Overview

Access to raw materials for monomers and polymers is clearly important for the rapid and successful development of high molecular weight compounds. This is particularly true of speciality polymers including heat- and fire-resistant polymers, mainly polyimides, whose production has been actively pursued during the last four decades [1 10].

One raw material potentially useful for the synthesis of monomers is chloral, whose annual output in the USA in 1971 amounted to 50,000 tonnes [11 13]. Chloral is a starting material used for the manufacture of drugs, highly purified chloroform, herbicides (sodium trichloroacetate, dichloral urea) and pesticides (such as chlorophos) including dichlorodiphenyl-trichloroethane (DDT), a widely utilised insecticide [14], whose world output in 1956 amounted to 80,000 tonnes [15]. Some 4.5 million tonnes of DDT were consumed between 1942 and 1972 for pest control in agriculture [16]. The use of DDT during the long-term antimalaria campaign saved more than 1 billion people from malaria [17].

The human toxicity of DDT has been a subject of intense study during the last 20 25 years. This led the World Health Organisation to prohibit the use of DDT as an insecticide. The long-term use of DDT resulted in the development of resistance to the insecticide in many pests (over 200 species). As a result, most developed countries initiated programmes for the gradual replacement of DDT. The manufacture of DDT, and consequently that of chloral, has been in gradual decline since 1963 [12, 13, 17].

At present DDT finds limited use only in certain developing countries since other...