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Thank you....... How do we calculate no. of Chain, Position, Metamerism, Tautomerism? please tell me formula

Thank you....... How do we calculate no. of Chain, Position, Metamerism, Tautomerism? please tell me formula

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1 Answers

SAGAR SINGH - IIT DELHI
878 Points
13 years ago

Dear anuvrat,

Chain isomerism

This type of isomerism arises from the difference in the nature, structure of the carbon chain. For example, for butane (C4H10), the following arrangements are possible.

butane in straight chain
iso butane in branched chain

Pentane (C5H12) exhibits the following three structures.

structures of pentane

 

Butanol (butyl alcohol) has the following two structures of the carbon chain.

structures of butanol

 

For butanal, (C3H7CHO), the following chain isomers are possible.

chain isomers of butanal

 

Position isomerism

This isomerism arises due to the difference in the position of the same functional group or the same substituent while the arrangement of carbon atoms remains same. For example,

Chloropropane (C3H7Cl) can have two positional isomers given below.

 

positional isomers of chloropropane

 

 

Butene (C4H8) can have two positional isomers.

 

positional isomers of butene

 

 

Propanol (C3H7OH) has the following positional isomers.

 

positional isomers of propanol

 

 

Functional isomerism

The compounds having the same molecular formula but different functional groups are said to exhibit functional isomerism. Such compounds are termed functional isomers. For example, there are two compounds having the molecular formula C2H6O viz.,

Ether

 

functional isomers of C2H6O

 

Alcohol

The molecular formula C3H6O represents two functional isomers.

Aldehyde

functional isomers of C3H6O

Ketone

Metamerism

This type of isomerism arises from the unequal distribution of carbon atoms on either side of the functional group in the molecule of compounds belonging to the same homologous series. For example, diethyl ether and methylpropyl ether are metamers.

diethyl ether and methylpropyl ether are metamers

A ketonic compound having the molecular formula C5H10O, has the following two metamers.

metamers of C5H10O

Tautomerism

This is a special case of functional isomerism. Certain substances can

exhibit properties of two functional groups as for instance, acetoacetic ester behaves like a ketone as well as an alcohol. This arises due to the migration of a labile hydrogen atom from one place to another.In acetoacetic ester, the inter-conversion between keto and enolic group takes place as follows.

 

inter-conversion between keto and enolic group

 

In amides, it happens as follows:

 

keto-enol tautomerisn in amides

 

Both these forms of the same molecule exist in equilibrium in a sample of compound. The migration of a labile hydrogen between two polyvalent atoms in the same molecule causes this type of dynamic isomerism. This is termed as tautomerism or keto-enol tautomerisn. Such isomers are termed as tautomers.

 

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Sagar Singh

B.Tech, IIT Delh



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