250 Organic Chemistry Reactions Flashcards for Revision

In organic reactions, the condition you miss is usually the mark you lose.

250 cardsLast updated 2026-08-30

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Organic chemistry reactions go wrong in revision for a simple reason: the same substrate can substitute, eliminate, add, rearrange, or do nothing useful depending on the conditions. You half remember a reagent, miss the heat, forget the solvent, or overlook the competing pathway, and suddenly near-identical questions have different answers. The slip is usually not a big idea. It is the detail that changes the outcome. This deck turns that into cards you can rehearse fast. It has 250 cards split across structure and bonding (35), substitution and elimination (45), alkenes alkynes and radicals (45), aromatics (35), carbonyls (55), and synthesis and analysis (35). Each card covers a single reaction or concept, with Meaning on the back for what it is, Conditions for when it happens, and Watch for to flag the rival pathway or common trap. So hybridisation, antiaromaticity, and alpha cleavage sit beside core reaction patterns in the same format. On a spaced repetition schedule, the cards you can answer cleanly stop showing up so often, while the ones you still confuse keep returning until the conditions and alternatives separate in your head. The deck leaves out long mechanism walk-throughs and broad spectroscopy tables on purpose, so your reviews stay focused on deciding what happens, when it happens, and what else could happen instead.

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Showing 100 representative cards from the full 250-card deck.

