Organic Chemistry: Functional Groups, Mechanisms, and Stereochemistry
Organic chemistry is pattern recognition plus electron flow. Learn functional groups cold-alkane, alkene, alkyne, alcohol, ether, amine, amide, carboxylic acid, ester, ketone, aldehyde, aromatic ring-and how each behaves as an acid, base, nucleophile, or electrophile. Nomenclature follows priority rules, and stereochemistry uses Cahn–Ingold–Prelog priorities: highest atomic number first, then compare outward.
Reaction mechanisms: SN1 proceeds through a carbocation, favors tertiary substrates and polar protic solvents, and gives racemization; SN2 is concerted, backside attack, favors primary substrates and polar aprotic solvents, and inverts stereochemistry. E1 accompanies SN1; E2 requires an anti-periplanar arrangement and a strong base. Electrophilic addition to alkenes follows Markovnikov's rule unless a peroxide reverses it; aromatic substitution requires an aromatic ring and an electrophile, with activating and deactivating substituents directing position.
Traps: forgetting that resonance stabilizes acids and bases; assuming a chiral center always means an optically active sample (racemic mixtures are not); and misassigning R/S by ignoring the lowest-priority group pointing toward you.
Worked example: 2-butanol has a chiral carbon. Priorities are OH > ethyl > methyl > H. If H points away and the remaining order is clockwise, the configuration is R; if H points toward you, reverse the result.
Rule of thumb: for mechanisms, ask three questions-what is the nucleophile, what is the electrophile, and what is the solvent? The answers usually identify substitution versus elimination and the stereochemical outcome.