Railway Science (Chemistry-Organic Chemistry)

Homologous series is a series of compounds with similar chemical properties and the same functional group. The general formula of the homologous series of alcohols is CₙH₂ₙ ₊₁ OH. So,the next higher homologue of CH₃OH (methanol) is C₂H₅OH (ethanol).

The IUPAC name of CH₂= CH₂ is Ethene. It is an alkene with the molecular formula C₂H₄. It is a colourless, flammable gas having a sweet taste and odour. It has less density than air hence it is lighter than air. Uses -In the manufacture of polymers like polyethene and polyvinyl chloride (PVC), make ethyle glycol, As a general anaesthetic, etc.

Unsaturated compounds. Hydrocarbons - The organic compounds that consist of Carbon and Hydrogen atoms. Hydrocarbons are two types. Unsaturated hydrocarbons - compounds that have double or triple covalent bonds between adjacent carbon atoms.
Saturated hydrocarbons - compounds that contain only single bonds between carbon atoms. Inorganic compounds - the organic compounds do not contain a carbon-to-carbon or carbon-to-hydrogen bond.

(Butene) belongs to the group Alkene (CₙH₂ₙ). Homologous series is a group of chemical compounds with the same functional group. Alkanes {(saturated hydrocarbons) (CₙH₂ₙ₊₂)} - Hydrocarbons with only carbon-to-carbon single bonds (C–C) and existing as a continuous chain of carbon atoms also bonded to hydrogen atoms. Example - Methane (CH₄), Ethane (C₂H₆), Propane (C₃H₈), Butane (C₄H₁₀).

Halo compounds are chemicals in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms (Group 17 - fluorine, chlorine, bromine, iodine, and astatine).
Esters, in which at least one –OH hydroxyl group is replaced by an –O– alkyl (alkoxy). Ketone {R−C−R functional group', formula (CH₃)₂CO}.Carboxylic ( R−COOH or R−CO₂H).

(Cyclohexane) is non-polar. Cyclohexane is a colourless, flammable liquid with a distinctive detergent-like odor. C₇H₁₆ (Heptane or n-heptane). C₅H₁₂ (Pentane). C₄H₁₀ (Butane or n-butane).

Homologous series: sequence of compounds with the same functional group and similar chemical properties. Examples - alkane, alkene. As the molecular mass increases in any homologous series, a gradation in physical properties is seen.
This is because the melting and boiling points increase with increasing molecular mass. Other physical properties such as solubility in a particular solvent also show a similar gradation. But the chemical properties, which are determined solely by the functional group, remain similar in a homologous series.

When ethanol (C₂H₅OH) reacts with acidified potassium dichromate (K₂Cr₂O₇) solution. It undergoes oxidation to form ethanoic acid (CH₃COOH) along with other by-products. Reaction: C₂H₅OH + 2 [Cr₂O₇ ]²⁻ + 8H+ → 2CH₃COOH + 2[Cr₃⁺] + 7H₂O. It is a strong oxidizing agent. Ethene (C₂H₄). Ethyl ethanoate (C₄H₈O₂).

Homologous series - Group of chemical compounds with the same functional group and similar chemical properties, differ by molecular formula of CH₂ . Alkenes - Class of unsaturated hydrocarbons (containing only carbon and hydrogen) compounds with at least one carbon-to-carbon double bond. General formula - CₙH₂ₙ.
Properties - Exist in all three states (solid, liquid & gaseous), Insoluble in water due to weak van der waal forces, boiling points depend on their molecular structure, Polarity of alkene depends on their functional group. Examples - Ethene(C₂H₄), Propene (C₃H₆) etc.

Ammonium cyanate [NH4]⁺ [OCN]⁻ : Neither acidic nor alkaline, discovered in 1828. Ammonium cyanate is transformed into urea during the Wohler Synthesis: NH₄(NCO) → NH₃ + HNCO ⇌ (NH₂)₂CO {Urea}.
Uses - fertilizer and feed supplement, as well as a starting material for the manufacture of plastics and drugs. Father of organic chemistry - Friedrich Wohler. Carbon monoxide (CO), Ammonia (NH₃).