Carbon and It's Compounds

                                                                  Chapter-4 

                                 Carbon and its Compounds

🌴🌴Introduction to Carbon Compounds

Carbon is one of the most important elements on Earth, forming the basis of almost all organic substances. Our body, food, fuels, medicines, plastics, fibres, and countless useful materials are made up of carbon compounds. Because of its ability to form millions of different compounds, carbon is often called the element of life.

👉Key Characteristics of Carbon

Carbon has four electrons in its outer shell, allowing it to form stable bonds with many other elements.
Carbon neither gains nor loses electrons easily. Instead, it shares electrons with other atoms, forming covalent bonds.
One of carbon’s most unique properties is its ability to form long chains, branches, and ring structures by bonding with itself. This property is not seen strongly in other elements.
Nearly 90% of known chemical compounds are carbon-based, proving how versatile carbon truly is.

1. Tetravalency (Valency = 4):   Carbon has four electrons in its outer shell, allowing it to form stable bonds with many other elements.

2. Covalent Bond Formation:    Carbon neither gains nor loses electrons easily. Instead, it shares electrons with other atoms, forming covalent bonds.

3. Catenation:  One of carbon’s most unique properties is its ability to form long chains, branches, and ring structures by bonding with itself. This property is not seen strongly in other elements.

4. Large Variety of Compounds:  Nearly 90% of known chemical compounds are carbon-based, proving how versatile carbon truly is.

👉Types of Covalent Bonds:

A covalent bond is a chemical bond formed when two atoms share electrons. Covalent bonds usually form between non-metal atoms.
There are three main types of covalent bonds:

1. Single Covalent Bond

(Sharing of 1 electron pair)
Features:
Examples:

A single covalent bond is formed when two atoms share one pair of electrons.

• Weakest among covalent bonds

• Longest in length

• Stable and very common

• H₂

• Cl₂

• CH₄ (Methane)

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2. Double Covalent Bond

(Sharing of 2 electron pairs)
Features:
Examples:

A double bond is formed when two atoms share two pairs of electrons.

• Stronger than a single bond

• Shorter in length

• More reactive

• O₂ (Oxygen)

• C₂H₄ (Ethene)

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3. Triple Covalent Bond

(Sharing of 3 electron pairs)

Features:
Examples:

A triple bond is formed when two atoms share three pairs of electrons.

• Strongest covalent bond

• Shortest in length

• Highly reactive

• N₂ (Nitrogen)

• C₂H₂ (Acetylene)

 🌴🌴What is Catenation?

Catenation is the property of an element to form long chains, branches, or ring structures by bonding with atoms of the same element.

This property is most strongly shown by carbon, which is why carbon can form millions of compounds.

1. Strong C–C Covalent Bonds

Carbon–carbon bonds are strong and stable, allowing long chains to exist.

2. Tetravalency (Valency = 4)

Carbon can form four covalent bonds, enabling the formation of:

• Straight chains

• Branched chains

• Ring structures

3. Small Atomic Size

Carbon’s small size makes its covalent bonds more stable.

Examples of Catenation by Carbon

1. Straight chain

   • C–C–C–C

2. Branched chain

   • Example: Iso-butane

3. Ring structure

• Example: Cyclohexane

👉Importance of Catenation

• Formation of millions of organic compounds

• Essential biomolecules: DNA, proteins, carbohydrates

• Industrial products: plastics, rubbers, fibres, medicines

Thus, catenation is the key reason why carbon chemistry is so vast and unique.

🌴🌴What Are Hydrocarbons?

Compounds made up of only carbon (C) and hydrogen (H) atoms are called hydrocarbons.

Based on the type of bonds between carbon atoms, hydrocarbons are of two major types:

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1. Saturated Hydrocarbons

Hydrocarbons with Only Single Bonds

Saturated hydrocarbons contain only carbon–carbon single bonds (C–C) and have the maximum number of hydrogen atoms attached.

Features:

• Contain only single covalent bonds

• Less reactive

• Chemically stable

• Alkanes belong to this category

General Formula:

Alkanes → CₙH₂ₙ₊₂

Examples:

• CH₄ (Methane)

• C₂H₆ (Ethane)

• C₃H₈ (Propane)

• C₄H₁₀ (Butane)

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👉2. Unsaturated Hydrocarbons

Hydrocarbons with Double or Triple Bonds

Unsaturated hydrocarbons contain either double bonds (C=C) or triple bonds (C≡C) between carbon atoms.

Features:

• Double or triple bonds

• More reactive

• Less hydrogen content

• Two types: Alkenes and Alkynes

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(A) Alkenes

Hydrocarbons with one or more double bonds.

General Formula: CₙH₂ₙ
Examples:

• C₂H₄ (Ethene)

• C₃H₆ (Propene)

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(B) Alkynes

Hydrocarbons with one or more triple bonds.

