The priority of groups `OH , COOH ,CHO, OCH_(3)` attached to a chiral carbon is in order ,

Options

A. `OH gt COOH gt CHO gt OCH_(3)`
B. `OCH_(3) gt OH gt CHO gt COOH`
C. `OCH _(3) gt OH gt COOH gt CHO`
D. `OCH_(3) gt COOH gt CHO gt OH`

Answer

To determine the priority of the groups OH, COOH, CHO, and OCH3 attached to a chiral carbon, we will use the Cahn-Ingold-Prelog (CIP) priority rules. Here's a step-by-step solution:

### Step 1: Identify the groups attached to the chiral carbon
The groups attached to the chiral carbon are:
1. OH (hydroxyl group)
2. COOH (carboxyl group)
3. CHO (aldehyde group)
4. OCH3 (methoxy group)

### Step 2: Assign priorities based on atomic numbers
According to the CIP rules, we assign priorities based on the atomic number of the atoms directly attached to the chiral carbon. If the first atoms are the same, we look at the next atoms in the chain.

- For **OH**: The first atom is O (atomic number 8).
- For **COOH**: The first atom is C (atomic number 6), but it is attached to O (atomic number 8) as well.
- For **CHO**: The first atom is C (atomic number 6), but it is also attached to O (atomic number 8).
- For **OCH3**: The first atom is O (atomic number 8).

### Step 3: Compare the first atoms
- OH and OCH3 both have O as the first atom.
- COOH and CHO both have C as the first atom.

### Step 4: Determine the next atoms for OH and OCH3
- For **OCH3**: The next atom is C (from CH3).
- For **OH**: The next atom is H (atomic number 1).

Since OCH3 has a carbon (atomic number 6) compared to OH's hydrogen (atomic number 1), OCH3 takes priority over OH.

### Step 5: Determine the next atoms for COOH and CHO
- For **COOH**: The next atom after C is O (from the carboxyl group).
- For **CHO**: The next atom after C is O (from the aldehyde group).

Both COOH and CHO have O as the next atom, so we need to look further:
- COOH has an additional O (from the carboxyl group) and H.
- CHO has H and O.

Since COOH has a higher atomic number due to the presence of an extra O, it takes priority over CHO.

### Step 6: Finalize the priority order
Based on the above comparisons, the priority order is:
1. OCH3 (1)
2. OH (2)
3. COOH (3)
4. CHO (4)

### Conclusion
The priority of the groups attached to the chiral carbon is:
1. OCH3
2. OH
3. COOH
4. CHO