ORGANIC CHEMISTRY · CHEMICAL SYNTHESIS · ONE-STEP

Name the change.
Then choose the conditions.

Forty bounded reaction rules connect ten study clusters to the ADA's single One-Step synthesis topic. Each card keeps substrate class, reagent order, product state, carbon count, regiochemistry, stereochemistry, and evidence limits together.

Start ten guided lessons →Build a mixed set ↗Open the library ↓
1official topic line
11official named cues
10bounded clusters
0invented weights

Official scope, conditional library

One topic is not one universal reaction rule.

The ADA lists One-Step under Chemical Synthesis and names 11 scope cues, including substitution, elimination, major functional-group families, and “Other Reactions.” It does not publish cue-level weights or quotas.

DAT TRAIN organizes ten explicit reaction-family clusters for study. “Other Reactions” remains visible as an official catch-all cue; it is not used to imply an unlimited or secretly weighted reagent list.

Three study objectives

Difference. Conditions. Product audit.

Every reaction card and practice item returns to the same three study objectives before longer multistep work begins.

01

Describe the one-step structural change

Compare starting material and target to identify the bond, functional-group, oxidation-state, or stereochemical change required in one step.

Must know
Target analysis begins with changed connectivity and functional groups. Unchanged atoms and stereocenters constrain acceptable reactions.
Evidence boundary
Do not choose reagents until the required transformation is explicit.
Common trap
Synthesis starts by scanning a memorized reagent list. Start with the structural difference, then select a compatible transformation.
02

Select compatible reagents and conditions

Choose a one-step reaction set that performs the required transformation on the supplied substrate.

Must know
Reagent function must match substrate class and desired product. Solvent, heat, equivalents, and workup can determine pathway and product state.
Evidence boundary
Only require named reagents and conditions supported by the official scope and cited instructional source.
Common trap
A reagent name alone fully specifies the outcome. Substrate and conditions are part of the reaction definition.
03

Predict selectivity and validate the product

Draw the major bounded product of a one-step substitution, elimination, addition, or functional-group reaction and verify regiochemical and stereochemical consequences.

Must know
Mechanism constrains regiochemistry and stereochemistry. Atom count, charge, and functional-group identity must reconcile after workup.
Evidence boundary
Call a product major only when the prompt supplies enough selectivity information.
Common trap
The most substituted product is always major. Mechanism, reagent size, substrate geometry, and kinetic conditions can change selectivity.

Ten clusters · forty bounded rules

Keep the whole reaction attached.

Each cluster contains four representative course-level mappings. The cards are study infrastructure, not claims about ADA frequency.

01Substitution4 rules · Substitution (SN1, SN2)

Official named scope: Substitution (SN1, SN2)

SUB-01sn2

Primary-halide cyanide substitution

1-bromopropane → butanenitrile

Conditions
sodium cyanide · DMSO at moderate temperature
Structural change
replace C–Br with C–C≡N and add the cyanide carbon to the skeleton
Selectivity
reaction at the carbon bearing bromine; backside displacement; inversion only if that carbon is stereogenic
Boundary
The primary substrate and polar-aprotic medium support the bounded SN2 mapping; the rule is not a universal rate claim.
Free reaction source ↗
SUB-02sn2

Stereochemical SN2 substitution

one enantiomer of 2-bromobutane → 2-azidobutane with inverted configuration at the reacting carbon

Conditions
sodium azide · DMF with an unhindered nucleophile
Structural change
replace C–Br with C–N₃ at one tetrahedral carbon
Selectivity
reaction at C2, the leaving-group carbon; inversion at the reacting stereogenic carbon
Boundary
Inversion describes geometry at the reacting center; an R/S label still requires a fresh CIP assignment after substitution.
Free reaction source ↗
SUB-03sn1

Tertiary-halide solvolysis

3-chloro-3-methylhexane → 3-methylhexan-3-ol as a stereochemical mixture

Conditions
water · aqueous ethanol without a strong base
Structural change
replace tertiary C–Cl with C–OH through ionization and solvent capture
Selectivity
capture at the ionized C3 center; loss of stereospecificity through a planar carbocation model
Boundary
The mixture claim is bounded to the supplied ionization model and does not promise perfectly equal enantiomer amounts.
Free reaction source ↗
SUB-04sn2

