Aromatic sulphonation. Part XLVII. Reaction of 1,2-dihydrobenzocyclobutene with sulphonating reagents
- 1 January 1974
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 10,p. 1206-1209
- https://doi.org/10.1039/p29740001206
Abstract
Reaction of 1,2-dihydrobenzocyclobutene (DHBCB) with sulphur trioxide addition complexes leads to the formation of DHBCB-3- and DHBCB-4-sulphonic acid and the sultone of 2-(o-sulphophenyl)ethanol. The ipso : 3- : 4-substitution ratio is (25 ± 5) : (5 ± 3) : (70 ± 4) for CH3NO2–SO3 in nitromethane at 0° and (32 ± 6) : (7 ± 4) : (61 ± 5) for dioxan–SO3 in trichlorofluoromethane at 0–20°. DHBCB on reaction with concentrated sulphuric acid is mainly converted (ca. 90%) into polyxylylene. At 90% H2SO4 the terminal group is the 4-DHBCB system; below 90% H2SO4 it is in part replaced by the 2-(p-phenylene)ethyl sulphate group. The ethylene bridges in the polymers have mainly the meta-orientation. In addition the sulphuric acid soluble 2-(p-sulphophenyl)ethyl sulphate (3) and 5-[β-(p-sulphophenyl)ethyl]DHBCB-4-sulphonic acid (4) are formed. The ratio of (3) to (4) decreases strongly with increasing sulphuric acid concentration. Mechanisms for the formation of the polymers and (3) and (4) are proposed.Keywords
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