Organic Chemistry

A systematic naming system for organic compounds based on functional groups, carbon chain length, and substituent positions. The IUPAC name consists of: prefix (number of carbons), parent name (functional group), and suffix (functional group type). Example: 2-methylpropanoic acid has a 3-carbon chain with a methyl branch at position 2. IUPAC nomenclature ensures unambiguous identification and enab

Organic Chemistry

Organic Chemistry

A series of organic compounds with the same functional group, differing by successive CH₂ units, showing gradual changes in physical properties but similar chemical properties. Example: alkanes (methane, ethane, propane, butane) differ by CH₂, have similar C-H bonding, but boiling points increase progressively. Homologous series demonstrate periodic trends in organic chemistry. Homologous series

Organic Chemistry

Organic Chemistry

Specific groups of atoms within molecules responsible for characteristic chemical reactions. Common functional groups: −OH (hydroxyl, alcohols/phenols), −COOH (carboxyl, carboxylic acids), C=O (carbonyl, aldehydes/ketones), −NH₂ (amino), −OR (ether), C=C (alkene), C≡C (alkyne). Functional groups determine reactivity; compounds with same functional group undergo similar reactions regardless of the

Organic Chemistry

Organic Chemistry

Isomers with the same molecular formula but different structural arrangements of atoms (different connectivity). Types: chain isomerism (different carbon skeleton, e.g., butane vs. isobutane), position isomerism (same functional group at different position, e.g., 1-propanol vs. 2-propanol), and functional group isomerism (different functional groups, e.g., ethanol vs. methoxyethane, CH₃CH₂OH vs. C

Organic Chemistry

Organic Chemistry

Isomers with the same molecular formula and same atomic connectivity but different 3D spatial arrangement. E-Z isomerism occurs with restricted rotation around C=C (double bond cannot rotate). Each carbon of the double bond is bonded to two different groups; priority is assigned by atomic number (Cahn-Ingold-Prelog rules). Z (zusammen, together) has higher-priority groups on same side; E (entgegen

Organic Chemistry

Organic Chemistry

A general formula describes the relationship between carbon and hydrogen atoms (and other elements) in a homologous series. Examples: alkanes CₙH₂ₙ₊₂, cycloalkanes CₙH₂ₙ, alkenes CₙH₂ₙ, alkynes CₙH₂ₙ₋₂, carboxylic acids CₙH₂ₙO₂. The general formula enables predicting molecular composition from carbon count (e.g., C₅ alkane is C₅H₁₂) without knowing structural details. Different functional groups h

Organic Chemistry

Organic Chemistry

Alkanes (CₙH₂ₙ₊₂) are nonpolar hydrocarbons with only C-C and C-H single bonds. Properties: boiling point increases with molar mass (van der Waals forces increase), immiscible in water (nonpolar, hydrophobic), viscosity increases with chain length, density increases slightly. Alkanes are relatively unreactive at room temperature (strong C-C and C-H bonds), but undergo combustion and free-radical s

Organic Chemistry

Organic Chemistry

Combustion is a redox reaction where alkane CₙH₂ₙ₊₂ burns in excess oxygen: CₙH₂ₙ₊₂ + (3n+1)/2 O₂ → nCO₂ + (n+1)H₂O. Combustion is exothermic (ΔH < 0), providing energy for heating and vehicle engines. Complete combustion produces only CO₂ and H₂O. Incomplete combustion (limited O₂) produces CO and other products. Bond enthalpy calculation: strong bonds form (C=O in CO₂, O-H in H₂O) releasing more

Organic Chemistry

Organic Chemistry

A reaction mechanism where a free radical attacks an alkane C-H bond, removing H and replacing it with another atom/group. The mechanism has three stages: initiation (homolytic bond cleavage creating radicals), propagation (radical attacks molecule, generating new radical), termination (radicals combine, reaction stops). Example: CH₄ + Cl₂ → CH₃Cl + HCl (photochemically initiated). Free radicals a

Organic Chemistry

Organic Chemistry

Stages of free-radical reactions: Initiation—heat or light causes homolytic cleavage of X-X bond (e.g., Cl-Cl → 2Cl•), creating radicals. Propagation—radical attacks alkane (Cl• + CH₄ → •CH₃ + HCl), producing products and new radicals that repeat the cycle (chain reaction, single photon produces many products). Termination—two radicals combine (Cl• + •CH₃ → CH₃Cl), removing reactive intermediates

Organic Chemistry

Organic Chemistry

Photochemical reaction: CH₄ + Cl₂ → CH₃Cl + HCl (with light, hv). Mechanism: initiation (Cl-Cl → 2Cl•), propagation (Cl• + CH₄ → •CH₃ + HCl, then •CH₃ + Cl₂ → CH₃Cl + Cl•), termination. Further chlorination produces CH₂Cl₂, CHCl₃, CCl₄. The reaction is exothermic and dangerous (explosion risk if mixture contains Cl₂ and hydrocarbon in explosive proportions). Chlorination shows poor selectivity—all

