo-compounds with Nal and DMF. ... 

Aromatic Polyhalogeno-compounds Heteroaromatic Polyhalogeno-compounds... 

Polyhalogeno-compounds covered by American rules which have been adopted also in Great Britain . 

Arbusov reactions have been observed with many different types of reactive halogeno compounds, e.g. with polyhalogeno-alkanes,1 esters of halogenocarboxylic acids,2 alkylaryl halides3 and certain heterocyclic halides.4 5 Acetyl chloride and benzoyl chloride react at room temperature to give esters of the corresponding acetyl and benzoyl phosphonic esters. ... 

Among the numerous polyhalogeno derivatives, we chose 1,2,4- and 1,2,3-trichlorobenzenes. Indeed several nucleophilic substitutions had already been studied with the first compound and results published44 did not give a good explanation of its reactivity. In fact, basic systems used by the authors chiefly lead to trisubstitutions and hardly give a good idea of the successive products formed. Moreover both trichlorobenzenes are side products of industrial benzene chlorination and are easily obtained in mixture. 

Colourless solids. Carbohydrates simple phenols high rnoLwt. carboxylic adds, their salts and amides sulphonic adds, their salts and amides simple imides polyhydric alcohols Mgher mol.wt. esters polyhalogeno-aromatic hydrocarbons halogen substituted aromatic acids, their salts and amides bisulphite compounds of aldehydes and ketones aldehyde-anunonias condensation products of aldehydo- and keto-compounds. 

Except for some polyfunctional aromatic amino-compounds (e.g. aminophenols, some amino-acids, phenylenediamines) aromatic amines are not soluble in water. Most dissolve in dilute hydrochloric acid, but some weak bases, e.g. nitroanilines, diphenylamines and polyhalogeno-anilines dissolve only in concentrated acids. A few aromatic amines (e.g. naphthylamines) dissolve in concentrated hydrochloric acid and then slowly precipitate as their sparingly soluble hydrochlorides. In all cases of doubt as to the solubility of a suspected amine in hydrochloric acid, a little of the filtered solution should be treated with an excess of alkali, when the amine (if insoluble in water) should be regenerated as an oil or solid. Amino-phenols and amino-acids are amphoteric substances (see pages 14-76). 

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