Ch-4: Carbon and its Compounds 💎
1. Introduction (परिचय)
- Carbon is a versatile element that forms the basis of all living structures.
- Earth’s Crust has 0.02% carbon (minerals); Atmosphere has 0.03% $CO_2$.
- कार्बन एक सर्वतोमुखी तत्व है जो सभी जीवित संरचनाओं का आधार है।
2. Covalent Bonding (सहसंयोजक बंधन)
- Carbon (Atomic No. 6) has configuration 2, 4.
- It needs 4 more electrons to attain noble gas configuration.
- Why not $C^{4+}$ or $C^{4-}$?
(i) $C^{4-}$: Difficult for 6 protons to hold 10 electrons.
(ii) $C^{4+}$: Requires huge energy to remove 4 electrons. - Solution: Sharing Electrons (Covalent Bond).
Electron Dot Structures (लुईस संरचना)
Properties of Covalent Compounds:
1. Low Melting & Boiling Points (Weak intermolecular forces).
2. Poor conductors of electricity (No ions/charged particles).
1. Low Melting & Boiling Points (Weak intermolecular forces).
2. Poor conductors of electricity (No ions/charged particles).
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3. Allotropes of Carbon (कार्बन के अपररूप)
- Same chemical properties, different physical structures.
- Diamond: Rigid 3D structure. Each C bonded to 4 others. Hardest substance.
- Graphite: Hexagonal arrays in layers. Each C bonded to 3 others. Good Conductor of electricity!
- Fullerenes: C-60 Buckminsterfullerene (Football shape).
4. Versatile Nature of Carbon (सर्वतोमुखी प्रकृति)
- Catenation (श्रृंखलन): Unique ability to form long chains/rings with other C-atoms. Strong & Stable bonds.
- Tetravalency: Valency of 4 allows bonding with Oxygen, Hydrogen, Nitrogen, Sulphur, etc.
- कार्बन में ‘श्रृंखलन’ का गुण होता है जिससे यह लंबी श्रृंखलाएँ बना सकता है।
Vital Force Theory: Initially thought organic compounds only made in living systems. Friedrich Wöhler disproved this by making Urea in 1828.
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5. Saturated & Unsaturated Compounds
- Saturated (संतृप्त): Only Single bonds between C-atoms. (Alkanes). Less reactive.
- Unsaturated (असंतृप्त): Double or Triple bonds. (Alkenes/Alkynes). More reactive.
Alkanes: $C_nH_{2n+2}$ | Alkenes: $C_nH_{2n}$ | Alkynes: $C_nH_{2n-2}$
6. Chains, Branches & Rings
- Carbon atoms can form straight chains, branched chains, or cyclic rings.
- Structural Isomers: Same molecular formula, different structures.
Ex: Butane ($C_4H_{10}$) has 2 isomers (Straight & Iso-butane).
Cyclohexane ($C_6H_{12}$) vs Benzene ($C_6H_6$)
7. Functional Groups (प्रकार्यात्मक समूह)
| Group | Formula |
|---|---|
| Halo (Cl/Br) | -Cl, -Br |
| Alcohol | -OH (Suffix: -ol) |
| Aldehyde | -CHO (Suffix: -al) |
| Ketone | >C=O (Suffix: -one) |
| Carboxylic Acid | -COOH (Suffix: -oic acid) |
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8. Homologous Series (समजातीय श्रेणी)
- Series of compounds where the same functional group substitutes for hydrogen.
- Successive members differ by $-CH_2-$ unit.
- Mass difference = 14 u.
- Properties: Chemical properties are similar; Physical properties (MP/BP) show a gradation as mass increases.
9. Nomenclature (नामकरण)
IUPAC पद्धति के अनुसार नामकरण के चरण:
- 1. Count C-atoms: 1 (Meth), 2 (Eth), 3 (Prop), 4 (But)…
- 2. Identify Functional Group suffix/prefix.
- 3. Modify “ane” $\to$ “ol”, “al”, “oic acid” etc. (Delete ‘e’ if suffix starts with vowel).
Propanone Example:
Propane – ‘e’ + ‘one’ = Propanone
Propane – ‘e’ + ‘one’ = Propanone
10. Chemical Properties (रासायनिक गुणधर्म)
- Combustion: All carbon compounds burn in $O_2$ to give $CO_2$, heat, and light.
Saturated $\to$ Clean blue flame. Unsaturated $\to$ Sooty yellow flame. - Oxidation: Alcohol $\xrightarrow{alk. KMnO_4}$ Carboxylic Acid.
- Addition Reaction: Hydrogenation of vegetable oils (Unsaturated $\to$ Saturated) using Nickel catalyst. Oils are healthier than fats.
- Substitution: In Alkanes, $Cl$ replaces $H$ in presence of Sunlight.
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11. Ethanol ($C_2H_5OH$)
- Liquid at room temp. Active ingredient of alcoholic drinks.
- Reaction with Na $\to$ Sodium Ethoxide + $H_2 \uparrow$
- Dehydration: Ethanol $\xrightarrow{conc. H_2SO_4}$ Ethene.
- Denatured Alcohol: Ethanol mixed with poisonous methanol + blue dye to prevent drinking.
12. Ethanoic Acid ($CH_3COOH$)
- Commonly called Acetic Acid. 5-8% solution = Vinegar.
- Esterification: Acid + Alcohol $\xrightarrow{Acid}$ Ester (Sweet smelling).
- Saponification: Ester + NaOH $\to$ Alcohol + Soap.
13. Soaps and Detergents
- Soap: Na/K salts of long chain carboxylic acids.
- Structure: Hydrophilic head (Ionic) & Hydrophobic tail (Hydrocarbon).
- Micelle Formation: Clusters where tails point inside (towards oil) and heads point outside.
Micelle & Cleaning Action
Detergents are effective in Hard Water (no scum).
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