Foundations

Characteristic structural groups organize organic compounds and recurring reactivity.

The same molecular formula can describe different connectivity or spatial arrangements.

Addition, elimination, substitution and rearrangement classify net structural changes.

Curved arrows record proposed changes in electron-pair bonding.

Conformations differ by rotations about bonds without changing connectivity.

For a tetrahedral stereogenic centre, rank attached groups by the Cahn–Ingold–Prelog rules: atomic number first, isotopic mass for isotopes, then the first point of difference with multiple-bond duplication.

For an alkene whose two substituents on each double-bond carbon can be distinguished, assign CIP priority independently on each carbon.

An SN2 step forms a bond to a nucleophile as the leaving group departs through one transition state.

In a simple SN1 pathway, slow substrate ionization forms a carbocation-containing intermediate before nucleophilic capture.

In an E2 step, removal of a β hydrogen, formation of an alkene bond and leaving-group departure occur together.

E1 elimination proceeds through ionization followed by loss of a proton from a carbocation intermediate.

In carbocation-mediated addition of HX to an alkene, protonation creates an intermediate that a nucleophile subsequently captures.

In the elementary Hückel description, a planar cyclic continuously conjugated π system with 4n+2 π electrons has a closed-shell aromatic pattern.

In a typical electrophilic aromatic substitution, the aromatic π system bonds to an electrophile, forming a nonaromatic σ intermediate.

A nucleophile adds to the electrophilic carbonyl carbon while the π electron pair moves toward oxygen, forming a tetrahedral intermediate.

For a carboxylic acid derivative, nucleophilic addition can form a tetrahedral intermediate whose collapse expels a leaving group and restores the carbonyl.

Removal of an α proton from a suitable carbonyl compound forms an enolate whose charge is distributed between oxygen and carbon by conjugation.

In a simple aldol pathway, an enolate or enol donor adds to another carbonyl acceptor to create a carbon–carbon bond.

A radical chain has initiation steps that generate radicals, propagation steps that transform reactants while regenerating a radical carrier, and termination steps that consume carriers.

Kinetic control favours products formed more rapidly before equilibration; thermodynamic control reflects an accessible equilibrium product distribution.

In a typical thermal Diels–Alder reaction, a conjugated diene and a dienophile form two σ bonds and a new π bond through a concerted cyclic pathway.

A conjugated carbonyl has an electrophilic β carbon as well as a carbonyl carbon.

An ester enolate attacks another suitable ester carbonyl.

Hydride-transfer reduction of an aldehyde or ketone forms an alkoxide that can be protonated to an alcohol.

An organomagnesium reagent can transfer its carbon group to an aldehyde or ketone carbonyl, forming an alkoxide and a new carbon–carbon bond.

Oxidation of a primary alcohol can give an aldehyde or continue to a carboxylic acid, while a secondary alcohol can give a ketone.

A primary amine adds to a suitable aldehyde or ketone and dehydration of the carbinolamine produces an iminium intermediate, which can lose an N proton to give an imine.

Alcohol addition to a carbonyl forms a hemiacetal.

In a Wittig transformation, a phosphorus ylide and an aldehyde or ketone give an alkene and a phosphine oxide.

In the elementary alkene hydroboration model, C–H and C–B bonds form together from the same face without a free carbocation intermediate.