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The Replacement of Halogen and Nitro Grups Substituted in the Benzene Nucleus

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The Replacement of Halogen and Nitro Grups Substituted in the Benzene Nucleus U.B.C LIBRARY GAT. m.L§2JbJU3L&l&2L THE REPLACEMENT OF HALOGEN AND NITRO GRUPS SUBSTITUTED IN THE BENZENE NUCLEUS ROBERT N. CROZlER SOME APPLICATION OF THE ELECTRONIC COHCSPTIOfl OF VALSNCB, A3 PRESENTED BY H. 3, FRY, TO THE REPLACEMENT OF HALOGEH AMD MITRO GROUPS SUBSTITUTED Iti THE BEiJZENE UUCLSU3. *J Robert Helaon Crosier A Theeia submitted for the Degree of MASTER OF ARTS In the Department of CHEMISTRY THE UUIVKRSITY 0*' BRITISH COLUMBIA April, 1925. (MAj*>jacx*->~ 1 z*hp TABLE 0? COiiTEiiTo. IHTBOPUCTIOfl: General Introduction. Review of the electronic conception of Telenoe as presented by ^arry ohipley Fry. PART I. A. Review and possible electronic explanation of the results of previous researches done on the replacement of groups la halogen substituted bensene derivatives. The work of; 1« Sohbpff- £• Grohaann. 3# Fischer 4, H. Ph. fioudet 6. fiolleoan. B. Experimental part. I* Geaeral prooedure followed. XI. Early methods and their results. Ill* Method now being used. a. Description of furnace. a. First determinations. 1. Table of results. 11. Explanation of results. o. Seoond determinations. 1. Table of results. 11. Explanation of results, ill. The action of silver nitrite on pentabromophenol. IT. Conclusion to experimental part. C. Conclusion to Part I. - £ - Table of Contents. (Cont'd) PART II. An Investigation and possible electronic explanation of the two forms of ortho-nitrotoluene. A. Introduction. 3. Results of previous work on this compound. C. Facts leading to the suggested explanation. D« Experimental part. I. Physical measurements. a. Determination of Index of Refraction. b» Determination of Density. c. Determination of Molecular Weights. IX. Chemical testa made. a* At law temperatures. b. At high temperatures. E. Conclusion. THE REPLACEMENT OF HALOSBU OftQUPS SUBSTITUTED IN THE BENZENE NUCLEUS. Introduction The problem of substitution in the benzene nucleus can be divided into two parts* namely, the replacement of hydrogen atoms, and the replacement of other atoms or groups. A great deal of work has been done on this subject with the result that many theories have been advanced to explain the different types of substitution and replacement which take 1 £ place. Among these are Flurscheim's , Holleman's and Obermillsr's^ theories. Lap worth's theory of induced polarity, and the electronic theory elaboratedAH. S. Fry . This last theory is based on the assumption that an atom can function either positively or negatively and it is the opposition of electronic character that binds the atoms in a molecule. Benzene is therefore represented by a ring of carbon atoms, linked alternately by positive and negative valenoies to the positive and negative valenoies of hydrogen. The abbreviated formula for benzene is: 1, 2, 3# 4 - "Organic Chemistry", Cohens Part 1, P.168 5 - "The Electronic Conception of Valence and the Constitution of Benzene" by H.3, Fry • 2 In this formula the double bonds of Kexule's formula and the oentrio bonds of Armstrong's formula are disregarded. This picture being assumed,it follows that in the formation of diderivatives the dominant valenoy in the ortho and para positions to the substituent group will be of the same sign, that in the meta position of opposite sign. Thus, a positive group will attach itself to a C- atom and a negative group to a C-f atom. Similar atoms or groups should therefore sub­ stitute in the meta position and groups of different sign in the ortho and para position. Sow although an atom or groups may react either -+• or - there will be,ordinarily,a difference in the tendency which it has to be + or -. Thus (OH, CI, Bar, I, HH£, C% etc.) have a greater tendency to reaot negatively than positively, whereas (COOfl, COB, 30 R M02 etc.) have a greater tendency to reaot positively than negatively* Accordingly>this theory would demand the existence of two mono-derivatives in which the substituent is attached to an electro-positive or an electro-negative carbon atom by an electro-positive or-negative valency; C6 Hg X"* and Cg % X. The difficulty is overcome by assuming a form of tautomerism, termed electronic tautomerism, in which isomeric equilibrium between the two forms is supposed to exist. It was with the object of seeing how this theory would conform to quantitative and qualitative experiments or the replacement of halogen - 3 - and nitro groups in the nucleus that this research was undertaken* PART I, A. A review and possible electronic explanation of the results of previous researches done on the replace­ ment of groups in halogen substituted benzene derivatives. The Work of Sohopff« Jfow M. Sohopff, working on the displacement of halogen atoms from the b enzene nucleus, arrived at the following general conclusions. If in the benzene ring, in which the halogen atom is contained, there are also two negative groups, like or unlike. In the ortho or para position relatively to this atom then other groups, such as HH, KHR and OH, can be easily substituted for this atom but if only one negative group is present no such replacement takes place except where this group is a nitro group. The negative groups may be iiOg, 3O3E, COOH, COB and CQH. Thus ortho and para brom meta nitro benzoic acid Pn treatment with aniline allow the bromine to be replaced by the (C6fl§ - ME)group N0 * I 1 NOA "toon \/ 6 Ber. 1889, 22, 900, 3281 ^cootf . 