Stereochemistry | Organic Chemistry | GPAT Mock Test

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Welcome to the Stereochemistry Mock Test, specifically designed for GPAT aspirants. This quiz comprehensively covers the fundamental and advanced concepts of stereochemistry, a critical topic in Organic Chemistry. You will face 25 multiple-choice questions spanning chirality, isomerism, conformational analysis of acyclic and cyclic systems, R/S configuration, stereoselective reactions, and more. This test will help you assess your understanding, identify areas for improvement, and build confidence for the GPAT examination. After submitting your answers, you’ll receive your score and see a detailed breakdown of correct and incorrect responses. You can also download a PDF of all questions with their correct answers for offline revision. Good luck!

1. A molecule is considered chiral if it:

Has a plane of symmetry. Is non-superimposable on its mirror image. Has a center of inversion. Is optically inactive.

2. Enantiomers are best described as:

Stereoisomers that are not mirror images of each other. Isomers with different connectivity. Non-superimposable mirror images. Conformational isomers.

3. Which of the following is an achiral molecule despite having two chiral centers?

(2R,3R)-Tartaric acid Meso-tartaric acid (2S,3R)-2,3-Dichlorobutane D-Glucose

4. In the Cahn-Ingold-Prelog (CIP) system, which of the following groups has the highest priority?

-CH3 -OH -NH2 -CHO

5. What is the most stable conformation of n-butane when viewed along the C2-C3 bond?

Gauche Eclipsed Anti-periplanar Syn-periplanar

6. A 50:50 mixture of two enantiomers is known as a:

Diastereomeric mixture Racemic mixture Meso compound Eutectic mixture

7. The process of separating a racemic mixture into its constituent enantiomers is called:

Resolution Racemization Isomerization Epimerization

8. A reaction that produces a predominance of one stereoisomer over others from a single starting material is known as:

Stereospecific Regioselective Stereoselective Enantiospecific

9. If a mixture contains 75% of the R-enantiomer and 25% of the S-enantiomer, what is the enantiomeric excess (e.e.)?

25% e.e. 50% e.e. 75% e.e. 100% e.e.

10. The most stable conformation of cyclohexane is the:

Boat conformation Chair conformation Twist-boat conformation Half-chair conformation

11. In the chair conformation of methylcyclohexane, the most stable arrangement has the methyl group in the:

Axial position Equatorial position Flagpole position Bow-sprit position

12. Atropisomerism is caused by:

Presence of a chiral carbon Geometric constraints in a ring system Restricted rotation around a single bond Presence of a chiral center other than carbon (e.g., N, P, S)

13. The relationship between cis-1,2-dimethylcyclohexane and trans-1,2-dimethylcyclohexane is:

Enantiomers Diastereomers Constitutional isomers Identical

14. Which isomer of decalin is conformationally rigid and cannot undergo a ring flip?

Cis-decalin Trans-decalin Both are rigid Neither are rigid

15. A reaction in which a specific stereoisomer of the starting material yields a specific stereoisomer of the product is called:

Stereoselective Stereospecific Regiospecific Non-selective

16. The steroid nucleus, perhydrophenanthrene, consists of:

Three fused six-membered rings Four fused rings: three 6-membered and one 5-membered Two fused six-membered rings Three fused rings: two 6-membered and one 5-membered

17. Which of the following elements CANNOT be a stereocenter (chiral center)?

Nitrogen in a quaternary ammonium salt Phosphorus in a phosphine oxide Sulfur in a sulfoxide All of the above can be stereocenters

18. Diastereomers have:

Identical physical properties Mirror image relationship Different physical properties Equal but opposite optical rotations

19. The Newman projection showing the least stable staggered conformation of n-butane is:

Anti Eclipsed Gauche Syn-periplanar

20. Which of the following disubstituted cyclohexanes is chiral?

cis-1,4-Dimethylcyclohexane cis-1,3-Dimethylcyclohexane trans-1,2-Dimethylcyclohexane cis-1,2-Dimethylcyclohexane

21. What is the R/S configuration of the natural amino acid Alanine (L-Alanine)?

R S It is achiral It is a racemic mixture

22. Two stereoisomers are epimers if:

They are mirror images of each other. They differ in configuration at all chiral centers. They are diastereomers that differ in configuration at only one chiral center. They are identical molecules.

23. In trans-1,4-di-tert-butylcyclohexane, the most stable conformation has:

Both groups equatorial. Both groups axial. One axial and one equatorial. The molecule adopting a twist-boat conformation.

24. What is the maximum number of stereoisomers possible for a molecule with ‘n’ chiral centers?

n 2n n² 2ⁿ

25. An example of a molecule that exhibits atropisomerism is:

Tartaric acid BINAP (2,2′-bis(diphenylphosphino)-1,1′-binaphthyl) Glucose cis-Decalin

Stereochemistry | Organic Chemistry | GPAT Mock Test

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