Reactions

Reaction index

• Chlorination: Alcohols → Chloroalkanes

  Alcohols can be converted into chloroalkanes to create a better leaving group for downstream substitution.

• Chlorination with thionyl chloride: Alcohols → Chloroalkanes

  Thionyl chloride converts alcohols into chloroalkanes with sulfur dioxide and hydrogen chloride as by-products.

• Bromination: Alcohols → Bromoalkanes

  Bromide and acid conditions convert alcohols into bromoalkanes.

• Iodination: Alcohols → Iodoalkanes

  Iodine and red phosphorus conditions convert alcohols into iodoalkanes.

• Hydrochlorination: Alkenes → Chloroalkanes

  Addition of hydrogen chloride across an alkene can form a chloroalkane.

• Hydrobromination: Alkenes → Bromoalkanes

  Addition of hydrogen bromide across an alkene can form a bromoalkane.

• Hydroiodination: Alkenes → Iodoalkanes

  Addition of hydrogen iodide across an alkene can form an iodoalkane.

• Hydrolysis: Chloroalkanes → Alcohols

  The C-Cl bond can be displaced by hydroxide to form an alcohol.

• Cyanation: Chloroalkanes → Nitriles

  Cyanide substitution forms a nitrile and extends the carbon chain by one carbon.

• Cyanation: Bromoalkanes → Nitriles

  Cyanide substitution forms a nitrile and extends the carbon chain by one carbon.

• Cyanation: Iodoalkanes → Nitriles

  Cyanide substitution forms a nitrile and extends the carbon chain by one carbon.

• Amination: Chloroalkanes → Amines

  Ammonia substitutes chloride to form a primary amine; excess ammonia limits further alkylation.

• Amination: Bromoalkanes → Amines

  Ammonia substitutes bromide to form a primary amine; excess ammonia limits further alkylation.

• Amination: Iodoalkanes → Amines

  Ammonia substitutes iodide to form a primary amine; excess ammonia limits further alkylation.

• Elimination: Chloroalkanes → Alkenes

  Base-promoted elimination removes HCl to form an alkene.

• Hydrolysis: Bromoalkanes → Alcohols

  The C-Br bond can be displaced by hydroxide to form an alcohol.

• Hydrolysis: Iodoalkanes → Alcohols

  The C-I bond can be displaced by hydroxide to form an alcohol.

• Elimination: Bromoalkanes → Alkenes

  Base-promoted elimination removes HBr to form an alkene.

• Elimination: Iodoalkanes → Alkenes

  Base-promoted elimination removes HI to form an alkene.

• Cyanohydrin formation: Aldehydes → Hydroxynitriles

  Cyanide addition to an aldehyde forms a hydroxynitrile, giving a carbonyl-route analogue of the nitrile chain-extension motif.

• Cyanohydrin formation: Ketones → Hydroxynitriles

  Cyanide addition to a ketone forms a hydroxynitrile, adding a second carbonyl route into the expanded organic network.

• Iodoform reaction: Methyl ketones → Triiodomethane products

  Alkaline iodine converts methyl ketones into yellow triiodomethane and a carboxylate with one fewer carbon.

• Iodoform reaction: Ethanal → Triiodomethane products

  Ethanal gives triiodomethane and methanoate in the alkaline iodine iodoform reaction.

• Iodoform reaction: Ethanol → Triiodomethane products

  Ethanol is oxidised and cleaved by alkaline iodine to give triiodomethane and methanoate.

• Iodoform reaction: Methyl secondary alcohols → Triiodomethane products

  Methyl secondary alcohols are oxidised to methyl ketones, then cleaved to triiodomethane and a one-carbon-shorter carboxylate.

• Oxidation: Alcohols → Aldehydes

  Controlled oxidation of a primary alcohol gives an aldehyde.

• Oxidation: Alcohols → Ketones

  Oxidation of a secondary alcohol gives a ketone.

• Oxidation: Alcohols → Carboxylic acids

  Full oxidation of a primary alcohol gives a carboxylic acid.

• Controlled oxidation: Primary alcohols → Aldehydes

  Controlled oxidation of a primary alcohol gives an aldehyde.

• Complete oxidation: Primary alcohols → Carboxylic acids

  Full oxidation of a primary alcohol gives a carboxylic acid.

• Oxidation: Secondary alcohols → Ketones

  Oxidation of a secondary alcohol gives a ketone.

