Chemistry · General Principles Of Organic Chemistry · NEET
No. Chain isomerism changes the shape of the carbon skeleton (straight vs branched), like pentane and 2-methylbutane. Metamerism keeps the same functional group but splits the alkyl groups differently on its two sides. In metamerism the functional group (say the ether oxygen) is fixed; only how carbons are divided across it changes. So diethyl ether (2+2) and methyl propyl ether (1+3) are metamers, not chain isomers.
Metamerism needs a functional group that sits between two carbon (alkyl) chains, so it can be flanked on both sides. The common ones for NEET are ethers (R-O-R'), ketones (R-CO-R'), secondary and tertiary amines (R-NH-R'), and esters. Alcohols and aldehydes cannot show metamerism because their functional group sits at the end of a chain with only one alkyl arm.
An ether needs two alkyl groups around oxygen. To get two different ways of splitting the carbons you need enough carbons to divide two different ways. With C4H10O you can make 2+2 (diethyl ether) and 1+3 (methyl propyl ether). With fewer carbons like C3H8O you only get one ether split (1+2), so no second metamer exists - it shows other isomerism instead.
Metamers are structural (constitutional) isomers - the atoms are connected in a different order. They are NOT stereoisomers. Metamerism sits alongside chain, position and functional isomerism under structural isomerism. Stereoisomerism (like cis-trans or enantiomers) is a separate branch where connectivity is the same but 3D arrangement differs.
Esters R-CO-O-R' can show metamerism, but you must be careful. CH3CH2COOCH3 (ethyl group and methoxy) and CH3COOCH2CH3 (methyl and ethoxy) look similar but the position of the C=O relative to the O differs, so NEET counts these as functional/position-type isomers, not classic metamers. True ester metamers keep the ester group fixed and vary the two alkyl arms.
The compound which shows metamerism is:
The pair of molecules that are metamers among the following is:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Metamerism is when two compounds have the same molecular formula and the same functional group, but the alkyl groups on the two sides of that functional group are different. The two compounds are called metamers.
Diethyl ether (CH3CH2-O-CH2CH3) and methyl propyl ether (CH3-O-CH2CH2CH3). Both are C4H10O, both are ethers, but the carbons are split 2+2 in one and 1+3 in the other.
Ethers, ketones, secondary and tertiary amines, and esters - any group that sits between two alkyl chains. Alcohols and aldehydes do not, because their group is at a chain end with only one alkyl side.
Yes. Metamerism is one of the four types of structural (constitutional) isomerism, along with chain, position and functional isomerism. It is not stereoisomerism.
NEET regularly asks which molecular formula or which pair shows metamerism (2021 and 2026 both did). Knowing that it needs the same functional group with different alkyl splits helps you eliminate chain and functional isomerism traps quickly.
