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We began by studying the tetraisopropyl pyrophosphoramide adduct of BChE because this adduct has two P - N bonds .
 Chemical: tetraisopropyl pyrophosphoramide; Chemical: P - N
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: tetraisopropyl pyrophosphoramide; Chemical: P - N