Primary sulfonate displacement

butyl tosylate → 1-iodobutane

Conditions
sodium iodide · acetone
Structural change
replace C–OTs with C–I without changing the carbon skeleton
Selectivity
reaction at the primary carbon bearing tosylate; backside displacement; no stereochemical label is needed for this achiral example
Boundary
The precipitation-driven laboratory context supports this example; it is not a blanket solvent rule for every nucleophile.
Free reaction source ↗
Study this cluster →
02Elimination4 rules · Elimination (E1, E2)

Official named scope: Elimination (E1, E2)

ELI-01e2

Small-base E2 elimination

2-bromobutane → 2-butene, with E-2-butene favored among its stereoisomers

Conditions
sodium ethoxide · ethanol with heat
Structural change
remove β-H and Br while increasing the adjacent C–C bond to C=C
Selectivity
Zaitsev internal alkene favored with the small base; anti-periplanar elimination; E alkene favored when accessible
Boundary
The major-product statement depends on the stated base and accessible anti geometry, not a universal substitution rule.
Free reaction source ↗
ELI-02e2

Bulky-base E2 elimination

2-bromo-2-methylbutane → 2-methyl-1-butene as the less substituted major alkene

Conditions
potassium tert-butoxide · tert-butanol with heat
Structural change
remove the most accessible β-H and Br while forming a terminal C=C bond
Selectivity
less substituted Hofmann alkene favored; anti-periplanar elimination where the acyclic conformation permits it
Boundary
Bulky-base preference is a comparative rule for the supplied substrate, not a guarantee for every elimination.
Free reaction source ↗
ELI-03e2

Cyclohexane trans-diaxial E2

bromocyclohexane → cyclohexene

Conditions
sodium ethoxide · ethanol with heat after adopting the axial-Br chair
Structural change
remove axial β-H anti to axial Br and form the ring C=C bond
Selectivity
either symmetry-equivalent adjacent carbon gives cyclohexene; trans-diaxial anti elimination
Boundary
A ring flip changes conformation, not connectivity; the reacting chair must actually contain the required axial pair.
Free reaction source ↗
ELI-04e1

Tertiary E1 elimination

2-bromo-2-methylbutane → 2-methyl-2-butene as the more substituted major alkene

Conditions
ethanol · polar-protic solvent with heat and no strong nucleophile
Structural change
ionize C–Br, then remove β-H to form the more substituted C=C bond
Selectivity
more substituted Zaitsev alkene favored; not stereospecific through the planar carbocation model
Boundary
Heat shifts the stated solvolysis competition toward elimination; a product ratio is not asserted without data.
Free reaction source ↗
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03Alkenes and Alkynes4 rules · Reactions of Alkenes/Alkynes

Official named scope: Reactions of Alkenes/Alkynes

ALK-01concerted addition

Alkene hydroboration–oxidation

1-hexene → hexan-1-ol

Conditions
1. borane in THF → 2. hydrogen peroxide and hydroxide · ordered hydroboration followed by oxidative workup
Structural change
decrease C=C to C–C and add H/OH with OH at the less substituted carbon
Selectivity
anti-Markovnikov alcohol; syn addition of H and OH
Boundary
The workup order is part of the reaction definition; no rearrangement is introduced by this concerted model.
Free reaction source ↗
ALK-02electrophilic addition

Alkene bromination

cyclohexene → trans-1,2-dibromocyclohexane

Conditions
bromine · dichloromethane without water
Structural change
decrease C=C to C–C and form one C–Br bond at each alkene carbon
Selectivity
one bromine at each alkene carbon; anti addition gives the trans vicinal dibromide
Boundary
Water is excluded because it would change the nucleophile and favor halohydrin formation.
Free reaction source ↗
ALK-03reduction

