Carbon and Its Compounds | Chemistry | Class 10th

Carbon is present on this planet from years in various forms like diamond, coal and graphite.

Occurrence of Carbon:

About 20% of human body is composed of carbon.

It is the 15th most abundant element on Earth and the 4th most abundant element on this universe.

Carbon occurs in both free and combined state in the nature.

Free State	Solid	Gas	Liquid
Diamond Graphite Coal	Wood	Petroleum Natural gas	Soluble Carbonates and Bicarbonates (in water)

Atomic No. : 6 | Atomic Mass : 12 | Electronic Configuration: 2,4 | Valency: 4

Allotropes of Carbon

The phenomenon in which an element exists in various physical states though with similar chemical properties is known as allotropy.

There are three existing Carbon allotropes, following are:

Diamond: One atom of carbon is bonded to four other atoms of the same constructing a 3D structure. It is the hardest substance present on this globe. It is also an insulator.

Graphite: One atom of carbon is bonded to three other atoms of the same. It is a good conductor of electricity.

Fullerene: 60 atoms of carbon combine to form spherical molecules. It is dark solid at room temperature.

Uses of Carbon

Sugar, glucose, proteins, etc. are composed of carbon.
Diamond, an allotrope of carbon is used in jewelries and for production and manufacture in industries.
Graphite is used as lead in pencils and for production of steel.
Carbon-14 (C-14) is used for carbon-dating to estimate the life of substances years old.

Bonding in Carbon Atoms: Covalent Bonds

Shells Atomic Number	K shell	L shell
Carbon (6)	2	4

Every element needs to fulfil the last shell so as to attain the nearest inert gas configuration. It is difficult for carbon to loose or gain 4 electrons to fulfil this requirement as it becomes difficult for the nucleus to either hold or loose the electrons.

To overcome this problem carbon shares its 4 valence electrons with others to form bonds. Such bonds formed by sharing the valence electrons are known as covalent bonds.

Types of Covalent Bond

Single covalent bond– Between two atoms, single pair of electrons are shared.

Double covalent bond– Between two atoms, two pair of electrons are shared.

Triple covalent bonds– Between two atoms, three pair of electrons are shared.

 Nature of Carbon: Versatility of carbon

Carbon has a versatile nature because it can form huge number of compounds.

These two properties make Carbon a unique atom in this world:

• Catenation: The unique ability of carbon to form bonds with other carbon atoms, these may be branched chains, chains in rings or long chains is called catenation.
• Tetravalency: Carbon has a valency of 4 electrons and can form bonds with other carbon atoms or other mono-valent atoms. This property of carbon is known as tetravalency.

HYDROCARBONS: Compounds formed by the sharing of electrons between carbon and hydrogen atoms.

i) Saturated hydrocarbons: Compounds of carbon formed using single bond with other carbon atoms. Example: Ethane

ii) Unsaturated hydrocarbons: Compounds of carbon formed using double or triple bond with other carbon atoms. Example: Ethene

Nomenclature of organic compounds

Structural Isomerism: Compounds having same molecular formula, but different structures are termed as structural isomers. For example:1-Bromobutane, 1-Bromo-2-Metylpropane,2-Bromo-2-methylpropane. these three have the same molecular formula but different structures.

Homologous series: Series of organic compounds having

• the same functional group and
• chemical properties and
• the successive members differ by a CH2​ unit.

Necessity of Nomenclature

For the infinite number of compounds, it is difficult to recognize each compound by its common name.

To tackle this situation, the IUPAC(International Union of Pure and Applied Chemistry) has suggested some rules for naming these compounds. These are as follows:

• Identify the root word and number of carbon atoms in the parent chain.
• Identify the functional group. An atom or a group of atoms present in a molecule largely specifying its chemical properties are known as Functional Groups.

If a functional group is there in a carbon chain, it is indicated in name of the compound as a prefix or suffix while naming.

• If functional group is to be used as a suffix and suffix starts with a vowel, then the final ‘e’ should be omitted. For example, propane+ ‘one’ = propanone. The final ‘e’ in ‘propane’ was omitted.
• If the chain is unsaturated, final ‘ane’ is supposed to be replaced with ‘ene’ or ‘yne’. For example, propene and propyne.

Chemical Properties of Carbon Compounds

Combustion Reaction

1.  Carbon, in all its allotropic forms, burns in oxygen to produce carbon dioxide along with the release of heat and light.

C+O₂​→CO₂​+Heat + light

Oxidation Reaction

1. Carbon compounds can be oxidised on combustion easily.
2. In addition  to this complete oxidation, we have reactions in which alcohols are converted to carboxylic acids.

CH₃​CH₂​OH  +  (Alkaline KMnO₄​/Acidified K₂​Cr₂​O₇​ + heat) –> ​CH₃​COOH

Oxidising Agent

• The substances which are capable of adding oxygen to others are known as Oxidising Agents
• Example-

1. KMnO4​-Potassium permanganate
2. K2​Cr2​O7​-Potassium dichromate

Addition Reaction

• The unsaturated hydrocarbons add hydrogen in presence of catalysts such as palladium or nickel to give saturated hydrocarbons as a result.
• Catalysts: Catalysts are substances that cause a reaction to occur at a faster rate without the reaction itself being affected.

Substitution Reaction

• The Saturated hydrocarbons are considered to be highly unreactive and are inert in presence of most reagents.
• However, in presence of sunlight, chlorine is added to hydrocarbons in a very fast reaction. Chlorine can replace the hydrogen atoms one by one.

CH₄​+Cl₂ (​in the presence of sunlight)  –> ​CH₃​Cl + HCl

Ethanol

Introduction to Ethanol

Ethanol is considered as one of the most important compounds in organic world.

