Types of Organic Reactions

There are four main types of organic reactions:

(1)   Substitution Reactions

Example: CH₄ + Cl₂ →CH₃Cl + HCl

(2)   Addition Reactions

 

Example: CH₂=CH₂ + Br₂ → BrCH₂CH₂Br

(3)   Elimination Reactions:

Example: BrCH₂CH₂Br + Zn → CH₂=CH₂ + ZnBr₂

(4)   Rearrangement Reactions:

Example: R-CH(Cl)-CH=CH₂ → R-CH=CH-CH₂(Cl)

Classification of Organic Compounds

Organic compounds are divided into four categories:

(1)   Aliphatic compounds- alkanes (H₃C-CH₃), alkenes (H₂C=CH₂) and alkynes (HC≡CH). Compounds containing open chain of atoms.

(2)   Alicyclic compounds- cyclopropane (C₃H₆).

(3)   Aromatic compounds- benzene (C₆H₆), toluene (C₆H₅CH₃)

(4)   Heterocyclic compounds- pyridine (C₅H₅N). Cyclic compounds in which the ring contains elements other than carbon.

Catagories (1), (2) and (3) are known as hydrocarbon (compounds of carbon and hydrogen).

Functional Groups

Ø      A functional group is the reactive part of an organic molecule.

Ø      It serves to classify organic compounds into classes/families.

Ø      It serves as a basis for nomenclature (naming) of organic compounds.

Alkenes (-C=C-), alkynes (-C≡C-), alcohols (-OH), ethers (-O-), aldehydes (-CHO), ketones (-CO), acids (-COOH), esters (-CO-O-), amines (-NH₂), halides (-F, -Cl, -Br, -I) etc.

Importance of Organic Chemistry

Organic chemistry is important because it is the chemistry associated with all living matter in both plants and animals.

(a)    As foods: Carbohydrate, fats and oils, proteins, vitamins, hormones, enzymes are organic compounds.

(b)   As medicine: Most of the drugs- antibiotics, analgesic, hypnotics etc are organic compounds.

(c)    As clothes: Wool, silk, cotton, linen and synthetic fibres- nylon, rayon, Dacron etc. contain organic compounds.

(d)   As fuels: Coal, crude, oil (kerosene, petrol, diesel etc.), natural gas and wood.

(e)    Others: perfumes, dyes, flavors, soaps, detergents, plastics etc.

Sources of Organic Compounds

(1)   Coal: It is about 80% organic compounds.

(2)   Crude oil: It is a complex mixture of organic compounds.

(3)   Natural gas: It is a mixture of low molecular weight organic compounds.

(4)   Wood and other plant materials:

(5)   Laboratory synthesis:

The number of organic compounds is very large, why?

Three Reasons:

(1)   Carbon has the ability to form strong covalent bonds with other carbon atoms to form chains and rings of varying sizes. This property of carbon is called catenation.

(2)   Carbon has the ability to form single, double and triple bonds.

(3)   Carbon has the ability to form strong covalent bonds with many other atoms such as H, O, N, S, Cl, Br and I.

Organic Compounds

Carbon containing compounds are organic compounds. For examples: food, clothes, medicine, fuel etc.

Organic Chemistry

The branch of chemistry that deals with carbon containing compounds is known as Organic Chemistry.

Few exceptions: CO, CO₂, CS₂, Na₂CO₃, NaHCO₃ and KCN etc.

Difference between organic and inorganic compounds

Organic compounds		Inorganic compounds
1	Low melting points	1	High melting points
2	Low boiling points	2	High boiling points
3	Low solubility in water, high solubility in non-polar solvent.	3	High solubility in water, low solubility in non-polar solvent.
4	Flammable	4	Nonflammable
5	Chemical reactions are usually slow	5	Chemical reactions are rapid
6	Exhibit isomerism	6	Isomers are limited to a few exceptions; (e.g. transition elements)
7	Exhibit covalent bonding	7	Exhibit ionic bonding