Abstract: The invention relates to novel thermochromic spiro heterocyclic compounds having one or the other of the following formulae: ##STR1## where R.sub.1 denotes hydrogen atoms or one or more electron-donor groups in positions 5, 6, 7 and 8 in formula (1); R.sub.i ' denotes hydrogen atoms or one or more electron-donor or electron-acceptor groups in positions 4', 5', 6' and 7' and 4", 5", 6" and 7" in formulae (1) and (2); and R.sub.j denotes hydrogen atoms or one or more electron-donor groups in positions 5, 6, 7, 8, 9 and 10 in formula (2). Use in thermographic recording material.

Abstract: Process for the selective ortho substitution of a halobenzene sulfonic acid compound with a hydroxyl group or a group convertible to same to prepare the corresponding halophenol sulfonic acid compound which process comprises reacting a halobenzene sulfonic acid compound having at least two halogen atoms at least one of which is ortho to the sulfonic group with an alkali metal hydroxide or other hydroxy containing compound which is capable of replacing a nuclear halogen atom with a hydroxyl group, said reaction being conducted in the presence of a liquid organic reaction medium which is responsible for the orientation of the hydroxyl substitution in the ortho position. The halophenol sulfonates thus prepared optionally may be desulfonated to obtain the ortho hydroxy halobenzene compound.