OC-01 Five Must-Know Facts for NEET

Carbocation stability: 3° > 2° > 1° > $CH_{3}^{+}$ — stabilized by +I effect and hyperconjugation from alkyl groups.
Carbanion stability is the OPPOSITE: $CH_{3}^{-}$ > 1° > 2° > 3° — alkyl +I effect destabilizes the negative carbon.
Hyperconjugation = number of alpha C-H bonds — count them directly for the number of hyperconjugative structures.
-OH is -I (sigma) but +M (pi) — in aromatic systems +M dominates, making -OH ortho/para-directing.
Geometrical isomerism needs TWO conditions: restricted rotation (C=C or ring) AND different substituents on each doubly-bonded carbon — if either is missing, no E/Z isomerism exists.