Reaction guide
Every key reaction drawn out — starting material, reagents over the arrow, product. Search by name or reagent, or filter by type. Part of the OChem study guide.
Markovnikov addition of H–X across C=C
Markovnikov addition of H–OH
Markovnikov alcohol, no rearrangement
Anti-Markovnikov, syn addition of H–OH
Anti addition of two halogens (halonium ion)
Anti addition of X and OH
Anti-Markovnikov H–Br (radical)
Syn addition of H–H → alkane
Alkene → epoxide (syn)
Adds two OH syn → cis diol
Cleaves C=C into carbonyls
Markovnikov twice → geminal dihalide
Markovnikov → methyl ketone (via enol)
Anti-Markovnikov → aldehyde
Alkyne → cis (Z) alkene
Alkyne → trans (E) alkene
Extend the chain at a terminal alkyne
Backside attack, inversion
Via carbocation, racemization
Anti-periplanar, one step, Zaitsev
Via carbocation → Zaitsev alkene
Make OH a good leaving group
OH → tosylate (great leaving group)
E1 loss of water → alkene
1° alcohol → aldehyde (stops there)
1° alcohol → carboxylic acid
Anti opening → 1,2-diol
Aldehyde/ketone → alcohol
Even acids/esters → alcohol
Adds R⁻ to a carbonyl (new C–C)
Stronger carbon nucleophile
Carbonyl → alkene
Protect a carbonyl as an acetal
Carbonyl + 1° amine → C=N imine
Carbonyl + 2° amine → enamine
Adds CN and OH across a carbonyl
Enolate + carbonyl → β-hydroxy carbonyl
Aldol + dehydration → enone/enal
Two esters → β-keto ester
Halogen on the α-carbon (via enol)
Acid + alcohol → ester (reversible)
Ester → carboxylate + alcohol
Acid chloride + amine → amide
Carbonyl + amine → amine
Puts a halogen on the ring (EAS)
Installs –NO2 (EAS)
Installs –SO3H (reversible, EAS)
Adds an alkyl group (EAS)
Adds an acyl group (ketone)
Ar–NO2 → aniline
Brominates the allylic position
Substitutes an alkane C–H
Concerted [4+2] → cyclohexene
Markovnikov HCl adds to the more subst. carbon
Markovnikov HI addition gives 2-iodoalkane
Epoxide opened by water to a trans-1,2-diol
Syn addition of two OH to give a cis-1,2-diol
Oxidative cleavage of alkene to carboxylic acids
Cleaves a 1,2-diol into two carbonyl fragments
Carbenoid adds CH2 across alkene to cyclopropane
Dichlorocarbene adds to give dichlorocyclopropane
Two terminal alkenes swap to an internal alkene
One HCl adds to terminal alkyne to a vinyl halide
Markovnikov HBr gives a 2-halo terminal alkene
Both pi bonds reduced fully to the alkane
Anti addition to a trans-1,2-dibromoalkene
Two Br2 add to give a tetrabromoalkane
Removes acidic sp C-H to form an acetylide
Acetylide adds to a carbonyl for propargyl alcohol
Kinetic 1,2-adduct across a conjugated diene
Thermodynamic 1,4-adduct across the diene
Diene + electron-poor dienophile to cyclohexene
Radical substitution at the allylic C-H position
Converts a primary or secondary alcohol into an alkyl chloride with retention/inversion; the leaving group departs as SO2 and HCl, avoiding carbocation rearrangements.
A primary alcohol is protonated, then bromide displaces water via SN2 to give the alkyl bromide.
A tertiary alcohol is protonated and loses water to form a stable 3deg carbocation, which is trapped by chloride via SN1.
A strong, non-nucleophilic base deprotonates the alcohol O-H to give the sodium alkoxide plus H2 gas.
An alkoxide acts as a nucleophile in an SN2 displacement on an unhindered alkyl halide to forge a new C-O bond, giving an ether.
A dialkyl ether is protonated then cleaved by iodide via SN2 (or SN1 for hindered cases), splitting the ether into an alkyl iodide and an alcohol.
Under basic conditions an alkoxide attacks the LESS hindered epoxide carbon via SN2, opening the ring to a beta-alkoxy alcohol.
Under acidic conditions the protonated epoxide is attacked at the MORE substituted carbon (more carbocation-like), giving a Markovnikov beta-methoxy alcohol.