Organic Chemistry

Organic Chemistry

A reaction where a nucleophile (electron-rich, seeking positive charge) replaces a leaving group on a carbon atom. Mechanism: SN1 (unimolecular) forms carbocation intermediate (slow step, rate = k[RX]); SN2 (bimolecular) proceeds via direct displacement with inversion of stereochemistry (rate = k[RX][Nu]). Conditions: SN1 favored by polar solvents, weak nucleophiles, good leaving groups (Br, I), a

Organic Chemistry

Organic Chemistry

SN1 (substitution, nucleophilic, unimolecular): rate = k[RX], two-step—first, alkyl halide dissociates slowly (RX → R⁺ + X⁻, carbocation forms), then nucleophile attacks fast (R⁺ + Nu⁻ → RNu). Carbocation is planar (sp²), allowing attack from either face (racemization). SN2 (bimolecular): rate = k[RX][Nu], one-step, nucleophile attacks from back (opposite to leaving group), displacing X⁻. Configur

Organic Chemistry

Organic Chemistry

A reaction where a small molecule (usually H₂O or HX) is removed from an alkyl halide or alcohol, forming an alkene with a C=C double bond. Mechanism E1 (unimolecular elimination): alkyl halide dissociates forming carbocation (slow), then H⁺ is removed by base (fast). E2 (bimolecular): base attacks H while X⁻ leaves (concerted, one step). Conditions: E1 favored by poor bases, polar solvents, stabl

Organic Chemistry

Organic Chemistry

Halogenoalkanes (RX, where X = Cl, Br, I) undergo nucleophilic substitution and elimination. Reactivity order for nucleophilic substitution: RI > RBr > RCl > RF (C-I bond is weakest, easiest to break). Reactivity for SN2: primary > secondary > tertiary (steric hindrance increases). For SN1: tertiary > secondary > primary (carbocation stability). Elimination favored over substitution at high temper

Organic Chemistry

Organic Chemistry

Chlorofluorocarbons (CFCs) like CFC-12 (CF₂Cl₂) were widely used as refrigerants and propellants. Released into atmosphere, they rise to stratosphere. UV light (hv) breaks C-Cl bond: CF₂Cl₂ + hv → CF₂Cl• + Cl•. Cl• radicals catalytically destroy ozone: Cl• + O₃ → ClO• + O₂, then ClO• + O → Cl• + O₂. One Cl atom can destroy ~100,000 O₃ molecules before being deactivated. Ozone depletion increases U

Organic Chemistry

Organic Chemistry

A reaction where an electrophile (electron-seeking, δ+) attacks the π electrons of an alkene C=C, adding across the double bond to form a saturated product. General mechanism: alkene π bond attacks electrophile (forming carbocation, slow), then nucleophile attacks carbocation (fast). Example: CH₂=CH₂ + H₂SO₄ → CH₃CH₂OSO₃H. Markownikoff's rule predicts which position the electrophile adds (to the m

Organic Chemistry

Organic Chemistry

HBr adds to alkene: C=C + HBr → CHBr-CH₂. Mechanism: π electrons attack H⁺ (forming more stable carbocation), then Br⁻ attacks from either face (carbocation is planar). Markownikoff's rule: H adds to the carbon with more hydrogen neighbors; Br adds to the more substituted carbon. Example: 2-methylpropene + HBr → 2-bromo-2-methylpropane (tert-butyl bromide, stable tertiary carbocation), not 2-bromo

Organic Chemistry

Organic Chemistry

When an unsymmetrical alkene adds an HX, the H adds to the carbon with more hydrogen neighbors (and X adds to the more substituted carbon). The rule predicts product: propene + HBr → 2-bromopropane (not 1-bromopropane). Explanation: reaction proceeds via the more stable carbocation intermediate. 2-bromopropane intermediate (secondary carbocation) is more stable than 1-bromopropane intermediate (pr

Organic Chemistry

Organic Chemistry

Bromine water (Br₂ in CCl₄, orange-brown color) decolorizes when added to an alkene or alkyne, indicating C=C or C≡C. The Br₂ adds across the double bond: C=C + Br₂ → CBr-CBr, removing Br₂ color and producing a clear, colorless (or pale yellow) solution. Saturated alkanes don't decolorize bromine water (no reaction). Aromatic rings require catalyst (FeBr₃) to react with Br₂, so don't readily decol

Organic Chemistry

Organic Chemistry

Polymerization where unsaturated monomers (with C=C or C≡C) sequentially add to a growing chain, forming a polymer without releasing byproducts. Free-radical mechanism: initiator generates •C, which attacks alkene (C=C + •R → •R-C-C), then chain grows as •R-C-C attacks another alkene (propagation). Example: n(C₂H₄) → (−C₂H₄−)ₙ (polyethylene). Markownikoff's rule applies in some cases. Radical poly

Organic Chemistry

Organic Chemistry

Alcohols are classified by the carbon bearing the −OH group: primary (RCH₂OH) has one R group, secondary (R₂CHOH) has two R groups, tertiary (R₃COH) has three R groups. Classification determines reactivity: primary alcohols oxidize to aldehydes then carboxylic acids; secondary oxidize to ketones only; tertiary resist oxidation (no H on the −OH carbon). Primary alcohols undergo SN2 nucleophilic sub

