CBSE Class 11-science Answered

NOMENCLATURE It is the system of assigning names to organic compounds. The systems of nomenclature are (i) Trivial system (ii) IUPAC (International Union of Pure and Applied Chemistry) system According to the IUPAC system, the name of an organic compound consists of three parts: (i) Root word (ii) Suffix (iii) Prefix (i) Root word It depends on the number of carbon atoms present in the longest carbon chain selected. Number of carbon atoms Root word One carbon atom C1 Meth Two carbon atoms C2 Eth Three carbon atoms C3 Prop Four carbon atoms C4 But Five carbon atoms C5 Pent Six carbon atoms C6 Hex Seven carbon atoms C7 Hept Eight carbon atoms C8 Oct Nine carbon atoms C9 Non Ten carbon atoms C10 Dec (ii) Suffix The root word is followed by an appropriate suffix, which represents the nature of the bond in a carbon–carbon atom. Nature of bond Suffix General name General formula Single bond (C–C) -ane Alkane CnH2n+2 Double bond (C=C) -ene Alkene CnH2n Triple bond ( ) -yne Alkyne CnH2n−2 Group (R-) -yl Alkyl CnH2n+1 (iii) Prefix It denotes the substituent, alkyl or functional group and its position in the carbon chain. Di-, tri- and tetra- are used for two, three and four groups of the same type, respectively.