Nomenclature
Whereas in IUPAC nomenclature in most cases the suffix "nitrile" or "carbonitrile" is used for organic cyanides (R-C≡N), names for isocyanides have the prefix "isocyano". IUPAC names become isocyanomethane, isocyanoethane, isocyanopropane, et cetera.
The use of the prefix "isonitrile" has a contradiction in the nomenclature. For example, ethyl nitrile ( CH3CN) and ethyl isonitrile (C2H5NC) are not isomers, as the prefix "iso" suggests. In contrast, ethyl cyanide (C2H5CN) and ethyl isocyanide (C2H5NC) are isomers.
The sometimes used term "carbylamine" conflicts with systematic nomenclature. An amine always has three single bonds, whereas an isocyanide has only one single and one multiple bond.
Read more about this topic: Isocyanide