Organic Chemistry

Organic Chemistry

Primary alcohols RCH₂OH oxidize to aldehydes RCHO (1 stage) then to carboxylic acids RCOOH (2 stages) using acidified potassium dichromate (orange turns green, Cr₂O₇²⁻ → Cr³⁺). Secondary alcohols R₂CHOH oxidize to ketones R₂C=O (1 stage) but not further (no H on C-OH). Tertiary alcohols don't oxidize (no H on C-OH). Gentle conditions (PCC pyridinium chlorochromate, or controlled stoichiometry) giv

Organic Chemistry

Organic Chemistry

Removal of water from an alcohol by heating with concentrated H₂SO₄ (acid catalyst and dehydrating agent) produces an alkene: R₂CHOH → R₂C=C + H₂O. Mechanism E1: alcohol protonates (forming R₂C⁺OH₂), water leaves (forming carbocation), then base (H₂O or HSO₄⁻) removes adjacent H⁺. Reactivity: tertiary > secondary > primary (carbocation stability). Markownikoff's rule predicts major alkene product

Organic Chemistry

Organic Chemistry

Condensation of carboxylic acid RCOOH and alcohol R'OH, forming ester RCOOR' and releasing H₂O. Reaction: RCOOH + R'OH ⇌ RCOOR' + H₂O (acid-catalyzed, reversible). Mechanism: acid protonates C=O, alcohol attacks (nucleophilic acyl substitution), eliminates H₂O. Equilibrium lies left; to drive toward ester, use excess alcohol, heat, or remove water (Dean-Stark apparatus). Esters are used in polyest

Organic Chemistry

Organic Chemistry

Anaerobic (without oxygen) metabolic process where glucose is converted to ethanol and CO₂ by yeast or bacteria: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂. Pathway: glycolysis (glucose → pyruvate), pyruvate → acetaldehyde → ethanol (NAD⁺ regeneration for continued glycolysis). Used historically for alcohol production (beer, wine), now also for biofuels. Yeast (Saccharomyces cerevisiae) is most common fermenter. Te

Organic Chemistry

Organic Chemistry

Qualitative tests identify functional groups: alcohols—Na reacts, fizz and heat (no fizz with ether); carbonyl (aldehydes/ketones)—2,4-DNP (yellow/orange precipitate), Fehling's (aldehydes give brick-red Cu₂O, ketones don't react); carboxylic acids—Na gives fizz, litmus turns red; esters—hydrolyze with NaOH, smell pleasant fruity odor; halogenoalkanes—AgNO₃ gives precipitate (Ag-X insoluble). Infr

Organic Chemistry

Organic Chemistry

IR spectroscopy measures absorption of infrared radiation by molecules, revealing functional groups. Characteristic absorptions: C-H stretch ~3000 cm⁻¹, O-H (alcohol) ~3300−3500 cm⁻¹ (broad, hydrogen bonding), O-H (carboxylic acid) ~2500−3300 cm⁻¹ (very broad), C=O ~1700 cm⁻¹ (carbonyl, exact frequency indicates aldehyde/ketone/carboxylic acid/ester), C=C ~1600−1680 cm⁻¹ (alkene, weak). Fingerprin

Organic Chemistry

Organic Chemistry

Mass spectrometry (MS) measures mass-to-charge ratio (m/z) of ions from organic molecules, revealing molecular mass and structure. Electron impact ionization (EI) removes electron, forming molecular ion M⁺ (peak at m/z = M). Molecule then fragments: bonds break, losing neutral species or forming cations. Fragmentation pattern (peaks at different m/z) reflects molecular structure. Common fragments:

Organic Chemistry

Organic Chemistry

In mass spectrometry, fragmentation patterns show peaks at m/z values where bonds break. The molecular ion M⁺ loses neutral molecules or rearranges. Common losses: loss of 18 (H₂O from alcohols), 17 (OH), 44 (CO₂ from carboxylic acids), 29 (CHO), or 43 (CH₃CO from methyl ketones). Peaks at characteristic m/z identify functional groups: carboxylic acids typically show m/z 45 (CHO₂⁺, McLafferty rear

Organic Chemistry

Organic Chemistry

A molecule is chiral if it has a stereocenter (usually a carbon with four different groups) and cannot be superimposed on its mirror image. The two forms are enantiomers. Most organic molecules with a chiral center exist as R and S isomers (Cahn-Ingold-Prelog rules assign priorities by atomic number). Chirality is important in pharmaceuticals: the drug (R)-isomer may be active; the (S)-isomer inac

Organic Chemistry

Organic Chemistry

Enantiomers are mirror-image stereoisomers that are non-superimposable. Chiral molecules with one stereocenter exist as a pair of enantiomers (R and S). Enantiomers have identical physical properties (mp, bp, density, solubility) and identical chemical properties with achiral reagents, but different optical activity (one is dextrorotatory (+), one levorotatory (−)). They react at different rates w

Organic Chemistry

Organic Chemistry

A racemic mixture (or racemate) contains equal amounts (50:50) of R and S enantiomers of a chiral compound. The mixture is optically inactive (equal (+) and (−) rotations cancel). Most synthetic routes produce racemates because they create chiral centers non-selectively. Separating enantiomers requires chiral chromatography or crystallization with chiral resolving agents. In nature, biosynthetic e