• Reduction: Aldehydes → Primary alcohols

  Reduction of an aldehyde gives a primary alcohol.

• Reduction: Ketones → Secondary alcohols

  Reduction of a ketone gives a secondary alcohol.

• Reduction: Carboxylic acids → Primary alcohols

  Reduction of a carboxylic acid gives a primary alcohol.

• Oxidation: Aldehydes → Carboxylic acids

  Oxidation of an aldehyde gives a carboxylic acid.

• Alkylation: Amines → Quaternary ammonium compounds

  Amines can be further alkylated to permanent cationic quaternary ammonium groups used in antimicrobial and ion-exchange materials.

• Surface immobilization: Quaternary ammonium compounds → Antibacterial coatings

  Immobilized quaternary ammonium groups are studied for contact-active antibacterial coatings.

• Hydrolysis: Nitriles → Carboxylic acids

  Nitriles can be hydrolysed to carboxylic acids, splitting the old aggregate nitrile-to-amide route into a single functional-group conversion.

• Reduction: Nitriles → Amines

  Nitriles can be reduced to primary amines, separating the amine feedstock route from later amide or materials chemistry.

• Activation for amide formation: Carboxylic acids → Amide chemistry

  Carboxylic acids or activated acid derivatives connect to amide-bond formation.

• Polycondensation: Amide chemistry → Polyamide-related materials

  Repeated amide bond formation gives polyamide-related materials such as nylon-family fibres and engineering plastics.

• Free radical chlorination: Alkanes → Chloroalkanes

  Photochemical chlorination can convert alkanes into chloroalkanes.

• Free radical bromination: Alkanes → Bromoalkanes

  Photochemical bromination can convert alkanes into bromoalkanes.

• Cracking: Alkanes → Alkenes

  Thermal or catalytic cracking converts long-chain alkanes into shorter molecules including alkenes.

• Hydrogenation: Alkenes → Alkanes

  Hydrogenation reduces alkenes to alkanes.

• Halogen addition: Alkenes → Dihalogenoalkanes

  Bromine addition converts alkenes into vicinal dibromoalkanes.

• Dihydroxylation: Alkenes → Diols

  Cold, dilute manganate(VII) oxidises an alkene to a vicinal diol without the oxidative cleavage associated with stronger conditions.

• Addition polymerisation: Alkenes → Addition polymers

  Alkenes can form addition polymers by chain-growth addition.

• Hydration: Alkenes → Alcohols

  Catalytic hydration converts alkenes into alcohols.

• Dehydration: Alcohols → Alkenes

  Dehydration converts alcohols into alkenes.

• Esterification: Carboxylic acids → Esters

  Carboxylic acids react with alcohols to form esters.

• Esterification co reactant: Alcohols → Esters

  Alcohols combine with carboxylic acids to form esters.

• Hydrolysis: Esters → Carboxylic acids

  Hydrolysis converts esters back into carboxylic acid products.

• Hydrolysis co product: Esters → Alcohols

  Hydrolysis of an ester also regenerates the alcohol component.

• Chlorination: Carboxylic acids → Acyl chlorides

  PCl5 converts carboxylic acids into acyl chlorides.

• Chlorination with thionyl chloride: Carboxylic acids → Acyl chlorides

  Thionyl chloride converts carboxylic acids into acyl chlorides with sulfur dioxide and hydrogen chloride as by-products.

• Hydrolysis: Acyl chlorides → Carboxylic acids

  Water hydrolyses acyl chlorides to carboxylic acids, releasing hydrogen chloride.

• Acylation: Acyl chlorides → Esters

  Alcohol acylation converts acyl chlorides into esters.

• Acylation: Acyl chlorides → Amides

  Ammonia acylation converts acyl chlorides into amides.

• Acylation: Acyl chlorides → N-substituted amides

  Amine acylation converts acyl chlorides into N-substituted amides.

• Acylation co reactant: Amines → N-substituted amides

  Amines are acylated by acyl chlorides to form N-substituted amides.

• Grignard formation: Chloroalkanes → Grignard reagents

  Chloroalkanes can react with magnesium in dry ether to form Grignard reagents.

• Grignard formation: Bromoalkanes → Grignard reagents

  Bromoalkanes can react with magnesium in dry ether to form Grignard reagents.

• Grignard formation: Iodoalkanes → Grignard reagents

  Iodoalkanes can react with magnesium in dry ether to form Grignard reagents.

