In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.
Q: It is one of the few groups that favor substitution on a cyclohexane ring in an axial position, due to steric considerations. When heated, they undergo the Curtius rearrangement and become isocyanate groups, which in the presence of water is converted to an amine group. Often used in explosive triggers due to their sensitivity, they behave much like halogens, since their instability makes their displacement easy. FTP, identify this chemical group, consisting of a chain of 3 nitrogen atoms.
A:
Science