A Grignard reagent adds a carbon nucleophile to the less hindered epoxide carbon, opening the ring and extending the chain to give a longer alcohol.
An amine nucleophile attacks the less hindered epoxide carbon, giving a beta-amino alcohol.
PCC is a mild oxidant that oxidizes a secondary alcohol to a ketone without over-oxidation.
A mild anhydrous oxidation converts a secondary alcohol to a ketone (or 1deg to aldehyde) via an alkoxysulfonium intermediate; no metal, no over-oxidation.
Periodic acid cleaves the C-C bond of a 1,2-diol via a cyclic periodate ester, giving two carbonyl compounds.
A protonated 1,2-diol loses water to a carbocation, then a 1,2-alkyl shift and loss of a proton give a ketone (pinacolone).
A hydroxyl is capped as a trimethylsilyl ether to protect it during later steps; readily removed with fluoride.
An alcohol is converted to a methanesulfonate ester, turning a poor OH leaving group into an excellent one for later substitution or elimination.
Hydrosulfide (SH-) is a strong nucleophile that displaces halide via SN2 to give a thiol.
A thiolate nucleophile displaces halide via SN2 to form a thioether (sulfide).
Two thiols are oxidatively coupled at sulfur to form a disulfide bond, the linkage found in cystine.
Adds H2 across the carbonyl pi bond, reducing a ketone to a secondary alcohol.
Water adds reversibly to the carbonyl carbon to give a gem-diol; favored for small/electron-poor aldehydes.
One alcohol adds to the carbonyl to give a hemiacetal (an -OH and -OR on the same carbon).
Acid-catalyzed condensation replaces the carbonyl O with =C-OR, giving a vinyl (enol) ether.
Hydroxylamine condenses with the carbonyl to give an oxime (C=N-OH).
Hydrazine condenses with the carbonyl to give a hydrazone (C=N-NH2).
Deoxygenates a ketone all the way to a methylene (C=O to CH2) via the hydrazone under strong base.
Acidic-conditions deoxygenation of a ketone to a methylene (C=O to CH2).
1,2-Ethanedithiol adds twice to the carbonyl to give a cyclic dithiolane (thioacetal).
Removes both sulfurs of a thioacetal, replacing the original C=O carbon with a CH2 (net deoxygenation).
Inserts an oxygen next to the carbonyl, converting a ketone into an ester.
Oxidizes an aldehyde to the corresponding carboxylic acid.
Mild, selective oxidation of an aldehyde to a carboxylic acid, depositing metallic silver.
Exhaustively halogenates a methyl ketone alpha carbon then cleaves it to a carboxylate plus iodoform (CHI3).
The acetylide anion adds to the carbonyl carbon, giving a propargylic (alkynyl) alcohol.
LDA forms the enolate, which is alkylated at the alpha carbon by an alkyl halide.
A cuprate adds 1,4 to an enone, installing an alkyl group at the beta carbon.
An amine adds 1,4 (Michael addition) to an enone to give a beta-amino ketone.
A stabilized phosphonate carbanion olefinates the aldehyde to give an E-alpha,beta-unsaturated ester.
Converts a carboxylic acid into a much more reactive acyl chloride, replacing OH with Cl; drives off SO2 and HCl gas.
Reduces a carboxylic acid all the way down to a primary alcohol; the strong hydride pushes past the acid to the CH2OH.
Condenses two carboxylic acids into an anhydride by loss of water, linking two acyl groups through one oxygen.
Water attacks the very reactive acyl chloride to regenerate the carboxylic acid, releasing HCl.
An alcohol displaces chloride from an acyl chloride to give an ester; fast and high-yielding versus Fischer esterification.
A carboxylate oxygen displaces chloride to build an anhydride; a mild route to mixed or symmetric anhydrides.
The mild cuprate delivers one alkyl group to an acyl chloride, stopping cleanly at the ketone without over-addition.
A bulky, mild hydride reduces an acyl chloride only to the aldehyde, avoiding further reduction to the alcohol.
Ammonia displaces the alkoxy group of an ester to give a primary amide plus an alcohol.
Two equivalents of Grignard add to an ester (through the ketone intermediate) to give a tertiary alcohol bearing two identical R groups.
One equivalent of DIBAL at low temperature reduces an ester only to the aldehyde via a stable tetrahedral intermediate.
