The major product of the following reaction is
`CH_3CH_2CH= CH_2 underset(Rh "catalyst")overset(H_2//CO)(to)`

Options

A. `CH_3CH_2CH=CH - CHO`
B. `CH_3CH_2 undersetoverset(|)(CHO)(C ) = CH_2`
C. `CH_3CH_2CH_2CH_2CHO`
D. `CH_3CH_2CH_2CHO`

Answer

To determine the major product of the given reaction, we need to analyze the reaction conditions and the starting material.

### Step-by-Step Solution:

1. **Identify the Starting Material**: The starting material is `CH3CH2CH=CH2`, which is 1-butene. It has a double bond between the second and third carbon atoms.

2. **Understand the Reaction Conditions**: The reaction is carried out in the presence of a Rhodium (Rh) catalyst and involves hydrogen (H2) and carbon monoxide (CO). This suggests that the reaction is likely an OXO process (also known as hydroformylation).

3. **Oxo Process Overview**: In the OXO process, alkenes react with carbon monoxide and hydrogen to form aldehydes. The reaction typically adds a formyl group (-CHO) to the alkene, resulting in an increase in the carbon chain length.

4. **Determine the Product**:
- The alkene (1-butene) has 4 carbon atoms.
- In the OXO process, one carbon atom is added from carbon monoxide (CO) to the alkene.
- Therefore, the total number of carbon atoms in the product will be 4 (from the alkene) + 1 (from CO) = 5 carbon atoms.

5. **Identify the Structure of the Product**: The major product will be an aldehyde with 5 carbon atoms. The possible structure is pentanal (also known as valeraldehyde), which can be represented as:
- CH3(CH2)3CHO

6. **Final Answer**: The major product of the reaction is pentanal (or valeraldehyde).