Match the compounds given in Column I with the effects given in Column II. Column I: (i) Chloramphenicol (ii)

NCERT Exemplar · Q79

Q. Match the compounds given in Column I with the effects given in Column II. Column I:

(i) Chloramphenicol

(ii) Thyroxine

(iii) Chloroquine

(iv) Chloroform
Column II:

(a) Malaria

(b) Anaesthetic

(d) Goiter

(e) Blood substituent

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Concept understanding — Organic Compound Applications

Organic Compound Applications: From Everyday Life to Industry

Imagine you wake up in the morning. The plastic of your toothbrush, the polyester in your shirt, the paracetamol you take for a headache, the LPG that cooks your breakfast, the soap you wash your hands with — every single one of these is an organic compound. You are literally surrounded by them.

The word "organic" here has nothing to do with food labels. In chemistry, an organic compound is any compound whose molecules contain carbon, almost always bonded to hydrogen, and often to oxygen, nitrogen, and other elements. The reason carbon is special is that it can form four stable bonds, allowing it to build chains, rings, and complex structures — millions of them. This is why organic compounds are the basis of life and of modern materials.

The Core Idea: Structure Determines Function

The entire field of organic chemistry rests on one principle: the way atoms are arranged in a molecule determines what that molecule does.

A small change in structure can completely change a compound's properties. For example:

Ethanol ( $C_2H_5OH$ ) — the alcohol in drinks — is a liquid that mixes with water and is consumed by humans.
Dimethyl ether ( $CH_3OCH_3$ ) — same atoms, same formula ( $C_2H_6O$ ), but arranged differently — is a gas used as a refrigerant and is toxic if inhaled.

This is called structural isomerism, and it's why organic chemistry is so rich and why applications are so diverse.

The Precise Statement

Organic compounds are carbon-based molecules (excluding simple oxides, carbonates, and carbides) whose applications arise directly from their molecular structure — specifically, the functional groups they contain and the size/shape of their carbon skeleton.

A functional group is a specific atom or group of atoms within a molecule that gives it characteristic chemical behaviour. For instance:

The –OH group (alcohol) makes a compound able to dissolve in water and act as a disinfectant.
The –COOH group (carboxylic acid) makes it acidic and able to form esters (fragrances, plastics).
The –NH₂ group (amine) makes it basic and crucial for dyes and medicines.

How Applications Flow from Structure

Let's see this in action with real examples you'll encounter in exams:

Functional Group	Example Compound	Application	Why?
–OH (alcohol)	Ethanol	Fuel, solvent, antiseptic	Small polar molecule; burns cleanly; kills bacteria by denaturing proteins
–COOH (carboxylic acid)	Acetic acid	Vinegar (food preservative)	Weak acid kills microbes; sour taste
–COO– (ester)	Ethyl acetate	Nail polish remover, fruit flavour	Pleasant smell; volatile (evaporates quickly)
–CONH– (amide)	Nylon-66	Fibres for clothing, ropes	Strong hydrogen bonds between chains give tensile strength
–C₆H₅ (benzene ring)	Paracetamol	Pain reliever	Ring structure fits into enzyme active sites in the body

Note

In Indian exams (JEE, NEET, board exams), you are often asked to match a compound with its application or explain why a particular functional group leads to a specific use. The key is to connect the functional group's chemical property (polarity, acidity, reactivity) to the real-world need.

The Three Big Application Domains

1. Pharmaceuticals and Medicine

Most drugs are organic compounds. The structure is designed to interact with a specific biological target (enzyme, receptor) in your body. For example:

Aspirin (acetylsalicylic acid) has an ester and a carboxylic acid group — the ester is hydrolysed in the body to release the active salicylic acid.
Chloroquine (antimalarial) has a quinoline ring and an amine side chain — the ring mimics natural molecules, allowing it to enter cells.

2. Polymers and Plastics

Long chains of repeating organic units (monomers) give materials with specific properties:

Polyethylene ( $-CH_2-CH_2-)_n$ — simple chain, flexible, used in bags and bottles.
Teflon ( $-CF_2-CF_2-)_n$ — fluorine atoms replace hydrogen, making it non-stick and chemically inert.

