General Organic Chemistry (GOC)

• General organic chemistry (GOC) involves fundamental principles governing the structure, properties, and reactions of organic compounds.
• Organic compounds are primarily composed of carbon and hydrogen, but may also contain other elements such as oxygen, nitrogen, sulfur, and halogens.

Bonding in Organic Compounds

• Carbon's tetravalency is fundamental; it forms four covalent bonds.
• Carbon can form single, double, and triple bonds with other carbon atoms and other elements.
• Hybridization describes the mixing of atomic orbitals to form new hybrid orbitals suitable for bonding.
• sp3 hybridization: Carbon atom bonded to four other atoms (single bonds), tetrahedral geometry, 109.5° bond angles.
• sp2 hybridization: Carbon atom bonded to three other atoms (one double bond), trigonal planar geometry, 120° bond angles.
• sp hybridization: Carbon atom bonded to two other atoms (one triple or two double bonds), linear geometry, 180° bond angles.
• Sigma (σ) bonds are formed by end-on overlap of atomic orbitals, stronger and allow free rotation.
• Pi (π) bonds are formed by sideways overlap of p orbitals, weaker and restrict rotation.
• Bond length decreases with increasing bond order (single > double > triple).
• Bond strength increases with increasing bond order (single < double < triple).

Inductive Effect

• The inductive effect is the polarization of a σ bond due to electronegativity differences between atoms.
• Electron-donating groups (+I effect) release electron density through the sigma bond.
• Electron-withdrawing groups (-I effect) pull electron density through the sigma bond.
• The inductive effect decreases with increasing distance from the substituent.

Resonance

• Resonance is the delocalization of π electrons in a molecule.
• Molecules with resonance structures are more stable.
• Resonance structures are connected by curved arrows showing electron movement.
• Resonance hybrid is the actual structure of the molecule, representing the average of all resonance contributors.
• Resonance contributors must have the same atomic connectivity.
• Resonance contributors must have the same number of paired and unpaired electrons.
• More stable resonance structures have: more complete octets, less charge separation, negative charge on more electronegative atoms, positive charge on less electronegative atoms.

Hyperconjugation

• Hyperconjugation is the delocalization of σ electrons from a σ bond (usually C-H or C-C) to an adjacent empty or partially filled p orbital or π orbital.
• Stabilizes alkenes and carbocations, also influences the conformation of alkanes.
• Greater the number of alpha hydrogens, the greater the hyperconjugation.
• Hyperconjugation is similar to resonance but involves sigma bonds.

Electromeric Effect

• Temporary effect observed in presence of attacking reagent.
• Involves the complete transfer of π electrons to one atom in a polyatomic system.
• +E effect: π electrons move to the atom to which the reagent attacks.
• -E effect: π electrons move away from the atom to which the reagent attacks.

Types of Organic Reactions

• Addition reactions: Two reactants combine to form a single product.
• Elimination reactions: Atoms or groups are removed from a molecule, forming a multiple bond.
• Substitution reactions: One atom or group is replaced by another.
• Rearrangement reactions: Atoms or groups are rearranged within the same molecule.

Reaction Intermediates

• Carbocations: positively charged carbon atoms with six electrons.
• Stability of carbocations: 3° > 2° > 1° > methyl, due to inductive effect and hyperconjugation.
• Carbanions: negatively charged carbon atoms with eight electrons.
• Stability of carbanions: methyl > 1° > 2° > 3°, due to inductive effect.
• Free radicals: species with an unpaired electron.
• Stability of free radicals: 3° > 2° > 1° > methyl, due to hyperconjugation.
• Carbenes: neutral species with a carbon atom having two substituents and two non-bonding electrons.
• Nitrenes: nitrogen analog of carbenes.

Isomerism

• Isomers are molecules with the same molecular formula but different structural or spatial arrangements of atoms.
• Structural isomers (constitutional isomers) have different connectivity.
• Chain isomers: differ in the arrangement of the carbon chain.
• Position isomers: differ in the position of a substituent or functional group.
• Functional group isomers: have different functional groups.
• Metamers: differ in the alkyl groups attached to the same functional group.
• Tautomers: Structural isomers that readily interconvert.
• Stereoisomers have the same connectivity but differ in spatial arrangement.
• Enantiomers: non-superimposable mirror images.
• Diastereomers: stereoisomers that are not mirror images.
• Conformational isomers (conformers) differ by rotation around sigma bonds.
• Newman projection and Sawhorse representation are used to visualize conformers.
• Eclipsed, staggered, gauche, and anti conformations.
• Baeyer's strain theory: explains the stability of cycloalkanes based on angle strain.
• Sachse-Mohr theory explains the absence of angle strain in larger cycloalkanes due to puckered ring conformations.

Nomenclature

• IUPAC nomenclature provides a systematic way to name organic compounds.
• Identify the parent chain (longest continuous carbon chain).
• Number the parent chain to give substituents the lowest possible numbers.
• Name and number the substituents.
• Combine the substituent names and numbers with the parent chain name.

Acids and Bases

• Arrhenius acids produce H+ in water, and Arrhenius bases produce OH- in water.
• Bronsted-Lowry acids are proton donors, and Bronsted-Lowry bases are proton acceptors.
• Lewis acids are electron pair acceptors, and Lewis bases are electron pair donors.
• Factors affecting acidity: electronegativity, size, resonance, inductive effect, hybridization.
• Stronger acids have weaker conjugate bases, and stronger bases have weaker conjugate acids.
• pKa is a measure of acid strength; lower pKa values indicate stronger acids.
• Acid-base reactions favor formation of the weaker acid and weaker base.

Functional Groups

• Alkanes: contain only single bonds.
• Alkenes: contain at least one carbon-carbon double bond.
• Alkynes: contain at least one carbon-carbon triple bond.
• Alcohols: contain a hydroxyl (-OH) group.
• Ethers: contain an oxygen atom bonded to two alkyl or aryl groups (R-O-R').
• Aldehydes: contain a carbonyl group (C=O) bonded to at least one hydrogen atom.
• Ketones: contain a carbonyl group (C=O) bonded to two alkyl or aryl groups.
• Carboxylic acids: contain a carboxyl group (-COOH).
• Esters: contain a carbonyl group bonded to an alkoxy group (-COOR).
• Amines: contain a nitrogen atom bonded to one, two, or three alkyl or aryl groups.
• Amides: contain a carbonyl group bonded to a nitrogen atom.
• Nitriles: contain a cyano group (-CN).
• Halides: contain a halogen atom (F, Cl, Br, I) bonded to a carbon atom.

Chromatography

• Chromatography is a separation technique based on differential distribution of substances between a stationary phase and a mobile phase.
• Substances with different affinities for the stationary phase will travel at different rates.
• Common types include thin-layer chromatography (TLC), column chromatography, gas chromatography (GC), and high-performance liquid chromatography (HPLC).