Front	Back
sp3 hybridisation	Meaning: One s and three p orbitals mix to give four sp3 orbitals that form σ bonds or hold lone pairs at a tetrahedral electron arrangement. Conditions: Four electron domains about the atom. Common at saturated carbon, nitrogen and oxygen centres. Watch for: Electron geometry is tetrahedral. Molecular shape can be pyramidal or bent when lone pairs are present.
sp hybridisation	Meaning: Two p orbitals stay unhybridised. Two sp orbitals form σ bonds and two p orbitals can form two π bonds, giving a linear centre. Conditions: Two electron domains about the atom. Common in alkynes and nitriles. Watch for: Greater s character holds electrons closer to the nucleus. This helps explain the acidity of terminal alkynes.
formal charge	Meaning: No bond changes occur. Charge is assigned as valence electrons minus lone-pair electrons minus half of bonding electrons. Conditions: Use a valid Lewis structure and compare each atom with its neutral valence count. Watch for: Formal charge is bookkeeping. It may not match actual charge distribution or oxidation state.
electron-donating inductive effect	Meaning: No bond changes occur. Alkyl groups push σ electron density toward a centre and can stabilise cations or destabilise nearby anions. Conditions: It is transmitted through σ bonds and is strongest at short range. Watch for: This is weaker than resonance. It does not explain allylic or benzylic stabilisation by itself.
Brønsted acid	Meaning: It donates H+. The H-A bond breaks and the product is its conjugate base A− after proton transfer. Conditions: A base or solvent able to accept the proton must be present. Watch for: Stronger acids have more stable conjugate bases. The strongest acid present controls protonation.
Lewis acid	Meaning: It accepts an electron pair. A new coordinate bond forms to the acceptor, often at B, Al or a carbocation centre. Conditions: A vacant orbital or low-lying antibonding orbital is needed. No proton transfer is required. Watch for: Many Lewis acids are electrophiles. Neutral species such as BF3 can be Lewis acids too.
pKa	Meaning: No bonds change. It measures the equilibrium for HA losing H+ to give A−. Lower pKa means the deprotonated product is favoured more. Conditions: Compare values only from the same solvent and temperature. Watch for: A pKa measured in water may not predict behaviour in DMSO or in the gas phase.
inductive stabilisation of anions	Meaning: After deprotonation, nearby electron-withdrawing groups pull σ density from the anion. The conjugate base is stabilised and acidity increases. Conditions: It is strongest when the withdrawing group is alpha or beta to the acidic site. Watch for: Distance matters a lot. A remote CF3 group has much less effect than a nearby one.
staggered conformation	Meaning: Rotation about a C-C σ bond places adjacent bonds 60° apart. The result is a lower-energy conformer with less torsional strain. Conditions: A rotatable single bond is required, as in ethane or butane. Watch for: Not all staggered forms are equal. Anti and gauche are both staggered.
anti conformation	Meaning: Looking down a single bond, the largest groups are 180° apart. This gives the lowest staggered conformer for many open-chain alkanes. Conditions: Define it with a Newman projection about a specific σ bond. Watch for: Anti describes a relationship between substituents, not the whole molecule.
chair conformation	Meaning: Cyclohexane puckers into a chair so C-C bonds are nearly staggered and bond angles stay near 109.5°. This is its lowest-strain conformer. Conditions: It applies to six-membered rings built from mainly sp3 carbons. Watch for: Do not treat cyclohexane as planar. Boat and twist-boat forms are higher in energy.
chiral centre	Meaning: No bonds must change. An sp3 atom bonded to four different groups can give two non-superposable mirror-image stereoisomers. Conditions: Usually a tetrahedral carbon with four distinct substituents and no symmetry that cancels chirality. Watch for: Two identical groups remove chirality. A molecule with chiral centres can still be meso and achiral.
Aromaticity	Meaning: No bonds break. A cyclic, planar, fully conjugated pi system with 4n+2 pi electrons is unusually stable and acts as an aromatic ring. Conditions: Needs a closed loop of adjacent p orbitals and near planarity. Benzene and the cyclopentadienyl anion fit. Watch for: A single sp3 atom interrupts it. A planar 4n pi system is antiaromatic, not aromatic.
Boat conformation	Meaning: No bonds break. Cyclohexane can adopt a boat with eclipsed bonds and close flagpole H atoms, so it is less stable than a chair. Conditions: Occurs in cyclohexane and other six-membered rings. It appears during chair to chair interconversion. Watch for: Twist-boat is lower in energy than boat. Extra strain comes from eclipsing and transannular crowding.
CIP priority rules	Meaning: No bonds break. Ranking groups by atomic number gives the correct R, S, E or Z stereodescriptor. Conditions: Compare the directly attached atoms first. If tied, move outward until the first difference. Watch for: Higher isotope mass ranks higher. Multiple bonds are treated as if bonded to duplicate atoms.
Meso compound	Meaning: No bonds break. A molecule with stereocentres can still be achiral if internal symmetry makes it superposable on its mirror image. Conditions: Usually needs at least two stereocentres and a symmetry element in a relevant conformation. Watch for: Stereocentres do not guarantee chirality. A meso compound is optically inactive without being racemic.
