Problem 78 - A Complete Resource Book in Chemistry for JEE Main

Question

OCC1CCCC1 \(\frac{\Delta}{\mathrm{H}^{+}}-\mathrm{P}\) Here \(\mathrm{P}\) is (a) CC1=CCCC1 (b) C=C1CCCC1 (c) CC1=CCCC1 (d) C1=CCCCC1

Step-by-Step Solution

Answer

The product (P) is (b): C=C1CCCC1.

Step 1: Analyze the reactant structure

The reactant molecule given is represented by the SMILES notation OCC1CCCC1. This describes a cyclopentanol, which is a five-membered ring containing an -OH group attached. The structure has one oxygen atom, indicating an alcohol functional group on a cyclopentane ring.

Step 2: Understand the reaction

The reaction condition given is \(\Delta/\mathrm{H}^+\), which implies heating around acid, commonly used for dehydration reactions. The -OH group in the cyclopentanol can be removed as water (\(\mathrm{H}_2\mathrm{O}\)) in the presence of strong acid and heating, leading to the formation of an alkene.

Step 3: Predict the reaction outcome

Cyclopentanol will undergo dehydration to form a cyclopentene. During dehydration, the hydroxyl group is generally removed, and a double bond is formed between the two adjacent carbon atoms in the ring. This results in the formation of cyclopentene.

Step 4: Match with given choices

The product of dehydration, cyclopentene, can be represented by C=C1CCCC1 in SMILES notation, reflecting a double bond in a cyclopentane ring. This matches option (b) among the choices provided in the problem statement.

Key Concepts

Dehydration Reactions

Dehydration reactions are a key concept in organic chemistry, where water (\(\mathrm{H}_2\mathrm{O}\)) is removed from a molecule. This type of reaction is common in alcohols that undergo the process to form alkenes.

• Often involves heating the substance with acid (\(\mathrm{H}^+\)) to aid the reaction.
• The \(-\mathrm{OH}\) group is typically removed, followed by a hydrogen next to the \(-\mathrm{OH}\) group, leading to water loss.
• This process forms a double bond between adjacent carbon atoms, transforming an alcohol into an alkene.

In our specific example, cyclopentanol undergoes dehydration. The \(-\mathrm{OH}\) group is lost as water, resulting in a cyclopentene with a new double bond formation in the ring. Understanding this process is crucial for predicting and identifying reaction products.

SMILES Notation

SMILES (Simplified Molecular Input Line Entry System) notation is a method used to describe chemical structures using short strings of text. It is an invaluable tool for chemists to quickly convey molecular configurations:

• It uses characters to represent atoms, bonds, and ring structures.
• For example, 'C' indicates a carbon atom, while '=' represents a double bond.
• In cyclic compounds, digits are used to represent the start and end of a ring.

In the provided exercise, "OCC1CCCC1" represents cyclopentanol. 'O' denotes the oxygen in the alcohol group, and 'C1CCCC1' forms the cyclopentane ring, with the '1' markers indicating the ring's closure. Recognizing these patterns helps with understanding complex molecular structures at a glance.

Cyclopentanol

Cyclopentanol is an organic compound characterized by a five-membered ring with an \(-\mathrm{OH}\) group, making it an alcohol. This structure has unique properties recognized in dehydration reactions.

• The \(-\mathrm{OH}\) group is reactive under conditions that provide heat and acid, forming water and facilitating the creation of a double bond.
• This reaction results in cyclopentene, a different compound with distinct chemical properties.

Understanding cyclopentanol is crucial when learning about alcohol reactions and ring-based chemistry, as it serves as a fundamental example for conversion processes essential in synthetic organic chemistry.

Alkene Formation

Alkene formation is the process of creating alkenes, which are hydrocarbons characterized by carbon-carbon double bonds, through reactions such as dehydration.

• Alkene formation usually involves eliminating substituents from adjacent carbon atoms.
• The double bond results in a planar structure, reducing the molecule's overall rotation.
• This process also alters the electron arrangement, giving alkenes unique reactivity.

In the case of cyclopentanol, dehydration swaps the placeholders of the \(-\mathrm{OH}\) and H atoms to set the stage for a new double bond, thus creating cyclopentene. Recognizing the transition from alcohol to alkene helps you grasp broader concepts of molecular transformation in organic chemistry.