Answer
a) 2,3-dimethyl-2-butene
b) 4-methyl-2-hexyne
c) 2,3-dimethyl-1-pentene
Work Step by Step
a) Count the no. of C atoms in straight chain. Here, it is 4. so, word root is 'but'. There is a double bond in the compound. So, the ending name is 'ene'. If we numbering the Carbon atoms in straight chain from 1 to 4 we see that double bond is in between C2 and C3 carbon. So, 2 is added before butene i.e. '2-butene'. Now, two methyl groups are present as substituents at C2 and C3 position. So, 2,3-dimethyl is added as prefix before '2-butene'. So, the complete name is : 2,3-dimethyl-2-butene.
b) No. of C in straight chain = 6. hence root name is 'hex'. A triple bond is present in the compound. So, ending name will be 'yne'. Now, if we numbering the C atoms in straight chain from 1 to 6 from left to right we see that triple bond is present in between C2 and C3 carbon. i.e. 2-hexyne. Now, one methyl group is present as a substituent at C4 position. so, '4-methyl' is added before '2-hexyne'. Complete name is ; 4-methyl-2-hexyne.
c)No. of C in straight chain = 5 (longest straight chain). so, root name is 'pent' and ending name is 'ene' (double bond present). If we numbering the C atoms from left to right we see that double bond is present at C1 position i.e. 1-pentene and two methyl groups are present as substituent at C2 and C3 position respectively. So, '2,3-dimethyl' is added before '1-pentene'. So, the complete name is : 2,3-dimethyl-1-pentene'.
