CLASSIFICATION OF ORGANIC COMPOUNDS

Classification of organic compounds based on structure or carbon skeleton

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Organic Compound are divided into two types they are

1. Open chain

2. Closed chain

1. Aliphatic or Open chain compounds :

Those compounds in which first & last carbon atoms are not connected with each other. Branched or unbranched chains are possible in these compounds.

For example :

Aliphatic or open chain compounds are two varieties in these compounds -

Saturated Hydrocarbons :

In such type, adjacent carbon are attached with single bonds. Example - CH₃–CH₂–CH₃
General formula of these compounds are C_nH_2n+2
These are also called as paraffins (Parum + Affins i.e. little reactivity) because these are less reactive due to absence of 𝝅-bonds.

Unsaturated Hydrocarbons :

There will be a double bond or a triple bond between any two carbon atoms, CH₂=CH–CH₃ Propene CH≡C–CH₃ Propyne
General formula is C_nH_2n or C_nH_2n–2
These are also called as olefins because they reacts with halogens to form oily substances olefins (Oleum + fines i.e. Oil forming).
Due to presence of 𝝅 bonds these are more reactive.

2. Closed chain compounds :

In closed chain compounds first & last carbon are attached with each other. Example. △ cyclopropane.

Homocyclic compounds :

These are the compounds in which the complete ring is formed by carbon atoms only. These are also of two types

Alicyclic compounds :

These are the compounds having the properties like aliphatic compounds. These may be saturated or unsaturated like aliphatic compounds.

Aromatic compounds :

Conditions for a compound to be aromatic -

(i) Compound should be cyclic.

(ii) Compound should be planar. (All carbon in ring should be sp² hybridised )

(iii) It follow Huckel's Rule :- [4n + 2] 𝝅 electrons. (Odd number of 𝝅 electron pairs)

n = 0 2𝝅 electrons or 1 pair

n = 1 6𝝅 electrons or 3 pairs

n = 2 10𝝅 electrons or 5 pairs

n = 3 14𝝅 electrons or 7 pairs

(iv) There should be cyclic resonance in ring.

Heterocyclic Compounds :

These are cyclic compounds having ring and rings builts up of more than one kind of atoms.

Normal Groups :

(a) It is represented by 'n' :

(b) Straight chain of carbon atoms is known as normal group.

n – propyl CH₃–CH₂–CH₂–

n – butyl CH₃–CH₂–CH₂–CH₂–

Iso group :

(a) It is represented by following structure

(b) When methyl groups are attached to the second last carbon atom, group is named as iso.

Neo group :

(a) When two methyl group are attached to second last carbon atom group is named neo group.

(b) It is represent by following structure -

Secondary group :

(a) When two alkyl groups attached to the same carbon atom, group is named as secondary.

(b) It is represented by following structure.

Tertiary group :

(a) When three alkyl groups (similar or dissimilar) are attached to the same carbon atom, group is name as tertiary.

(b) It is represented by following structure -

Groups :

When a hydrogen is removed from saturated hydrocarbon then alkyl group is formed. It is represented by R & its general formula is CnH2n+1. A bond is vacant on alkyl group, on which any functional group may come.

Alkyl groups :

Aryl Radical

Basic chemistry

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