Bromobenzene sulphonation

The melting points of a number of sulphonacetamides are —benzene-sulphonic acid, 125° p-toluenesulphonic acid, 137° p-bromobenzene-sulphonic acid, 203° m-nitrobenzenesulphonic acid, 189° p-nitroben-zenesulphonic acid, 192° naphthalene-a-sulphonic acid, 185° and naphthalene-p-sulphonic acid, 146°. 

The following substances have also been mercuratedj but analysis indicates that the products are mixtures benzene sulphonic acid and its sodium salt, sodium p-bromobenzene sulphonate, p-iodobenzeiie sub phonic acid, 2 5-dichlorobenzene sulphonic acid, m-nitrobenzene sulphonic acid, o-toluene sulphonic acid and its sodium salt, sodium p-toluene sulphonate, 2-chlorotoluene 5-sulphonic acid. The mercuration of the sodium salts is a much slower process than in the case of the free acids. 

Saxitoxin, the paralytic shellfish poison, has finally revealed its structure as (87) by X-ray crystallographic analysis of its ethyl hemiketal " and p-bromobenzene-sulphonate derivatives. C n.m.r. studies show that saxitoxin exists primarily as its ketone hydrate in aqueous solution. ... 

The solvolysis rates of the C-5-substituted epimeric 2-norbomyl p-bromobenzene-sulphonates (92) and (93) and their 2-methyl homologues have been investigated in 60% aqueous ethanol and in 97% hexafluoropropan-2-ol at various temperatures. The rate ratio exo-(92) endo-(92) is solvent-dependent, rising to the value 1746in hexafluoro-propan-2-ol at 25 °C, indicating the absence of internal return for exo-(92) and nucleophilic solvent assistance for endo- 92). The rates for the epimeric brosylates (93) are lower, the exo-brosylate being affected more, even in hexafluoropropan-2-ol. The rate ratio reductions are much less pronounced in the tertiary series. The results are as expected for the stabilization of the transition state from exo-(92) by 0-delocalization or some other electronic effect. 

From this work a relative reactivity for chlorobenzene to benzene of 0.065 is obtained and this may be compared with a value of 0.34 obtained by Kilpatrick and Meyer163 for bromobenzene at 12.3 °C this is rather a large difference in view of the fact that there is very little ortho sulphonation of either substrate. 

For the synthesis of orfbo-bromotoluene we use a sulphonic acid. o-Bromotoluene could be synthesised by bromination of toluene or by Friedel-Crafts alkylation of bromobenzene (Fig. T). However, the reaction would also give the para substitution product and this is more likely if the electrophile is hindered from approaching the ortho position by unfavourable steric interactions. Alternatively we can substitute a group at the para position before carrying out the bromination. 

Chemicals which can damage (a) the liver, include carbon tetrachloride, paracetamol, bromobenzene, isoniazid, vinyl chloride, ethionine, galactosamine, halothane, dimethylnitrosamine (b) the kidney, include hexachlorobutadiene, cadmium and mercuric salts, chloroform, ethylene glycol, aminoglycosides, phenacetin (c) the lung, include paraquat, ipomeanol, asbestos, monocrotaline, sulphur dioxide, ozone, naphthalene (d) the nervous system, include MPTP, hexane, organophosphorus compounds, 6-hydroxydopamine, isoniazid (e) the testes, include cadmium, cyclophosphamide, phthalates, ethanemethane sulphonate, 1,3-dinitrobenzene (f) the heart, include allylamine, adriamycin, cobalt, hydralazine, carbon disulphide (g) the blood, include nitrobenzene, aniline, phenylhydrazine, dapsone. 

This need became still more important when Melander and Berglund-Larsson (Berglund-Larsson, 1957 Berglund-Larsson and Melander, 1953 Melander, 1950) found that the sulphonation of bromobenzene-4-d and -4-1 showed small isotope effects ( h/ d = h/ t = 2-0). 

Benzo- and Dibenzo-1,4-dithiins.—An improved synthesis of benzo-l,4-dithiin and -oxathiin is based on a novel intramolecular sulphenylation of the thiol-sulphonates PhY(CHa)2SSOaMe (Y = S or O) in the presence of aluminium chloride. Phenyl-lithium reacts with bromobenzene and carbon disulphide to give 2,3-diphenyl-l,4-benzodithiin via a benzyne intermediate. ... 

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