Lindlar partial hydrogenation

2-butyne → cis-2-butene

Conditions
hydrogen gas → Lindlar catalyst · poisoned heterogeneous catalyst
Structural change
decrease C≡C to C=C while adding one H to each alkyne carbon
Selectivity
one hydrogen added to each alkyne carbon; syn delivery gives the cis alkene
Boundary
The poisoned catalyst is essential to the bounded stop-at-alkene prediction.
Free reaction source ↗
ALK-04reduction

Dissolving-metal alkyne reduction

2-butyne → trans-2-butene

Conditions
sodium metal · liquid ammonia at low temperature
Structural change
decrease C≡C to C=C while delivering hydrogens to opposite faces
Selectivity
one hydrogen added to each alkyne carbon; anti delivery gives the trans alkene
Boundary
This rule applies to the stated dissolving-metal conditions and should not be merged with catalytic hydrogenation.
Free reaction source ↗
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04Alcohols4 rules · Reactions of Alcohols

Official named scope: Reactions of Alcohols

ALC-01oxidation

Mild primary-alcohol oxidation

1-butanol → butanal

Conditions
Dess–Martin periodinane · anhydrous dichloromethane
Structural change
increase the alcohol carbon–oxygen bond order to C=O and remove two hydrogens
Selectivity
oxidation at the carbon bearing OH; not applicable to the planar aldehyde carbonyl
Boundary
Anhydrous mild conditions support the aldehyde stop; stronger aqueous oxidation changes the endpoint.
Free reaction source ↗
ALC-02oxidation

Strong primary-alcohol oxidation

1-butanol → butanoic acid

Conditions
sodium dichromate → sulfuric acid · aqueous acetone
Structural change
oxidize the terminal primary alcohol carbon to a carboxylic acid
Selectivity
oxidation at the terminal alcohol carbon; not applicable
Boundary
The aqueous strong-oxidant context permits oxidation beyond the aldehyde; no yield is inferred.
Free reaction source ↗
ALC-03oxidation

Secondary-alcohol oxidation

2-butanol → 2-butanone

Conditions
pyridinium chlorochromate · dichloromethane
Structural change
increase the secondary C–O bond to C=O and remove C–H/O–H
Selectivity
oxidation at C2, the alcohol carbon; the tetrahedral alcohol center becomes planar carbonyl carbon
Boundary
Ordinary ketones do not undergo the same simple further oxidation without carbon-skeleton cleavage conditions.
Free reaction source ↗
ALC-04dehydration

Acid-catalyzed alcohol dehydration

cyclohexanol → cyclohexene

Conditions
sulfuric acid · concentrated acid with heat
Structural change
remove OH and β-H as water while increasing the adjacent C–C bond to C=C
Selectivity
symmetry gives one cyclohexene constitutional product; not stereospecific under the supplied acid-catalyzed model
Boundary
Heat and acid define dehydration; calling OH a leaving group without prior activation would omit necessary proton bookkeeping.
Free reaction source ↗
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05Ethers and Epoxides4 rules · Reactions of Ethers (including Epoxides)

Official named scope: Reactions of Ethers (including Epoxides)

ETH-01sn2

Williamson ether synthesis

1-bromopropane plus sodium ethoxide → 1-ethoxypropane

Conditions
sodium ethoxide · primary bromide in a polar-aprotic medium
Structural change
replace propyl C–Br with C–OEt and join the two supplied carbon fragments
Selectivity
attack at the primary carbon bearing bromine; backside displacement; no stereocenter in this example
Boundary
A tertiary alkyl halide would redirect a strong alkoxide toward elimination rather than this SN2 map.
Free reaction source ↗
ETH-02ether cleavage

Aryl methyl ether cleavage

anisole → phenol plus iodomethane

Conditions
hydroiodic acid · concentrated HI with heat
Structural change
cleave the methyl–oxygen bond, form C–I, and retain the aryl–oxygen bond
Selectivity
cleavage at the methyl side, not the sp² aryl carbon; not applicable
Boundary
The bounded SN2 cleavage occurs at methyl; ordinary backside displacement at the aromatic sp² carbon is not asserted.
Free reaction source ↗
ETH-03epoxide opening

