Question

The compounds which can show stereoisomerism is (A) Polyvinyl chloride (B) Gutta Purcha (C) Buna-S (D) Polyvinyl acetate

Short answer

The compound that can exhibit stereoisomerism among the given options is (B) Gutta Purcha. This is because it has a stereocenter at the attachment of each isoprene monomer in the chain and its trans configuration leads to different spatial arrangements of atoms.

Step-by-step solution

Overview of the Compounds

Before we analyze each compound, let's briefly define them: (A) Polyvinyl chloride (PVC) is a polymer derived from vinyl chloride monomers. (B) Gutta Purcha is a natural rubber composed of trans-polyisoprene. (C) Buna-S is a synthetic rubber polymer formed by the copolymerization of butadiene and styrene monomers. (D) Polyvinyl acetate (PVAc) is a polymer derived from vinyl acetate monomers. Now, let's analyze each compound to determine if they can exhibit stereoisomerism.

(A) Polyvinyl chloride (PVC)

Polyvinyl chloride (PVC) is a polymer formed by polymerizing vinyl chloride monomers. Vinyl chloride is a simple alkene, and its double bond gets converted to a single bond during polymerization. Since there are no stereocenters in the PVC chain, it cannot exhibit stereoisomerism.

(B) Gutta Purcha

Gutta Purcha is a trans-1,4-polyisoprene polymer, which consists of isoprene monomers in a trans configuration. Gutta Purcha has a stereocenter at the attachement of each isoprene monomer in the chain. The trans configuration leads to different spatial arrangements of atoms, which allows Gutta Purcha to exhibit stereoisomerism.

(C) Buna-S

Buna-S is a copolymer formed by polymerizing butadiene and styrene monomers. Both butadiene and styrene have double bonds that get converted to single bonds in the copolymers. Buna-S does not have any stereocenters in its polymer chain, so it cannot exhibit stereoisomerism.

(D) Polyvinyl acetate (PVAc)

Polyvinyl acetate (PVAc) is a polymer formed by polymerizing vinyl acetate monomers. The double bond in the vinyl acetate monomer gets converted to a single bond during polymerization. The absence of any stereocenters in the PVAc polymer chain means that it cannot exhibit stereoisomerism. Based on our analysis, the correct option is: (B) Gutta Purcha

Key concepts

Understanding Polymers

Polymers are large molecules made up of repeating structural units called monomers, which are bonded together in long chains. These fascinating substances include everything from natural materials, like rubber, to everyday synthetic products, such as plastics and synthetic fibers. This makes them incredibly versatile and commonly found in many aspects of daily life.

The process of forming polymers from monomers is known as polymerization. This can occur through various mechanisms, mainly "addition polymerization" or "condensation polymerization."

• Addition Polymerization: This process involves the linking of monomers with unsaturated bonds (like double or triple bonds), without the loss of any small molecules. Polyvinyl chloride (PVC) and Buna-S are examples of polymers formed this way.
• Condensation Polymerization: During this process, monomers join by the elimination of small molecules like water or methanol. This is typical in the formation of polyesters and nylons.

Polyvinyl acetate (PVAc) and Polyvinyl Chloride (PVC) are both polymers formed via addition polymerization. Their lack of stereocenters means they do not exhibit stereoisomerism. In contrast, Gutta Purcha, a natural rubber, has a characteristic stereochemistry that allows it to show such isomerism.

Exploring Stereochemistry

Stereochemistry is a subdiscipline of chemistry that examines the spatial arrangement of atoms within molecules. This area of study is essential to understanding how molecules interact and function, particularly in biological contexts. Stereoisomerism, which is part of stereochemistry, occurs when molecules have the same molecular formula but differ in the three-dimensional placement of their atoms.

There are two main types of stereoisomerism:

• Geometric Isomerism: Also known as cis-trans isomerism, this occurs in molecules with restricted rotation, typically around double bonds or within rings. An example is the difference between the trans arrangement in Gutta Purcha and other isomers.
• Optical Isomerism: This form involves isomers that differ in how they rotate plane-polarized light. It's due to the presence of chiral centers within the molecule.

Gutta Purcha shows stereoisomerism due to the trans configuration of its monomeric units, which differ from potential cis configurations, making it an interesting study subject in stereochemistry.

Diving into Organic Chemistry

Organic chemistry is the study of carbon-containing compounds and their properties. It's a vast field that encompasses everything from simple molecules, like methane, to complex polymers such as Gutta Purcha. Essential to every aspect of organic chemistry is the concept of bonding, specifically covalent bonding, where atoms share electrons to achieve stability.

Polymers, made through organic chemical processes, are a core focus because of their practical applications and fascinating molecular structures. These include everyday items such as plastics, rubber, and fibers, highlighting their importance in industries ranging from construction to healthcare.

Consider the compounds like Gutta Purcha and Buna-S, both of which fall under the umbrella of organic materials. While Gutta Purcha is a natural product with interesting stereoisomeric properties due to its trans arrangement, Buna-S is a synthetic product that doesn't exhibit stereoisomerism. These differences illustrate the diversity and complexity of organic compounds and their behavior.

Understanding these fundamentals of organic chemistry, such as the role of stereoisomerism and polymerization, is crucial not only for chemists but also for industries reliant on these materials for innovative applications.