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0 H E M :[ S T R Y under which the unbenzoylated acid is entirely converted the nitrogen atom would also be unsaturated; as a consequence, the centric mechanism might break down and into tribromophenol. Results such as these show that the introduction of lapse into the ethenoid condition. If, at such a moment, various radicles in place of the hydroxylic hydrogen most hydrogen chloride were again to combine with the molematerially affects the character of the influence exercised cule, a compound might be formed which could undergo by the oxygen in phenol, and they afford a clue to the decomposition in such a way that the chlorine atom manner in which the action takes place. It can scarcely remained in the orthoposition, the hydrogen atom separatbe doubted that initially the oxygen attracts the bromine ing with the chlorine atom attached to the nitrogen to itself, and that when the bromine has thus been made atom or the two chlorine atoms might attract each a part of the molecule, it is capable—under proper condi- other, in which case the chloramine would be reduced. tions—of producing further changes, and eventually of As a matter of fact, only a relatively small proportion displacing hydrogen in the hydrocarbon portion of the mole- of orthochloracetanilide is formed, the para-compound cule. “ Ce n’est que le premier pas qui co'dte ”—everything being always the chief, and under most conditions, the sole depends on the bromine becoming introduced into the product; it therefore seems probable that when the condimolecule. The affinity of oxygen for bromine—and it tions permit, instead of the two chlorine atoms actually may be supposed for other agents—is evidently of a some- separating from the system in the manner pictured, they what fickle character; it varies greatly according to the attack the para-position, removing the hydrogen atom nature of the groups with which the oxygen is associated, and taking its place. With regard to the possible reduction of the chloramine, although unobserved in the case of some rendering the oxygen altogether indifferent.1 The properties of anilineparasulphonic acid are modi- phenylacetylchloramine, such an action actually does take fied in precisely the same way as are those of phenol- place in some cases, parachlorophenylacetylchloramine, parasulphonic acid by introducing hydrocarbon and acid for example, being converted into parachloracetanilide radicles in place of the hydrogen atoms in the NH2 group. and chlorine by the action of a concentrated solution of Thus dimethylanilineparasulphonic acid yields only a hydrogen chloride, although if heated with water and a monobromo-derivative, whereas the unmethylated acid is trace of hydrogen chloride it undergoes isomeric change at once converted into tribromaniline by bromine; in into dichloracetanilide. No more striking proof could this case the sulphonic group does not become displaced. well be given that the hydrocarbon radicle is insensitive If, however, acetyl or benzoyl be introduced in place of to direct attack by chlorine, and that its chlorination is one of the hydrogen atoms of the NH2 group, bromine effected indirectly. That sulphonation involves a similar series of changes is at once able to displace the sulphonic group, parabrom-acet- or benz-anilide being formed together with the there can be little if any doubt, as acetanilide behaves monobrominated sulphonic acid. Evidently, therefore, the towards sulphonating agents just as it does on chlorination; influence of nitrogen, like that of oxygen, varies greatly when cautiously dissolved in moderately strong fuming sulphuric acid, it is in the first instance converted into the according to the nature of its associates. Assuming that the first stage in the formation of the sulphaminic acid CcH5.N(C2Hg0)(S03H). If the liquid substitution derivative from the phenol or amine consists mixture be at once poured into water, and the solution boiled, only aniline para-sulphonic acid is obtained, but Chan es in the attraction by the oxygen or nitrogen of the if the mixture be preserved at a low temperature and involved particular agent used, it remains to determine in chlorin- what are the consequent changes. With this allowed gradually to hydrate, and then boiled with water, ation, etc. object in view, the behaviour of acetanilide on besides para-acid a considerable amount of ortho-acid is chlorination is especially deserving of study. Initially this also produced. In this case, as on chlorinating acetanilide, compound exchanges its aminic hydrogen for chlorine, the ortho-compound is formed when the substituting and probably a change of this kind invariably takes place radicle is, as it were, let down gently; otherwise the parawhen amines are chlorinated. The compound thus pro- derivative is alone produced. As compounds such as dime thy laniline, C6H5.N(CH3)2, duced, phenylacetylchloramine, C6H5.N(C2H30)C1, when carefully purified, is a fairly stable substance, but if it are chlorinated, sulphonated, &c., without difficulty, it canbe brought into contact with a trace of hydrogen chloride, not be supposed that the introduction either of chlorine it is rapidly converted into parachloracetanilide, much or of the sulphonic group into the aminic group is an heat being developed; on this account, in preparing it essential preliminary to the introduction of either the one and similar compounds it is necessary to avoid the or the other of these radicles into the nucleus. The presence of hydrogen chloride. The transference of chlorine explanation given above, in fact, does not necessarily require the direct transference of the radicle from the from the nitrogen atom into the hydrocarbon radicle aminic group into the nucleus, but it is clear that such a NAcCl NAcH direct transference may take place, in view of the fact that nitrosomethylaniline, C6H5.N(CH3)(NO), for example, is entirely converted into paranitrosomethylaniline, NO. C0H4. NH. CH3, by the action of hydrogen chloride, which is provoked by hydrogen chloride, would seem inasmuch as it can scarcely be doubted that if the NO to be dependent on the combination of the chloramine group ever became separated from the molecule, it would with hydrogen chloride, whereby a condition of extreme not be entirely returned. A similar argument may be instability is engendered. Probably the first change to based on the complete conversion of diorthonitroparafollow this is one in which the atom of chlorine associated bromophenol into orthoparadinitroorthobromophenol by with the nitrogen atom escapes together with an atom of the action of bromine; and on the formation from hydrogen from the hydrocarbon complex. It may be sup- orthiodauisol of pariodorthonitranisol on nitration posed that this would lead to a “wave of disturbance being generated within the ring, and that for the moment

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1 The discovery of diethylperoxide, C2Hs.O.O.C2H5, a relatively stable compound, by Baeyer and Villiger, has afforded direct proof that the “ activity ” of oxygen is much reduced by association with hydrocarbon radicles.

Br NO* As iodine substitution derivatives are rarely formed by