Lesson 2 of 13 · 7 min
Structural representations
NCERT § "Structural Representations of Organic Compounds"
The label on Riya's vinegar bottle says 'acetic acid'. Her chemistry teacher might write CH₃COOH, draw every bond, or sketch just two short lines and an OH. All of them describe the same molecule.
The lesson in notes
In short
A complete (Lewis or dash) structural formula shows every bond as a dash and may show lone pairs.
A condensed formula omits some or all dashes and groups identical units, for example CH₃(CH₂)₆CH₃.
In bond-line formulas carbon and hydrogen atoms are not written; each line end or bend is a carbon, and hydrogens are assumed to fill each carbon's valence.
Heteroatoms such as O, N and Cl, and the hydrogens on them, are always written explicitly in bond-line formulas.
Three-dimensional structures are drawn with solid wedges for bonds coming towards the viewer, dashed wedges for bonds going away, and plain lines for bonds in the plane of the paper.
In past papers
NEET and JEE Main