Give the uses of freon 12, DDT, carbon tetrachloride and iodoform.

Exercises · 6.13

Q. Give the uses of freon 12, DDT, carbon tetrachloride and iodoform.

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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 question asks for the uses of four important organic compounds — freon 12, DDT, carbon tetrachloride, and iodoform. Each has a distinct application: freon 12 as a refrigerant, DDT as an insecticide, carbon tetrachloride as a solvent and fire extinguisher, and iodoform as an antiseptic.

The key to answering such questions in exams is to recall the specific, well-known uses of each compound — not just general properties. Let's go through them one by one, with the reasoning behind each use.

1. Freon 12 (Dichlorodifluoromethane, $\text{CCl}_2\text{F}_2$ )

Freon 12 is a chlorofluorocarbon (CFC). Its uses stem from its unique physical properties: it is a gas at room temperature but easily liquefies under pressure, it is non-toxic, non-flammable, and chemically stable.

Refrigerant in air conditioners and refrigerators: Because it can absorb heat when it evaporates and release it when compressed, it was widely used in cooling systems.
Propellant in aerosol sprays: Its low boiling point and inertness made it ideal for dispensing products like deodorants and paints.
Foam-blowing agent: Used in manufacturing insulating foams.

Watch out

Freon 12 is now banned under the Montreal Protocol because it depletes the ozone layer. In modern exams, you may be asked about its environmental impact alongside its uses.

2. DDT (Dichlorodiphenyltrichloroethane, $\text{C}_{14}\text{H}_9\text{Cl}_5$ )

DDT is an organochlorine compound. Its primary use is as an insecticide, but its story is complex.

Insecticide in agriculture: It was massively used after World War II to control crop pests like mosquitoes, beetles, and moths.
Disease vector control: It was sprayed to kill mosquitoes that transmit malaria and typhus, saving millions of lives.
Household pest control: Used in powders and sprays for flies, cockroaches, and lice.

Note

DDT is persistent in the environment and accumulates in food chains, causing harm to wildlife (especially birds). It is now banned in most countries, but is still used in some regions for malaria control under strict guidelines.

3. Carbon Tetrachloride ( $\text{CCl}_4$ )

Carbon tetrachloride is a dense, non-flammable liquid. Its uses are based on its ability to dissolve oils and fats, and its fire-suppressing property.

Solvent for oils, fats, and greases: Used in dry cleaning and as a degreasing agent in industries.
Fire extinguisher (under the name Pyrene): Its non-flammable nature and ability to form a heavy vapour that smothers flames made it a common fire extinguisher for electrical fires. …

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Here is a clear, concept-first solution method for this type of question.

Method: Functional Group & Property Mapping

This method works by linking the chemical structure (specifically the functional group or key element) of a compound to its physical/chemical properties, and then mapping those properties to a real-world application.

Core Concept: A compound's use is almost always a direct consequence of one of its dominant properties (e.g., non-flammability, toxicity to insects, antiseptic action).

Steps to Solve

Step 1: Identify the Key Structural Feature

Look at the compound's formula or name and identify the atom or group that makes it special.

Freon 12 ( $CCl_2F_2$ ): Contains Chlorine (Cl) and Fluorine (F) atoms. It is a halogenated hydrocarbon (a CFC).
DDT ( $C_{14}H_9Cl_5$ ): Contains multiple Chlorine (Cl) atoms attached to two benzene rings. It is a polychlorinated hydrocarbon.
Carbon tetrachloride ( $CCl_4$ ): Contains four Chlorine (Cl) atoms. It is a non-polar, dense liquid.
Iodoform ( $CHI_3$ ): Contains Iodine (I) atoms. It is a trihalomethane.

Step 2: Link Structure to a Dominant Property

Connect the structural feature to its most important chemical or physical behavior.

