Induced vapour phase chlorination of arenes at about 200°C

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Abstract
The vapour phase (thermal) reaction of arenes (benzene, chlorobenzene, benzonitrile) with molecular chlorine ‐ setting in at roughly 250° ‐ can be made to occur even below 200° by adding small proportions of CCl3‐SO2‐CCl3 (“S”). Products (chlorinated arenes) and relative rates are highly comparable under both sets of conditions. Depending on inter alia, the concentration of S in the feed, from a few to well over 2000 moles of product per mole of S are formed.Both modes of reaction are interpreted as radical chain processes, chlorine atoms ‐ and their arene adducts ‐ being intermediates. In the initiated reactions. S is thought to form CCl3 radicals, which lead to chlorine atoms by reaction with Cl2.