SN2 substitution	Meaning: A nucleophile forms C-Nu as C-LG breaks in one step. The product is the substituted alkane. Conditions: Strong nucleophile such as I-, CN- or N3-. Polar aprotic solvent like DMSO or acetone. Best with methyl or primary halides. Watch for: Backside attack gives inversion at a chiral center. Tertiary halides fail. Strong base can divert to E2.
Racemization	Meaning: A planar carbocation is attacked from either face, forming both configurations in the substitution product. Conditions: SN1 conditions with a chiral center at the reacting carbon. Polar protic solvent and a good leaving group. Watch for: It is often partial, not perfectly 50:50, because ion pairs can shield one face. E1 may compete.
E2 elimination	Meaning: A base removes a beta-H as C-LG breaks in one step. A C=C alkene forms. Conditions: Strong base such as EtO- or t-BuO-. Often heat. Works well with secondary or tertiary halides. Watch for: Needs anti-periplanar H and leaving group. SN2 can compete on primary substrates. Regioselectivity depends on base size.
Heat	Meaning: Higher temperature shifts many substitution-elimination mixtures toward alkene formation by breaking C-H and C-LG and forming C=C. Conditions: Apply reflux or warming, especially with alcoholic solvent or weak nucleophile. Most noticeable in E1 and E2 competition. Watch for: It does not rescue a bad substrate. Primary halides with good nucleophiles may still give SN2.
Good leaving group	Meaning: The group departs with the bonding pair, so C-LG breaks easily and substitution or elimination products form faster. Conditions: I-, Br-, Cl-, OTs and OMs are common. Use when the substrate must ionize or react in one step. Watch for: Better leaving groups speed both substitution and elimination. F- and OH- are poor unless activated.
Weak nucleophile	Meaning: It attacks carbon slowly, so substitution usually needs a carbocation. The product forms after ionization then capture. Conditions: H2O and ROH are typical. Use polar protic solvent and substrates like tertiary, allylic or benzylic halides. Watch for: SN2 is poor. Heat can turn the same conditions toward E1.
Methyl substrate	Meaning: A nucleophile can replace the leaving group by SN2. No beta carbon exists, so elimination cannot make an alkene. Conditions: Use CH3-LG with a strong nucleophile in polar aprotic solvent. Watch for: SN1 is impossible because a methyl carbocation is too unstable. E2 cannot occur.
Tertiary alkyl halide	Meaning: It ionizes easily to a carbocation for SN1 or E1, and with strong base it loses beta-H to give E2 alkene. Conditions: SN1 or E1 in polar protic solvent with weak nucleophile. E2 with strong base, often heat. Watch for: SN2 fails because backside attack is blocked. Heat pushes carbocation pathways toward E1.
Benzylic substrate	Meaning: Departure or displacement at a benzylic carbon gives substitution or elimination products stabilized by resonance with the aryl ring. Conditions: Benzylic halides react fast in SN1 or SN2. Weak nucleophiles can substitute in polar protic solvent. Watch for: Benzylic carbocations form easily, so E1 can compete. Aryl halides themselves do not do normal SN1 or SN2.
SN2 rate law	Meaning: C-Nu forms as C-LG breaks in one step to give the substitution product. Rate = k[RX][Nu-]. Conditions: Strong nucleophile. Usually methyl or primary RX in a polar aprotic solvent. Watch for: Inversion at a stereocenter. Tertiary substrates fail and strong base can divert to E2.
E2 rate law	Meaning: A base removes a beta H as C-LG breaks and C=C forms in one step. Rate = k[RX][base]. Conditions: Strong base. Usually secondary or tertiary substrate. A beta H anti to the leaving group is required. Watch for: Geometry is stereospecific. Small bases often give the more substituted alkene.
Halide leaving group order	Meaning: When C-X must break, RI and RBr give substitution or elimination products more readily than RCl, while RF is usually sluggish. Conditions: Compare simple alkyl fluorides, chlorides, bromides, and iodides under the same nucleophile or base and solvent. Watch for: Sulfonates such as OTs, OMs, and OTf are usually even better leaving groups.
Mesylate	Meaning: ROMs converts a poor OH leaving group into an excellent one, enabling later substitution or elimination at carbon. Conditions: Form it with MsCl and a base such as Et3N or pyridine, then treat with nucleophile or base. Watch for: Mesylation occurs at oxygen. Any inversion or elimination happens only in the next step.
PBr3	Meaning: An alcohol is converted to an alkyl bromide by replacing C-O with C-Br. The product is a better substrate for later reactions. Conditions: Use PBr3, often in ether, on primary or secondary alcohols under mild, anhydrous conditions. Watch for: Reaction at a stereogenic carbon gives inversion. Tertiary alcohols are poor substrates.
Sodium iodide in acetone	Meaning: I- displaces Cl or Br by SN2 to form an alkyl iodide, which usually reacts faster in later substitution steps. Conditions: Use NaI in acetone. Primary substrates work best because NaCl or NaBr precipitates and drives the exchange. Watch for: Tertiary substrates do not undergo SN2. Some secondary halides can eliminate instead.
Beta hydrogen	Meaning: A hydrogen on the carbon next to the leaving-group carbon can be removed, and the new C=C bond forms in elimination. Conditions: E2 needs a base and a beta H. E1 also needs a beta H after ionization. No beta H means no simple dehydrohalogenation. Watch for: Methyl halides cannot eliminate because they lack beta H. Which beta H is removed controls the alkene formed.
