Name the following compounds according to IUPAC system of nomenclature :
` (a) CH_3 CH= CHCHO`
` (b) CH_3 CH(CH_3) CH_2 CH_2 CHO`
`(c ) OHC C_6 H_4 CHO -p`
(d) `CH_3 COCH_2CO CH_3`
`(e ) CH_3 CH_2 COCH(C_2 H_5 )CH_2 CH_2Cl`

Explanation

Let's solve the question step by step.

### Step 1: Naming Compound (a) CH₃CH=CHCHO
1. **Identify the longest carbon chain**: The longest chain contains 4 carbon atoms (butanal).
2. **Identify functional groups**: There is a double bond between the second and third carbon atoms.
3. **Number the chain**: Start numbering from the end nearest to the aldehyde group (CHO), which gives us:
- C1: CHO
- C2: CH
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