Write the structures of the following compounds.
(i) `alpha`-Methoxypropionaldehyde
(ii) 3-Hydroxybutanal
(iii) 2-Hydroxycyclopentane carbaldehyde
(iv) 4-Oxopentanal
(v) Di-sec. butyl ketone
(vi) 4-Fluoroacetophenone

Explanation

To write the structures of the specified compounds, we will analyze each compound based on its name, identifying the functional groups and the carbon skeleton. Here’s the step-by-step solution:

### (i) Alpha-Methoxypropionaldehyde
1. **Identify the carbon chain**: The name indicates a propionaldehyde, which means there are 3 carbons in the main chain.
2. **Identify the functional groups**: The term "methoxy" indicates the presence of a methoxy group (-OCH3) at the alpha position (the first carbon next to the aldehyde).
3. **Draw the structure**:
- Start with the propionaldehyde: CH3-CH2-CHO.
- Add the methoxy group to the alpha position: CH3-CH(OCH3)-CHO.
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