Aryl halide	Meaning: With X directly on benzene, ordinary substitution does not occur, so the aryl halide usually stays intact. Conditions: Typical alkyl-halide conditions fail. Substitution needs strong ring activation for SNAr or transition-metal catalysis. Watch for: Do not confuse with benzylic halides, where X is on the side chain and substitution is often fast.
Hydrohalogenation	Meaning: H and X add across a C=C to form C-H and C-X bonds, giving an alkyl halide. Conditions: HX such as HCl, HBr or HI, often in ether or as concentrated solution, usually no peroxides. Watch for: Unsymmetrical alkenes usually give Markovnikov products and rearrangements can occur through carbocations.
Anti-Markovnikov addition	Meaning: Across an unsymmetrical pi bond, H bonds to the more substituted carbon, so the incoming group ends up on the less substituted carbon. Conditions: Seen with HBr plus ROOR under heat or hv, or with BH3 in THF then H2O2 and NaOH. Watch for: HCl and HI do not show the peroxide effect. Hydroboration is syn, not radical.
Hydroboration-oxidation of alkenes	Meaning: H and OH add across C=C. The C-OH bond ends up at the less substituted carbon, giving an alcohol. Conditions: 1. BH3·THF. 2. H2O2, NaOH, water. Watch for: Addition is syn and no carbocation rearrangement occurs.
Organoborane oxidation	Meaning: An existing C-B bond is replaced by C-OH, converting an organoborane into an alcohol or enol. Conditions: H2O2 and NaOH in water after hydroboration. Watch for: Configuration at carbon is retained. No reaction happens unless the substrate already has a C-B bond.
Alkene halogenation	Meaning: Br2 or Cl2 adds across C=C to form vicinal dihalides by making two C-X bonds. Conditions: Br2 or Cl2 in CCl4, CH2Cl2 or another inert solvent, with no water. Watch for: Addition is anti through a halonium ion. Water changes the product to a halohydrin.
Halohydrin formation	Meaning: X and OH add across C=C to give a halohydrin. The C-OH bond forms at the more substituted carbon. Conditions: Br2 or Cl2 in H2O or aqueous solvent. Watch for: Addition is anti. In dry solvent the competing product is the vicinal dihalide.
Catalytic hydrogenation	Meaning: H2 adds across C=C or C≡C to form C-H bonds and reduce the pi bond, usually to an alkane. Conditions: H2 with Pd/C, Pt or Ni, often in ethanol or ethyl acetate, at room temperature or pressure. Watch for: Addition is syn on the metal surface. Alkynes usually reduce all the way unless a poisoned catalyst is used.
Dissolving metal reduction	Meaning: An alkyne gains H across the triple bond in a stepwise radical anion pathway to give a trans alkene. Conditions: Na or Li in liquid NH3, often at low temperature. Watch for: Gives the E alkene. This is the complement of Lindlar reduction.
Radical chain initiation	Meaning: A weak bond breaks homolytically to create the first radicals that start the reaction chain. Conditions: Heat, hv or a peroxide initiator, often with an O-O or X-X bond present. Watch for: Initiation makes radicals but usually little product. The chain needs propagation to continue.
Radical chain termination	Meaning: Two radicals form a new sigma bond or transfer H, making stable nonradical products and ending the chain. Conditions: Becomes more likely when radical concentration is high or diffusion is limited. Watch for: Termination lowers chain length and can give coupling side products.
Acid-catalyzed hydration of alkenes	Meaning: A C=C gains H and OH to give an alcohol. Water attacks the carbocation and deprotonation gives the neutral product. Conditions: H2O with dilute H2SO4 or H3O+, often warm. Best with alkenes that can form stable carbocations. Watch for: Hydride or alkyl shifts can rearrange the skeleton. A new stereocenter usually forms without stereocontrol.
Keto-enol tautomerism	Meaning: An enol and a carbonyl interconvert by proton transfer and C=C to C=O bond shift. The keto form is usually favored. Conditions: Acidic or basic aqueous conditions. Common after hydration of an alkyne. Watch for: It is not resonance because atoms move. Alpha hydrogens can exchange during repeated tautomerization.
Four-center transition state	Meaning: B-H adds across a pi bond in one concerted step. C-B and C-H bonds form together, giving a syn organoborane with no carbocation. Conditions: Hydroboration with borane reagents in ether or THF, usually at low to room temperature. Watch for: No rearrangement occurs. Sterics place boron on the less substituted carbon.
Trialkylborane	Meaning: Three alkenes can add to one borane source, replacing all three B-H bonds and forming a trialkylborane with three C-B bonds. Conditions: Excess alkene with BH3 ether complex in THF or ether, then separate workup as needed. Watch for: One borane reagent can react three times. Later oxidation converts each C-B bond into C-O.
Ozone cycloaddition	Meaning: O3 adds across a C=C in a 1,3-dipolar cycloaddition to form a primary ozonide and begin double-bond cleavage. Conditions: O3 in CH2Cl2 or MeOH at about -78 °C, before workup. Watch for: The first adduct is unstable. Final products are determined only after later fragmentation and workup.
Carbonyl oxide	Meaning: A carbonyl oxide is the Criegee intermediate from molozonide cleavage. It recombines with a carbonyl to form a secondary ozonide. Conditions: Produced during low-temperature ozonolysis after O3 adds to an alkene. Watch for: It is a 1,3-dipole. Trapping or different workup changes the carbonyl products eventually obtained.
Homolytic cleavage	Meaning: A bond breaks so each atom keeps one electron, forming two radicals. No ions are produced. Conditions: Heat or hv, especially with weak bonds such as O-O or X-X. Watch for: Use fishhook arrows. Do not confuse it with heterolysis, which gives cations and anions.
