DDT (1,1,1‐trichloro‐2,2‐bis(4‐chlorophenyl)ethane), a contact insecticide with a rich and controversial history since its activity was discovered in 1939, has long been thought to be monomorphic. Herein we report the discovery and characterization of a second polymorph, designated Form II, which can be isolated as single crystals, but converts very slowly at room temperature to the form reported previously, now designated as Form I. Computations based on an evolutionary algorithm for crystal structure prediction revealed that Forms I and II are among the four lowest energy crystal structures of fifty calculated. A preliminary study of the contact insecticidal activity toward fruit flies (Drosophila melanogaster) indicates that Form II is more active, suggesting opportunities for more effective solid‐state formulations that would allow reduced amounts of DDT, thereby minimizing environmental impact.

中文翻译：

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DDT多态性与晶体形式的致命性

自从1939年发现DDT（1,1,1-三氯-2-1,2-双（4-氯苯基）乙烷）以来，它一直是一种具有丰富争议性的接触杀虫剂，长期以来一直被认为是单态的。本文中，我们报告了第二种多晶型物的发现和表征，该多晶型物称为晶型II，可以将其分离为单晶，但在室温下转换非常慢，从而转变为先前报道的晶型，现在称为晶型I。基于进化算法的计算晶体结构预测表明，晶型I和II是计算出的五十种晶体中四个最低能级晶体结构之一。对果蝇（Drosophila melanogaster）的接触杀虫活性的初步研究表明，II型具有更高的活性，