Fundamental Principles of Organic Chemistry
According to ‘Vital Force Theory’ organic compounds were believed to be the compounds prepared by living organisms.
But later on , in 1828, Friedrick Wholer ( a German chemist), prepared Urea (an organic compound) in laboratory by heating Ammonium cyanate.
It proved the vital force theory to be wrong.
Organic compounds are hydrocarbons & their derivatives .
Now-a-days organic compounds are defined as “Compounds of carbon with few exceptions are called organic compounds”. These exceptions are CO, CO2, CS2, Carbonates (CO32-), Bicarbonates (HCO3–), Cyanides (CN–), Cyanates (CNO –), Metal Carbides C4-) etc.
Organic Chemistry is defined as “The study of structure, properties, composition, reactions and preparations of hydrocarbons and their derivatives.”
- All other organic compounds are believed to be derivatives of hydrocarbons.
Characteristics of Organic Compounds:
Organic compounds have following common characteristic properties:
- They must contain Carbon.
- They have low melting and boiling points.
- They decompose at low temperature.
- They are mostly flammable.
- Their reactions are usually slow.
- They mostly show isomerism.
- Organic compounds are usually non-ionic in nature.
- Mostly organic compounds are soluble in non polar solvents.
- They are covalent compounds.
- Mostly organic compounds have similar structures so they show similar chemical and physical properties.
e.g. CO2 is not organic compound as it has some of the above mentioned characteristics but not all on the other hand sucrose (C12H22O11) is an organic compound as it possesses all of the above mentioned characteristics.
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Reasons for very large number of organic compounds:
Due to following reasons number of organic compounds is very large.
1. Tetra valency of Carbon:
As carbon has tetra valency so it can give various combinations with other atoms e.g. carbon gives 5 combinations with H and Cl i.e. CH4, CH3Cl, CH2Cl2, CHCl3, CCl4.
2. Catenation ( Self linkage of atoms of an element)
Catenation: Self linkage of atoms of an element is called catenation; this ability is maximum in carbon. Due to this reason carbon can form long chains, branched chains and rings. This ability is also a reason for large number of carbon compounds.
Organic compounds show isomerism e.g (i) Pentane C5H12 shows 3 isomers i.e. n-pentane, iso pentane, neo pentane etc. e.g. (ii) molecular formula C2H6O represents two isomers CH3-O-CH3 & C2H5OH. Isomerism is also responsible for large number of carbon compounds.
4. Multiple Bonds:
Carbon is capable of forming multiple bonds among its own atoms as well as with other atoms e.g. CH3-CH3, CH2=CH2, CH≡CH etc. This ability is also a reason for large number of carbon compounds.
Importance or uses of Organic Compounds:
Organic compounds have great importance in our daily life
- Our body is made up of organic compounds.
- Our food is mostly organic.
- Clothes we wear are made up of organic compounds.
- Leather we use is organic in nature.
- Paper we use for writing is organic in nature.
- Fuels we use in automobiles are organic compounds
- Woolen products, rubber, plastics, cosmetics, paints, medicines, shoe polish, and many other daily use items are mainly organic in nature.
- Plastics are organic in nature and plastic have replaced wood, metal etc.
Sources of Organic Compounds:
The major sources of organic compounds are Plants, Coal, Petroleum and Natural Gas.
Plants are one of the important source of organic compounds. They absorb CO2 from air, water and minerals from soil and then prepare various organic compounds. They are actually factories of organic compounds. They produce Carbohydrates, Oils, Vitamins, Dyes, drugs, medicines, natural fibers (Cotton & Jute) etc.
The other three sources are also plant in origin.
It is a black colour mineral found under earth crust. Plants, which were buried under, earth crust million of years ago, they due to different bacterial and chemical reactions first converted into coal precursor called peat which under high temperature and pressure was slowly converted to coal.
Coal is an important solid fossil fuel. Coal is used as domestic as well as industrial fuel. It is also used as fuel to generate electricity.
