(2R,3r)-2,3 bantanediol is :

Options

A.
B.
C.
D.

Answer

To determine the correct structure of (2R,3R)-2,3-butanediol, we need to analyze the stereochemistry of the compound based on the given R configurations at the 2nd and 3rd carbon atoms. Here’s a step-by-step breakdown of how to approach this problem:

### Step 1: Understand the Structure of Butanediol
Butanediol has the formula C4H10O2 and consists of a four-carbon chain with hydroxyl (-OH) groups attached to the 2nd and 3rd carbon atoms. The structure can be represented as follows:

```
CH3-CH(OH)-CH(OH)-CH3
```

### Step 2: Identify the Stereocenters
In (2R,3R)-2,3-butanediol, the stereocenters are at the 2nd and 3rd carbon atoms. Each of these carbons is attached to four different groups, which allows us to assign R or S configurations.

### Step 3: Assign Priorities to the Groups
Using the Cahn-Ingold-Prelog priority rules, we assign priorities to the substituents attached to the stereocenters:

- For carbon 2:
- -OH (hydroxyl group) has the highest priority (1)
- -CH3 (methyl group) has the next priority (2)
- -CH2- (the carbon chain) has the next priority (3)
- The hydrogen atom (H) has the lowest priority (4)

- For carbon 3:
- -OH (hydroxyl group) has the highest priority (1)
- -CH3 (methyl group) has the next priority (2)
- -CH2- (the carbon chain) has the next priority (3)
- The hydrogen atom (H) has the lowest priority (4)

### Step 4: Determine the Configuration
To determine the configuration (R or S), we look at the arrangement of the groups:

- For carbon 2, if we position the lowest priority group (H) at the back, the order of the remaining groups (1, 2, 3) is clockwise, which gives it an R configuration.

- For carbon 3, if we position the lowest priority group (H) at the back, the order of the remaining groups (1, 2, 3) is also clockwise, which gives it an R configuration.

### Step 5: Conclusion
Since both stereocenters are R, the compound is correctly designated as (2R,3R)-2,3-butanediol.

Therefore, the correct answer is option A.

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