Q.40

Which of the following is/are CORRECT for the two molecules shown?

(A) They are stereoisomers

(B) Each of them has two stereogenic centers

(C) They are mirror images of each other

(D) They are diastereoisomers

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Stereochemistry MCQ – Detailed Explanation

Question

Which of the following is/are CORRECT for the two molecules shown?

Options:
(A) They are stereoisomers
(B) Each of them has two stereogenic centers
(C) They are mirror images of each other
(D) They are diastereoisomers

Step-by-Step Structural Analysis

From the given molecular structures:

• Each molecule contains:

  • A phenyl (benzene) ring

  • An –OH group

  • An –NHMe group

• The carbon atoms attached to these functional groups are chiral (asymmetric).

🔹 Number of Stereogenic Centers

• Each molecule has two stereogenic (chiral) carbon atoms.

• Therefore, statement (B) is TRUE.

Comparison of the Two Molecules

• The two structures are not identical.

• They differ in the configuration of only one stereocenter, while the other remains the same.

• Because not all stereocenters are inverted, the molecules are not mirror images.

Correct Classification

✅ Diastereomers

• Molecules with:

  • Same molecular formula

  • Same connectivity

  • Different configuration at some but not all stereocenters

✔ The given molecules fit this definition perfectly.

Correct Answer

✅ (D) They are diastereoisomers

Explanation of All Options

Option (A): They are stereoisomers

✔ TRUE, but not the best answer

• Diastereomers are a type of stereoisomers, so this is a general statement.

Option (B): Each of them has two stereogenic centers

✔ TRUE

• Both molecules clearly show two chiral carbons.

Option (C): They are mirror images of each other

❌ FALSE

• Mirror images require all stereocenters to be inverted.

• That is not the case here.

Option (D): They are diastereoisomers

✔ TRUE and MOST CORRECT

• Only one stereocenter differs → diastereomers

Final Conclusion

✔ The molecules have two stereogenic centers
✔ They are not mirror images
✔ They differ at only one stereocenter

🎯 Correct Answer: (D) They are diastereoisomers

Exam Tip 🔥

If two molecules differ at some but not all chiral centers → Diastereomers
If all chiral centers are inverted → Enantiomers