Test: Isomerism of organic compounds - JEE MCQ

In amines, N is sp³ hybridised and thus has pyramidal shape. In the given structure, since the three alkyl groups are different, and the fourth corner of the pyramid is occupied by lone pair of electrons, the molecule is chiral. However, the two enantiomers of the amine are not resolvable because of their rapid interconversion through a transition state having planar structure (sp² hybridised nitrogen)

Most of the simple amines those having smaller alkyl (groups) can't be resolved, although they may contain three different alkyl groups.

Identify possible configurations:
- Cis Configuration: Both - COOH groups on the same side.
- Trans Configuration: -COOH groups on opposite sides.
Geometric Isomerism:
- 1 Cis isomer
- 1 Trans isomer
Optical Isomerism:
- Cis isomer can exist as two enantiomers (mirror images).
Count the stereoisomers:
- 1 Trans (achiral)
- 2 Cis (chiral enantiomers)
Total stereoisomers = 1 (Trans) +2 (Cis enantiomers) = 3

• Geometrical Isomerism: Geometrical isomerism occurs when there is restricted rotation around a double bond, leading to different spatial arrangements of atoms.
• Optical Isomerism: Optical isomerism arises due to the presence of a chiral center in a molecule, resulting in non-superimposable mirror images known as enantiomers.

In the given compounds:

- A: 4 - Bromopent - 2- ene: This compound has a double bond, which can exhibit geometrical isomerism. Additionally, it does not have a chiral center, so it does not show optical isomerism.
- B: 3-Bromo-2-methylbut-1-ene: This compound has a double bond and a chiral center, leading to both geometrical and optical isomerism.
- C: 1 - Bromobut-2-ene: This compound has a double bond, which can exhibit geometrical isomerism. However, it does not have a chiral center, so it does not show optical isomerism.
- D: 3-Bromo-2-methylpropene: This compound has a double bond but lacks a chiral center, so it only exhibits geometrical isomerism.
Therefore, the compound that exhibits both geometrical and optical isomerism is B: 3-Bromo-2-methylbut-1-ene.No solution. Refer to answer key.

The given compounds are identical

Total 5 structural isomers

In option (d) there are two different functional groups i.e., −OH and −O−. So, these are functional isomers.

The compounds containing
group adjacent to asymmetric carbon atom carrying a hydrogen easily racemise.

The molecule contains two similar chiral centres.

1. Reaction type: Nal in acetone is an S_N2 reaction.
2. Mechanism: S_N2 causes inversion of configuration at the chiral center.
3. Outcome: Inversion of configuration retains optical activity.

In the field of chemistry, the two types of geometric isomers that are encountered most frequently are those that originate from a double bond and those that originate from a ring structure. Both cis and trans geometric isomers have distinct differences in their physical characteristics, such as their densities, boiling points, melting points, reactivities, and solubilities.
In our case,
Dipole moment: I < II
Boiling point: I < II
Melting point: I < II
Stability: I < II

SbCl₅ pulls Cl⁻ to form SbCl₆⁻ leaving behind planar C₆H₅ − CH⁺ − CH₃ carbonium ion. It can be attacked from either side leading to racemic mixture.

The number of optical isomers possible for 2 - Bromo-3 - Chlorobutane are

Five cyclic structures are possible for C₄H₆. These are as following:

Prop-2-enoic acid will not show geometrical isomerism. Geometrical isomers occur where we have restricted rotation somewhere in a molecule, between carbon atoms like - but-2-ene.

Prop-2-eneonic acid does not show geometrically isomerism.

No olefinic is present in butyric acid , aspartic acid
and palmitic acid .
Cinnamic acid is able to show geometrical isomerism.

The site I contains two identical CH₃ groups attached to double bond. This site will not show geometrical isomerism.

Gauche conformation is comparatively more stable due to hydrogen linkage in between F and H (at O-atom), hence order is Eclipse, Anti (staggered), Gauche.

Structure of D-(-)-Ribose is:

The number of chiral carbon atoms is 3.