Some aspects of the formation of addition products in the chlorination of polycyclic aromatic compounds

Abstract

This thesis describes some aspects of the formation of addition products in the chlorination of polycyclic aromatic compounds. The chlorinations of polycyclic hydrocarbons, represented by naphthalene and related compounds, have been investigated mainly from the point of view of adduct formation, and numbers of new addition products derived from those, as well as old ones of still un-known structure, have been clarified with regard to their structures and properties, using infrared, ultra-violet and proton magnetic resonance spectroscopy. As a chlorinating agent, either sulphuryl chloride or mole-cular chlorine has been used, and the electrophilic nature of the former reagent has also been qualitatively established. Naphthalene, alkylnaphthalenes and halonaph-thalenes, when treated with sulphuryl chloride with or without a solvent, give products similar to those obtained with molecular chlorine By heating naphthalenes with sulphuryl chloride in excess, more highly chlorinated addncts were obtained together with some poly-chlorotetralones. Under conditions in which naptha-1mm reacts slowly with sulphuryl chloride, chlorotetralones do not react signif icntly, whereas alkylnaphtha lenes react more rap idly, than naphthalene itself does, and give sd ducts as well as products of eubstitution -Addition of chlorine always occur in the ring, to vJiich the substitution takes place in accordance with the r?ales governing the electrophilic substitution l-ilkylnaphthalenes with straight chain and acenapht h

ene give side-cbainchlorinated tetrachlorides as the ir.ain addition products. 32he formation of these imsxp acted ad ducts has been explained on the basis of the hyper conmutativo loss of proton during the chlorine addition process Chlorination of naphthols in acetic acid gives various ketopolychlorides, the structures of which have been spectroscopically investigated 2,4-chloro-nsplith-l-ol and related naphth-l-ols of similar structure have been found to involve the initial electrophilic attack on the 2- rather than on the 4-position, giving unstable 1-keto-l,2-dihydronaphthalen:?s which then undergo the anionotropic isomorisation to yield stable 1-keto-l94 dihydronaphthale?es Esters of naphth-l-ols behave differently, depending on the solvents used; in acetic acid the products are similar to those obtained from naphth-l-ols, however, in chloroform, 2,3,4-triehloro-l tetralones are formed, which are not highly stable and gradually lose hydrogen chloride to give 2,4-dichloro-naphth-l-ols. By similar treatment with chlorine, naphthyl-araines readily afford polychlorotetralones, for which a sequence involving the hydrolysis of the intermediary ketimine hydrochlorides has been suggested. Infrared, ultraviolet and proton magnetic resonance spectra of more than forty addition products have been recorded.