Organic Chemistry — 60 Terms Defined

Electrophilic Substitution Organic Chemistry Dimensionless A reaction in which an electrophile replaces a hydrogen atom on an aromatic ring. ArH + E⁺ → ArE + H⁺

Enantiomer Organic Chemistry degrees One of a pair of stereoisomers that are non-superimposable mirror images of each other. (+) and (−), or R and S

Ester Organic Chemistry Dimensionless A compound formed by replacing the acidic hydrogen of a carboxylic acid with an alkyl group. R–COO–R′

Ether Organic Chemistry Dimensionless A compound in which an oxygen atom is bonded to two carbon atoms. R–O–R′

Free Radical Organic Chemistry Dimensionless A highly reactive species containing an unpaired electron. R·

Friedel–Crafts Reaction Organic Chemistry Dimensionless The introduction of an alkyl or acyl group onto an aromatic ring using a Lewis acid catalyst. ArH + RCl + AlCl₃ → ArR + HCl

Functional Group Organic Chemistry Dimensionless An atom or group of atoms within a molecule that determines its characteristic chemical behaviour.

Functional Group Isomerism Organic Chemistry Dimensionless Structural isomerism in which compounds of the same formula contain entirely different functional groups.

Geometric Isomerism Organic Chemistry Dimensionless Stereoisomerism arising from restricted rotation about a double bond or within a ring. cis / trans or E / Z

Grignard Reagent Organic Chemistry Dimensionless An organomagnesium halide that acts as a source of a carbanion-like nucleophilic carbon. R–Mg–X

Haloalkane Organic Chemistry Dimensionless An alkane in which one or more hydrogen atoms have been replaced by halogen atoms. R–X (X = F, Cl, Br, I)

Homologous Series Organic Chemistry Dimensionless A family of compounds sharing the same functional group and general formula, with successive members differing by CH₂. differ by −CH₂−

Hydrocarbon Organic Chemistry Dimensionless A compound composed exclusively of carbon and hydrogen. CₓH_y

Hyperconjugation Organic Chemistry kJ/mol The stabilising delocalisation of electrons from a sigma C–H bond into an adjacent empty or partly filled p orbital.

Hückel's Rule Organic Chemistry Dimensionless The rule that a planar cyclic conjugated system is aromatic if it contains 4n + 2 pi electrons. 4n + 2 π electrons

Inductive Effect Organic Chemistry Dimensionless The permanent polarisation of a sigma bond caused by the differing electronegativity of the attached atoms. −I and +I effects

Isomerism Organic Chemistry Dimensionless The existence of two or more compounds with the same molecular formula but different arrangements of atoms.

Ketone Organic Chemistry Dimensionless A compound containing a carbonyl group bonded to two carbon atoms. R–CO–R′

Markovnikov's Rule Organic Chemistry Dimensionless In the addition of a protic acid to an unsymmetrical alkene, the hydrogen attaches to the carbon already bearing more hydrogens.

Nitrile Organic Chemistry Dimensionless A compound containing a carbon–nitrogen triple bond. R–C≡N

Nucleophile Organic Chemistry Dimensionless An electron-rich species that donates a pair of electrons to form a new covalent bond. Nu⁻ or Nu:

Nucleophilic Substitution Organic Chemistry Dimensionless A reaction in which a nucleophile replaces a leaving group attached to a saturated carbon. Nu⁻ + R–X → R–Nu + X⁻

Optical Activity Organic Chemistry degrees The ability of a substance to rotate the plane of polarised light passing through it. [α] = α / (l × c)

Optical Isomerism Organic Chemistry degrees Stereoisomerism in which molecules are non-superimposable mirror images and rotate plane-polarised light in opposite directions.