Organic Chemistry

Organic Chemistry

Chiral compounds rotate plane-polarized light, exhibiting optical activity. The rotation angle (α) is measured in degrees, with (+) or (−) indicating dextrorotatory or levorotatory. Specific rotation [α] = α / (c × l), where c is concentration (g/100mL) and l is path length (dm). Each enantiomer has opposite specific rotation (R is +, S is −, approximately). Racemic mixtures don't rotate light (eq

Organic Chemistry

Organic Chemistry

The C=O carbonyl (δ+ carbon) is attacked by nucleophiles (−, electron-rich), adding across the C=O to form C−OH intermediate. Mechanism: nucleophile attacks carbon (π bond breaks), forming negatively charged intermediate, then protonation gives product. Examples: RCN + HCN → RC(OH)CN (cyanohydrin, H added in workup), RCHO + NH₂-NH₂ → RCH=N-NH₂ (hydrazone), RCHO + H₂O → RCH(OH)₂ (geminal diol). Ald

Organic Chemistry

Organic Chemistry

Aldehydes and ketones are reduced to primary and secondary alcohols respectively: RCHO + 2H → RCH₂OH (aldehyde → primary alcohol), RCOR' + 2H → RCHOHR' (ketone → secondary alcohol). Reducing agents: NaBH₄ (mild, reduces aldehydes/ketones but not carboxylic acids), LiAlH₄ (strong, reduces aldehydes/ketones, esters, carboxylic acids), H₂ + catalyst (Ni, Pt). Mechanism involves hydride (H⁻) attacking

Organic Chemistry

Organic Chemistry

Aldehydes are oxidized to carboxylic acids: RCHO + [O] → RCOOH using oxidizing agents like acidified potassium dichromate (orange turns green), permanganate, or Tollens reagent. The key difference from alcohols: aldehydes have one more H on the carbonyl carbon, which is oxidized to −OH (carboxylic acid). Ketones cannot be oxidized under these conditions (no H on carbonyl carbon). Mild oxidizing ag

Organic Chemistry

Organic Chemistry

Tollens reagent is ammoniacal silver nitrate (Ag⁺ in ammonia solution); Fehlings is alkaline copper(II) sulfate. Both are oxidizing agents used as qualitative tests: aldehydes give positive test, ketones don't. With Tollens: aldehyde reduces Ag⁺ to Ag (metal mirror forms on test tube—'silver mirror test'). RCHO + 2Ag(NH₃)₂⁺ + 3OH⁻ → RCOO⁻ + 2Ag↓ + 4NH₃ + 2H₂O. With Fehlings: aldehyde reduces Cu²⁺

Organic Chemistry

Organic Chemistry

2,4-Dinitrophenylhydrazine (2,4-DNPH) is a reagent that reacts with aldehydes and ketones (not alcohols, amines). Forms yellow/orange precipitate (2,4-DNP derivative): R₂C=O + H₂N-NH-C₆H₃(NO₂)₂ → R₂C=N-NH-C₆H₃(NO₂)₂ + H₂O. The precipitate can be filtered, recrystallized, and melting point determined (unique for each carbonyl compound). This is a classic qualitative test and identification method:

Organic Chemistry

Organic Chemistry

Carboxylic acids (R−COOH) are weakly acidic (Ka ~ 10⁻⁵ for aliphatic acids), hydrogen bond extensively (−COOH forms dimers and polymers), have high boiling points (hydrogen bonding), and are soluble in water (polar −COOH, hydrogen bonding). Reactivity: undergo nucleophilic acyl substitution (esterification with alcohols, forming amides with amines), dimerization (intermolecular hydrogen bonding),

Organic Chemistry

Organic Chemistry

Acyl chlorides (R−COCl, acid chlorides) are highly reactive compounds formed by treating carboxylic acids with SOCl₂ or PCl₃. Reactivity: readily undergo nucleophilic acyl substitution (with alcohols → esters, with amines → amides, with water → carboxylic acids). Mechanism: nucleophile attacks the δ+ carbonyl carbon; −Cl is an excellent leaving group (Cl⁻ is very stable). The high reactivity stems

Organic Chemistry

Organic Chemistry

Acid anhydrides (R−CO−O−CO−R, or (RCO)₂O) are formed by dehydration of carboxylic acids or reaction of acyl chloride with carboxylate salt. Reactivity: undergo nucleophilic acyl substitution (with alcohols → esters, with amines → amides, with water → carboxylic acids), less reactive than acyl chlorides but more reactive than esters. Mechanism: nucleophile attacks carbonyl carbon; either RCO₂⁻ (car

Organic Chemistry

Organic Chemistry

Organic compounds with the functional group −COOR (or −OCOR), formed by esterification (condensation of a carboxylic acid R−COOH and an alcohol R'−OH). Esters are generally unreactive toward nucleophiles at room temperature (unlike acid halides or anhydrides). Esters have pleasant odors (e.g., ethyl ethanoate smells fruity) and are used as flavorings, solvents, and in polymer synthesis. Esters ar

Organic Chemistry

Organic Chemistry

Fischer esterification is the reaction of carboxylic acid and alcohol in acid catalyst to form ester: R−COOH + R'−OH ⇌ R−COO−R' + H₂O (H₂SO₄ or HCl catalyst). Mechanism: acid protonates C=O (activating), alcohol attacks nucleophilically, proton transfers, and H₂O leaves. The reaction is reversible; equilibrium favors products when excess alcohol is used or water is removed. Ester formation is nucl

