 On 15 October 2016, due to these chemicals contribution to climate change, negotiators from 197 nations meeting at the summit of the United Nations Environment Programme in Kigali, Rwanda reached a legally-binding accord to phase out hydrofluorocarbons (HFCs) in an amendment to the Montreal Protocol.As indicated throughout this article, fluorine-substituents lead to reactivity that differs strongly from classical organic chemistry.The premier example is difluorocarbene, CF2, which is a singlet whereas carbene (CH2) has a triplet ground state.