Organic Chemistry

Definition: Branch of chemistry dealing with the study of hydrocarbons and their derivatives.

Vital Force Theory: Proposed by Berzelius. Stated organic compounds could only be synthesized by living organisms. Rejected by Wohler (1828) who synthesized Urea (Organic) from Ammonium Cyanate (Inorganic).

Formulae Types:

• Molecular Formula: Actual number of atoms (e.g., C₄H₁₀).
• Structural Formula: Exact arrangement of atoms (e.g., n-Butane vs Iso-butane).
• Condensed Formula: Groups of atoms joined to carbon (e.g., CH₃CH₂CH₂CH₃).
• Dot and Cross: Electronic sharing.

Open Chain (Acyclic):

• Straight Chain: Carbon atoms in straight line (e.g., n-Butane).
• Branched Chain: Branch along straight chain (e.g., Iso-butane).

Closed Chain (Cyclic):

• Homocyclic (Carbocyclic): Ring of carbon atoms only.
  • Aromatic: Contain benzene ring (e.g., Benzene).
  • Alicyclic: No benzene ring (e.g., Cyclobutane).
• Heterocyclic: Ring containing atoms other than carbon (e.g., Thiophene, Pyridine).

Reasons for Diversity: Catenation (Self-linking of Carbon), Isomerism, Strength of Covalent bonds, Multiple bonding.

Sources:

• Coal: Formed by carbonization of wood. Types: Peat (60% C), Lignite (70% C), Bituminous (80% C), Anthracite (90% C). Destructive distillation yields Coal Gas, Amonical Liqour, Coal Tar, Coke.
• Petroleum: Fractional distillation yields Gasoline, Kerosene, Diesel etc.
• Natural Gas: 85% Methane. Fuel.
• Plants/Animals: Proteins, Fats, Vitamins.

Definition: An atom or group of atoms or presence of double/triple bond that determines the characteristic properties of an organic compound.

Types:

• Alcoholic Group (-OH): General formula ROH. Test: Sodium metal (H₂ gas), Ester formation (Fruity smell).
• Ether Linkage (C-O-C): General formula R-O-R'.
• Aldehydic Group (-CHO): General formula RCHO. Test: Sodium bisulphite (White ppt), Fehling's Solution (Red ppt).
• Ketonic Group (>C=O): General formula R-CO-R'. Test: Phenyl Hydrazine (Orange-red ppt), Sodium Nitroprusside (Red color), No reaction with Fehling's.
• Carboxyl Group (-COOH): General formula RCOOH. Test: Litmus (Red), NaHCO₃ (CO₂ gas/Effervescence).
• Ester Group (-COOR): General formula RCOOR'. Fruity smell.
• Amine Group (-NH2): Derivative of Ammonia. General formula RNH₂. Test: Carbyl amine test (Foul smell).
• Alkyl Halide (R-X): X = F, Cl, Br, I.
• Alkenes (>C=C<): Double bond. Test: Bromine water (Decolorizes), Baeyer's Test (Pink KMnO₄ decolorizes).
• Alkynes (-C≡C-): Triple bond.

Homologous Series: Group of compounds with similar chemical properties and same general formula. Successive members differ by -CH₂- unit and 14 amu mass. Physical properties change regularly.

Alkyl Radicals: Formed by removing one Hydrogen from Alkane. Formula C_nH_2n+1. Represented by 'R'. (e.g., Methane -> Methyl, Propane -> n-Propyl, Isopropyl).