Organic Chemistry — Prelims Strategy

Prelims Strategy

Read molecular formula, connectivity and functional group as separate levels of information. If two compounds share a formula, compare their atom connections before deciding whether they are identical or isomeric. A rotated drawing or isotopic substitution is not, by itself, evidence of the connectivity change required for structural isomerism.

Attach the stated conditions to general formulas. CnH2n+2 describes an open-chain alkane, while CnH2n does not uniquely identify an alkene because a saturated monocyclic structure can fit. For homologous-series arithmetic, count the complete CH2 increment rather than carbon alone: 12 + 2 = 14 using the supplied relative masses.

In application questions, distinguish micellar dispersion from chemical destruction and hard-water soap precipitation from other processes such as acidification or carbonate softening. Avoid category shortcuts about safety, natural origin or environmental fate. A correct statement about a functional group can still be insufficient for a claim about the whole molecule or a commercial formulation. Select the conclusion supported by the precise structure and conditions supplied.