The phenomenon of metamerism is shown by

Metamerism is a form of structural isomerism exhibited by compounds belonging to the same homologous series that possess a polyvalent functional group (such as -O-, -S-, or -NH-). It arises due to the unequal distribution of alkyl groups on either side of the functional group [t2][t4]. Methyl propyl ether (CH3-O-C3H7) and diethyl ether (C2H5-O-C2H5) both share the molecular formula C4H10O but differ in the alkyl groups attached to the divalent oxygen atom, making them classic examples of metamers [t2][t3][t4]. In contrast, ethyl alcohol and dimethyl ether are functional isomers (C2H6O) [t3]. Propionic acid and acetic acid are members of a homologous series but have different molecular formulas (C3H6O2 and C2H4O2), while oxalic and lactic acids are distinct carboxylic acids with different functional arrangements and formulas [c2][t6].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 2: Acids, Bases and Salts > Table 2.3 Some naturally occurring acids > p. 28
2. [2] https://sist.sathyabama.ac.in/sist_coursematerial/uploads/SCY1315.pdf