• Carbonyl addition: Grignard reagents → Primary alcohols

  Grignard addition to methanal gives primary alcohols after work-up.

• Carbonyl addition: Grignard reagents → Secondary alcohols

  Grignard addition to aldehydes gives secondary alcohols after work-up.

• Carbonyl addition: Grignard reagents → Tertiary alcohols

  Grignard addition to ketones gives tertiary alcohols after work-up.

• Carboxylation: Grignard reagents → Carboxylic acids

  Grignard carboxylation gives carboxylic acids after acidic work-up.

• Grignard addition co reactant: Methanal → Primary alcohols

  Methanal plus a Grignard reagent gives a primary alcohol after acidic work-up.

• Grignard addition co reactant: Aldehydes → Secondary alcohols

  Aldehydes plus Grignard reagents give secondary alcohols after acidic work-up.

• Grignard addition co reactant: Ketones → Tertiary alcohols

  Ketones plus Grignard reagents give tertiary alcohols after acidic work-up.

• Grignard carboxylation co reactant: Carbon dioxide → Carboxylic acids

  Carbon dioxide plus a Grignard reagent gives a carboxylic acid after acidic work-up.

• Charged polymer network: Quaternary ammonium compounds → Ion-exchange materials

  Quaternary ammonium groups can form fixed cationic sites in ion-exchange resins and membranes.

• Complete combustion: Alkanes → Carbon dioxide

  Alkanes burn completely in excess oxygen to form carbon dioxide and water.

• Complete combustion: Alcohols → Carbon dioxide

  Alcohols burn completely in excess oxygen to form carbon dioxide and water.

• Combustion: Benzene → Carbon dioxide

  Benzene combusts to carbon dioxide and water and tends to burn with a smoky flame.

• Salt formation: Carboxylic acids → Carboxylate salts

  Carboxylic acids react with bases, carbonates and reactive metals to form carboxylate salts.

• Bromination: Benzene → Halogenoarenes

  Benzene undergoes bromination with a halogen carrier catalyst to form bromobenzene.

• Nitration: Benzene → Nitroarenes

  Benzene is nitrated by concentrated nitric and sulfuric acids to form nitrobenzene.

• Friedel Crafts alkylation: Benzene → Alkylarenes

  Friedel-Crafts alkylation attaches an alkyl group to benzene.

• Friedel Crafts acylation: Benzene → Acylbenzenes

  Friedel-Crafts acylation attaches an acyl group to benzene.

• Bromination: Phenols → Bromophenols

  Phenol decolourises bromine water and forms a pale precipitate of 2,4,6-tribromophenol.

• Reduction: Nitroarenes → Aromatic amines

  Nitroarenes are reduced to aromatic amines using tin and hydrochloric acid followed by alkali.

• Weak base equilibrium: Amines → Aqueous alkylammonium ions

  Amines are weak bases in water and form alkylammonium and hydroxide ions.

• Salt formation: Amines → Amine salts

  Amines react with acids to form alkylammonium salts.

• Copper(II) complex formation: Amines → Copper-amine complexes

  Amines react with aqueous copper(II) ions and form a deep-blue complex in excess amine.

• Peptide formation: Amino acids → Peptides and proteins

  Controlled amino-acid coupling forms peptide bonds; the displayed equation is a net relationship rather than a complete experimental procedure.

• Peptide hydrolysis: Peptides and proteins → Amino acids

  Peptide bonds are hydrolysed by prolonged heating with aqueous hydrochloric acid, followed by work-up when free amino acids are required.

• Polyester formation: Dicarboxylic acids → Polyesters

  Dicarboxylic acids condense with diols to form polyesters.

• Polyester formation co reactant: Diols → Polyesters

  Diols condense with dicarboxylic acids to form polyesters.

• Polyamide formation: Dicarboxylic acids → Polyamide-related materials

  Dicarboxylic acids condense with diamines to form polyamides.

• Polyamide formation co reactant: Diamines → Polyamide-related materials

  Diamines condense with dicarboxylic acids to form polyamides.

• Epoxidation: Alkenes → Epoxides

  A peroxyacid transfers oxygen across the alkene in a concerted step, forming two C-O bonds while breaking the C=C pi bond. Both bonds form from one face, retaining the alkene substituents’ relative stereochemistry in the epoxide.

• Epoxide hydrolysis: Epoxides → Diols

  Protonation activates the strained ring toward attack by water. Backside attack breaks one C-O bond; proton transfer leaves hydroxyl groups on adjacent carbons, with an anti relationship when ring geometry makes that distinction meaningful.