Organic Chemistry

Organic Chemistry

Esters hydrolyze (break apart) in acid or base to regenerate carboxylic acid and alcohol. Acid hydrolysis (reversible): RCOOR' + H₂O ⇌ RCOOH + R'OH (H⁺ catalyst, equilibrium favors reactants). Base hydrolysis (saponification, irreversible): RCOOR' + NaOH → RCOONa + R'OH (OH⁻ nucleophile attacks, salt formed). Mechanism: nucleophile (H₂O or OH⁻) attacks carbonyl carbon (nucleophilic acyl substituti

Organic Chemistry

Organic Chemistry

Benzene (C₆H₆) has alternating C−C and C=C bonds (Kekule structure), but experimental evidence (constant bond lengths ~1.39 Å, not 1.48 Å for C−C or 1.34 Å for C=C) reveals delocalized π electrons. Modern understanding: π electrons delocalize over all 6 carbons (resonance structures). Representation: hexagon with circle inside (indicates delocalization). The delocalization stabilizes benzene (reso

Organic Chemistry

Organic Chemistry

In aromatic electrophilic substitution, benzene ring (π electrons, nucleophilic) attacks an electrophile (electron-poor, δ+), replacing a hydrogen. General mechanism: electrophile attacks ring (forming carbocation intermediate), then H⁺ is removed, restoring aromaticity. Example: Br₂ + FeBr₃ → Br⁺ (electrophile), attacks benzene, forms bromobenzene. Nitration: HNO₃ + H₂SO₄ → NO₂⁺ (electrophile), p

Organic Chemistry

Organic Chemistry

Nitration: benzene + HNO₃ (with conc. H₂SO₄ catalyst) → nitrobenzene (C₆H₅NO₂) + H₂O. Mechanism: HNO₃ + H₂SO₄ → NO₂⁺ (nitronium ion, electrophile) + HSO₄⁻. NO₂⁺ attacks benzene π electrons (electrophilic aromatic substitution), forming carbocation intermediate. H⁺ removed by HSO₄⁻ (restoring aromaticity). Nitrobenzene is pale yellow, used as solvent and intermediate for reducing to aniline (C₆H₅NH

Organic Chemistry

Organic Chemistry

Friedel-Crafts alkylation: benzene + RCl + AlCl₃ → alkylbenzene + HCl. Mechanism: RCl + AlCl₃ → R⁺ (carbocation, electrophile) + AlCl₄⁻. R⁺ attacks benzene π electrons (electrophilic aromatic substitution), forming carbocation intermediate. H⁺ removed (restoring aromaticity). Example: benzene + CH₃Cl + AlCl₃ → toluene (C₆H₅CH₃). The alkyl group (−R) is electron-donating, activates ring (makes furt

Organic Chemistry

Organic Chemistry

Friedel-Crafts acylation: benzene + RCOCl + AlCl₃ → benzophenone/phenyl alkyl ketone + HCl. Mechanism: RCOCl + AlCl₃ → RCO⁺ (acylium ion, electrophile, resonance-stabilized). RCO⁺ attacks benzene π electrons, forming carbocation intermediate. H⁺ removed (restoring aromaticity). Example: benzene + CH₃COCl + AlCl₃ → acetophenone (C₆H₅COCH₃, methyl phenyl ketone). Unlike alkylation, acylation doesn't

Organic Chemistry

Organic Chemistry

Amines are classified by carbon-nitrogen bonds: primary (RNH₂, one carbon on N), secondary (R₂NH, two carbons on N), tertiary (R₃N, three carbons on N). Affects reactivity: primary amines are most nucleophilic (lone pair unhindered), secondary intermediate, tertiary least (steric hindrance). Primary amines can be oxidized (to imines → aldehydes); secondary can't be oxidized easily (no H on N). Bas

Organic Chemistry

Organic Chemistry

Amines are prepared by: (1) nucleophilic substitution—halogenoalkane + NX (where X = Br, I, or CN with KCN → nitrile → amine via LiAlH₄ reduction), (2) reduction—nitrile RCN + LiAlH₄ → RCH₂NH₂ (primary amine); amide RCON R' + LiAlH₄ → amine; carbonyl + NH₃ + reducing agent (imine reduction), (3) arene + HNO₃/H₂SO₄ → nitrobenzene → reduction (Sn/HCl or Fe/AcOH) → aniline. Nucleophilic substitution

Organic Chemistry

Organic Chemistry

Amines are weak bases due to lone pair on nitrogen. Primary amines RNH₂ (most basic, pKb ~3−4), secondary (pKb ~3−5), tertiary (pKb ~3−4). Aromatic amines (aniline pKb ~9, much weaker) because lone pair delocalizes into aromatic ring (unavailable for protonation). Inductive effects: electron-donating alkyl groups increase basicity (primary < secondary because steric hindrance), electron-withdrawin

