Problem 5 - A Complete Resource Book in Chemistry for JEE Main

Question

The following structural formula refers to Clc1ccc(C(c2ccc(Cl)cc2)C(Cl)(Cl)Cl)cc1 (a) DDT (b) RNA (c) DNA (d) \(\mathrm{BHC}\)

Step-by-Step Solution

Answer

The correct answer is (a) DDT.

Step 1: Understand SMILES Notation

The SMILES (Simplified Molecular Input Line Entry System) notation provided describes the structure of a chemical compound. Each character or sequence in SMILES represents a particular structure or atom. The provided SMILES is `Clc1ccc(C(c2ccc(Cl)cc2)C(Cl)(Cl)Cl)cc1`.

Step 2: Interpret the SMILES Structure

The SMILES string begins with `Cl`, indicating the presence of chlorine atoms. The sequence `c1ccc(C(c2ccc(Cl)cc2)C(Cl)(Cl)Cl)cc1` describes a benzene ring (`c1ccc...cc1`) with substituents attached. This structure includes a dichlorodiphenyltrichloroethane core, suggesting a substituted aromatic ring.

Step 3: Identify the Compound

The chemical structure described by this SMILES is that of DDT, known chemically as Dichloro-Diphenyl-Trichloroethane. The "C" denotes a carbon atom connected to another carbon atom that has two chlorine substituents and a benzene group, which is characteristic of DDT.

Step 4: Match with Options

Option (a) is DDT, which matches the SMILES structure we interpreted. Therefore, the correct answer based on this analysis is (a) DDT.

Key Concepts

Chemical Structure Interpretation

Interpreting chemical structures is crucial for understanding molecular compositions and reactions. This process involves deciphering various notations and diagrams that represent molecules. The most common notations are **SMILES**, which stands for Simplified Molecular Input Line Entry System.
SMILES uses alphanumeric symbols to represent atoms and bonds in a molecule. For example, 'C' stands for carbon, 'O' for oxygen, and 'Cl' for chlorine. **Bonds** are implicitly assumed by the order and symbols of the notation.

• Structural rings are represented in SMILES by numbering carbons in the ring, like `c1ccc...cc1`.
• Branching, which involves substituents attached to a main molecule, is shown using parentheses.

The SMILES notation represents both the structural details and molecular connectivity. It efficiently conveys complex structures simply and is widely used in chemical informatics for data storing and analysis.

Organic Chemistry

Organic chemistry focuses on carbon-containing compounds and their properties, reactions, and synthesis. Carbon's ability to form stable bonds with many elements, including itself, makes it the backbone of organic molecules.
Recognizing these compounds involves identifying characteristic groups and patterns.
In the context of the SMILES notation, understanding the basics of organic chemistry allows one to infer:

• **Hydrocarbons** - Compounds made entirely of carbon and hydrogen such as alkanes, alkenes, and aromatics.
• **Functional groups** - These are specific atoms or groups of atoms within molecules that determine the chemical behavior of the whole compound, such as -OH (alcohol) or -COOH (carboxylic acid).

Organic chemistry is also about predicting how these structures change during reactions, helping chemists to design new compounds or synthesize existing ones.

Aromatic Compounds

Aromatic compounds are a special class of organic molecules that feature one or more planar rings of atoms bonded in a conjugated system. This conjugation leads to significant stability due to delocalized electrons.
Benzene is the most basic aromatic compound with a six-carbon ring ( `c1ccc...cc1` in SMILES) and alternating double bonds, though it's often depicted with a circle to represent electron delocalization.
Aromaticity gives these compounds:

• **Stability** - More so than typical linear or branched structures due to resonance.
• **Unique Reactivity Patterns** - They undergo **electrophilic aromatic substitution**, rather than addition reactions - typical of alkenes.

Understanding aromaticity is broader than just benzene; it's essential for interpreting more complex structures like DDT, which features aromatic rings linked to chlorine and carbon groups.