• Anhydride hydrolysis: Acid anhydrides → Carboxylic acids

  Water attacks an anhydride carbonyl, and collapse of the tetrahedral intermediate breaks the acyl-oxygen linkage. Proton transfer gives carboxylic-acid products; a mixed anhydride yields two different acids.

• Anhydride alcoholysis: Acid anhydrides → Esters

  Alcohol oxygen attacks an anhydride carbonyl and the tetrahedral intermediate expels carboxylate. Proton transfer produces the ester and a carboxylic acid; one acyl fragment transfers to the alcohol.

• Anhydride ammonolysis: Acid anhydrides → Amides

  Ammonia attacks the anhydride carbonyl to form a tetrahedral intermediate. Carboxylate departure and proton transfer give an amide; excess ammonia also converts the acid co-product into ammonium carboxylate.

• Oxidation: Propanal → Propanoic acid

  Propanal is oxidised to propanoic acid.

• Partial oxidation: Ethanol → Ethanal

  Ethanol is oxidised to ethanal.

• Oxidation: Ethanol → Ethanoic acid

  Ethanol is oxidised to ethanoic acid.

• Partial oxidation: Propan-1-ol → Propanal

  Propan-1-ol is oxidised to propanal.

• Oxidation: Propan-1-ol → Propanoic acid

  Propan-1-ol is oxidised to propanoic acid.

• Oxidation: Propan-2-ol → Propanone

  Propan-2-ol is oxidised to propanone.

• Oxidation: Ethanal → Ethanoic acid

  Ethanal is oxidised to ethanoic acid.

• Reduction: Ethanal → Ethanol

  Ethanal is reduced to ethanol.

• Reduction: Propanal → Propan-1-ol

  Propanal is reduced to propan-1-ol.

• Reduction: Propanone → Propan-2-ol

  Propanone is reduced to propan-2-ol.

• Esterification: Ethanoic acid → Ethyl acetate

  Ethanoic acid and ethanol combine reversibly to form ethyl acetate and water.

• Esterification: Ethanol → Ethyl acetate

  Ethanoic acid and ethanol combine reversibly to form ethyl acetate and water.

• Acid hydrolysis: Ethyl acetate → Ethanoic acid

  Ethyl acetate and water react reversibly to form ethanoic acid and ethanol.

• Acid hydrolysis: Ethyl acetate → Ethanol

  Ethyl acetate and water react reversibly to form ethanoic acid and ethanol.

• Hydration: Ethene → Ethanol

  Ethene gives ethanol through hydration.

• Dehydration: Ethanol → Ethene

  Ethanol gives ethene through dehydration.

• Hydration: Propene → Propan-2-ol

  Propene gives propan-2-ol through hydration.

• Dehydration: Cyclohexanol → Cyclohexene

  Cyclohexanol gives cyclohexene through dehydration.

• Ring hydrogenation: Benzene → Cyclohexane

  Benzene gives cyclohexane through ring hydrogenation.

• Ring hydrogenation: Toluene → Methylcyclohexane

  Toluene gives methylcyclohexane through ring hydrogenation.

• Nitration: Benzene → Nitrobenzene

  Benzene gives nitrobenzene through nitration.

• Nitro reduction and basification: Nitrobenzene → Aniline

  Nitrobenzene gives aniline through nitro reduction and basification.

• Side chain oxidation: Toluene → Benzoic acid

  Toluene gives benzoic acid through side-chain oxidation.

• Partial hydrogenation: But-2-yne → cis-But-2-ene

  The alkyne binds to the catalyst surface and receives both hydrogen atoms from the same face. This syn addition gives cis-but-2-ene; the deactivated Lindlar catalyst helps limit further reduction to butane.

• Dissolving metal reduction: But-2-yne → trans-But-2-ene

  Successive electron transfers and protonations convert the triple bond into a double bond. The intermediate sequence favours the less crowded arrangement that gives trans-but-2-ene, so this is not the same process as hydrogen delivery on a metal surface.

• Intermolecular dehydration: Ethanol → Diethyl ether

  Protonation turns one ethanol OH group into a better leaving group. The oxygen of another ethanol molecule displaces water, and deprotonation gives diethyl ether; stronger dehydration conditions instead favour ethene.

