Chemistry mechanisms definitions

Functional group

An atom or group of atoms within a molecule responsible for the characteristic reactions of a particular compound

Nucleophile

A substance that donates a pair of electrons in a reaction

Electrophile

A substance that accepts a pair of electrons in a reaction

Sigma bond

A type of covalent bond formed by head-on overlap of atomic orbitals in which the majority of the electron density is in the same plane as the nuclei, the strongest type of covalent bond

Pi bond

A type of covalent bond formed by the side-by-side overlap of orbitals with the electron density concentrated above and below the plane of the nuclei

Alkyl group

A functional group of an organic molecule that only contains C and H atoms

Chiral

Describes molecules that cannot be superimposed on its mirror image

Free radical

Molecules or ions with unpaired electrons

Isomer

Compounds with the same molecular formula but different chemical structure

Substitution reaction

A reaction in which one atom or group of atoms is replaced by another atom or group of atoms

Addition reaction

A reaction in which an atom or group of atoms is added to a molecule across a double bond

Elimination reaction

A reaction in which atoms are removed from a molecule

Oxidation

A reaction in which the oxidation number is increased or the proportion of electronegative substituents in a compound is increased

Reduction

A reaction in which the oxidation number is decreased or the proportion of electronegative substituents in a compound is decreased

Hydrolysis

The addition of water to a substance to break it down

Lone pair

A pair of electrons in a molecule not shared between two atoms

Steric hindrance

The physical blockage of a particular site within a molecule by the presence of local atoms or groups of atoms

Transition state

A short-lived configuration of atoms formed during a chemical reaction that is the least stable and associated with the highest energy level on a reaction path

Intermediate

A chemical substance produced during the conversion of reactant to product

Electronegativity

The tendency for atoms in a molecule to attract a bonding pair of electrons