Radical inhibitor	Meaning: A radical inhibitor traps chain-carrying radicals and forms unreactive species, stopping the substitution or addition chain. Conditions: Trace O2, BHT or hydroquinone are enough under radical conditions. Watch for: Very small amounts can halt bromination or polymerization. Inhibitors lower rate rather than altering regiochemistry.
Antiaromaticity	Meaning: A cyclic conjugated planar π system with 4n π electrons is destabilized and very reactive. Conditions: Requires a continuous planar ring of p orbitals and 4n π electrons. Watch for: Many molecules avoid antiaromaticity by puckering and become nonaromatic instead.
Planarity requirement	Meaning: Ring atoms must align p orbitals around the loop. Twisting stops delocalization and kills aromatic stabilization. Conditions: Near-coplanar geometry with one p orbital on every atom in the conjugated loop. Watch for: Steric crowding, bridges, or sp3 centers can force nonplanarity.
Pyrrole aromaticity	Meaning: Pyrrole is aromatic with 6 π electrons because one N lone pair joins the ring π system. Conditions: Flat five-membered conjugated ring with two C=C bonds and one p-orbital lone pair on N. Watch for: That lone pair is less available for protonation than a pyridine lone pair.
Electrophilic aromatic substitution	Meaning: A ring H is replaced by E to give an aryl-substituted product. Aromaticity is restored after deprotonation. Conditions: Generate a strong electrophile with a Lewis or Brønsted acid, then lose H+ from the sigma complex. Watch for: Addition is disfavored because it would leave a nonaromatic ring.
Nitration of benzene	Meaning: A ring H is replaced by NO2 to form nitrobenzene. Conditions: Concentrated HNO3 and concentrated H2SO4. Warm if needed. Watch for: The electrophile is NO2+. Harsh heating can give dinitration.
Friedel-Crafts acylation	Meaning: A ring C-H becomes C-C(O)R to give an aryl ketone. Conditions: Acyl chloride or acid anhydride with AlCl3 under dry conditions. Watch for: No rearrangement occurs. The acyl group deactivates the ring, so monoacylation is usual.
Halogens as ortho para directors	Meaning: F, Cl, Br, and I direct EAS to ortho and para by lone-pair donation, despite overall deactivation. Conditions: A halobenzene substrate under standard EAS conditions. Watch for: Halogens withdraw strongly by induction. They are ortho para directors but not activators.
Wohl-Ziegler bromination	Meaning: A benzylic C-H is replaced by C-Br under radical conditions, giving a benzylic bromide. Conditions: NBS with hv, heat, or peroxide, usually in CCl4 or CH2Cl2. Watch for: Targets benzylic or allylic C-H. Avoid high Br2 levels that promote addition or ring bromination.
Side-chain oxidation of alkylbenzenes	Meaning: Any alkyl side chain with at least one benzylic H is oxidized completely to CO2H, giving benzoic acid derivatives. Conditions: Hot KMnO4 in water or OH-, then acid workup. Na2Cr2O7 can also work. Watch for: No benzylic H means no oxidation of the side chain. The whole chain shortens to CO2H.
Benzylic SN1 substitution	Meaning: A benzylic leaving group departs to a resonance-stabilized carbocation, then Nu attacks to give substitution. Conditions: Benzylic halide or sulfonate in polar protic solvent with weak or neutral nucleophile. Watch for: Racemization occurs at a chiral benzylic center. Heat can also promote E1 elimination.
Cyclopentadienyl anion aromaticity	Meaning: A C-H bond in cyclopentadiene breaks on deprotonation to give C5H5−, a planar conjugated ring with equalized C-C bonds. Conditions: Strong base such as n-BuLi or NaH in THF. The anion must remain planar and fully conjugated. Watch for: Neutral cyclopentadiene is not aromatic. Proton sources quench the anion at once.
Gattermann-Koch formylation	Meaning: A formyl group replaces an aromatic H, forming an aryl aldehyde with a new ring-C(=O)H bond. Conditions: CO and HCl with AlCl3 and CuCl, usually on benzene or activated arenes under anhydrous conditions. Watch for: Strongly deactivated rings and basic amines fail. Polyformylation is uncommon because CHO deactivates the ring.
Reimer-Tiemann reaction	Meaning: Phenoxide undergoes formylation, usually at ortho, forming a new ring-CHO bond and giving salicylaldehyde-type products. Conditions: CHCl3 and aqueous NaOH with heat, then acid workup. The electrophile is generated from dichlorocarbene. Watch for: Para product is minor. Unactivated benzenes do not react, and strong base can cause side reactions.
Meisenheimer complex	Meaning: A nucleophile adds to an activated aryl halide, forming a ring C-Nu bond and an anionic nonaromatic intermediate before X leaves. Conditions: Needs a strong electron-withdrawing group such as NO2 ortho or para to the leaving group. Polar aprotic solvent helps. Watch for: Meta nitro gives little activation. Aryl fluorides can react faster than chlorides in this pathway.
Benzylic deprotonation	Meaning: A benzylic C-H bond breaks to give a resonance-stabilized benzyl anion, which can then form a new C-C bond with an electrophile. Conditions: Use strong base such as LDA, NaNH2, or n-BuLi in dry ether or THF. Low temperature helps control alkylation. Watch for: Plain alkylbenzenes are only mildly acidic. Overalkylation or E2 on the alkyl halide electrophile can compete.
Sodium borohydride reduction	Meaning: A hydride adds to an aldehyde or ketone C=O. Protonation gives a 1° or 2° alcohol. Conditions: NaBH4 in methanol or ethanol, then aqueous workup at room temperature. Watch for: Usually stops at aldehydes and ketones. Esters and amides are normally untouched.