Basic epoxide opening

1,2-epoxypropane → 1-methoxypropan-2-ol

Conditions
sodium methoxide · methanol, then protonation
Structural change
break the attacked epoxide C–O bond and form C–OCH₃ at the less substituted carbon
Selectivity
attack at the less substituted epoxide carbon; backside attack gives anti ring opening at the attacked carbon
Boundary
The methoxy carbon is reagent-derived; carbon accounting must include it rather than treating the product as a three-carbon molecule.
Free reaction source ↗
ETH-04epoxide opening

Acidic epoxide opening

2,2-dimethyloxirane → 2-methoxy-2-methylpropan-1-ol

Conditions
methanol → sulfuric acid catalyst · acidic methanol
Structural change
protonate the epoxide, break the more substituted C–O ring bond, and form C–OCH₃ there
Selectivity
attack at the more substituted epoxide carbon under the stated acidic model; anti opening relative to the departing ring oxygen bond
Boundary
The regioselectivity requires the stated tertiary-substituted acidic case; primary/secondary-only epoxides need a more qualified comparison.
Free reaction source ↗
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06Radical Reactions4 rules · Radical Reactions

Official named scope: Radical Reactions

RAD-01radical chain

Controlled methane chlorination

methane → chloromethane as the intended monochlorination product

Conditions
one equivalent of chlorine · ultraviolet light
Structural change
replace one C–H bond with C–Cl through a radical chain
Selectivity
only one hydrogen environment exists; not applicable
Boundary
Limiting chlorine supports the intended monochlorination, but further substitution is a real competing possibility rather than impossible chemistry.
Free reaction source ↗
RAD-02radical chain

Selective propane bromination

propane → 2-bromopropane as the major monobromination product

Conditions
bromine · heat or ultraviolet light
Structural change
replace the secondary C–H with C–Br through the favored secondary radical pathway
Selectivity
secondary bromination favored over primary bromination; not applicable
Boundary
Major does not mean exclusive; the bounded ranking compares radical stability and bromination selectivity.
Free reaction source ↗
RAD-03radical chain

NBS allylic bromination

cyclohexene → 3-bromocyclohexene

Conditions
N-bromosuccinimide · light in an inert solvent
Structural change
replace an allylic C–H with C–Br while retaining the alkene
Selectivity
symmetry-equivalent allylic positions give one constitutional product; not specified for the planar allylic-radical model
Boundary
NBS maintains a low bromine concentration; ordinary Br₂ addition across the alkene is a different condition set.
Free reaction source ↗
RAD-04radical chain

Peroxide-promoted HBr addition

propene → 1-bromopropane

Conditions
hydrogen bromide → peroxide initiator · radical-initiating conditions
Structural change
decrease C=C to C–C and add Br to the less substituted carbon and H to the more substituted carbon
Selectivity
anti-Markovnikov bromide; not stereospecific in this acyclic example
Boundary
The peroxide effect is taught for HBr under the supplied scope; it must not be generalized automatically to HCl or HI.
Free reaction source ↗
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07Aromatic Reactions4 rules · Reactions of Aromatics

Official named scope: Reactions of Aromatics

ARO-01electrophilic aromatic substitution

Benzene bromination

benzene → bromobenzene

Conditions
bromine → iron(III) bromide · Lewis-acid-catalyzed electrophilic aromatic substitution
Structural change
replace one aromatic C–H with C–Br while restoring the aromatic pi system
Selectivity
one product by benzene symmetry; not applicable
Boundary
FeBr₃ activates the electrophile; the outcome is substitution, not ordinary alkene addition.
Free reaction source ↗
ARO-02electrophilic aromatic substitution

Benzene nitration

benzene → nitrobenzene

Conditions
nitric acid → sulfuric acid · controlled nitration temperature
Structural change
replace one aromatic C–H with C–NO₂ while restoring aromaticity
Selectivity
one product by benzene symmetry; not applicable
Boundary
Temperature and equivalents bound nitration extent; the rule does not promise that overreaction is impossible.
Free reaction source ↗
ARO-03electrophilic aromatic substitution