Organic Chemistry

Organic Chemistry

Amines are nucleophiles (lone pair attacks electrophiles). Key reactions: (1) nucleophilic substitution—RNH₂ + RX → RNH−R + HX (primary amine displaces halide), (2) acylation—RNH₂ + RCOCl → RCONHR + HCl (amide formation, used for protection), (3) with nitrous acid—RNH₂ + HNO₂ → unstable diazonium (decomposes, gives alcohol or carbocation), (4) with carbonyls—RNH₂ + R'CHO → RN=CHR' + H₂O (imine for

Organic Chemistry

Organic Chemistry

Addition polymers form when monomers with C=C bonds add to each other sequentially, without losing byproducts. Mechanism: free-radical initiator creates •C, attacks alkene (C=C + •R → •R−C−C), chain grows as •R−C−C attacks more alkenes. Examples: polyethylene (−CH₂−CH₂−)ₙ from ethene, polypropylene from propene, polystyrene from styrene, PVC from chloroethene, PTFE from tetrafluoroethene. Markowni

Organic Chemistry

Organic Chemistry

Condensation polymers form when monomers join by eliminating small molecules (H₂O, MeOH, HCl). Require difunctional monomers: dicarboxylic acid + diol → polyester (−CO−O−), dicarboxylic acid + diamine → polyamide (−CO−NH−). Reaction is reversible (equilibrium), so high conversion requires removing water or using activated monomers (acid chlorides, anhydrides). Polyesters: HOOC−R−COOH + HO−R'−OH →

Organic Chemistry

Organic Chemistry

Polyesters are condensation polymers with repeating −CO−O− ester linkages, formed from dicarboxylic acids and diols. Reaction: HOOC−R−COOH + HO−R'−OH → [−CO−R−CO−O−R'−O−]ₙ + nH₂O (esterification, acid-catalyzed, reversible). Key examples: PET (polyethylene terephthalate, from terephthalic acid + ethylene glycol)—bottles, fibers; unsaturated polyester (with C=C in backbone)—composite resins. Proper

Organic Chemistry

Organic Chemistry

Polyamides (nylons) are condensation polymers with repeating −CO−NH− amide linkages. Reaction: HOOC−(CH₂)ₘ−COOH + H₂N−(CH₂)ₙ−NH₂ → [−CO−(CH₂)ₘ−CO−NH−(CH₂)ₙ−NH−]ₓ + xH₂O. Named by carbon counts: nylon-6,6 (adipic acid m=4 + hexamethylene diamine n=6). Properties: strong, durable, flexible, excellent for textiles and engineering. Strength from hydrogen bonding between −CO and −NH on adjacent chains

Organic Chemistry

Organic Chemistry

Amino acids have general structure: H₂N−CHR−COOH (amino group, chiral center, carboxylic acid). R is the side chain, varying for each amino acid (glycine R = H, alanine R = CH₃, etc.). Chiral center: all amino acids except glycine are chiral (have R and S enantiomers); naturally occurring amino acids are L-enantiomers (by convention, not absolute configuration). In solution pH-dependent: at low pH

Organic Chemistry

Organic Chemistry

Zwitterions (dipolar ions) have both positive and negative charges on the same molecule, characteristic of amino acids. At the isoelectric point (pI), amino acids exist as zwitterionic H₃N⁺−CHR−COO⁻ (protonated amino, deprotonated carboxyl). At low pH, both groups protonated (H₃N⁺−CHR−COOH); at high pH, both deprotonated (H₂N−CHR−COO⁻). The pI is the pH where the amino acid is zwitterionic and ele

Organic Chemistry

Organic Chemistry

Peptide bonds (−CO−NH−) form between amino acids during protein synthesis: carboxyl (−COOH) of one amino acid reacts with amino (−NH₂) of another, releasing water (condensation). Reaction: R₁CH(NH₂)COOH + H₂N−CHR₂COOH → R₁CH(NH₂)CO−NH−CHR₂COOH + H₂O. The bond is planar (resonance: C=O ↔ C-O⁻, restricted rotation around C-N). Polypeptides are chains of amino acids linked by peptide bonds (backbone

Organic Chemistry

Organic Chemistry

Protein structure has four levels: primary (amino acid sequence, determined by peptide bonds), secondary (α-helices, β-sheets stabilized by backbone hydrogen bonds between −CO and −NH), tertiary (3D shape from side chain interactions: H-bonds, disulfide bonds S-S, hydrophobic interactions), and quaternary (multiple polypeptide chains assembled together, like hemoglobin 4 subunits). Primary determi

Organic Chemistry

Organic Chemistry

DNA nucleotides consist of three components: a deoxyribose sugar (5-carbon), a phosphate group (−PO₄²⁻), and a nitrogenous base (purine: adenine A, guanine G; pyrimidine: cytosine C, thymine T). Nucleotides link via phosphodiester bonds (phosphate oxygen bonds to 3'−OH of sugar to 5'−OH of next sugar), forming the DNA backbone (−sugar−phosphate−sugar−phosphate− repeating). Bases attach via glycosi

Organic Chemistry

Organic Chemistry

Multi-step synthesis combines multiple reactions to convert a starting material into a desired product through intermediates. Strategy: identify functional group transformations needed, choose compatible reactions, consider regiochemistry and stereochemistry, and plan protecting group use if needed. Example: converting ethylbenzene to phenylacetic acid requires: (1) oxidize methyl to carboxylic ac