Grignard addition	Meaning: A C-C bond forms when R− from RMgX adds to a carbonyl. After workup, formaldehyde gives 1° alcohols, aldehydes 2°, ketones 3°. Conditions: RMgX in dry ether or THF, strictly anhydrous, then aqueous acid workup. Watch for: Any acidic H quenches the reagent. Esters and acid chlorides react twice to give 3° alcohols.
Hemiacetal formation	Meaning: An alcohol adds to an aldehyde or ketone. One C-O bond forms and the product bears OH and OR on the same carbon. Conditions: ROH, often as solvent, with mild acid catalysis. Equilibrium is usually at room temperature. Watch for: Usually unstable except in cyclic sugars or when 5- and 6-membered rings form intramolecularly.
Acetal hydrolysis	Meaning: Both C-O bonds to OR are broken stepwise and the carbonyl is regenerated from an acetal or ketal. Conditions: Aqueous acid such as H3O+ with heat, usually in water or aqueous alcohol. Watch for: Acetals are stable to base and many nucleophiles. Acid-sensitive groups elsewhere may also react.
Acyl chloride formation	Meaning: The OH of a carboxylic acid is replaced by Cl. The product is an acid chloride. Conditions: SOCl2, often with pyridine or catalytic DMF, in dry dichloromethane or neat reagent, then gentle heating. Watch for: Water hydrolyzes the product. HCl and SO2 are released.
Saponification	Meaning: Hydroxide cleaves an ester acyl C-O bond to give a carboxylate and an alcohol. Acid workup gives the carboxylic acid. Conditions: NaOH or KOH in water with ethanol or methanol, usually heat, then acidic workup if needed. Watch for: Irreversible because carboxylate is formed. Amides are much less reactive under the same conditions.
LDA enolate formation	Meaning: A strong base removes an α-H to give a lithium enolate. This creates a nucleophile at the α-carbon. Conditions: LDA in dry THF at low temperature, commonly −78 °C, under anhydrous conditions. Watch for: Requires an α-hydrogen. LDA is bulky and usually gives the kinetic enolate.
Thermodynamic enolate	Meaning: Deprotonation gives the more substituted and more stable enolate after equilibration. Conditions: Smaller base or alkoxide under reversible conditions, often at higher temperature. Watch for: Needs time to equilibrate. Strong irreversible base at low temperature instead favors kinetic control.
Aldol addition	Meaning: An enolate adds to another aldehyde or ketone. A new C-C bond forms and the product is a β-hydroxy carbonyl. Conditions: Dilute base such as NaOH or alkoxide in alcohol or water. Keep temperature low to avoid dehydration. Watch for: Needs at least one enolizable partner. Self-condensation mixtures arise unless one partner lacks α-H.
Crossed aldol reaction	Meaning: An enolate from one carbonyl adds to a different carbonyl partner to make a mixed β-hydroxy carbonyl or enone. Conditions: Use a preformed enolate, or pair an enolizable carbonyl with one lacking α-H, under base in THF or alcohol. Watch for: Without control, product mixtures from self-aldol and crossed aldol are common.
Tollens oxidation	Meaning: An aldehyde is oxidized to a carboxylate, while Ag+ is reduced to metallic silver. Conditions: Ammoniacal AgNO3 in water, mildly basic, often with gentle warming. Watch for: Most ketones are negative. Alpha-hydroxy ketones can also reduce Tollens reagent.
Cannizzaro reaction	Meaning: Two molecules of a non-enolizable aldehyde disproportionate. One becomes a primary alcohol and one becomes a carboxylate. Conditions: Concentrated NaOH or KOH in water or alcohol-water. Heat is common. Watch for: Requires no alpha hydrogen. Aldehydes with alpha H usually give aldol chemistry instead.
Oxime formation	Meaning: Hydroxylamine adds to a carbonyl and water is lost. The C=O becomes C=N-OH. Conditions: NH2OH·HCl with base or buffer, often in ethanol-water. Mild acid and water removal help. Watch for: Ketones are slower than aldehydes. Syn and anti geometrical isomers may form.
Semicarbazone formation	Meaning: Semicarbazide condenses with a carbonyl compound. Water is lost and a C=N-NHCONH2 group forms. Conditions: Semicarbazide hydrochloride with sodium acetate, usually in ethanol-water, often with mild heat. Watch for: Often gives crystalline derivatives. Very hindered ketones may react slowly.
Wolff-Kishner reduction	Meaning: Aldehydes and ketones are deoxygenated to methylene groups. The C=O is replaced by CH2. Conditions: H2NNH2 with KOH or NaOH in ethylene glycol or similar high-boiling solvent, strong heat. Watch for: Useful for acid-sensitive substrates. Base-sensitive or heat-sensitive groups can fail.
Thioacetal formation	Meaning: A carbonyl reacts with thiols and loses water. The C=O is replaced by two C-S bonds to give a thioacetal or dithiolane. Conditions: A thiol or 1,2-ethanedithiol with BF3·Et2O or strong acid, under dry conditions. Watch for: Water suppresses formation. Ketones are usually slower than aldehydes.
Nucleophilic acyl substitution	Meaning: A nucleophile adds to an acyl derivative, then a leaving group departs. The product is a substituted acyl compound. Conditions: Occurs with acid chlorides, anhydrides, esters or amides, often using base or acid in dry or alcoholic solvent. Watch for: Aldehydes and ketones usually stop at addition because they lack a leaving group.
Alcoholysis of acid chlorides	Meaning: An alcohol attacks an acid chloride and chloride leaves. The product is an ester. Conditions: ROH with pyridine or Et3N in dry CH2Cl2 or ether, often from 0°C to room temperature. Watch for: Water competes to give the acid. A base is needed to trap HCl.