Coal deposits are found at Lakhra of Sind, Dandot and Katha hills of Punjab, Mach and various other parts of Baluchistan, Dera Adam Khel of Khyber Pakhtunkhwa.
Coal on the basis of its carbon contents is divided into four types.
- Anthracite: Its carbon contents are 92-98%. It has high calorific values.
- Bituminous Coal: Its carbon contents are 80-90%. It is the most abundant form of coal. It
is used as domestic fuel and to obtain organic compounds.
- Sub-bituminous Coal: Its carbon contents are 65-80%. It is used as commercial fuel.
- Lignite or Peat: Its carbon contents are 50-60%. It is soft and is of brown colour. Its
calorific values are very low so it is not used as fuel.
Destructive distillation of Coal:
When coal is heated in absence of air, its destructive distillation or carbonization occurs.
The coal gas is also called town gas. It is mixture of H2, CO, CH4. Hydrogen and carbon monoxide (water gas) obtained from coal gas is converted to petroleum by Fischer-Tropsch (FT) process.
(2n+1) H2 + n CO → CnH2n+2 + n H2O where n = number of carbon atoms in the alkane.
This reaction is catalyzed by transition metals like Cobalt, Iron, Ruthenium and Nickel. The mixture is heated to 150-300oC.
Ammoniacal Liquor is ammonia solution which is used for making fertilizers like ammonium sulphate, ammonium super phosphate.
Coal tar is mixture of aromatic compounds. The compounds obtain from coal tar are used in making soaps, fats, dyes, plastics, perfumes, drugs, pesticides, explosives etc.
Coke is used as domestic and industrial fuel. Coke is also used as reducing agent in industries to obtain metals from their ores.
Petr means rock and oleum means oil. So petroleum is also called rock oil. It is thick viscous liquid of brown or greenish black colour. It is produced by the decay of living organisms buried in the earth crust million of years ago. Petroleum in unrefined form is called crude oil. Petroleum reserves are found in Sanghar and Badin of Sind, Dera Ghazi Khan, Tallagung and Cambalpur district of Punjab province. Kohat and Karak district of Khyber Pakhtunkhwa.
Refining of Petroleum:
Suspended solids, sulphur impurities and gases are first removed from crude oil and it is then subjected to fractional distillation. Various fractions of hydrocarbons are obtained at different boiling ranges.
|1||Refinery Gas||Below 20oC||C1-C4||Fuel, making other organic compounds|
|2||Petroleum ether||30-70 oC||C5-C6||Solvent for fats, oil for varnish|
|3||Petrol or Gasoline||70-120 oC||C6-C8||Fuel for automobiles|
|4||Benzine||120-150 oC||C9-C10||Dry cleaning, solvent for varnish and fats|
|5||Kerosene oil or Paraffin oil or jet oil||150-250 oC||C11-C12||Fuel in oil stoves, illuminant in lamps and lantern, jet fuel|
|6||Diesel oil or Gas oil or Heavy oil||250-400 oC||C13-C18||Fuel in Diesel engines|
|7||Residue||Above 400 oC||C17 and higher||Its vacuum distillation Gives following fractions.|
|(ii)||Paraffin wax||C20-C30||Candles, boot polish, wax paper, Ointments, Vaseline|
|(iii)||Pitch or Asphalt||C30-C40||Road surfacing|
Refinery Gas (B.R = below 20oC)
Petroleum ether (B.R = 30-70oC)
Petrol or Gasoline (B.R = 70-120oC)
Benzine (B.R = 120-150oC)
Kerosene oil or Paraffin oil or Jet oil (B.R = 150-250oC)
Diesel oil or Gas oil or Heavy oil (B.R = 250-400oC)
Residue (B.R = Above 400oC)
- Natural Gas:
Natural gas is usually found above the petroleum reservoirs.
Natural gas reserves are found in Sui (Baluchistan), Mari (Sind) and Gurguri (Pakhtunkhwa).
Natural gas is mixture of methane, ethane, propane and butane. But mainly it is methane (85%).
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