General Organic Chemistry Fundamentals

General Organic Chemistry (GOC) is the conceptual backbone of all organic chemistry topics in NEET. Carbon's tetravalency and ability to undergo hybridization govern the shapes and reactivity of all organic molecules.

Hybridization: sp3 hybridization (four equivalent orbitals, 109.5 degrees, tetrahedral — CH₄ C), sp2 (three orbitals in a plane, 120 degrees, trigonal planar — C₂H₄ C=C), and sp (two orbitals linear, 180 degrees — C₂H₂ C#C). The percentage s-character increases from sp3 (25%) to sp2 (33.3%) to sp (50%), directly affecting bond strength, bond length, and electronegativity of the hybrid orbital.

IUPAC Nomenclature follows: (1) identify the longest continuous carbon chain containing the principal functional group, (2) number from the end nearer to the highest priority group, (3) use appropriate prefix/suffix for substituents and functional groups. Functional groups include hydroxyl (-OH, suffix: -ol), aldehyde (-CHO, suffix: -al), ketone (C=O, suffix: -one), carboxyl (-COOH, suffix: -oic acid), and amino (-NH₂, suffix: -amine).

Isomerism: Structural isomers share molecular formula but differ in connectivity — chain (different carbon skeletons), position (different functional group location), functional group (different groups, same formula), and metamerism (different alkyl groups around a heteroatom). Stereoisomers have the same connectivity but differ in spatial arrangement — geometrical (E/Z, requiring restricted rotation and different groups on each doubly-bonded carbon) and optical (non-superimposable mirror images, requiring a chiral center).

Electronic Effects: The inductive effect is a permanent polarization through $\sigma$ bonds. +I groups (alkyl groups like -CH₃, -C₂H₅) donate electron density; -I groups (-F, -Cl, -OH, -NO₂, -COOH) withdraw it. The effect diminishes with distance. The mesomeric (resonance) effect operates through conjugated $\pi$ systems: +M groups (-OH, -NH₂, -OR) donate electrons into the ring, while -M groups (-NO₂, -CHO, -COOH, -CN) withdraw them. Hyperconjugation is a no-bond resonance involving the $\sigma$ C-H bond adjacent to a double bond or carbocation — more $\alpha$-H atoms mean more hyperconjugative structures and greater stabilization.

Reaction Intermediates: Covalent bond fission can be homolytic (producing free radicals, equal sharing) or heterolytic (producing carbocations and carbanions, unequal sharing). Carbocation stability: 3 degree > 2 degree > 1 degree > CH₃+ (stabilized by +I effect and hyperconjugation). Carbanion stability is the reverse: CH₃- > 1 degree > 2 degree > 3 degree (electron-donating alkyl groups destabilize the negative charge). Free radical stability follows the carbocation pattern: 3 degree > 2 degree > 1 degree > CH₃ radical.

Reaction Types: Substitution (one group replaces another), addition (two reactants combine into one product, at unsaturated bonds), elimination (removal of atoms/groups to form unsaturation), and rearrangement (structural reorganization within a molecule).

The key testable concept is the opposite stability orders of carbocations (3 degree > 2 degree > 1 degree) and carbanions (CH₃- > 1 degree > 2 degree > 3 degree), and recognizing that hyperconjugation stabilizes both carbocations and alkenes.