3. Fuels and Energy

Hydrocarbons (only C and H) are the simplest organic compounds. Their combustion releases energy:

Methane ( $CH_4$ ) — natural gas, cleanest burning. …

Why this formula?

Organic Compound Applications: Understanding the Why Behind the Key Ideas

In organic chemistry, applications often revolve around reaction mechanisms, functional group transformations, and physical property trends. The "formulae" here are not always mathematical — they are conceptual frameworks and reaction patterns that explain why a compound behaves a certain way.

Let’s break down the core reasoning behind the most important applications.

1. Why Do Functional Groups Determine Reactivity?

Key idea: The functional group is the reactive site — the rest of the molecule (the carbon skeleton) is mostly a spectator.

Reasoning:

Electron density distribution is uneven in a functional group.
- Example: In a carbonyl group ( $\ce{C=O}$ ), oxygen is more electronegative than carbon.
- This creates a partial positive charge on carbon ( $\delta^+$ ) and a partial negative charge on oxygen ( $\delta^-$ ).
Nucleophiles (electron-rich species) attack the $\delta^+$ carbon.
Electrophiles (electron-deficient species) attack the $\delta^-$ oxygen or lone pairs.

Why this matters: This explains why aldehydes undergo nucleophilic addition, while alkenes undergo electrophilic addition — the type of charge separation dictates the reaction.

2. Why Do Boiling Points Follow a Trend?

Key formula (conceptual):

Boiling point $\propto$ (molecular mass) + (intermolecular force strength)

Reasoning:

Van der Waals forces increase with molecular size (more electrons → more temporary dipoles).
Hydrogen bonding (in alcohols, carboxylic acids, amines) adds a strong intermolecular force — much stronger than dipole-dipole or London forces.
Branching reduces surface area → weaker London forces → lower boiling point.

Example comparison:

Compound	Type	Boiling point (°C)	Why?
Butane ( $\ce{C4H10}$ )	Alkane	-0.5	Only London forces
Propanol ( $\ce{C3H7OH}$ )	Alcohol	97	H-bonding dominates
Acetone ( $\ce{C3H6O}$ )	Ketone	56	Dipole-dipole only

Takeaway: The type of intermolecular force matters more than molecular mass alone.

3. Why Do Substitution Reactions Follow SN1 or SN2?

Key formula (rate law):

SN2: Rate $= k[\text{RX}][\text{Nu}^-]$
SN1: Rate $= k[\text{RX}]$

Reasoning (the why):

SN2 is a one-step process: nucleophile attacks from the back while the leaving group departs.
- Requires no carbocation intermediate.
- Favored by primary alkyl halides (less steric hindrance).
SN1 is a two-step process:
1. Leaving group leaves → forms a carbocation (slow, rate-determining step).
2. Nucleophile attacks the carbocation (fast).
- Favored by tertiary alkyl halides (carbocation is more stable due to hyperconjugation and inductive effects).

Why this matters: The structure of the alkyl halide determines which pathway dominates — this is why tertiary halides react via SN1 (no backside attack possible) and primary halides via SN2.

4. Why Do Aromatic Compounds Resist Addition?

Key concept: Aromaticity — the delocalized $\pi$ -electron cloud stabilizes the ring.

Reasoning:

Benzene ( $\ce{C6H6}$ ) has 6 $\pi$ -electrons in a cyclic, planar, conjugated system.
Hückel's rule: Aromatic if $4n+2$ $\pi$ -electrons (here $n=1$ ).
Addition would break the aromatic ring → lose the resonance stabilization energy (~150 kJ/mol for benzene).
Instead, electrophilic substitution occurs — the ring keeps its aromaticity.

Why this matters: This explains why benzene undergoes nitration, halogenation, etc., but not addition reactions like alkenes do.

5. Why Do Carboxylic Acids Have Higher Acidity Than Alcohols? …

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This is a matching problem linking common drugs and hormones to their primary medical applications. The correct pairings are: Chloramphenicol → Typhoid fever, Thyroxine → Goiter, Chloroquine → Malaria, and Chloroform → Anaesthetic.

