Test: Stereochemistry Level - 3 - Chemistry MCQ

The number of isomeric products N is 6 and the number of isomeric products M is 4.  They are as shown.
M d, l cannot be separated by fractional distillation.

The molecules in options A, B and D contain plane of symmetry. Hence, these are achiral. The molecule in option C contains no plain of symmetry. It contains a carbon atom which is attached to four different atoms or groups. Hence, the molecule is chiral. 

Correct Answer :- c

Explanation : The maximum number of diastereomers is 2n−2

n = 2

=> 2(2) - 2

= 4 - 2

= 2

(a) 

Here only the acidic hydrogen, the one attached to the double bond carbon atoms will be changed to D and the rest of the compound will remain the same.

Mass difference = 4 × 2 − 4 = 4

Compound give Atropi isomerism and is optically active due to absence of plane and centre of symmetry.

From above options:

B) is meso compound, so, it won't show optical activity

A) N is sp3 hybridized to 4 different atoms connected, so, it will show optical activity

C) Sulfur is attached to 4 different atoms including lone pair and there is no chance of flipping due to large size to sulfur as compared to nitrogen, so, it will also show optical activity

 D) is asymmetric carbon with for different atoms and obviously, it will show optical activity.

Hence B is the answer.

Correct Answer :- a,b

Explanation : A meso compound is a molecule that has chiral centers but also has an internal plane of symmetry. This renders the molecule achiral: it does not have an enantiomer, and it does not rotate plane polarized light . Therefore option a amd b are correct.

To determine which amino acid is the (S)-enantiomer, we need to apply the Cahn-Ingold-Prelog priority rules. This involves assigning priorities to the groups attached to the chiral carbon based on atomic numbers and considering the 3D arrangement of these groups.

• Option A:

  • The structure shows a chiral center with NH2, COOH, CH3, and H attached to the central carbon. By applying the Cahn-Ingold-Prelog rules, this seems to follow the configuration for (R).

• Option B:

  • The structure here shows a chiral center with NH2, COOH, CH3, and H. By the same reasoning as option A, this also seems to follow the (R) configuration.

• Option C:

  • This structure shows NH2, H, COOH, and CH3 attached to the chiral center. When applying the Cahn-Ingold-Prelog rules, this configuration corresponds to the (S)-enantiomer, as the priorities of the groups arranged around the chiral center indicate an (S) configuration.

• Option D:

  • This structure shows COOH, H, NH2, and CH3 attached to the chiral center. This also corresponds to the (R)-configuration when analyzed using the Cahn-Ingold-Prelog system.

Therefore,

The correct answer is: Option C

Ans: d

Explanation: Stereoisomer contrasts with structural isomers, which share the same molecular formula, but the bond connections or their order differs. By definition, molecules that are stereoisomers of each other represent the same structural isomer.

3-Methylhexane shows optical activity as shown below: