As food, medicines, pesticides, paints, dyes contain a common element carbon, they are called organic compounds. Petroleum, coal, natural gas, plants, animals are the important sources of these compounds. Wohler prepared urea (NH2CONH2) by heating ammonium cyanate (NH4CNO). The first organic compound, acetic acid was prepared by Kolbe from the elements C, H, O.
All the elements in the periodic table (except C) can form about 50,000 compounds. Where as 'C' can only form about 5 million compounds (due to catenation, isomerism, formation of multiple covalent bonds). Atomic number of C is 6. Its 1st excited state electronic configuration is 1S2 2S1 2Px1 2Py1 2Pz1. So 'C' can form 4 covalent bonds. We leant in chemical bonding that alkanes undergo sp3, alkenes - sp2, alkynes - sp hybridization.
Organic compounds either isolated from natural sources or prepared in the laboratory or industry usually contaminated with impurities. It is very essential to purify the compounds inorder to identify and characterise organic compounds.
Some of the purification methods are crystallisation (on cooling, dissolved compound crystallises out), sublimation (compound sublimates on heating and solidifies on cooling), distillation (volatile liquids having boiling points difference more than 40°C), fractional distillation (liquids having B.P.S. difference less than 40°C), distillation under reduced pressure (liquids have very high B.P. and those decompose at or below their B.P.S.), steam distillation (liquids which are immiscible in water, contain non volatile impurities, possess high B.P. and steam volatile), solvent extraction (organic compound miscible with organic solvent, separates on distillation) and chromatography.
Chromatography is the latest method, discovered by Russian botanist Tswett (separated Xanthophyll and Chlorophyll). Depending upon the stationary phase (solid or liquid), mobile phase (liquid or gas) chromatographic methods are classified into column (adsorption) chromatography, Thin layer chromatography, Gas liquid chromatography, partition (paper) chromatography.
Quantitative organic analysis:
After purification of organic compounds, we have to detect the elements present in it by qualitatively (and quantitatively later)
Detection of C&H:
If compound contain C, H, on combustion it gives CO2 (lime water turns milky) and H2O (colourless CuSO4 becomes blue due to formation of CuSO4. 5 .H2O)
C + 2 CuO 
2 Cu + CO2
Ca(OH)2 + CO2 CaCO3 + H2O
2 H + CuO Cu + H2O
CuSO4 + 5H2O CuSO4. 5 H2O
Detection of N:
A prussian blue precipitate Ferric Ferro Cyanide is formed when sodium fusion extract (Na + C + N NaCN) reacts with NaOH, FeCl3 solution and acidified with Conc. HCl.
3 Na4 [ Fe ( CN )6 ] + 4 FeCl3 Fe4 [ Fe ( CN )6 ] + 12NaCl
% of O = 100 - total % of other elements present in O.C.
Homologous series:
A series of carbon compounds having same general formula, same functional group, and the difference between any 2 consecutive members is - CH2. They are prepared by similar methods. There is a regular trend in physical properties and have similar chemical properties.
IUPAC Nomenclature:
International Union of pure and applied chemistry has set rules for naming the organic compounds.
IUPAC name = Prefix + Root word + Suffix (primary & secondary) Root word represents the number of C atoms in the longest chain of organic compound. The root words are Meth (C1), Eth (C2), Prop (C3), But (C4), Pent (C5), Hex (C6), Hept (C7), Oct (C8), Non (C9) and Dec (C10). Primary suffix indicates the saturation (single bonds - ane) or Unsaturated bonds (double bonds - ene, triple bonds - yne), Secondary suffix indicates the functional group (Alcohol - OH - Ol, Aldehyde - CHO-al, Ketone - O = C - one, Ester - COO - Oate). Prefix indicates the substituted groups other than functional groups (Methyl - CH3, Ethyl - C2H5, Propyl - C3H7....)
Root word : Hex,
Primary suffix : ane,
Secondary suffix : - oic acid,
Prefix : 4 - Hydroxy - 5 - Methyl
IUPAC name: 4 - Hydroxy - 5 - Methyl Hexanoic acid
IUPAC rules:
¤ Select the longest possible carbon chain in the compound.
¤ Sum of the numbers given to the substituents must be lowest.
¤ Numerical prefixes di, tri, tetra are given before the functional group if 2, 3, 4 identical groups are present.
¤ If the chain terminal group contain carbon [- CHO, - COOH], numbering must be given from there only.
Irrespective of lowest sum rule.
¤ When carbon chain contains more than one functional group, the order of preference for giving the lowset number is
Carboxylic acid > Aldehyde > Nitrite > Ketone > Alcohol > Amine > Ether > Alkene > Alkyne
Bond line formula:
Simplified representation of (C - C bonds are drawn in zig zag manner) of a compound is known as bond line formula. Intersection of lines represents 'C' atoms with appropriate number of 'H' atoms.
Bicyclo compounds:
Compounds with 2 fused bridged rings are called as bicyclo compounds.
eg: Norbornane is Bicyclo (2, 2, 1) Heptane
We write the number of carbon atoms in each bridge in the order of decreasinglength (a, c, b)
Isomerism:
The existence of 2 or more compounds with the same molecular formula but different physical or chemical properties or both.
Structural isomerism:
The isomerism that arises due to different arrangement of atoms within the molecule (with out reference to space)
Chain isomerism:
The isomerism that arises due to the difference in the nature of the carbon chain (straight chain or branched chain)
eg: C4H10 has 2 isomers
Position isomerism:
The isomerism that arises due to the difference in the position of multiple bonds or functional group or substituent.
eg: C3H7OH has 2 isomers
Functional group isomerism:
The isomerism that arises due to the difference in the functional group
eg: C2H6O
isomers : CH3CH2OH, 
Ethyl alcohol
Metamerism:
The isomerism that arised due to the difference in the nature of the alkyl groups attached to the same functional group.
eg: C4H10O
metamers: 
Tautomerism:
The isomerism (functional) that arises when a H atom migrates from one polyvalent atom to other atom within the molecule to give isomers which exist in dynamic equilibrium with each other.
eg: Keto-enol tautomerism
Stereo isomerism:
The isomerism that arises due to different special arrangement of atoms or groups
Conformational isomerism:
The isomerism that arises due to the rotation of atoms or groups in space around a single bond.
eg: Conformers of ethane (Newman Projections)
Configurational isomerism:
The isomerism that arises due to bond breaking and bond reforming of covalent bonds.
Geometrical isomerism:
The isomerism that arises due to different arrangement of atoms or groups around double bonded carbon atoms (due to restricted rotation of double bond). If similar groups are on the same side of carbon atoms, it is called cis-isomer and if they are on the opposite side of carbon atoms it is called trans-isomer.
E-Z System:
If different groups or atoms are bonded to the double bonded carbon atoms, and the atoms of higher atomic number are present on same side it is Z-configuration, if present of either sides it is E-configuration.
Optical isomerism:
The isomerism that arises due to the difference in the configuration and the behaviour towards plane polarised light (due to presence of chiral carbon, object & mirror image are not super imposable). The compounds which rotate plance polarised light towards right hand side are called dextro (d) rotatory and towards right hand side are called laevo rotatory.
Specific rotation 
Pair of non-super imposable mirror images are called "Enantiomers" and stereo isomers which are not mirror images are called "diastereo isomers".
D-L System
In this system if -OH group is present on the right hand side of the last chiral centre in its Fischer's projection formula is called D-configuration.
(assigned with respect to D-glyceraldehyde) and left hand side of the chiral Centre is called L-configuration.
R-S System
Cahn-Ingold-Prelog assigned priorities (Just like in E-Z System) to 4 atoms or groups attached to the chiral centre (For a Fischer projection formula).
If the order of decreasing precedence of 3 highest ranked substituents is in clockwise direction, the configuration is called "R"and if it is in anti-clockwise direction, the configuration is called "S".
Electronic displacements in a covalent bond:
Practically it is not possible to maintain equal distance by the shared pair of ebetween 2 atoms. Due to this reason electronic displacements may cause permanent polarising effects (Inductive effect or reasonance effect) or temporary effects (electromeric effect).
Inductive effect:
The phenomenon in which permanent displacement of a electrons takes place (either by donating or by withdrawing) along a saturated carbon chain towards the more electronegative atom or group
eg: CH3
CH2 CH2 Cl
+I effect:
Groups or atoms donate e- to the carbon chain order of +I effect:
(CH3)3 C > (CH3)2CH > C2H5 > CH3 > H
-I effect:
Groups or atoms withdraw e- from the carbon chain order of -I effect:
Electromeric effect:
The phenomenon in which complete transfer of a shared pair of π electrons (of a multiple bond) to one of the more electronegative atoms (joined by a multiple bond) in presence of an attacking reagent.