Friedel–Crafts acylation

benzene → acetophenone

Conditions
acetyl chloride → aluminum chloride · anhydrous Lewis-acid conditions
Structural change
replace one aromatic C–H with C–COCH₃
Selectivity
one constitutional product from benzene symmetry; not applicable
Boundary
The acylium mapping avoids the rearrangement issue of Friedel–Crafts alkylation, but substrate deactivation limits still matter.
Free reaction source ↗
ARO-04electrophilic aromatic substitution

Directed anisole nitration

anisole → ortho- and para-nitroanisole, with para favored in the bounded comparison

Conditions
nitric acid → sulfuric acid · cold, controlled nitration
Structural change
replace an ortho or para aromatic C–H with C–NO₂ while retaining methoxy
Selectivity
methoxy directs ortho/para; para favored here by sterics; not applicable
Boundary
The directive claim compares the stated monosubstituted ring; exact product ratios require experimental data.
Free reaction source ↗
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08Aldehydes and Ketones4 rules · Reactions of Ketones and Aldehydes

Official named scope: Reactions of Ketones and Aldehydes

CAR-01reduction

Ketone hydride reduction

cyclohexanone → cyclohexanol

Conditions
sodium borohydride · methanol, then water
Structural change
decrease C=O to C–O and add H to the carbonyl carbon
Selectivity
hydride adds to the carbonyl carbon; no configurational issue in achiral cyclohexanone
Boundary
NaBH₄ is used here for the stated aldehyde/ketone reduction; broader functional-group compatibility is not assumed without evidence.
Free reaction source ↗
CAR-02nucleophilic addition

Grignard addition to an aldehyde

ethanal → 2-propanol

Conditions
1. methylmagnesium bromide in ether → 2. hydronium · strictly dry carbon–carbon bond formation before aqueous workup
Structural change
decrease C=O to C–O and form a bond from carbonyl carbon to the reagent methyl carbon
Selectivity
methyl adds to the electrophilic carbonyl carbon; two faces are equivalent for this achiral product
Boundary
Water must follow, not precede, the organomagnesium addition because proton sources quench the reagent.
Free reaction source ↗
CAR-03olefination

Wittig olefination

benzaldehyde → styrene

Conditions
methylenetriphenylphosphorane · anhydrous THF
Structural change
replace C=O with C=CH₂ using the ylide carbon
Selectivity
new terminal CH₂ attaches at the former carbonyl carbon; no E/Z designation because one alkene carbon is CH₂
Boundary
The product audit includes the reagent carbon and oxygen-containing coproduct; a bare deoxygenation description is incomplete.
Free reaction source ↗
CAR-04oxidation

Aldehyde oxidation

propanal → propanoic acid

Conditions
sodium dichromate → sulfuric acid · aqueous conditions
Structural change
oxidize aldehyde C–H to C–OH while retaining the carbonyl
Selectivity
oxidation at the aldehyde carbon; not applicable
Boundary
This aldehyde endpoint should not be generalized to ordinary ketones under the same simple oxidation model.
Free reaction source ↗
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09Carboxylic Acids and Derivatives4 rules · Reactions of Carboxylic Acids/Derivatives

Official named scope: Reactions of Carboxylic Acids/Derivatives

DER-01nucleophilic acyl substitution

Acid-chloride alcoholysis

acetyl chloride plus ethanol → ethyl ethanoate

Conditions
ethanol → pyridine · anhydrous nucleophilic acyl substitution
Structural change
replace acyl C–Cl with C–OEt while retaining C=O
Selectivity
attack at the acyl carbon; not applicable at planar acyl carbon
Boundary
Pyridine captures acid and supports the stated product state; the reagent list is part of the reaction contract.
Free reaction source ↗
DER-02nucleophilic acyl substitution

Acid-chloride aminolysis

acetyl chloride plus two equivalents of ammonia → acetamide plus ammonium chloride

