Aromatic sulphonation. Part 65. On the sulphonation of 1-methylnaphthalene and polymethylbenzenes
- 1 January 1978
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Perkin Transactions 2
- No. 8,p. 719-724
- https://doi.org/10.1039/p29780000719
Abstract
The isomer distributions for the mono-, di-, and tri-sulphonation of 1-methylnaphthalene in respectively 90.1, 98.4, and 110% sulphuric acid at 25 °C have been determined. The degree of sulphonation at the 2-position is smaller for sulphonation in 98.4 than 90.1% H2SO4. The results are discussed in terms of sulphonation by H3SO4 +, H2S2O7, and H2S4O13 as sulphonating entities and compared with those of the polymethylbenzenes. The mechanistic conclusion that the sulphonation with H3SO4 + has a ‘later’ transition state than that with H2S2O7 is in agreement with the results of simple Hückel MO calculations. The deviating behaviour for the 2-substitution of 1-methylnaphthalene is ascribed to enhanced steric control, because of the shorter C(1)–C(2) bond distance in 1-methylnaphthalene as compared with toluene. The isomer distribution for the mono-, and di-sulphonates resulting from 1-methylnaphthalene with SO3 in nitromethane is also reported.Keywords
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