MP Board · Class 10 · Science · Carbon and its CompoundsExplain the chemical properties of carbon compounds with respect to (i) Combustion, (ii) Oxidation, (iii) Addition reaction, and (iv) Substitution reaction. Support each with a balanced chemical equation.

Chemical Properties of Carbon Compounds

\nCarbon compounds are fuels and form the basis of organic chemistry. Their major chemical reactions include:

(i) Combustion (दहन)\nCarbon and its compounds burn in the presence of oxygen to release heat and light, carbon dioxide, and water. Most carbon compounds release a large amount of heat and light on burning.

• Saturated hydrocarbons generally burn with a clean blue flame in sufficient oxygen supply. In limited supply, they produce a sooty flame.
• Unsaturated hydrocarbons burn with a yellow, sooty flame due to incomplete combustion because of the higher carbon-to-hydrogen ratio.
• Equation: $$CH_3CH_2OH + 3O_2 \xrightarrow{\text{Heat}} 2CO_2 + 3H_2O + \text{Heat and Light}$$ $$\text{or } C + O_2 \rightarrow CO_2 + \text{Heat and Light}$$

(ii) Oxidation (ऑक्सीकरण)\nCarbon compounds can be easily oxidized on combustion. Alcohols can be converted to carboxylic acids by oxidizing them using alkaline potassium permanganate ($KMnO_4$) or acidified potassium dichromate ($K_2Cr_2O_7$). These oxidizing agents add oxygen to the starting material.

• Equation: $$CH_3CH_2OH \xrightarrow{\text{Alkaline } KMnO_4 + \text{Heat}} CH_3COOH$$ $$( \text{Ethanol} \xrightarrow{\text{Oxidation}} \text{Ethanoic Acid} )$$

(iii) Addition Reaction (संकलन अभिक्रिया)\nUnsaturated hydrocarbons (alkenes and alkynes) add hydrogen in the presence of catalysts such as nickel ($Ni$) or palladium ($Pd$) to give saturated hydrocarbons. This process is called hydrogenation and is extensively used in industry for converting vegetable oils (unsaturated fats) into vegetable ghee (saturated fats).

• Equation: $$R_2C = CR_2 + H_2 \xrightarrow{Ni/Pd \text{ catalyst}} R_2CH - CHR_2$$ $$\text{Example: } CH_2 = CH_2 + H_2 \xrightarrow{Ni \text{ catalyst}, 573K} CH_3 - CH_3 \text{ (Ethane)}$$

(iv) Substitution Reaction (प्रतिस्थापन अभिक्रिया)\nSaturated hydrocarbons are unreactive in most cases because all valence electrons of carbon are tightly bound in single covalent bonds. However, in the presence of sunlight, chlorine can replace hydrogen atoms one by one in a saturated hydrocarbon. This is known as a substitution reaction.

• Equation: $$CH_4 + Cl_2 \xrightarrow{\text{Sunlight}} CH_3Cl + HCl$$ $$( \text{Methane} + \text{Chlorine} \xrightarrow{\text{Sunlight}} \text{Chloromethane} + \text{Hydrogen Chloride} $$