+E effect:
The e- of π bond are transferred to the atom joined by multiple bond to which reagent gets attached.
-E effect:
The electrons of π bond are transferred to the atom joined by multiple bond to which reagent is not attached.
Mesomeric effect:
The phonomenon in which electron pair displaced by an atom or group along a chain by a conjugate mechanism
+M effect:
Group which donate electrons to the double bond
eg: OH, ---- NH2, ---- OR, ---- X
-M effect:
Group which withdraw electrons from the double bond
eg: > C = O, ---- CHO, ---- COOR, ---- CN, ---- NO2
Resonance:
The phenomenon of existence of one molecule in 2 or more different (non convertable, more stable) structures (Lewis) in order to explain all the properties.
e.g.: Kekule structures of Benzene
Actual Structure (Resonance Hybrid):
Fission of a Covalent bond
Homolytic Fission:
The process of equal breaking of a covalent bond to form free radicals (odd e- Species). This type of fission takes place in presence of non polar solvents, peroxide, UV light, electricity or high temperature ( > 500° C).
Stability of free radicals: 3° > 2° > 1° > 
Heterolytic Fission:
The process of unequal breaking of a covalent bond to form cation and anion. This type of fission takes place when greater difference in Electronegativity observed between two elements.
Stability of Carbonium ions : 3o > 2o > 1o > +CH3
Stability of Carbanion ions : -CH3 > 1o > 2o > 3o
Types of Organic reagents
Electrophiles:
Electron loving chemical species (Lewis acids, electron deficient species, cations, free radicals) are called Electrophiles.
e.g. : H+ , H3O+, Cl+, NO2+, NO+, R+ , R., BF3 , AlCl3
Nucleophiles:
Nucleus loving chemical species (Anions, electron rich species, Lewis bases) are called nucleophiles.
e.g.: Cl-, R-, OH-, NH2-, H2O, NH3, ROH, ROR, alkenes, alkynes.
R4N + cannot act as electrophile. (N has 8e-), 
can not acts as nucleophile (cannot donate electron pair), Organic Compounds containing multiple bond between C and more electronegative atom can act as both electophile and Nucleophile.
Types of Organic Reactions
Organic reactions are mainly classified in 4 types as below.
Substitution Reactions:
Reactions involving the substitution of an atom or a group of atoms of a substance by another atom or group of atoms. Substitution may be either free radical, electrophilic or nucleophilic. Alkanes, alkylhalides, Benzene undergo susbtitution.
e.g.: RX + KOH (aq.) 
R ---- OH + KX
Addition Reactions:
reactions involving the addition of a reagent (electrophile or nucleophile or free radical) with unsaturated compound (alkene or alkyne) to form a single product.
eg. H2C = CH2 + HBr CH3 ---- CH2Br
Elimination Reactions:
Reactions involving the loss of 2 atoms or groups present on the same carbon or different carbon atoms to form an unsaturated compound (alkene or alkyne)
eg. C2H5Br + KOH (alc.) 
C2H4 + KBr + H2O
Rearrangement reactions:
Reactions involving the migration of an atom of a group from one C atom to another C atom within the molecule
Hdrocorbons
Compounds containing Only C & H are called hydrocarbons.
Cyclo Alkanes
Hydro Carbons in which carbons are arranged in one or more rings. Carbons undergo SP3 hybridization. They have general formula CnH2n (if only one ring). They are prepared by various methods as below.
Cyclohexane can be prepared by Wislicenus method (distillation followed by reduction of calcium heptane dioate), Dieckmann condensation reaction (intra molecular condensation of ethyl heptane dioate). Due to angle strain & torsional strain cyclopropane and cyclobutane are more reactive than cyclopentane and cyclohexane.
ALKANES
Alkanes are open chain saturated hydrocarbons with C-C bonds (σ). They have gneral formula CnH2n +2 . Each C undergoes sp3 hybridization. Any alkane contain 3n+1 σ bonds. They undergo substitution reactions.
ETHANE
Preparation of Ethane:
Wurtz reaction:
Ethane is formed when Na metal in dry ether is heated with Methyl iodide
Sabaties−Senderen's reaction:
Ethane is prepared by catalytic hydrogenation of ethene.
