Question

Naming Aromatic compounds is a challenge because of the conflicting IUPAC and Common naming rules; discuss one situation where using O, M, P in a name would be appropriate, and one situation where you would not use O, M, P in a name.

Answer 1

O(ortho), M(meta), P(para) nomenclature is used in naming of aromatic compounds which are disubstituted

In the case of disubstituted aromatic compounds, relative positions of non-hydrogen substituents is described by ortho, meta, para prefixes.

If the two substituents are present at adjacent carbons or 1,2 carbons of the aromatic ring then the prefix ortho(O) is used before compound name.

If the two substituents are present at alternative carbons or 1,3 carbons of the aromatic ring then the prefix meta(M) is used before compound name.

If the two substituents are present at opposite diagonal carbons or 1,4 carbons of the aromatic ring then the prefix para(P) is used before compound name.

For example
сн, CH Сн, OH OH OH o-cresol m-cresol p-cresol