Reduces an ester fully to a primary alcohol; the acyl carbon becomes CH2OH and the alkoxy group leaves as its own alcohol.
Swaps the alkoxy group of an ester for a new one from an added alcohol; an equilibrium driven by excess of the incoming alcohol.
Vigorous acid or base hydrolysis of the sturdy amide bond gives back the carboxylic acid (plus the amine/ammonia).
LiAlH4 reduces an amide to an amine, replacing the C=O with CH2 and keeping the C-N bond intact.
Full hydrolysis of a nitrile through the amide gives a carboxylic acid, adding one carbon relative to the starting halide.
Reduces a nitrile to a primary amine, adding two hydrogens across the C-N triple bond.
A Grignard adds once to a nitrile to give an imine salt that hydrolyzes on workup to a ketone.
Cyanide displaces a primary halide in an SN2 reaction, installing a nitrile and extending the carbon chain by one.
A carboxylic acid beta to a carbonyl loses CO2 on heating through a cyclic six-membered transition state, giving a ketone.
Brominates the alpha carbon of a carboxylic acid via its enol, giving an alpha-bromo acid useful for further substitution.
A bulky, strong, non-nucleophilic base removes the least hindered alpha-hydrogen to give the kinetic enolate irreversibly.
The carbonyl (keto) form interconverts with its enol via alpha-proton transfer; the keto form usually predominates at equilibrium.
The enolate carbon acts as a nucleophile in an SN2 attack on an alkyl halide, installing a new alpha-alkyl group.
A preformed enolate of one carbonyl adds to a second, different carbonyl to give a controlled beta-hydroxy carbonyl product.
An enolate attacks a carbonyl within the same molecule to close a ring, favoring five- and six-membered rings.
An intramolecular Claisen of a diester: one ester enolate attacks the other ester to form a cyclic beta-keto ester.
Diethyl malonate is deprotonated, alkylated, then hydrolyzed and decarboxylated to give a substituted acetic acid.
Ethyl acetoacetate is alkylated at the alpha carbon, then hydrolyzed and decarboxylated to yield a substituted methyl ketone.
A stabilized enolate donor adds in conjugate fashion to the beta carbon of an enone to give a 1,5-dicarbonyl.
A ketone is converted to an enamine that acts as a mild carbon nucleophile toward alkyl/acyl halides, then hydrolyzed back to the alpha-substituted ketone.
A Michael addition followed by an intramolecular aldol condensation builds a fused cyclohexenone ring.
An enol/enolate attacks an iminium ion (from an amine and formaldehyde) to install an aminomethyl group alpha to the carbonyl.
A carboxylic acid is brominated at its alpha carbon via the acyl bromide enol to give an alpha-bromo acid.
Electrophilic aromatic substitution installs a chlorine on the ring; AlCl3 polarizes Cl2 to generate the Cl+ electrophile.
Acylation adds a ketone (avoiding carbocation rearrangement), then reduction of the C=O gives a straight, unrearranged alkyl chain on the ring.
Reduces the carbonyl of an aryl ketone side chain all the way to a CH2, converting an acylbenzene into an alkylbenzene.
Basic-conditions reduction of an aryl ketone carbonyl to a methylene, giving the alkylbenzene (acid-sensitive alternative to Clemmensen).
Any benzylic C-H bearing carbon is oxidized down to a carboxylic acid; a methyl group on the ring becomes COOH.
Oxidation cleaves the alkyl chain back to the benzylic carbon, converting any alkylbenzene with a benzylic H into benzoic acid.
Radical bromination selective for the weak benzylic C-H bond, placing Br on the carbon next to the ring.
Under radical conditions (light) chlorine substitutes at the benzylic position rather than on the ring, giving benzyl chloride.
A nitro group ortho/para to the leaving group stabilizes the Meisenheimer complex, letting hydroxide displace chloride on the ring.
Ammonia displaces the activated aryl chloride via addition-elimination, giving the nitro-substituted aniline.
A very strong base eliminates HX to form a benzyne triple bond, which is then attacked by the nucleophile to give an aniline.
Dissolving-metal reduction of the ring gives an unconjugated 1,4-cyclohexadiene, leaving two double bonds intact.
Forcing conditions add hydrogen across all three formal double bonds, fully reducing the arene to a cyclohexane.
A primary aryl amine is converted to a stable-at-cold aryl diazonium ion, the key branch point for many aromatic substitutions.
