Answer
a) butene
b) 4-methyl-2-hexene
c) 2,5-dimethyl-3-heptene
Work Step by Step
a) Count the no. of C in straight chain. here, it is 4. So, root name is 'but'. Now, one double bond is present between C1 and C2 position. Hence, ending name is 'ene'. So, the name is : butene.
b) Count the no. of C in longest straight chain. Here, it is 6. Numbering the C atoms in straight chain so that the double bonded C gets the minimum number. so, numbering will be done from left side. Now, we see that double bond is present between C2 and C3 position. so, 2 is added before 'hex' and ending name is 'ene'. Also there is one substituent methyl present at C4 position. So, '4-methyl' is added before '2-hexene'.
c) Count the no. of C in straight chain. here, it is 7. so, root name is 'hept'. Numbering the C atoms in straight chain so that the double bonded C gets the minimum number. So, numbering is done from right side. double bonded C gets the number 3. So, 3 is added before 'hept' and ending name is ene. '2,5-dimethyl' is added before '3-heptene' because two methyl groups are present at C2 and C5 position respectively.
