Answer
a. 4,5-dichloro-3-hexanone
b. 2,3-dimethylpentanal
c. 3-methylbenzaldehyde or m-methylbenzaldehyde
Work Step by Step
a. count the no. of C in longest straight chain. Here it is 6. so, root name is 'hex'. now, CO group is present so, the ending name is 'anone'. Numbering is done so that CO group Carbon gets the minimum number. So, the numbering will be done from right to left. So, CO group Carbon gets the number 3. i.e. 3-hexanone. Now, two Cl group present at C4 and C5 position. So, '4,5-dichloro' is added before '3-hexanone'. We get the complete name: 4,5-dichloro-3-hexanone.
b. No. of C atom in longest straight chain = 5. hence, root name is 'pent'. CHO group present so, the ending name is 'anal' and the C atom of CHO is always at C1 position. so, numbering is done from left to right and we see that two methyl groups are present at C2 and C3 position. So, '2,3-dimethyl' is added before root name. We get the complete name 2,3-dimethylpentanal.
c. When CHO group is present at the benzene ring the compound is called benzaldehyde. Now, a methyl group is present at meta position to CHO. So, the name is m-methylbenzaldehyde.
