Write the structure of the main products when propanal `(CH_(3)-CH_(2)-CHO)` reacts with the following regents :
(i) `HCN`

Explanation

To determine the structure of the main product when propanal (CH₃-CH₂-CHO) reacts with HCN, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactant is propanal, which has the structure:
\[
\text{CH}_3-\text{CH}_2-\text{C}(=O)-\text{H}
...