Aromatic sulphonation. Part 74. Sulphonation of some 9-alkenylanthracenes and the corresponding benzenes with dioxan–SO3

Abstract

The sulphonation of six alkenylarenes with dioxan–SO₃ in dioxan has been studied at 17 °C. With the substrates 9-vinyl-(3a), 9-(prop-2-enyl)-(3b), and 9-[(E)-but-2-enyl]-anthracene (3c), and (E)-prop-1- and -2-enylbenzene (3d and e) unsaturated pyrosulphonic acids are obtained with the double bond at C-α and the pyrosulphonic acid group at C-β- for the substrates (3a, b, d, and e), and the double bond at C-β and the pyrosulphonic acid group at C-γ for (1c). The prop-2-enyl derivatives (3b and e) yielded, besides a minor quantity of the above mentioned pyrosulphonic acids, mainly 2-arylprop-1-ene-3-sulphonic acids, and substrate (3d) the cis- and trans-isomer of the cyclic sulphonate sulphate anhydride (5d). All these sulpho-products result from direct attack of SO₃ on the side-chain double bond. 9-[(E)-prop-1-enyl]anthracene yields sodium (E)-1-(9-anthryl)prop-1-ene-3-sulphonate as the main product. It is suggested that this product results from initial attack of SO₃ at the 10-position of the anthryl group followed by the reaction sequence proposed in the preceding paper. The behaviour of the presently investigated anthracene derivatives is compared with the behaviour of both the corresponding saturated anthracene analogues and the corresponding side-chain benzene analogues.