Organic Chemistry

Organic Chemistry

Retrosynthesis works backward from a target molecule, breaking bonds and proposing precursors for each step. Strategy: identify key functional groups and bonds to break, suggest synthetic equivalents (umpolung for disconnections), and repeat until reaching available starting materials. Example: to synthesize acetophenone C₆H₅COCH₃, disconnect C-CO bond: retro-Friedel-Crafts suggests benzene + CH₃C

Organic Chemistry

Organic Chemistry

Synthetic routes are sequences of reactions chosen to convert starting material to product. Considerations: (1) available starting materials, (2) required transformations (oxidation, reduction, substitution, elimination, addition), (3) functional group compatibility (protecting groups if needed), (4) regio/stereochemistry control, (5) yield and cost of reagents. Example: ethylbenzene → benzoic aci

Organic Chemistry

Organic Chemistry

Protecting groups are functional groups temporarily attached to prevent reactivity of sensitive groups during synthesis. Strategy: (1) protect sensitive group (e.g., −OH as −O−TMS), (2) perform desired transformation on another group, (3) remove protecting group (−O−TMS + F⁻ → −OH). Common: −OH protected as −O−Ac (acetyl), −O−Bn (benzyl), −O−TMS (trimethylsilyl); −NH₂ protected as −N−Boc (tert-but

Organic Chemistry

Organic Chemistry

¹³C NMR shows carbon chemical shifts (δ, ppm relative to TMS at 0 ppm), revealing carbon environments in molecules. Chemical shift ranges: alkyl C (0−50 ppm), C-O or C-N (50−100 ppm), unsaturated C (100−150 ppm), aromatic C (120−150 ppm), carbonyl C (150−220 ppm). Each carbon atom produces a peak (or splits into multiplets via ¹H-¹³C coupling if protons attached). DEPT (Distortionless Enhancement

Organic Chemistry

Organic Chemistry

¹H NMR shows proton chemical shifts (δ, ppm relative to TMS at 0 ppm), revealing proton environments and their numbers in molecules. Chemical shifts: alkyl (0−3 ppm), α to electron-withdrawing (3−5 ppm), aromatic (7−8 ppm), aldehyde (9−10 ppm), carboxylic acid/phenol (10−13 ppm). Integrations (peak areas) indicate relative numbers of protons. Spin-spin coupling (J-values, Hz) to nearby protons spl

Organic Chemistry

Organic Chemistry

Chemical shift (δ) measures the difference in resonance frequency between a nucleus and a reference standard (TMS, tetramethylsilane, arbitrarily set to 0 ppm), expressed in parts per million (ppm). Calculated as: δ = (ν_sample − ν_reference) / ν_reference × 10⁶. Chemical shift indicates electronic environment: nuclei shielded by electrons resonate at lower frequency (upfield, smaller δ), deshield

Organic Chemistry

Organic Chemistry

Spin-spin coupling (J-coupling) causes NMR signals to split into multiplets due to interaction with neighboring magnetic nuclei (usually ³J for vicinal protons, three bonds away). Coupling constant J (in Hz) indicates coupling strength (independent of spectrometer field strength). ³J(HH) ~ 6−8 Hz for vicinal coupling (e.g., −CH−CH−), ²J for geminal (two bonds, −CH₂−, ~12−15 Hz), ⁴J for long-range

Organic Chemistry

Organic Chemistry

Integration (peak area in ¹H NMR) indicates the number of protons in an environment (proportional to number of equivalent protons). Example: ethanol CH₃CH₂OH has 3H (methyl CH₃, integral = 3), 2H (methylene CH₂, integral = 2), 1H (−OH, integral = 1). Equivalent protons (same chemical environment due to symmetry or rapid rotation) produce single peak. Example: cyclohexane all 12 H are equivalent (r

Organic Chemistry

Organic Chemistry

A chromatographic technique where a thin layer of adsorbent (usually silica gel or alumina) on a plate is used to separate organic compounds. A mixture is applied to the baseline, and a mobile phase (solvent) moves up the plate. Different compounds move at different rates based on their affinity for the stationary phase. In thin-layer chromatography (TLC), a glass or plastic plate is coated with

Organic Chemistry

Organic Chemistry

Gas chromatography (GC) separates volatile organic compounds into individual components before detection. Apparatus: sample injector (evaporates sample), heated column (packed or capillary with stationary phase, e.g., silica), carrier gas flow (mobile phase, usually He or N₂), and detector (FID flame ionization, measures organic compounds; ECD electron capture, detects halogenated compounds). Sepa

Organic Chemistry

Organic Chemistry

The retardation factor in chromatography, defined as the ratio of the distance traveled by a compound to the distance traveled by the solvent front. Rf = (distance traveled by compound) / (distance traveled by solvent front). Rf values are characteristic of compounds under specific conditions and range from 0 to 1. The Rf value is a quantitative measure of a compound's movement in chromatography.