Acid-catalyzed alpha-halogenation	Meaning: The enol of an aldehyde or ketone reacts with X2. A C-X bond forms at the alpha carbon. Conditions: Br2 or Cl2 under acidic conditions, often in acetic acid, from cold to room temperature. Watch for: Usually gives monohalogenation. Base changes the selectivity and can lead to multiple halogenations.
Michael addition	Meaning: A soft nucleophile adds to the beta carbon of an alpha,beta-unsaturated carbonyl. A 1,4-addition product forms. Conditions: Use an enolate, malonate, beta-dicarbonyl or cuprate donor, usually with base in ethanol or THF. Watch for: Hard nucleophiles like RMgX or RLi often give 1,2-addition instead. The acceptor must be conjugated.
Imine hydrolysis	Meaning: Water adds to C=N, then the C-N bond breaks to regenerate an aldehyde or ketone and release the amine. Conditions: Aqueous acid, often H3O+, with heat if needed. Water is the solvent or present in excess to drive the equilibrium. Watch for: Anhydrous conditions favor the reverse imine formation. Acetals survive mild base better than imines do.
Wittig reaction	Meaning: A C=C bond forms between the carbonyl carbon and the ylide carbon. An aldehyde or ketone becomes an alkene, with Ph3P=O as byproduct. Conditions: React the carbonyl compound with a phosphonium ylide in dry THF or ether. Generate the ylide from a phosphonium salt with strong base under anhydrous conditions. Watch for: Non-stabilized ylides often give mainly Z-alkenes. Stabilized ylides are less reactive and usually give more E-alkene.
Cyclic acetal formation	Meaning: An aldehyde or ketone C=O is converted to a cyclic acetal C(OR)2, masking the carbonyl as a base-stable protected group. Conditions: Use ethylene glycol or 1,3-propanediol, catalytic p-TsOH or H+, in toluene or benzene. Remove water. Heat if needed. Watch for: Aldehydes react faster than ketones. Acetals fall apart in aqueous acid, so acid-sensitive steps must wait.
Boc carbamate formation	Meaning: An amine N-H is converted into an N-CO2tBu carbamate, protecting the amine from alkylation or acylation. Conditions: Use (Boc)2O with Et3N or NaHCO3 in CH2Cl2, THF or water-dioxane at 0 to 25 C. Watch for: Very hindered amines react slowly. The Boc group is acid-labile, so later strong acid will remove it.
Synthon	Meaning: A synthon is an idealized nucleophilic or electrophilic fragment produced by a retrosynthetic bond disconnection. Conditions: In planning, map each synthon onto a real synthetic equivalent such as an enolate, Grignard reagent or acyl chloride. Watch for: Some charged synthons have no isolable direct reagent. Choose an equivalent that matches both polarity and reactivity.
PCC oxidation	Meaning: A primary alcohol is oxidized to an aldehyde and a secondary alcohol to a ketone without going on to the acid. Conditions: Use PCC in CH2Cl2 under anhydrous conditions at room temperature. Watch for: Water promotes overoxidation or messy mixtures. It does not oxidize isolated alkenes.
Swern oxidation	Meaning: A primary alcohol becomes an aldehyde and a secondary alcohol becomes a ketone under nonaqueous mild conditions. Conditions: Use DMSO activated by oxalyl chloride, then Et3N, in CH2Cl2 at about -78 C to 0 C. Watch for: Warm addition can cause side products. The reaction gives a strong sulfur odor and needs dry conditions.
Carbonyl IR stretch	Meaning: A strong band from C=O stretching shows a carbonyl group such as an aldehyde, ketone, ester, acid or amide is present. Conditions: Record IR by ATR, neat film or KBr. Most C=O bands appear near 1650 to 1750 cm^-1. Watch for: Conjugation lowers the frequency. Amides absorb lower than simple ketones. Acid chlorides absorb higher.
Integration	Meaning: The area under a 1H NMR signal is proportional to the number of equivalent protons that produced it. Conditions: Use quantitative 1H NMR acquisition with adequate relaxation delay in a deuterated solvent. Watch for: OH and NH often integrate poorly because of exchange. Overlapping peaks can give misleading proton counts.
Bromine isotope pattern	Meaning: One bromine gives molecular ion peaks at M and M+2 in about a 1:1 ratio because 79Br and 81Br are nearly equally abundant. Conditions: Observe it in MS when the molecular ion or a bromine-containing fragment survives the ionization method. Watch for: Chlorine instead gives about 3:1 for M to M+2. Two bromines give roughly 1:2:1 across M, M+2 and M+4.
Manganese dioxide oxidation	Meaning: Activated MnO2 oxidizes allylic or benzylic alcohols to aldehydes or ketones. Conditions: Use excess activated MnO2 in CH2Cl2 or hexane, usually at room temperature. Watch for: Unactivated saturated alcohols react poorly. Old or damp MnO2 is often sluggish.
MOM ether protection	Meaning: An alcohol O-H is converted into a methoxymethyl ether by forming an O-CH2OCH3 bond. Conditions: MOMCl with DIPEA or Et3N in CH2Cl2, usually 0 °C to rt under dry conditions. Watch for: MOM is acid-labile. Phenols and amines can also be alkylated if chemoselectivity is poor.
Luche reduction	Meaning: An alpha,beta-unsaturated carbonyl is reduced at C=O to give an allylic alcohol. The C=C bond is retained. Conditions: NaBH4 with CeCl3·7H2O in MeOH, usually 0 °C to rt. Watch for: Without CeCl3, selectivity drops. Saturated carbonyls gain little from this method.
DEPT-135	Meaning: In a 13C NMR DEPT-135 spectrum, CH and CH3 signals point up, CH2 signals point down, and quaternary carbons vanish. Conditions: Run DEPT-135 with a normal proton-decoupled 13C spectrum in a deuterated solvent such as CDCl3. Watch for: Quaternary carbons give no peak. Overlap can hide phase, so use the regular 13C trace to count carbons.