• Hydrolysis: Bromoethane → Ethanol

  Hydroxide attacks the saturated carbon bearing bromine while the C-Br bond breaks. This primary-substrate SN2 route replaces bromide with OH and preserves both carbon atoms; aqueous conditions favour this branch over elimination.

• Elimination: Bromoethane → Ethene

  The base removes a hydrogen from the carbon next to bromine. The C-H electrons form the C=C pi bond as bromide departs, so elimination removes H and Br without changing the two-carbon skeleton.

• Cyanide substitution: Bromoethane → Propanenitrile

  The carbon end of cyanide attacks the primary carbon of bromoethane as bromide leaves. The new C-C bond joins cyanide’s carbon to the original chain, giving a three-carbon nitrile rather than acetonitrile.

• Ammonia substitution: Bromoethane → Ethylamine

  Ammonia attacks the carbon bearing bromine to give an alkylammonium intermediate. A further ammonia molecule removes a proton to release ethylamine; the product can undergo additional alkylation if haloalkane remains.

• Nitrile hydrolysis: Propanenitrile → Propanoic acid

  Acid-assisted water addition converts the nitrile through an amide before hydrolysis gives the acid. The nitrile carbon becomes the carboxyl carbon, while its nitrogen leaves the organic skeleton as ammonium.

• Nitrile reduction: Propanenitrile → Propylamine

  Hydride additions reduce the carbon-nitrogen triple bond; the separate aqueous work-up protonates the nitrogen-containing intermediates. The nitrile carbon becomes CH2NH2, preserving the enlarged three-carbon skeleton.

• Complete oxidation: Benzyl alcohol → Benzoic acid

  Oxidation first changes the benzylic CH2OH group into an aldehyde and then into carboxylate under the alkaline conditions. Acid work-up gives benzoic acid; the ring is retained while the side-chain carbon becomes more oxidised.

• Carbonyl reduction: Benzaldehyde → Benzyl alcohol

  Hydride attacks the aldehyde carbon and the C=O pi electrons move to oxygen. Protonation of the alkoxide gives benzyl alcohol; neither a new carbon-carbon bond nor reduction of the aromatic ring is involved.

• Aldehyde oxidation: Benzaldehyde → Benzoic acid

  Water reversibly adds to the aldehyde to form a hydrate, which can then be oxidised. The aldehyde carbon becomes the acid carbonyl carbon; acid work-up converts the initially formed benzoate into benzoic acid.

• Acyl chloride preparation: Benzoic acid → Benzoyl chloride

  Reaction with phosphorus(V) chloride replaces the carboxyl OH group with chlorine, retaining the acyl carbon and aromatic ring. The new acyl chloride is more susceptible to nucleophilic substitution, while POCl3 and HCl account for the remaining atoms.

• Amide formation: Benzoyl chloride → Benzamide

  Ammonia adds to the acyl carbonyl to form a tetrahedral intermediate. Carbonyl re-formation expels chloride, and proton transfer gives benzamide; additional ammonia captures the acid as ammonium chloride.

• Ester formation: Benzoyl chloride → Ethyl benzoate

  Ethanol oxygen attacks the acyl carbonyl carbon. Loss of chloride and proton transfer restore C=O and form the ester, with ethanol contributing the ethoxy group and HCl produced in the overall equation.

• Amide formation: Acetyl chloride → Acetamide

  Ammonia attacks the carbonyl carbon and chloride leaves when the tetrahedral intermediate collapses. Deprotonation gives acetamide, while another ammonia equivalent neutralises the acid to form ammonium chloride.

• O acetylation: Salicylic acid → Aspirin

  The phenolic oxygen of salicylic acid receives an acetyl group from ethanoic anhydride. Acyl substitution forms an ester while retaining the separate carboxyl group; proton transfer gives ethanoic acid as the co-product.

• N acetylation: Aniline → Acetanilide

  The aniline nitrogen attacks an anhydride carbonyl and displaces an acetate-derived leaving group. Proton transfer forms acetanilide and ethanoic acid; attachment to C=O makes the product nitrogen an amide nitrogen.

• Secondary alcohol oxidation: Cyclohexanol → Cyclohexanone

  Oxidation removes hydrogen from the O-H group and its attached carbon, creating a C=O bond. Because that carbon already bonds to two other carbons, the product is a ketone and the six-membered ring is retained.

• Ketone reduction: Cyclohexanone → Cyclohexanol

  Hydride adds to the planar carbonyl carbon while the pi electrons move onto oxygen. Subsequent protonation gives cyclohexanol; the existing carbon ring remains intact.