Uses of C2H6:
It is used as fuel, to prepare artificial camphor (C2Cl6)
Alkenes
Open chain unsaturated hydrocarbons with C=C bond. They have general formula CnH2n. Each C undergoes sp2 hybridization. Any alkene contain 3n-1 σ bonds. They undergo additon reactions.
Ethene
PREPARATION OF ETHENE:
By controlled Hydrogenation of acetylene:
Acetylene on controlled hydrogenation with Lindlar's Catalyst (a mixture of palladised charcoal, BaSO4 in presence of Quinoline) gives Ethene.
Chemical Properties
OZONOLYSIS:
Ozone gives ethene ozonide with ethene. Which on reduction with Zn & H2O gives formaldehyde. This process is called ozonolysis
Oxidation:
When C2H4 is passed through Baeyer's reagent (Cold, dilute, alkaline KMnO4), KMnO4 decolourises due to formation of ethylene glycol (Antifreeze)
Reaction with O2 & Ag :
Ethene on heating with O2, Ag upto 200°C gives epoxide
Uses:
Used to prepare polythene, Ethylene glycol and mustard gas.
Alkynes
Alkynes are open chain unsaturated hydrocarbons with C ≡ C. Their general formula CnH2n-2. Total number of σ- bonds formed by alkyne are 3n-3. They undergo addtion reactions.
Acetylene
Preparation:
Dehydrohalogenation:
When 1, 2 dibromo or 1, 1 dibromo ethane treated with alc. KOH followed by NaNH2 at 160oC gives ethyne (Acetylane)
Dehalogenation
When 1, 1, 2, 2 tetra bromo ethane is heated with Zn dust, acetylen is formed
Kolbe's electrolysis:
Acetylene is prepared by the electrolysis of concentrated potassium maleate (or funarate) solution.
Addition of O3
C2H2 reacts with O3 to form Ozonide, which further reacts with Zn & H2O to form glyoxal (reaction is reductive Ozonolysis)
( Note: C2H2 on oxidative Ozonolysis give HCOOH)
Action of Ammonical AgNO3
C2H2, when passed through ammonical AgNO3, a white precipitate of Ag2C2 is formed
Action of Ammonical Cu2Cl2:
C2H2, when passed through ammonical Cu2, Cl2, a red precipitate of Cu2C2 is formed.
Polymerisation:
When C2H2 is passed through red hot iron tube, C6H6 is formed
Addition of HCN:
C2H2 reacts with HCN gives Acrylonitrile
( Note: Acrylonitrile on polymerisation with 1, 3 Buta diene gives Buna - N)
Uses:
Used in oxyacetylene flame, to prepare vinyl plastics, westron, westrol , C6H6, Acetic acid, Ethyl alcohol
BENZENE
Benzene (C6H6) is highly unsaturated but does not behave like alkene due to resonance (C - C & C = C bond length is 1.39 A° for both). According to Huckel rule it has (4n +2)π , that is 6e- so C6H6 is aromatic.
Preparation of C6H6 from Coaltar:
Coal on destructive distillation upto 1000°C gives coal gas, coaltar, Ammonical liquor and solid residue. Coaltar on fractional distillation gives light oil, middle oil, heavy oil and anthracene oil.
Light oil is treated with H2SO4 and washed with water and later treated with NaOH to remove basic, acidic impurities. It's subjected to fractional distillation to get benzene at 81°C
Preparation of Benzene (Laboratory Methods)
From Benzene sulphonic acid:
Benzene Sulphonic acid on hydrolysis gives C6H6.
By Polymerization:
C2H2 When passed through red hot iron tube gives C6H6
Sulphonation:
Benzene on reaction with Oleum (funing H2SO4) gives benzene sulphonic acid. (In this reaction electrophile is SO3)
Addition reactions:
Addition of H2:
C6H6 reacts with H2 to give cyclohexane
Addition of Cl2:
C6H6 reacts with Cl2 in presence of sun light gives Benzene Hexa chloride
Addition of O3
C6H6 reacts with O3 followed by reductive hydrolysis gives glyoxal
Uses:
Solvent for fats, in dry cleaning, to prepare phenol, styrene, aniline, BHC (insecticide), as a motor fuel.
