Chemistry · Class 9-10 · CBSE
Carbon Compounds: Covalent Bonding and Functional Groups
Explore the versatile nature of carbon, tetravalency, catenation, covalent bonding in methane, homologous series of alkanes/alkenes/alkynes, IUPAC functional groups, and the cleaning action of soaps & detergents.
1Versatile Nature of Carbon and Covalent Bonding
Carbon has atomic number 6 with electronic configuration (2, 4). To achieve noble gas stability, it cannot gain 4 electrons (nucleus of 6 protons cannot hold 10 electrons) nor lose 4 electrons (requires enormous ionization energy). Therefore, carbon formsCovalent Bondsby sharing electrons.
The Two Unique Abilities of Carbon
| Unique Property | Scientific Definition | Chemical Significance |
|---|---|---|
| Catenation | Unique ability of carbon atoms to form strong covalent bonds with other carbon atoms | Forms long open chains, branched chains, and closed rings containing thousands of carbon atoms |
| Tetravalency | Possesses 4 valence electrons capable of bonding with 4 other univalent atoms | Can bond with H, O, N, S, Cl, Br forming millions of organic compounds with diverse properties |
Catenation
- Scientific Definition
- Unique ability of carbon atoms to form strong covalent bonds with other carbon atoms
- Chemical Significance
- Forms long open chains, branched chains, and closed rings containing thousands of carbon atoms
Tetravalency
- Scientific Definition
- Possesses 4 valence electrons capable of bonding with 4 other univalent atoms
- Chemical Significance
- Can bond with H, O, N, S, Cl, Br forming millions of organic compounds with diverse properties
2Hydrocarbons: Alkanes, Alkenes and Alkynes
Comparison of Saturated and Unsaturated Hydrocarbons
| Family Name | General Formula | Bond Type | Degree of Saturation | First Member |
|---|---|---|---|---|
| Alkanes | CₙH₂ₙ₊₂ | Single covalent bond (C—C) | Saturated (unreactive substitution reactions) | Methane (CH₄) |
| Alkenes | CₙH₂ₙ | Double covalent bond (C=C) | Unsaturated (readily undergoes addition reactions) | Ethene (C₂H₄) |
| Alkynes | CₙH₂ₙ₋₂ | Triple covalent bond (C≡C) | Unsaturated (highly reactive) | Ethyne / Acetylene (C₂H₂) |
Alkanes
- General Formula
- CₙH₂ₙ₊₂
- Bond Type
- Single covalent bond (C—C)
- Degree of Saturation
- Saturated (unreactive substitution reactions)
- First Member
- Methane (CH₄)
Alkenes
- General Formula
- CₙH₂ₙ
- Bond Type
- Double covalent bond (C=C)
- Degree of Saturation
- Unsaturated (readily undergoes addition reactions)
- First Member
- Ethene (C₂H₄)
Alkynes
- General Formula
- CₙH₂ₙ₋₂
- Bond Type
- Triple covalent bond (C≡C)
- Degree of Saturation
- Unsaturated (highly reactive)
- First Member
- Ethyne / Acetylene (C₂H₂)
Characteristics of a Homologous Series
- 1
1. Members share the same general formula and identical functional group.
- 2
2. Any two successive members differ by a -CH₂- unit.
- 3
3. Any two successive members differ by 14 unified mass units (atomic mass: C=12, 2H=2).
- 4
4. Members show similar chemical properties, while physical properties (melting point, boiling point) show a smooth gradual gradation.
3Functional Groups and Soaps/Detergents
Nomenclature of Major Organic Functional Groups
| Functional Group | Chemical Formula | IUPAC Suffix | Example Molecule |
|---|---|---|---|
| Halo (Halogen) | -Cl, -Br | Prefix: Chloro-, Bromo- | Chloromethane (CH₃Cl) |
| Alcohol | -OH | Suffix: -ol | Ethanol (CH₃CH₂OH) |
| Aldehyde | -CHO | Suffix: -al | Ethanal (CH₃CHO) |
| Ketone | -CO- (non-terminal) | Suffix: -one | Propanone / Acetone (CH₃COCH₃) |
| Carboxylic Acid | -COOH | Suffix: -oic acid | Ethanoic / Acetic acid (CH₃COOH) |
Halo (Halogen)
- Chemical Formula
- -Cl, -Br
- IUPAC Suffix
- Prefix: Chloro-, Bromo-
- Example Molecule
- Chloromethane (CH₃Cl)
Alcohol
- Chemical Formula
- -OH
- IUPAC Suffix
- Suffix: -ol
- Example Molecule
- Ethanol (CH₃CH₂OH)
Aldehyde
- Chemical Formula
- -CHO
- IUPAC Suffix
- Suffix: -al
- Example Molecule
- Ethanal (CH₃CHO)
Ketone
- Chemical Formula
- -CO- (non-terminal)
- IUPAC Suffix
- Suffix: -one
- Example Molecule
- Propanone / Acetone (CH₃COCH₃)
Carboxylic Acid
- Chemical Formula
- -COOH
- IUPAC Suffix
- Suffix: -oic acid
- Example Molecule
- Ethanoic / Acetic acid (CH₃COOH)
Micelle Formation and Cleansing Action of Soap
- 1
1. Soap molecule is a sodium/potassium salt of long-chain fatty acid: ionic hydrophilic head (COO⁻Na⁺) + hydrophobic hydrocarbon tail.
- 2
2. Hydrophobic tail dissolves in oily dirt/grease at fabric center, while ionic head faces outwards towards surrounding water.
- 3
3. Molecules assemble into a spherical cluster called a Micelle, trapping the oil droplet in the core.
- 4
4. Agitation pulls the micelle into water as an emulsion, washing away grease.
4Exam Corner: Tips, Mistakes & Board Questions
High-Yield Board Revision Takeaways
- Soaps form insoluble curdy white scum with hard water due to Ca²⁺ and Mg²⁺ ions, wasting soap. Synthetic detergents work effectively even in hard water.
- Esterification: Reaction of an alcohol with a carboxylic acid in presence of concentrated H₂SO₄ produces sweet-smelling Esters: CH₃COOH + C₂H₅OH → CH₃COOC₂H₅ + H₂O.
- Saponification: Alkaline hydrolysis of esters using NaOH regenerates soap and alcohol.
Exam question · CBSE Class 10 Board
- A.C₂H₄ (Ethene)
- B.C₃H₆ (Propene)
- C.C₄H₈ (Butene)
- D.CH₂ (Methene)
- The general formula for alkenes is CₙH₂ₙ with n ≥ 2 (a double bond requires at least two carbon atoms).
- First member (n = 2): Ethene (C₂H₄).
- Second member (n = 3): Propene (C₃H₆).
- Correct answer is option B (Propene).
Answer: B. C₃H₆ (Propene)
Remember
- Carbon achieves stable electronic configuration solely throughCovalent Sharing.
- CatenationandTetravalencyenable carbon to form millions of organic compounds.
- Homologous series members differ by-CH₂-and14 unified mass units.
- Soap cleans viaMicelle Formation; detergents work even inhard water.
Check yourself
Question 1
Vegetable oils are converted into solid vegetable ghee (vanaspati) by which chemical process?