4 - 7 Also ortho ana paj* brom meta nltro bensophenone at 130tt° C. react with alcohollo ammonia, ethylamlne and aniline with replacement of the bromine a ton. In the compound dipara bromo meta nltro bensophenone only one bromine atom Is replaced by 5H£, KHCgHs, or ftHOgHg but in the compound dipara brom dimeta nltro bensophenone where a second nltro group has been Introduced both bromine atoms are replaced. He also showed that para brommeta nltro bensaldehyde when helled with aqueous soda yields para hydroxy meta nltro hensaldehyde. He found that In the presence of only on© group near the halogen the exchange of the latter with aniline only took place when the nltro group was in the ortho position while the same In the para position did not permit a change. Exceptions to this latter observation have since been found. The chlorine in para ehlornltro bensene Is quantitatively replaced by (OCHg) on treatment for five hours at 100° C. In a sealed tube with a normal solution of sodium methylate. The meta nitre halogen compounds do not react at all with ammonia, aniline or potassium hydroxide. Thp Introduction of a second nitro group provided that It stands in ortho or para position to the halogen causes easier displacement of the halogen by (CcfiLSH) i.e. - 7. Bar. 1891, 24, 3771 - 5 - 2, 4 dinltrochlor benzene. While a third group, as In picrylchloride. Increases the ease" of replacement still more. Sohb'pff's conforms to the results required by the electronic theory as presented by $ry. In stroh a compound as para brommeta nltro benzoic acid a negative halogen is replaced by a negative group, such as - t, as expected. + H £>r . CQOH +- The bromine atom in this case is para to a positive carboxyl group or ortho to a positive nitro group there­ fore it mast bear the opposite sign to these two groups - It must be negative and so may be replaced by the two negative gronpa ment1oned. In the brommeta nitro benzophenones given, as long as the bromine atom is ortho or para to the nitro group it is found to be replaceable by (IHg) and (CgHgfiH)"". It is only when in these positions that it would bear a - sign. He also found that an increase in the number of nitro groups ortho or para to the halogen rendered it more mobile* This would be expected as the increase in positive groups ortho and para to the halogen would tend to make its - 6 - negative properties stronger. THE fiORK OF GROHi&M. In a paper on the action of ammonia and aniline on 8 halogen substituted nitro benzoic aoids Grohmann arrives at results similar to Schopff. He found that the bromine in 4*3 brora nitro benzoic acids was readily replaceable by the araido and anilido groups* Likewise the chloride can be converted into the anilido compound by gently heating with aniline. But the halogen in 2.4 ohloro nitro ethyl benzoate and 4.2 chlornitro ethyl benzoate cannot be dis­ placed by heating with ammonia or aniline. From these results he concluded that when the nitro group and the earhoxyl group are simultaneously in ortho and para position relative to the halogen the latter is readily displaced but this is no longer possible when one of these groups takes up the meta position. This earn be explained on an electronic basis for when the halogen group is in the meta position to a positive groups such as the nitre group it reacts positively so that no substitution (or very little) by a negative group takes place. 8 Ber. 1891, 24, 3808 7 - THE WORK OF FISCHER. And On investigating the action of ammonia aniline on A negatively substituted halogen benzene sulphonio acids, 9 P. Fischer found that in the case of two nitro benzene sulphonic acids, the brom benzene disulphonie afiids and two bromo sulpho benzoic acids the ammonia or aniline replaces the halogen. cow H~ O These replacements are easily explainable on an electronic basis as in each case the halogen is negative, indicated,, and so may be replaced by (Mg)" and (C6HglfH) THE WORK Qg H. Ph. BOUSBT. 1st a study of 1 ehloro and 1 bromo- £ cyano -4 nitro- 10 benzene 1, Ph. Baadet found that the halogen is replaced when above compounds are treated with sodium methylate, sodium ethylate, sodium phenylat©, ammonia, methyl amine, ethyl amine, dimethyl amino, aniline, p-diamino benzene, hydrazine, phenyl hydrazine and meta and para amino toluene, but that there is n© reaction with ortho amino toluene or methyl aniline.
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