Ethanol, also known as ethyl alcohol, exhibits a unique property of being a liquid at room temperature. With a molecular formula of C2H5OH, it consists of two carbon atoms, six hydrogen atoms, and one oxygen atom. This clear, colorless liquid possesses a characteristic odor and is highly flammable.

Ethanol finds extensive use in various industries, such as pharmaceuticals, cosmetics, solvents, and fuel production. Its liquid state at ambient conditions enables its easy handling and application in a wide range of processes and products.

Preparation of Ethanol

Ethanol is generally prepared by fermentation of molasses.

The processes are:

i) Dilution: Molasses is first diluted with water to lower the concentration of sugar to about 8 to 10 percent.

ii) Addition of ammonium salts: If the nitrogen content of the molasses is poor, it may be secured by the addition of ammonium sulphate (or) ammonium phosphate.

iii) Addition of Yeast : Yeast is added to the solution and the mixture is kept at 303K for a few days. During this period the enzymes invertase and bring about the conversion of sucrose into ethanol.

iv) Distillation of wash :

• The fermented liquid contains 15 to 18 percent alcohol and the rest of the water. This liquid is now sent for fractional distillation.
• The main fraction drawn is an aqueous solution of ethanol which contains 95.5$\%$ ethanol and 4.5$\%$ of water. This is known as rectified spirit.
• This mixture is then heated under reflux over quicklime for about 5 hours and then allowed to sit for 12 hours.

On distillation of this mixture, pure alcohol is obtained. This is known as absolute alcohol.

Chemical properties of ethanol

• Reaction with sodium:

2Na+2CH3​CH2​OH→2CH3​CH2​ONa ⁺+H2

Alcohol reacts with sodium to produce sodium ethoxide and evolution of hydrogen gas.

• Reaction with concentrated Sulphuric acid:

C0H3​−CH2​−OH +(HotConc.H2​SO4​​) –> CH2​=CH2​+H2​O

Ethanol heated with conc. H2SO4 produces ethene.

• Oxidation:

CH3​−CH2​−OH+K2​Cr2​O7​→CH3​−CHO→CH3​−COOH
Ethanol on oxidizing with potassium dichromate forms ethanol and further ethanoic acids.

• Esterification:

CH3​CH2​OH+CH3​COOH→CH3​COOC2​H5​+H2​O

It is the reaction of ethanol with carboxylic acids.

Uses of Ethanol:

i) Used in manufacture of chemicals like cough syrups ,tincture of iodine and so on.

ii) Used in manufacture of organic compounds such as acetaldehyde , chloroform, etc.

iii) Used as preservative for biological specimen.

Ethanoic acid

Introduction to Ethanoic acid:

• It is commonly called acetic acid and belongs to group of carboxylic acids.
• 5-8% solution of acetic acid in water is known as vinegar.

Physical properties of Ethanoic Acid:

• Ethanoic acid is a colourless and corrosive liquid with a pungent smell.
• Melting point of pure ethanoic acid is 290 K and so it often freezes during winter in cold climates.
• Ethanoic acid freezes during winter and is also named as glacial acetic acid.
• It is miscible in water,ether and ethyl alcohol.

Chemical Properties of Ethanoic acid

• Esterification reaction:

Reaction of ethanol with ethanoic acid is known as esterification reaction.

CH3​CH2​OH+CH3​COOH→CH3​COOC2​H5​+H2​O

• Reaction with a base:

Ethanoic acid reacts with base like sodium hydroxide to give a salt (sodium ethanoate) and water

NaOH+CH3​COOH→CH3​COONa+H2​O

Reaction with Carbonates and Hydrogen Carbonates

Ethanoic acid reacts to carbonates and hydrogen carbonates to produce salt, carbon dioxide and water. The salt produced is commonly known as sodium acetate.
2CH3​COOH+Na2​CO3​→2CH3​COONa+H2​O+CO2​CH3​COOH+NaHCO3​→CH3​COONa+H2​O+CO2

Uses of Ethanoic acid:

• Used to preserve food items and manufacture of certain fibres.
• Used for coagulating latex to manufacture rubber from it.
• Used as an important reagent in laboratory.
• Used in the preparation of perfumes.

Soaps and Detergents

Soaps:

• Soap is a sodium or potassium salt of long-chain carboxylic acid.
• The ionic end dissolves in water and the carbon chain dissolves in oil.
• Used as a cleansing agent to remove dirt and oil from clothes.

Preparation of Soap:

• Generally, soaps are prepared by heating animal fat or oil with alkalies such as sodium hydroxide or potassium hydroxide.
• It is known as saponification reaction.

$\text{Fat or oil}+\text{Alkali}\to \text{Soap}+\text{Glycerol}$

Structure of Soap:

• Soap molecule has two ends with different properties. They are hydrophilic end and hydrophobic end.
• Hydrophilic end dissolves in water.
• Hydrophobic which dissolves in oil.

Micelle Formation:

• The cleaning process is characterized by micelle formation.
• The ionic part of soap dissolves in water and other end dissolve in the oil.

Most dirt is oily in nature and the hydrophobic end attaches itself with dirt, while the ionic end is surrounded by molecules of water. This results in formation of a radial structure called micelles.

Scum:

In hard water, soap doesn’t give lather. Hard water contains calcium and magnesium salts, which combine with soap molecules to produce insoluble precipitates known as scum.

Detergents:

• Detergents generally have the same properties as soaps but they are comparitively more effective in hard water
• Detergents are generally sodium salts of sulphonic acids or ammonium salts with chlorides or bromides ions, etc.
• The charged ends of these compounds do not form insoluble precipitates with the calcium and magnesium ions in hard water. Therefore, they remain effective in hard water.
• Detergents are usually used to produce shampoos and products for cleaning clothes.

Carbon and Its Compounds