Give the structures and IUPAC names of monohydric phenols of molecular formula, ${C_7}{H_8}O.$

Hint: Phenols are aromatic alcohols. Monohydric phenol has one hydroxyl group attached to a benzene ring.

Complete step by step answer:
Molecular formula of the compound is ${C_7}{H_8}O.$ We have to find monohydric phenols. Phenols are aromatic alcohols in which one hydroxyl group is attached to a benzene ring.
Benzene ring has 6-carbon atoms in a ring, but total 7-carbon atoms are given in molecular formula.
Therefore, each phenol is methyl substituted phenol. They are:Common name of monohydric phenol is cresol.
When two hydrogen atoms of benzene are replaced by two monovalent atom or group of atoms, then resulting product have three different forms:

 (i) Ortho (or 1,2): Substituents present on adjacent carbon atom. i.e., $ - C{H_3}$and $ - OH$group are present at adjacent C-atom
(ii) Meta (or 1,3): Substituents are present on alternate C-atoms. i.e., $ - C{H_3}$ and $ - OH$are present on alternate C-atoms.

(iii) Para (or 1,4): Two substituents i.e. $ - C{H_3}$ and $ - OH$are present on diagonally situated $C - atoms.$

Ortho, meta and para are generally represented as $O - ,m - $ and $p - $respectively.

Note: The formation of different structures by using one molecular formula is called isomerism. In the given compound three isomers are formed in which position of $ - C{H_3}$group is different with respect to $ - OH$ group on benzene ring.