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 CnH2n+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 CnH2n or CnH2n–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.
(c) Free bond will come either on Ist carbon atom or on last carbon atom.
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
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