• Amide hydrolysis: Acetamide → Ethanoic acid

  Acid activates the amide carbonyl for water addition. Proton transfer makes nitrogen a better leaving group before C-N cleavage; the acyl fragment becomes ethanoic acid and the nitrogen ends as ammonium.

• Catalytic oxidation: Methanol → Methanal

  Removing hydrogen from methanol creates a carbonyl while retaining its single carbon. Oxygen accepts the removed hydrogen as water in this overall catalytic-oxidation equation.

• Carbonyl reduction: Methanal → Methanol

  Hydride addition forms a new C-H bond and converts the C=O pi bond into an alkoxide. Protonation then gives methanol without introducing another carbon.

• Aldehyde oxidation: Methanal → Methanoic acid

  Oxidation changes the aldehyde hydrogen into acid functionality through the hydrated carbonyl. The carbon count stays at one, but further oxidation remains possible.

• Esterification: Methanol → Methyl acetate

  Methanol attacks an acid-activated carbonyl; proton transfers and water loss give methyl acetate. The ester oxygen linking to the methyl group comes from the alcohol.

• Acid hydrolysis: Methyl acetate → Ethanoic acid

  Water adds to the protonated ester carbonyl. Proton transfer allows methanol to leave as the carbonyl reforms, producing the acid and alcohol together.

• Acid hydrolysis: Methyl acetate → Methanol

  Water adds to the protonated ester carbonyl. Proton transfer allows methanol to leave as the carbonyl reforms, producing the acid and alcohol together.

• Controlled oxidation: Butan-1-ol → Butanal

  Oxidation removes hydrogen from the O-H bond and the OH-bearing carbon to form C=O. Separating butanal as it forms limits its further oxidation.

• Carbonyl reduction: Butanal → Butan-1-ol

  Hydride adds to the aldehyde carbon and the carbonyl oxygen becomes an alkoxide. Protonation completes the return to butan-1-ol.

• Aldehyde oxidation: Butanal → Butanoic acid

  The hydrated aldehyde is oxidised to a carboxyl group. All four starting carbon atoms remain together in butanoic acid.

• Esterification: Butanoic acid → Ethyl butyrate

  Ethanol oxygen bonds to the acid carbonyl carbon, followed by proton transfer and water loss. The product joins a butanoyl fragment to an ethoxy group.

• Acid hydrolysis: Ethyl butyrate → Butanoic acid

  Water attack and proton transfers permit the ethoxy fragment to leave as ethanol. Re-forming the carbonyl produces butanoic acid on the other branch.

• Acid hydrolysis: Ethyl butyrate → Ethanol

  Water attack and proton transfers permit the ethoxy fragment to leave as ethanol. Re-forming the carbonyl produces butanoic acid on the other branch.

• Esterification: Butan-1-ol → Butyl acetate

  The alcohol oxygen attacks an activated ethanoic-acid carbonyl. The four-carbon chain remains on oxygen while the two-carbon acetate fragment supplies the carbonyl.

• Acid hydrolysis: Butyl acetate → Butan-1-ol

  Hydrolysis breaks the acyl-to-oxygen connection after water addition and proton transfer. The original butyl group stays attached to oxygen and leaves as butan-1-ol.

• Hydrobromination: Propene → 2-Bromopropane

  Protonation of propene favours the secondary carbocation over a primary one. Bromide then forms the C-Br bond at the central carbon.

• Hydrolysis: 2-Bromopropane → Propan-2-ol

  Replacing the carbon-bromine bond with carbon-oxygen bonding produces propan-2-ol. Its central carbon remains secondary, explaining its subsequent oxidation to propanone.

• Esterification: Benzoic acid → Ethyl benzoate

  Acid activation allows ethanol to add to benzoic acid; proton transfers and water loss produce ethyl benzoate. The aromatic ring stays intact throughout the acyl substitution.

• Acid hydrolysis: Aspirin → Salicylic acid

  Water attacks the acid-activated acetyl carbonyl. Acyl-oxygen cleavage and proton transfer restore the phenolic OH of salicylic acid, while the removed acetyl group becomes ethanoic acid.

• Alkaline hydrolysis and acidification: Methyl salicylate → Salicylic acid

  Hydroxide adds at the ester carbonyl and displaces the methoxy fragment, which becomes methanol. Alkaline conditions leave the salicylate groups deprotonated; subsequent acidification restores the neutral acid and phenolic OH.