Question

The compound that is chiral is : (1) 3-methyl-3-hexene (2) 4-chloro-1-methylcyclohexane (3) 2-phenylpentane (4) 1,3-diisopropylbenzene

Short answer

2-phenylpentane is the chiral compound.

Step-by-step solution

- Define Chirality

Chirality refers to a molecule that is non-superimposable on its mirror image. A molecule is chiral if it has at least one carbon atom bonded to four different groups.

- Analyze 3-methyl-3-hexene

Identify the connectivity of atoms in 3-methyl-3-hexene. On the 3rd carbon, there is a double bond, meaning it cannot have four different groups. Thus, it is not chiral.

- Analyze 4-chloro-1-methylcyclohexane

Identify the structure of 4-chloro-1-methylcyclohexane. Determine if any carbon atoms in the cyclohexane ring are bonded to four different groups. In this structure, no single carbon is bonded to four different groups; hence, it is not chiral.

- Analyze 2-phenylpentane

Identify the connectivity in 2-phenylpentane. The 2nd carbon attaches to a phenyl group, a hydrogen atom, a methyl group, and a propyl group. Since the 2nd carbon is bonded to four different groups, it is chiral.

- Analyze 1,3-diisopropylbenzene

Identify the structure of 1,3-diisopropylbenzene. Check if any carbon atoms in the benzene ring are bonded to four different groups. This structure does not have a carbon atom bonded to four different groups, so it is not chiral.

Conclusion

Based on the analysis, the only compound with a carbon atom bonded to four different groups (making it chiral) is 2-phenylpentane.

Key concepts

chirality in organic chemistry

Chirality is a fascinating and vital concept in organic chemistry. A molecule is considered chiral if it cannot be superimposed on its mirror image. This usually happens when a carbon atom, known as the chiral center, is bonded to four different groups.

Imagine your left and right hands. They are mirror images but cannot be perfectly overlaid on each other. Molecules can exhibit this same property. Chiral molecules have unique properties and behaviors, especially in biological systems. For instance, one chiral form of a molecule could be a beneficial drug, while its mirror image might be ineffective or even harmful.

To find chirality in a compound, look for a carbon atom bonded to four distinct groups. If you find even one such carbon, the molecule is chiral. Identifying chirality is central in understanding the molecular world, particularly in designing and studying pharmaceuticals.

carbon connectivity

Understanding carbon connectivity is crucial in identifying chiral compounds. Carbon atoms can bond in various configurations with other atoms, forming complex structures. In chiral compounds, the unique arrangement around the chiral center gives rise to distinct three-dimensional shapes.

When analyzing a molecule for chirality, examine each carbon atom's bonds. Check if a carbon atom is connected to four different groups. For example, in the exercise, 3-methyl-3-hexene has a double bond on the 3rd carbon, preventing four different attachments hence, it’s not chiral.

Conversely, the 2nd carbon in 2-phenylpentane is bonded to a phenyl group, a hydrogen atom, a methyl group, and a propyl group, making it chiral. The connectivity of atoms is essential in determining the overall shape and properties of molecules, and it is a fundamental concept in organic chemistry.

• Single bonds allow rotation
• Double and triple bonds restrict rotation
• Ring structures add complexity

IIT JEE chemistry

Chirality and carbon connectivity are significant topics in the IIT JEE chemistry syllabus. Students aspiring to ace this prestigious examination must master these concepts.

In the IIT JEE, students are often tested on their ability to identify chiral centers in complex molecules. They need to understand not only basic definitions but also how to apply these concepts to different structures. This requires practice and a deep understanding of molecular geometry and bonding.

By focusing on exercises like the one presented, students can develop a keen eye for identifying chiral centers. They will be well-prepared to tackle questions on stereochemistry, which is a critical part of organic chemistry in the IIT JEE syllabus.

• Practice identifying chiral centers
• Understand the impact of molecular geometry
• Learn to visualize molecules in 3D