Answer
a) pentane
b) 3-ethyl-2,5-dimethylhexane
c) 4-ethyl-5-isopropyloctane
Work Step by Step
a) Count the total no. of C in straight chain. Here, it is 5. So, the root name is 'pent' and ending name is 'ane' for alkane.
b) No. of C in longest straight chain = 6. so, the root name is 'hex'. ending name is 'ane' for alkane. Now, numbering the C atoms in straight chain so that the substituents present gets the minimum number. so, the numbering is done from left to right. two methyl groups are present at C2 and C5 position respectively. one ethyl groups are present at C3 position. So, '3-ethyl-2,5-dimethyl' is added before root name. So, the complete name is '3-ethyl-2,5-dimethylhexane'.
c) No. of C in longest straight chain = 8. so, the root name is 'oct'. ending name is 'ane' for alkane. Now, numbering the C atoms in straight chain so that the substituents present gets the minimum number. so, the numbering is done from right to left. one ethyl groups are present at C4 position and one isopropyl group is present at C5 position. So, '4-ethyl-5-isopropyl' is added before root name. So, the complete name is '4-ethyl-5-isopropyloctane.
