Organic Chemistry II - Summary of Reactions | Chemistry

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Study GuideOrganic Chemistry II–Summary of Reactions1.Reactions of Alkyl HalidesAlkyl halides (R–X) are very reactive compounds because thecarbon–halogen bond is polar. Thismakes them useful starting materials for many important organic reactions.1. Hydrolysis (Formation of Alcohols)Alkyl halides can be converted intoalcoholsby hydrolysis.Reaction:•Alkyl halide reacts withaqueous NaOH•Heating is requiredWhat happens:•The halogen atom is replaced by ahydroxyl (–OH) group•Analcohol (R–OH)is formedThis reaction usually occurs bynucleophilic substitution.2. Williamson Ether Synthesis (Formation of Ethers)This reaction is used to prepareethers.Reaction:•Alkyl halide reacts withsodium alkoxide (R′O⁻Na⁺)What happens:•The halogen is replaced by an–OR′ group•Anether (R–OR′)is formed

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Study GuideImportant note:•This method works best withprimary alkyl halides•It follows anSN2 mechanism3. Formation of NitrilesAlkyl halides react withcyanide ion (CN⁻)to form nitriles.Reaction conditions:•NaCNin aqueous medium•HeatingWhat happens:•The halogen is replaced by a–CN group•Anitrile (R–C≡N)is formedKey advantage:•The carbon chain lengthincreases by one carbon4. Formation of AminesAlkyl halides can react withammonia or aminesto form different classes of amines.(a) With ammonia:•Formsprimary amines (R–NH₂)(b) With primary amines (R′NH₂):•Formssecondary amines (R–NHR′)(c) With secondary amines (R′₂NH):

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Study Guide•Formstertiary amines (R–NR′₂)Conditions:•Heating•Followed by treatment with base (OH⁻)5. Alkene Formation (Elimination Reaction)Alkyl halides can undergoeliminationto form alkenes.Reaction conditions:•Alcoholic KOH or alkoxide (RO⁻K⁺)•HeatWhat happens:•A hydrogen atom and halogen are eliminated•Adouble bond forms•Analkeneis producedThis reaction generally follows anE2 mechanism.

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Study Guide6. Formation of Grignard ReagentsAlkyl halides react with magnesium to formGrignard reagents, which are very important in organicsynthesis.Reaction conditions:•Magnesium metal•Dry ether(absence of moisture)Product:•R–Mg–X (Grignard reagent)These reagents are highly reactive and used to formnew carbon–carbon bonds.Key Takeaway•Alkyl halides are reactive due to thepolar C–X bond.•Hydrolysisconverts alkyl halides into alcohols.•Williamson ether synthesisis used to prepare ethers.•Reaction withNaCNforms nitriles and increases chain length.•Alkyl halides react with ammonia and amines to form1°, 2°, and 3° amines.•Elimination reactionsproduce alkenes under alcoholic conditions.•Reaction with magnesium formsGrignard reagents, essential for synthesis.•Alkyl halides undergo bothsubstitution and elimination reactions.2.Reactions of PhenolsPhenols are aromatic compounds where a hydroxyl group (–OH) is directly attached to a benzenering.

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Study GuideBecause of this–OH group, phenols show reactions that are different from both alcohols andbenzene.1. Neutralization (Acidic Nature of Phenols)Phenols areweak acids.Reaction:•Phenol reacts withNaOH•Formssodium phenoxideWhat this shows:•Phenols can lose a proton (H⁺)•They aremore acidic than alcohols•Butless acidic than carboxylic acidsPhenols donotreact with NaHCO₃, confirming their weak acidity.2. Ester FormationPhenols react with acid derivatives to formesters.(a) With acid anhydrides:•Producesphenyl esters•A carboxylic acid is formed as a by-product(b) With acid chlorides:

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Study Guide•Producesphenyl esters•HXis releasedKey idea:•Phenols do not easily undergo esterification with carboxylic acids•More reactive reagents (acid chlorides or anhydrides) are needed3. Ether Formation (Williamson-Type Reaction)Phenols can form ethers through theirphenoxide ion.Steps:1.Phenol reacts with NaOH → sodium phenoxide2.Sodium phenoxide reacts with an alkyl halide (R–X)Result:•Aryl alkyl ether (Ar–O–R)is formedThis reaction is similar to Williamson ether synthesis.

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Study Guide4. HalogenationThe–OH group is astrong activating groupand directs substitution toortho and para positions.(a) In aqueous medium:•Reaction is very fast•Forms2,4,6-trihalophenol(b) In non-polar solvent (CS₂) at low temperature:•Mainlymono-substitution•Ortho and para products are formed

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Study Guide5. NitrationPhenols undergo nitration easily due to ring activation.Reaction conditions:•DiluteHNO₃at room temperatureProducts:•Mixture ofortho-nitrophenolandpara-nitrophenolStrong nitrating mixtures lead to polysubstitution.6. SulfonationPhenols react withconcentrated H₂SO₄, and the product depends on temperature.At low temperature (≈25°C):

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Study Guide•Ortho-phenol sulfonic acidis majorAt high temperature (≈100°C):•Para-phenol sulfonic acidis majorThis showstemperature control of orientation.7. Kolbe Reaction (Kolbe–Schmitt Reaction)This reaction is used to preparesalicylic acid.Steps:1.Sodium phenoxide reacts withCO₂2.Acidification withH₃O⁺Result:•Formation ofo-hydroxybenzoic acid (salicylic acid)This reaction is important in pharmaceutical chemistry.

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Study GuideKey Takeaway•Phenols areweak acidsand react with NaOH to form phenoxides.•Phenols formesterswith acid chlorides and anhydrides.•Ether formation occurs via thephenoxide ion.•The–OH group strongly activates the benzene ring.•Phenols undergoortho-and para-directed electrophilic substitution.•Halogenation in water gives2,4,6-trihalophenol.•Nitration giveso-and p-nitrophenols.•Sulfonation istemperature dependent.•TheKolbe reactionconverts phenol into salicylic acid.3.Reactions of Aryl HalidesAryl halides are compounds in which a halogen atom is directly attached to abenzene ring.Because theC–X bond is strengthened by resonance with the aromatic ring, aryl halides aremuch less reactivethan alkyl halides in substitution reactions.1. Grignard ReactionAryl halides can react with magnesium to formGrignard reagents.Reaction conditions:

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