Chemistry › Definitions › Introduction to organic chemistry

Introduction to organic chemistry definitions

Every term the lessons in this unit define, lesson by lesson, worded as the lessons use them. Each lesson title links to its notes.

32 terms

Naming and representing organic molecules

Empirical formula: The simplest whole-number ratio of atoms of each element in a compound.
Molecular formula: The actual number of atoms of each element in one molecule of a compound.
General formula: An algebraic formula that can describe any member of a homologous series, such as CₙH₂ₙ₊₂ for the alkanes.
Structural formula: The minimal detail that shows the arrangement of atoms in a molecule, such as CH₃CH₂CH₂COOH.
Displayed formula: A formula showing the relative positioning of all the atoms in a molecule and every bond between them.
Skeletal formula: A simplified formula showing the carbon skeleton as lines, with hydrogen atoms on carbon removed and functional groups shown.
Homologous series: A series of organic compounds with the same functional group and general formula, in which each member differs from the next by CH₂.
Functional group: An atom or group of atoms in a molecule that is responsible for its characteristic chemical reactions.
Hydrocarbon: A compound containing carbon and hydrogen only.
Saturated: Containing only single bonds between carbon atoms.
Unsaturated: Containing at least one carbon–carbon double or triple bond.

Isomers: Compounds with the same molecular formula but a different arrangement of atoms.
Structural isomers: Compounds with the same molecular formula but a different structural formula.
Stereoisomers: Compounds with the same structural formula but a different arrangement of the atoms in space.
Chain isomers: Structural isomers with the same functional group but a different arrangement of the carbon skeleton.
Position isomers: Structural isomers with the same carbon skeleton and functional group, the functional group being attached to a different carbon atom.
Functional group isomers: Structural isomers with the same molecular formula but different functional groups.
E/Z isomerism: A form of stereoisomerism caused by restricted rotation about a C=C double bond, where each carbon of the double bond carries two different groups.
Cahn–Ingold–Prelog priority rule: On each carbon of the double bond, the group whose first atom has the higher atomic number has the higher priority.
Cis–trans isomerism: A special case of E/Z isomerism in which the two carbons of the C=C carry one identical group each, such as H; cis has those groups on the same side, trans on opposite sides.

Addition: A reaction in which two molecules join together to form a single product.
Substitution: A reaction in which an atom or group of atoms in a molecule is replaced by a different atom or group.
Elimination: A reaction in which a small molecule is removed from a larger one, leaving a double bond.
Hydrolysis: The splitting of a molecule by reaction with water.
Condensation: A reaction in which two molecules join together with the loss of a small molecule such as water.
Percentage atom economy: The mass of the desired product as a percentage of the total mass of all the reactants in the balanced equation.
Homolytic fission: The breaking of a covalent bond in which each atom takes one electron from the shared pair, forming two radicals.
Heterolytic fission: The breaking of a covalent bond in which one atom takes both electrons from the shared pair, forming a positive and a negative ion.
Radical: A species with an unpaired electron, shown by a dot in its formula.
Nucleophile: An electron pair donor, which is attracted to an electron-deficient atom such as a δ+ carbon.
Electrophile: An electron pair acceptor, which is attracted to a region of high electron density.
Curly arrow: An arrow showing the movement of a pair of electrons, from a lone pair or a bond to where a new bond or lone pair forms.