Forms of Carbon
* Carbon is the sixth most abundant element in the universe.
* In the free state, carbon occurs as diamond, graphite, fullerene and coal.
* In the combined state, carbon can be in the form of carbon dioxide, carbon monoxide, petroleum, vegetable oils, lime stone, magnetite, dolomite and calamine.
* Allotropy is the property of an element that allows it to exist in more than one form.
* Diamond, graphite and fullerenes are crystalline allotropes.
* Coal, coke, wood charcoal, lampblack, gas carbon, petroleum coke and sugar charcoal
* are the amorphous allotropes of carbon.
* A diamond is a rigid, compact, three dimensional structure and is hard to break. It is a bad conductor of heat and electricity.
* Graphite contains carbon atoms in hexagonal rings. It has a two dimensional layer structure.
* Graphite is smooth and slippery.
* Graphite is a good conductor of heat and electricity.
* A fullerene molecule consists of 60 carbon atoms arranged in pentagons and hexagons.
* Fullerenes are also called Buckminsterfullerene’s.
Bonding in Carbon
* Covalent compounds have low melting and boiling points.
* Carbon achieves stability by sharing electrons.
* Bond formation is represented using Lewis Structures.
* A shared electron pair is known as bond pair.
* A single covalent bond is formed by sharing a pair of electrons.
* A double covalent bond is formed by sharing two pairs of electrons.
* A triple covalent bond is formed by sharing three pairs of electrons.
* In a methane molecule, the carbon atom shares electrons with four hydrogen atoms.
Hydrocarbons
* Carbon exists in large number of organic compounds.
* Carbon shares its four electrons with other atoms forming four covalent bonds. This property is known as tetra valency.
* Carbon atoms are capable of forming multiple bonds with other carbon compounds.
* The phenomenon of self linkage among identical atoms to form long chains is known as catenation.
* The members of a homologous series are represented by a general formula.
* The difference between any two consecutive members in a homologous series by a CH2 group
* The members of a homologous series are prepared by similar methods.
* There is a gradation in the physical properties of the members of a homologous series.
Nomenclature of Hydrocarbons
* Functional groups are specific atoms, ions or groups of atoms that have consistent properties.
* Heteroatoms have characteristic properties that are independent of the length and nature of the carbon chain.
* Heteroatoms are called functional groups.
The name of an organic compound consists of a root word, a suffix and a prefix.
* The root word indicates the number of carbon atoms in the basic skeleton.
* The suffix indicates the nature of a functional group in the molecule.
* The prefix comes before the root word.
Chemical Properties of Carbon Compounds
* Petroleum is formed from the preserved remains of organisms at the bottom of seas.
* Coal is formed when the remains of dead plants and animals get impacted by heat and pressure.
* The reaction of carbon with oxygen to produce heat, light, carbon dioxide and water is called combustion.
* Incomplete combustion of saturated compounds produces a sooty flame.
* Alcohol gets oxidised to form carboxylic acid and water.
* Potassium dichromate and potassium permanganate are oxidising agents.
* A chemical reaction in which two substances combine and form a third substance is called addition.
* During hydrogenation, hydrogen is added to unsaturated hydrocarbons to produce saturated hydrocarbons.
* Nickel is used as a catalyst in hydrogenation.
* Hydrogenation is used in the food industry.
* A reaction in which an atom or group of atoms replaces another atom or group of atoms in a saturated hydrocarbon molecule or ion is known as substitution.
Important Carbon Compounds
* Ethanol is prepared by the fermentation of cane sugar or molasses.
Properties of Ethanol:
* Ethanol readily reacts with sodium metal to give sodium ethoxide and hydrogen gas.
* Ethanol, on heating to a temperature of 443 degrees Kelvin with excess concentrated sulphuric acid, gives ethene.
Uses of Ethanol:
* Ethanol is used in the manufacture of alcoholic beverages, pharmaceutical products and anti freezing agents for automobiles.
* Ethanol acid is colourless pungent odoured liquid which is miscible with water, ether and ethyl alcohol.
Properties of Ethanoic acid:
* Reacts with carbonates and bicarbonates to give sodium acetate and carbon dioxide.
* Reacts with bases like sodium hydroxide to give sodium acetate and water.
* Reacts with ethanol in the presence of concentrated sulphuric acid to undergo an esterification reaction.
Saponification is getting back ethanol and ethanoic acid form an ethyl acetate.
Ethanoic acid is used:
* As a preservative of food items.
* In the manufacture of artificial fibres.
* For the coagulation of latex.
Soaps and Detergents
* Soaps and detergents are sodium salts of organic acids.
* Soapiness comes from the sodium salts of stearic acid, oleic acid and palmitic acid.
* A soap molecule has an organic tail that dissolves in grease and an ionic head that dissolves in water.
* The positively charged heads of the soap molecules form a closed structure called a micelle. Dirt is pulled and absorbed into the interior of the micelle. The micelle is then removed by water in the cleaning process.
* A soap solution is a colloid.
* Detergents and soaps have almost the same properties.
* Detergents are more effective than soaps in hard water.