General Formula: CₙH₂ₙ₋₂
Examples:

• C₂H₂ (Ethyne)

• C₃H₄ (Propyne)

🌴🌴What is a Homologous Series?

A homologous series is a group of organic compounds that have:

1. The same functional group,

2. The same general formula,

3. Each successive member differing by one –CH₂– unit (14u).

The compounds in a homologous series have similar chemical properties and gradually changing physical properties.

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👉Characteristics of a Homologous Series

1. –CH₂– (Methylene) Difference

Each successive member differs from the previous one by one –CH₂– group.
Example:

• CH₄ → C₂H₆ → C₃H₈ → C₄H₁₀

2. Same Functional Group

All compounds in the series contain the same functional group.
Examples:

• Alcohols → –OH

• Acids → –COOH

3. Similar Chemical Properties

Because of the same functional group, their chemical reactions are almost similar.

4. Gradual Change in Physical Properties

As the molecular size increases:

• Boiling point increases

• Density increases

• Solubility changes gradually

5. Can Be Extended Infinitely

New compounds can be added by simply adding a –CH₂– group.

🌴🌴What is Isomerism?

Isomerism is the phenomenon in which compounds having the same molecular formula possess different structural arrangements of atoms.
In short:
Same formula, different structure.

These compounds are called isomers.

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👉Why Does Isomerism Occur?

Because carbon atoms can bond in different ways:

• Straight chains

• Branched chains

• Different arrangements of functional groups

This results in different physical and chemical properties.

1. Structural Isomerism

It occurs when compounds have the same formula but different structural arrangements.

Example: C₄H₁₀ (Butane)

It has two isomers:

1. n–Butane (Straight chain)
   CH₃–CH₂–CH₂–CH₃

2. Iso–butane (Branched chain)
   CH₃–CH(CH₃)–CH₃

Both have the same molecular formula, but different structures and properties.

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Importance of Isomerism

• Leads to different physical properties

• Important in medicine, industry, and organic chemistry

• Shows the versatility of carbon

🌴🌴What is a Functional Group?

A functional group is a specific atom or group of atoms in an organic compound that determines its characteristic chemical properties.

In simple words:
Functional Group = The reactive part of a molecule that defines its nature.

Example:

• –OH → Alcohol

• –COOH → Carboxylic acid

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👉Why Are Functional Groups Important?

• They determine the compound's chemical behavior

• Used for naming (IUPAC nomenclature)

• Help classify organic compounds

• Responsible for reactions and properties

1. Alcohol

Group: –OH
Example: Ethanol (CH₃–CH₂–OH)

2. Aldehyde

Group: –CHO
Example: Ethanal (CH₃–CHO)

3. Carboxylic Acid

Group: –COOH
Example: Ethanoic acid (CH₃–COOH)

4. Ketone

Group: –CO– (carbonyl in the middle)
Example: Propanone (CH₃–CO–CH₃)

5. Haloalkanes

Group: –Cl, –Br, –I
Example: Chloromethane (CH₃–Cl)

6. Alkenes

Group: C=C (double bond)
Example: Ethene (C₂H₄)

7. Alkynes

Group: C≡C (triple bond)
Example: Ethyne (C₂H₂)

🌴🌴What is Esterification?

Esterification is a chemical reaction in which a carboxylic acid reacts with an alcohol to form an ester and water.

It is a type of condensation reaction where a molecule of water is eliminated.

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General Reaction:

$$\text{Carboxylic Acid} + \text{Alcohol} \xrightarrow{\text{H⁺}} \text{Ester} + H₂O$$

Example Reaction:

$$CH₃COOH + CH₃OH \xrightarrow{H₂SO₄} CH₃COOCH₃ + H₂O$$

Ethanoic acid + Methanol → Methyl ethanoate + Water

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Characteristics of Esters

1. Esters usually have a pleasant, sweet smell.

2. Most esters are liquid, volatile, and oily.

3. Reaction is acid-catalyzed (commonly H₂SO₄).

4. Widely used in industry, perfumes, and food flavorings.

🌴🌴What is Saponification?

Saponification is a chemical process in which triglycerides (fats/oils) react with a strong base to produce soap and glycerol.

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General Reaction

$$\text{Fat / Oil} + NaOH \xrightarrow{\text{Heat}} Soap + Glycerol$$

Example:

$$C₃H₅(OOCR)₃ + 3NaOH → 3RCOONa + C₃H₅(OH)₃$$

Triglyceride + Sodium Hydroxide → Sodium Soap + Glycerol

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Key Points

1. 
   Saponification occurs in a basic medium (NaOH or KOH).

2. NaOH → Solid soap, KOH → Soft/liquid soap.

3. Soap acts as a surfactant and helps remove grease and dirt.

4. Important for cleaning and hygiene.

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