Glossary: Key GOC Terms

Term	Definition
Hybridization	Mixing of atomic orbitals of similar energy to form new, equivalent hybrid orbitals with defined geometry
sp3 hybridization	Mixing of 1s + 3p orbitals → 4 tetrahedral hybrid orbitals (109.5°, 25% s-character)
sp2 hybridization	Mixing of 1s + 2p orbitals → 3 trigonal planar hybrid orbitals (120°, 33.3% s-character)
sp hybridization	Mixing of 1s + 1p orbitals → 2 linear hybrid orbitals (180°, 50% s-character)
% s-character	The fraction of s-orbital character in a hybrid orbital; determines bond length, strength, and electronegativity
IUPAC nomenclature	Systematic naming rules: longest chain + lowest locant + alphabetical prefixes + correct suffix
Structural isomerism	Same molecular formula, different connectivity/bonding; subtypes: chain, position, functional group, metamerism
Chain isomerism	Structural isomers with different carbon skeleton arrangements (straight vs. branched)
Position isomerism	Same carbon skeleton, same functional group, different position of the functional group
Functional group isomerism	Same molecular formula but different functional groups (e.g., alcohol vs. ether, aldehyde vs. ketone)
Metamerism	Different alkyl groups on either side of the same heteroatom (O, N, S)
Stereoisomerism	Same connectivity, different 3D spatial arrangement; includes geometrical and optical isomerism
Geometrical $\frac{E}{Z}$ isomerism	Restricted rotation + different groups on each doubly-bonded carbon; E = higher-priority groups opposite; Z = same side
Optical isomerism	Non-superimposable mirror images (enantiomers); requires chiral center (4 different groups on C)
Chirality	Property of a molecule that cannot be superimposed on its mirror image; causes optical activity
Meso compound	Has chiral centers but is optically inactive due to internal plane of symmetry
Inductive effect (I)	Permanent polarization of sigma bonds due to electronegativity differences; decreases with distance
+I effect	Electron donation through sigma bonds by alkyl groups
-I effect	Electron withdrawal through sigma bonds by electronegative groups (-F, -Cl, -NO2, etc.)
Mesomeric (resonance) effect (M)	Delocalization of electrons through conjugated pi systems
+M effect	Donation of lone pair electrons into an adjacent pi system; shown by -OH, -NH2, -OR
-M effect	Withdrawal of electrons from pi system; shown by -NO2, -CHO, -COOH, -CN
Hyperconjugation	No-bond resonance involving sigma electrons of alpha C-H bonds; stabilizes carbocations and alkenes
Alpha carbon	The carbon directly adjacent to a functional group or charged center
Carbocation	sp2 hybridized carbon with a positive charge (empty p-orbital); stabilized by +I and hyperconjugation
Carbanion	sp3 hybridized carbon with a negative charge (lone pair); stabilized by -I, -M, and higher s-character
Free radical	Neutral species with one unpaired electron; produced by homolytic fission; stabilized like carbocations
Homolytic fission	Equal bond cleavage; each atom gets one electron; produces free radicals
Heterolytic fission	Unequal bond cleavage; one atom gets both electrons; produces ions (carbocation + anion or carbanion + cation)
CIP rules	Cahn-Ingold-Prelog priority rules: higher atomic number = higher priority; used for E/Z and R/S assignment