Railway Science (Chemistry-Organic Chemistry) (Part-II)

Homologous series - series of hydrocarbons, having same functional group due to which they have the same chemical properties. Example - Alkanes, Alkenes and Alkynes.
Unsaturated hydrocarbons are those compounds in which carbon atoms are linked together by double or triple bonds.
Example - Alkenes has one or more carbon double bonds. General Formula - (CₙH₂ₙ) and Alkynes has one or more carbon triple bonds. General Formula - (CₙH₂ₙ₋₂).
Saturated hydrocarbons are those compounds in which carbon atoms are linked together by single bonds. Example - Alkanes (CₙH₂ₙ₊₂).

In IUPAC, nomenclature prefixes depend upon the number of carbon atoms present in a molecule of hydrocarbon. These are: meth- (1), eth- (2), prop- (3), but-(4), pent- (5), hex- (6), hept- (7), oct- (8), non- (9), dec- (10), undec- (11), dodec- (12), tridec- (13), tetradec- (14), and icos- (20).

Saturated hydrocarbons are molecules with only single bonds. Alkanes are saturated hydrocarbons. Each single bond in a saturated hydrocarbon is a covalent bond.
Unsaturated hydrocarbons are compounds that contain at least a single double or triple bond in their structure. Example : C₂H₂ (ethyne), C₂H₄ (ethylene).

Methylene - All members of a homologous series differ by a CH₂ group known as the methylene group. Example: methane (CH₄), ethane (C₂H₆), and propane (C₃H₈). Methyl Group - CH₃ , Ethyl Group - CH₃CH₂ , Ethylene Group - C₂H₄ .

Propanone (Acetone) is a colorless liquid used in the production of plastics and other industrial products. Compound and Functional Group: Alkenes (>C=C<), Alcohols (-OH), Aldehydes (-CHO), Ketones (>C=O), Ethers (-R-O-R-), Carboxylic acids (-COOH), Esters (RCOOR).

Ethanol can be dehydrated to give ethene by heating it with an excess of concentrated sulphuric acid at about 170°C. Chemical reaction : CH₃CH₂OH + conc.H₂SO₄ + heat → CH₂=CH₂ + H₂O.

A colorless or light yellow liquid at room temperature. It has a sweet odor (aromatic) and is highly flammable. Structure: Six Carbon - Hydrogen ring consist of three double bonds.
Uses - To make plastics, Resins, Synthetic fibers, Rubber lubricants, Dyes, Detergents, Drugs and Pesticides. Cyclohexane (C₆H₁₂). Naphthalene (C₁₀H₈). Cycloheptane (C₇H₁₄).

Alkanes are saturated open chain hydrocarbons containing carbon - carbon single bonds. Alkenes are unsaturated hydrocarbons containing at least one double bond. Alkynes are also unsaturated hydrocarbons. They contain at least one triple bond between two carbon atoms.

Alkynes are the hydrocarbons containing a triple bond between two carbon atoms. Example - Propyne (C₃H₄), Ethyne (C₂H₂), 1-Butyne (C₄H₆). Other Hydrocarbons formula - CₙH₂ₙ₊₂ (Alkanes),CₙH₂ₙ (Alkenes).
Uses : Alkynes - For making polymers, Organic Solvents, Artificially ripe fruits. Alkanes - Constituent of Gasoline, Lubricant oils. Alkenes - Synthesis of Alcohol, Plastics, Lacquers, Detergents.

Propane is a three-carbon alkane gas. Other chemical formulas: Methane (CH₄), Butane (𝐶₄𝐻₁₀), Ethane (C₂H₆), Hexane (C₆H₁₄).