Conditions
excess ammonia · cold addition followed by warming
Structural change
replace acyl C–Cl with C–NH₂ while a second ammonia neutralizes HCl
Selectivity
attack at the acyl carbon; not applicable
Boundary
The second ammonia equivalent belongs to the acid/base ledger and prevents an incomplete neutral-product equation.
Free reaction source ↗
DER-03nucleophilic acyl substitution

Base-promoted ester hydrolysis

ethyl ethanoate → sodium ethanoate plus ethanol

Conditions
sodium hydroxide → water · aqueous heat without an acid workup
Structural change
cleave the acyl C–OEt bond and replace it with carboxylate oxygen under basic conditions
Selectivity
hydroxide attacks the ester acyl carbon; not applicable
Boundary
Without an acid workup, drawing neutral ethanoic acid would silently change the supplied product state.
Free reaction source ↗
DER-04reduction

Ester hydride reduction

ethyl ethanoate → two equivalents of ethanol

Conditions
1. lithium aluminum hydride in ether → 2. hydronium · strictly dry reduction before aqueous workup
Structural change
reduce the acyl carbon to CH₂OH and cleave the acyl–alkoxy bond after hydride addition
Selectivity
reduction at the ester acyl carbon; not applicable
Boundary
Aqueous workup must follow hydride delivery; NaBH₄ should not be substituted automatically for this ester rule.
Free reaction source ↗
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10Alpha-Carbonyl Chemistry4 rules · Reactions of Alpha-Carbonyl Compounds

Official named scope: Reactions of Alpha-Carbonyl Compounds

ALP-01enolate substitution

Acidic alpha bromination

cyclohexanone → 2-bromocyclohexanone

Conditions
bromine · acetic acid
Structural change
replace one alpha C–H with C–Br while retaining the carbonyl
Selectivity
symmetry-equivalent alpha positions give one constitutional product; no single configuration asserted at the newly stereogenic alpha carbon
Boundary
Acidic enol halogenation is distinguished from exhaustive base-promoted haloform conditions.
Free reaction source ↗
ALP-02enolate substitution

Directed enolate alkylation

cyclohexanone → 2-methylcyclohexanone

Conditions
1. lithium diisopropylamide in THF → 2. iodomethane · −78 °C enolate formation followed by methylation
Structural change
replace one alpha C–H with C–CH₃ while retaining C=O
Selectivity
one alpha site by cyclohexanone symmetry; no single product configuration asserted
Boundary
The ordered base-then-electrophile sequence is essential; combining all reagents at once is not equivalent.
Free reaction source ↗
ALP-03aldol addition

Aldol addition

two equivalents of ethanal → 3-hydroxybutanal

Conditions
dilute sodium hydroxide · cold aqueous conditions
Structural change
form an alpha-to-carbonyl C–C bond and reduce the acceptor C=O to C–OH
Selectivity
ethanal symmetry gives one constitutional aldol product; no single stereoisomer asserted
Boundary
Cold dilute conditions support the addition endpoint; heating can drive dehydration to a different product.
Free reaction source ↗
ALP-04aldol condensation

Aldol condensation

two equivalents of ethanal → but-2-enal plus water

Conditions
sodium hydroxide · aqueous heat
Structural change
form the aldol C–C bond, then eliminate water to create the conjugated C=C bond
Selectivity
ethanal symmetry gives one constitutional condensation product; more stable E alkene can be favored, but no exact ratio is asserted
Boundary
Heat distinguishes condensation from the cold aldol-addition endpoint; the two should not be keyed as interchangeable.
Free reaction source ↗
Study this cluster →

Source ladder

Official boundary, free reaction references.

Official Organic Chemistry specificationDefines Chemical Synthesis, One-Step, and all named cues—not quotas. ↗OpenStax Substitution and EliminationFree reaction summaries for SN1, SN2, E1, and E2 boundaries. ↗OpenStax Carbonyl ReactionsFree mappings for aldehydes, ketones, additions, reductions, and olefination. ↗OpenStax Acid DerivativesFree mappings for acyl substitution, hydrolysis, and reduction. ↗