Copper(I) chloride replaces the diazonium group with chloride, installing a ring chlorine that EAS alone cannot place cleanly.
Copper(I) bromide swaps the diazonium group for bromide, giving the aryl bromide.
Copper(I) cyanide replaces the diazonium group with a nitrile, adding a one-carbon handle to the ring.
Warming the aryl diazonium ion in water substitutes the group with a hydroxyl, giving a phenol.
Replaces the diazonium group with hydrogen, letting an amino group be used as a temporary director and then removed.
The diazonium tetrafluoroborate decomposes thermally to install a fluorine, one of the few practical routes to aryl fluorides.
Phthalimide nitrogen alkylates an alkyl halide, then is cleaved to release a clean primary (1o) amine with no over-alkylation
Azide ion displaces a leaving group by SN2, then the alkyl azide is reduced to a primary (1o) amine
A nitrile is reduced to a primary amine, adding one carbon to the chain (CH2NH2)
Ammonia displaces a halide to give a primary amine; over-alkylation to 2o/3o/quaternary is a common caveat, so large excess NH3 is used
An amide carbonyl is reduced all the way to an amine (C=O removed, no oxygen retained)
Exhaustive methylation makes a quaternary ammonium hydroxide that eliminates on heating to give the LESS substituted (Hofmann) alkene
A tertiary amine oxide undergoes a concerted syn elimination to give an alkene plus a hydroxylamine
A primary or secondary amine attacks an acyl chloride to form an amide; useful for protecting an amine
Anhydride acylates the amine nitrogen to give an acetamide, a common amine-protecting step
A primary amide is converted to a primary amine with LOSS of one carbon (via isocyanate), shortening the chain
An acyl azide loses N2 and rearranges to an isocyanate, which hydrolyzes to a primary amine (one carbon shorter)
A primary aromatic amine is converted to a diazonium salt, a versatile aryl electrophile for further substitution
An amine acts as a Bronsted base, accepting a proton to form a water-soluble ammonium salt
An aromatic nitro group is reduced to a primary aryl amine, a key aniline synthesis
A tertiary amine is oxidized at nitrogen to give an amine N-oxide
Repeated N-alkylation converts an amine into a quaternary ammonium salt with a permanent positive charge on nitrogen
A [4+2] cycloaddition of 1,3-butadiene with the electron-poor maleic anhydride dienophile forms a new six-membered ring bearing the fused anhydride.
The reverse [4+2]: on heating, cyclohexene fragments back into a diene and a dienophile, driven by entropy and loss of a stable small alkene.
A [3,3]-sigmatropic shift converting a 1,5-diene into an isomeric 1,5-diene through a concerted six-membered chair-like transition state.
A [3,3]-sigmatropic rearrangement of an allyl vinyl ether that delivers a gamma,delta-unsaturated carbonyl compound.
A conjugated triene undergoes a disrotatory/conrotatory electrocyclization, forming one new sigma bond to give a cyclohexadiene ring.
A lithium dialkylcuprate couples with a primary alkyl halide, forging a new carbon-carbon bond to give an extended alkane.
A Gilman reagent adds one alkyl group to an acyl chloride and stops at the ketone stage, unlike Grignard/organolithium reagents.
A palladium-catalyzed cross-coupling of an aryl halide with an aryl boronic acid builds a biaryl carbon-carbon bond.
A palladium-catalyzed coupling of an aryl halide with an alkene installs the aryl group on the alkene to give a substituted (usually trans) alkene.
Ozone cleaves the carbon-carbon double bond; an oxidative H2O2 workup carries the fragments up to carboxylic acids.
Hot, concentrated permanganate fully cleaves an alkene, oxidizing each carbon to a carboxylic acid (or ketone if fully substituted).
Catalytic hydrogenation reduces a nitrile all the way to a primary amine by adding two equivalents of H2.
With excess hydrogen and an active catalyst, an alkyne is fully reduced through the alkene to the corresponding alkane.
One equivalent of DIBAL-H partially reduces a nitrile to an imine intermediate that hydrolyzes on workup to an aldehyde.
A ruthenium carbene scrambles alkene partners; two terminal alkenes exchange ends to give an internal alkene plus ethylene.
A lithium dialkylcuprate reacts with an alkyl halide to couple two alkyl fragments into a larger alkane with a new C-C bond.