Frequently asked

Why does a reactions deck start with structure and bonding?

Because reactivity depends on the basics. The structure and bonding section (35) puts hybridisation, resonance, acidity, basicity, conformations, and stereochemistry into the same Meaning, Conditions, and Watch for format as the reaction cards, so later choices make more sense.

How are substitution and elimination reactions handled in this deck?

The substitution and elimination section (45) is built around the fact that the same substrate can go different ways. Cards separate what happens from the conditions that favour it and use Watch for to flag the rival pathway, leaving group issue, or selectivity trap that usually causes the mistake.

What is covered in synthesis and analysis?

It mixes route-planning and interpretation cards, so you review how to choose a transformation and how to read clues from products or fragments. That is where alpha cleavage sits, alongside synthesis decisions that depend on conditions rather than memorised lists.

Can I import the whole deck on the free plan?

Yes. Importing a saved deck runs no new AI generation and spends no AI credits, so the free plan imports all 250 cards. You can study, edit and delete them afterwards.

Will importing it twice create duplicates?

No. Cards you already have are skipped and only cards added in a revision come through. Including re-imports after deleting it, one official deck can be imported three times per account.

Can I use it on the web and in the mobile app?

Yes. The deck is added to your account rather than to a device, so the same cards and the same progress are there on the web, on iOS and on Android.

Can I edit the cards after importing?

Yes. Imported cards are yours: you can edit both sides, delete cards you do not need, change tags, and move cards to another deck.