The question tests your knowledge of organic compounds in medicine — specifically, which well-known substances are used to treat which conditions. This is a standard application-based topic in chemistry and biology, where you need to recall the primary use of each compound rather than its chemical structure.

Let’s go through each compound one by one.

Chloramphenicol is a broad-spectrum antibiotic. It is particularly effective against Salmonella typhi, the bacterium that causes typhoid fever. It was one of the first antibiotics used for this disease. So (i) matches with ** (c)**.
Thyroxine is a hormone produced by the thyroid gland. When the thyroid is underactive (hypothyroidism), it leads to a condition called goiter — an enlargement of the thyroid. Thyroxine supplements are used to treat this. So (ii) matches with ** (d)**.
Chloroquine is an antimalarial drug. It works by interfering with the parasite Plasmodium inside red blood cells. It has been a frontline treatment for malaria for decades. So (iii) matches with ** (a)**. …

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Concept: Medicinal Chemistry & Drug-Target Matching

This question tests your ability to match drugs/compounds with their primary therapeutic use or biological effect. The key is to recall the specific disease or condition each compound is known to treat.

Method: Direct Recall + Elimination

Steps:

Identify the most famous use of each compound (from NCERT / standard syllabus).
Match directly — if a compound has a well-known single use, lock that pair first.
Eliminate — remove matched options from Column II to avoid confusion.
Check for any secondary uses (e.g., chloroform as anaesthetic is primary).

Step-by-step matching:

Column I	Known Use	Matches Column II
(i) Chloramphenicol	Broad-spectrum antibiotic — typhoid fever	(c) Typhoid fever
(ii) Thyroxine	Thyroid hormone — deficiency causes goiter	(d) Goiter
(iii) Chloroquine	Antimalarial drug — treats malaria	(a) Malaria

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Here are the common mistakes students make when matching these compounds with their effects, along with how to avoid each.

Mistake 1: Confusing Chloramphenicol with Chloroquine

The Error: Students often match Chloramphenicol with Malaria (a) because both names start with "Chloro-". They then incorrectly match Chloroquine with Typhoid fever (c).
Why it happens: The similar prefixes cause a memory slip. Students rely on the sound of the word rather than the specific function.
How to Avoid:
- Remember the "Phenicol" suffix: Chloramphenicol is an antibiotic. The key is to link it to Typhoid fever (c). Think: "Phenicol for Fever."
- Remember the "Quine" suffix: Chloroquine is an antimalarial. Link it directly to Malaria (a). Think: "Quine for Malaria."

Mistake 2: Forgetting the Function of Thyroxine

The Error: Students match Thyroxine with Goiter (d) but often confuse why. They might think it causes goiter, or they might match it with a different gland-related effect.
Why it happens: Students memorize "Thyroxine = Thyroid" but forget that a deficiency of thyroxine causes goiter (an enlarged thyroid). They might also confuse it with insulin or adrenaline.
How to Avoid:
- Understand the feedback loop: Thyroxine is the hormone produced by the thyroid gland. When the body doesn't produce enough (hypothyroidism), the gland overworks to try to make more, leading to swelling (goiter).
- Direct Link: Thyroxine is the treatment for goiter. Match Thyroxine with Goiter (d).

Mistake 3: Misidentifying Chloroform as a Blood Substitute

The Error: Students match Chloroform with (e) Blood substituent, thinking it sounds like a medical fluid.
Why it happens: The word "Chloroform" sounds clinical, and students might vaguely recall it being used in medicine. They forget its specific historical use.
How to Avoid:
- Recall the "form" suffix: Chloroform is a volatile liquid used historically as an Anaesthetic (b). Think: "Chloroform puts you to sleep."
- Eliminate the odd one out: Blood substituent (e) is a distractor. No common exam compound in this list is a blood substituent. If you know the other four matches, (e) is automatically left unmatched.

Mistake 4: Leaving "Blood substituent" Unmatched or Forcing a Match …

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Q.Match the compounds given in Column I with the effects given in Column II.
Column I:

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