Organic Chemistry

Organic Chemistry

Carbocation stability depends on alkyl substitution: tertiary (R₃C⁺) > secondary (R₂CH⁺) > primary (RCH₂⁺) > methyl (CH₃⁺). Stabilization from electron-donating alkyl groups (hyperconjugation and inductive effects). Alkyl groups donate electron density via σ bonds (hyperconjugation: C-H bonds overlap with empty p orbital, stabilizing C⁺). Resonance stabilization: allylic (CH₂=CH−CH₂⁺ ↔ CH₂−CH=CH⁺)

Organic Chemistry

Organic Chemistry

Benzene (C₆H₆) is the simplest aromatic hydrocarbon, a planar six-membered ring of carbon atoms with alternating σ and π bonds. The π electrons (6 total) are delocalized over all six carbons, stabilizing the ring (resonance energy ~150 kJ/mol). Experimental evidence: all C−C bond lengths are identical (~1.39 Å, between single ~1.48 Å and double ~1.34 Å), confirming delocalization. Kekule structure

Organic Chemistry

Organic Chemistry

Aromaticity describes the stability and reactivity of aromatic compounds like benzene. Requirements (Hückel's rule): (1) monocyclic, (2) planar, (3) fully conjugated π system, (4) 4n+2 π electrons (n = 0, 1, 2...), so 2, 6, 10, 14... electrons. Benzene (6 π electrons, n=1) is aromatic. Cyclopentadienyl anion (C₅H₅⁻, 6 π electrons) is aromatic (stable). Cyclobutadiene (4 π electrons, 4n with n=1) i

Organic Chemistry

Organic Chemistry

Nitriles (RCN, also called isocyanides or isonitriles for R−NC) contain a C≡N triple bond (two π bonds and one σ bond). Formed by: nucleophilic substitution (RX + KCN → RCN + X⁻), dehydration of primary amides (RCONH₂ → RCN), or oxidation of primary amines. Nitriles are polar (δ+ carbon, δ− nitrogen), making them good electrophiles for nucleophilic addition. Reactions: reduce to primary amines (RC

Organic Chemistry

Organic Chemistry

Disulfide bonds (S−S, disulfide bridges) form between two cysteine residues via oxidation of their sulfhydryl (−SH) groups: 2 R−SH → R−S−S−R + 2H⁺ + 2e⁻. Disulfide bonds are covalent, strong (100 kJ/mol), and crucial for stabilizing protein tertiary and quaternary structure. Found in extracellular proteins (harsh conditions favor disulfide formation) and intracellular proteins (reducing environmen

Organic Chemistry

Organic Chemistry

Tertiary structure is the 3D folding of a single polypeptide chain, determined by interactions between side chains (R groups): hydrogen bonds between backbone and side chains, electrostatic interactions (salt bridges) between charged residues, disulfide bonds between cysteines, hydrophobic interactions (nonpolar residues cluster in protein core), and van der Waals forces. The folding is driven by

Organic Chemistry

Organic Chemistry

Phosphodiester bonds link nucleotides in DNA/RNA backbone: the 3'−OH of one sugar's ribose forms an ester bond with phosphate, which esterifies the 5'−OH of the next sugar. Reaction: sugar1-3'−OH + HO−PO₃²⁻ + 5'−OH−sugar2 → sugar1-3'−O−PO₃−O−5'−sugar2 (with net release of water). The phosphodiester linkage is negatively charged (PO₃²⁻ at physiological pH), making DNA/RNA polyanionic (repulsion req

Organic Chemistry

Organic Chemistry

Nucleophilic acyl substitution is a reaction where a nucleophile attacks the δ+ carbonyl carbon of an acyl compound (RCOX), displacing the leaving group X⁻ and forming a new acyl product (RCONY). General mechanism: nucleophile attacks C=O (π bond breaks, σ bond to X becomes weaker), tetrahedral intermediate forms, then X⁻ leaves (restoration of C=O double bond). Reactivity order (most to least rea

Organic Chemistry

Organic Chemistry

Amides (RCONR'₂, primary RCONH₂, secondary RCONHR', tertiary RCONR'₂) contain C(=O)−N bonds. Formed by: nucleophilic acyl substitution of acyl chlorides, anhydrides, or esters with amines (RCOCl + R'NH₂ → RCONHR' + HCl), or condensation of carboxylic acids with amines (requires activation or dehydrating agent). Amides are relatively unreactive (N lone pair is delocalized into C=O via resonance, re

Organic Chemistry

Organic Chemistry

Carbocation rearrangement occurs when a carbocation is unstable; adjacent C-H or C-C bonds shift to form a more stable carbocation. Mechanisms: (1) hydride shift (1,2-hydride), (2) methyl/alkyl shift (1,2-alkyl shift). Example: 1,2-dimethylpropyl cation (primary) is unstable; methyl shifts from adjacent carbon to form tertiary carbocation (more stable). Rearrangement: CH₃−CH(CH₃)⁺−CH₃ → CH₃−C(CH₃)

Organic Chemistry

Organic Chemistry

Decarboxylation is loss of CO₂ (carbon dioxide) from a molecule, typically carboxylic acids (RCOOH → RH + CO₂) or related compounds. Reactions: (1) thermal decarboxylation (heating carboxylic acids loses CO₂, especially β-keto acids, β-dicarboxylic acids), (2) photochemical (α-amino acids under UV), (3) enzymatic (carboxylases, particularly important in biochemistry—pyruvate decarboxylase converts

Organic Chemistry