Problem 46 - A Complete Resource Book in Chemistry for JEE Main

Question

The maximum number of carbon atoms arranged linearly in the molecule, \(\mathrm{CH}_{3}-\mathrm{C} \equiv \mathrm{C}-\mathrm{CH}=\mathrm{CH}_{2}\) are (a) 3 (b) 4 (c) 5 (d) 6

Step-by-Step Solution

Answer

5 carbon atoms can be arranged linearly in the molecule.

Step 1: Understanding the Molecular Structure

The given molecular formula is \( \text{CH}_{3}-\text{C} \equiv \text{C}-\text{CH}=\text{CH}_{2} \). This indicates a series of carbon atoms connected by various types of bonds: a single bond (\(-\)), a triple bond (\(\equiv\)), and a double bond (\(=\)). We're tasked with determining the maximum number of carbon atoms that are arranged linearly.

Step 2: Mapping the Carbon Atoms

Read the structure from left to right: \( \text{CH}_3 \) indicates a methyl group, followed by a single carbon (\(\text{C}\)) connecting to the next carbon with a triple bond (\(\equiv\)). After the triple bond, there's another carbon (\(\text{C}-\)), then a connecting double bond to a subsequent carbon (\(=\)), and finally a \(\text{CH}_2\) group representing a carbon connected with a double bond to the preceding one.

Step 3: Counting the Carbons

Counting each distinct carbon in the sequence: \( \text{CH}_3 \) is one carbon, \( \equiv \text{C}- \) is another, and the pattern continues as follows: \( - \text{C}= \text{C} \) provides two more carbons. Counting each gives us a total of 5 connected carbon atoms.

Step 4: Final Determination

Assess the sequence \( \text{CH}_{3}-\text{C} \equiv \text{C}-\text{C}=\text{CH}_{2} \) in its entirety to conclude there's a linear sequence involving five carbon atoms. Therefore, the maximum number of carbon atoms in a direct line is 5.

Key Concepts

Carbon Atom Structure

Every organic molecule is built on the backbone of carbon atoms. The carbon atom forms the basis of countless compounds due to its unique structural properties. Let's explore the carbon atom's structure:

• At the core of an atom is the nucleus, consisting of protons and neutrons.
• Electrons orbit around the nucleus in specific paths called orbitals.
• Carbon has four valence electrons available for forming bonds.

Carbon’s ability to form four covalent bonds allows it to act as a versatile central atom. This flexibility enables carbon to create stable chains and rings of various lengths and complexities. In particular, carbon's ability to form single, double, and triple bonds with itself and other atoms makes it essential in organic chemistry.

Molecular Bonds

Molecular bonds are the glue that holds atoms together in molecules. In organic chemistry, understanding the different types of bonds is crucial. Here's what you need to know:- **Single Bonds (-):** Allow free rotation of bonded atoms and form the basis of alkanes.- **Double Bonds (=):** Restrict rotation due to \(\) and \( \pi \) bonding, providing rigidity crucial for compounds like alkenes.- **Triple Bonds (≡):** Composed of one sigma (\( \sigma \)) and two pi (\( \pi \)) bonds, these are the shortest and strongest, seen in alkynes.Each bond type impacts the molecule's physical and chemical properties, determining aspects like melting points, boiling points, and reactivity. Understanding these bonds helps in crafting more complex molecules and comprehending their reactions and behaviors.

Linear Hydrocarbons

Linear hydrocarbons consist of carbon atoms arranged in a straight sequence, connected by molecular bonds. These structures are fundamental in organic chemistry, serving as the backbone for more complex molecules.- **Identifying Linear Structures:** Linear hydrocarbons can appear in various forms, including alkanes, alkenes, and alkynes, each characterized by their distinct types of carbon-carbon bonds.- **Impact of Bond Types:** Single bonds result in saturated hydrocarbons, whereas double and triple bonds introduce unsaturation, affecting the molecule's geometry and reactivity.- **Examples and Applications:** The linear hydrocarbon sequence in the formula \( \text{CH}_{3}-\text{C} \equiv \text{C}-\text{CH}=\text{CH}_{2} \) illustrates how a straightforward linear arrangement can have varying bond types, impacting its properties and potential uses.Grasping the concept of linear hydrocarbons is key when delving deeper into organic synthesis and understanding how molecular configurations influence chemical behavior.