Problem 89 - A Complete Resource Book in Chemistry for JEE Main

Question

Which is correct about Gutta parcha rubber? (1) a very hard material (2) a synthetic polymer (3) a trans 1,4 -polyisoprene polymer (a) 2 only (b) 3 only (c) 1 and 3 only (d) 1,2 and 3

Step-by-Step Solution

Answer

The correct answer is (b) 3 only.

Step 1: Understanding Gutta Percha Rubber

Gutta percha rubber is a natural polymer. It is not synthetic but derived from the latex of certain tropical trees. Hence, it cannot be described as a synthetic polymer.

Step 2: Analyzing its Hardness

Gutta percha is known for being a rigid and tough material, but describing it as 'very hard' might not entirely capture its characteristics accurately. It is used in dentistry and other applications for its toughness and stability.

Step 3: Chemical Structure Analysis

Gutta percha is a trans 1,4-polyisoprene. It has a similar structure to natural rubber but with a different geometric isomerism (trans vs. cis), which contributes to its unique properties and differentiates it from synthetic polymers.

Step 4: Checking Each Option

- Option (1) 'a very hard material' is debatable due to varying interpretations of 'very hard.' - Option (2) 'a synthetic polymer' is incorrect, as gutta percha is natural. - Option (3) 'a trans 1,4-polyisoprene polymer' is correct.

Step 5: Selecting the Correct Answer

Matching our findings with the options, the correct option that matches the chemical description of gutta percha being a 'trans 1,4-polyisoprene polymer' is Option (3) only. Thus, the correct choice is (b) 3 only.

Key Concepts

Polymer Chemistry

Polymer chemistry is a field that focuses on the study of polymers, which are large molecules composed of repeating structural units. These units are linked together by covalent chemical bonds. Polymers can be found in various forms in nature and are also made synthetically. The two main types of polymers are addition polymers and condensation polymers.

• Addition polymers are formed when monomers add to each other without the loss of any molecules.
• Condensation polymers form through a reaction where molecules join and release a small molecule like water as a byproduct.

Understanding polymer chemistry is crucial because it underlies the development and use of materials we encounter daily, from plastics to rubber.

Natural vs Synthetic Polymers

Polymers can be either natural or synthetic. Natural polymers are those that occur in nature and are found in plants, animals, and other organisms. Examples include proteins and DNA. **Gutta percha** is a natural polymer, derived from the latex of trees found in Southeast Asia.
Synthetic polymers are man-made and are usually derived from petrochemicals. These include familiar materials like nylon, polyester, and polystyrene. Unlike gutta percha, which is natural, these polymers are crafted through specific chemical processes in industrial settings.

• Natural polymers are generally biodegradable and eco-friendly.
• Synthetic polymers might offer more durability and flexibility in terms of design and application.

Gutta percha's classification as a natural polymer highlights its unique place in both historical and modern applications.

Geometric Isomerism

Geometric isomerism is a form of stereoisomerism where molecules have the same formula but differ in spatial orientation. Two common geometric isomers are **cis** and **trans**. In **cis** isomers, **substituents are on the same side**, whereas in **trans** isomers, they are on opposite sides. This slight difference in arrangement can significantly affect a molecule's physical and chemical properties.
Gutta percha is a form of trans 1,4-polyisoprene. The **trans** configuration gives gutta percha its rigidity and durability. Meanwhile, natural rubber, which is also polyisoprene, has a **cis** configuration, lending it more flexibility.
Recognizing geometric isomerism is key to differentiating between materials like gutta percha and natural rubber, which although chemically similar, serve different purposes due to this fundamental difference.

• **Trans** structures often result in more straight and rigid compounds.
• **Cis** structures tend to be more bent and flexible.