Freon 12: The C-F and C-Cl bonds are very strong and stable. This makes the compound non-toxic, non-flammable, and a good heat transfer agent (it evaporates easily, absorbing heat).
DDT: The chlorine atoms make the molecule highly stable (persistent) and toxic to the nervous system of insects.
Carbon tetrachloride: It is a non-polar solvent (dissolves oils, fats, grease) and is non-flammable. It is also denser than water.
Iodoform: The iodine atom is easily released. Iodine is a powerful antiseptic (kills bacteria).

Step 3: Map Property to Application

Match the dominant property to a real-world need.

Freon 12 (Property: Non-toxic, non-flammable, good heat transfer) …

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Here are the common mistakes students make when answering questions on the applications of freon 12, DDT, carbon tetrachloride, and iodoform, along with clear strategies to avoid them.

1. Freon 12 (Dichlorodifluoromethane, $\text{CCl}_2\text{F}_2$ )

Common Mistake:

Writing that Freon 12 is used as a fuel or solvent.
Confusing it with Freon 11 or other CFCs.

Why it happens:

Students often memorise "CFCs are refrigerants" but don't distinguish between specific numbers. They also confuse "refrigerant" with "fuel" because both involve gases.

How to avoid:

Remember: Freon 12 is a chlorofluorocarbon (CFC). Its primary use is as a refrigerant in air conditioners and refrigerators.
It is non-flammable and non-toxic, so it was ideal for cooling — never a fuel.
Key exam point: It is also used as a propellant in aerosol sprays (though now banned in many countries due to ozone depletion).

Correct use: Refrigerant and aerosol propellant.

2. DDT (Dichlorodiphenyltrichloroethane)

Common Mistake:

Writing that DDT is used as a medicine or insecticide for crops (without mentioning its ban).
Forgetting to mention its environmental impact (bioaccumulation).

Why it happens:

Students recall "DDT kills insects" but don't read the question carefully — many exam questions expect you to note its historical use and current status.

How to avoid:

Always mention: DDT is an insecticide used to control malaria-carrying mosquitoes and agricultural pests.
Crucial addition: It is banned in many countries because it is non-biodegradable and causes bioaccumulation in food chains.
Do not say it is used as a medicine — it is not a drug.

Correct use: Insecticide (now restricted/banned due to environmental persistence).

3. Carbon Tetrachloride ( $\text{CCl}_4$ )

Common Mistake:

Writing that it is used as a fire extinguisher (without noting the danger).
Saying it is used as a cleaning agent without mentioning toxicity.

Why it happens:

Students remember "carbon tetrachloride puts out fires" but forget that it produces phosgene gas ( $\text{COCl}_2$ ) when heated, which is highly toxic.

How to avoid:

Correct use: It was used as a solvent for oils, fats, and as a dry cleaning agent.
Fire extinguisher use: Mention it was formerly used in fire extinguishers, but now avoided because it forms toxic phosgene gas on contact with hot surfaces.
Key exam point: It is non-flammable but toxic — never say it is safe.

Correct use: Solvent, dry cleaning agent, formerly in fire extinguishers (now discontinued due to toxicity).

4. Iodoform ( $\text{CHI}_3$ )

Common Mistake:

Writing that it is used as a general antiseptic (without specifying its limited use).
Confusing it with iodine ( $\text{I}_2$ ) or tincture of iodine.

Why it happens:

Students know "iodoform is an antiseptic" but don't realise it is not used on open wounds because it is irritating and stains.

How to avoid: …

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Q.Give the uses of freon 12, DDT, carbon tetrachloride and iodoform.

1. Freon 12 (Dichlorodifluoromethane, CCl2F2\text{CCl}_2\text{F}_2CCl2​F2​)

2. DDT (Dichlorodiphenyltrichloroethane, C14H9Cl5\text{C}_{14}\text{H}_9\text{Cl}_5C14​H9​Cl5​)

3. Carbon Tetrachloride (CCl4\text{CCl}_4CCl4​)

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1. Freon 12 (Dichlorodifluoromethane, $\text{CCl}_2\text{F}_2$ )

2. DDT (Dichlorodiphenyltrichloroethane, $\text{C}_{14}\text{H}_9\text{Cl}_5$ )

3. Carbon Tetrachloride ( $\text{CCl}_4$ )

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