An organic compound (A) `(C_(10)H_(20))`on reductive ozonolysis gives `2-` methyl butanal. Based on this information, answer the following question.
If the stereochemistry about the double bond in (A) is cis, the total number of stereoisomers for (A) is :

Options

A. 2
B. 3
C. 4
D. 5

Answer

To solve the question regarding the total number of stereoisomers for the organic compound (A) with the molecular formula \(C_{10}H_{20}\) that produces 2-methylbutanal upon reductive ozonolysis, we can follow these steps:

### Step 1: Identify the structure of compound (A)
Given that the compound (A) has the molecular formula \(C_{10}H_{20}\) and produces 2-methylbutanal upon reductive ozonolysis, we can deduce that (A) likely contains a double bond. The ozonolysis reaction suggests that the double bond is cleaved to form aldehydes.

### Step 2: Determine the structure of 2-methylbutanal
2-methylbutanal has the following structure:
```
CH3
|
CH3-CH-CHO
|
CH2-CH3
```
This indicates that the double bond in compound (A) must be positioned such that when cleaved, it yields two molecules of 2-methylbutanal.

### Step 3: Construct the possible structure of (A)
To yield 2-methylbutanal, compound (A) could be a compound with a double bond between carbons that allows for the formation of this aldehyde. A possible structure for (A) could be:
```
CH3
|
CH3-CH=CH-CH2-CH3
```
This structure has a cis double bond.

### Step 4: Identify chiral centers
In the proposed structure of (A), we need to identify chiral centers. A chiral center is a carbon atom that is attached to four different groups. In our structure:
- The carbon adjacent to the double bond (C2) is attached to CH3, CH (from the double bond), CH2 (from the chain), and H, making it chiral.
- The carbon at C3 is also chiral for the same reason.

### Step 5: Calculate the number of stereoisomers
The formula for calculating the number of stereoisomers based on chiral centers is:
\[ \text{Number of stereoisomers} = 2^n \]
where \(n\) is the number of chiral centers.

In our case, we have 2 chiral centers:
\[ n = 2 \]
Thus, the number of stereoisomers is:
\[ 2^2 = 4 \]

### Step 6: Consider meso compounds
However, since the question specifies that the stereochemistry about the double bond is cis, we need to check for meso compounds. A meso compound has multiple stereocenters but is superimposable on its mirror image, effectively reducing the number of unique stereoisomers.

In this case, the presence of the cis double bond means that one of the stereoisomers will be a meso compound. Therefore, we need to adjust our calculation:
- Total stereoisomers = 4 (from \(2^n\)) - 1 (for the meso compound) = 3

### Final Answer
Thus, the total number of stereoisomers for compound (A) is **3**.