Organic Chemistry: Chemical Bonding, Isomerism, and Reactions

Comprehensive vocabulary flashcards focusing on chemical bonding, molecular structures, intermolecular interactions, reaction mechanisms, and various forms of isomerism as detailed in lecture notes.

Chemical Bond

An attractive force holding atoms together in a molecule or compound, caused by electromagnetic force attraction between opposite charges of nuclei (+) and electrons (-).

Covalent bond

A chemical bond formed by the sharing of electron pairs between atoms, usually non-metals, due to electromagnetic force attraction between nuclei and shared electrons.

Valence bond theory

Describes a chemical bond as the overlap of atomic orbitals that allows electrons to be shared between atoms.

Dative bond

A covalent bond where both electrons in the shared pair are donated by one atom; also referred to as a coordinate covalent bond.

Sigma ($\sigma$) bond

A bond found in single bonds formed by the head-on overlap of atomic orbitals.

Pi ($\pi$) bond

A bond found in double and triple bonds formed by the sideways overlap of p orbitals; these are weaker than sigma bonds due to a lower degree of orbital overlap.

Hybridization

The mixing of atomic orbitals in an atom to form new hybrid orbitals and determine molecular shape.

Saturability

A characteristic of covalent bonds where each bond connects only two atoms.

Delocalized Covalent Bond

A bond where the electrons are not fixed between two atoms but are spread over several atoms, common in ions like carbonate ($CO_3^{2-}$), nitrate ($NO_3^-$), and sulfate ($SO_4^{2-}$).

Resonance

The delocalization of $\pi$ electrons or lone pairs over several atoms, resulting in equivalent bonds that are between single and double bonds.

Conjugated system

A system of alternating single and double bonds with overlapping p orbitals allowing delocalization of $\pi$ electrons, which increases stability and lowers the energy of the molecule.

Polar covalent bond

A bond formed between atoms with different electronegativities where the shared electron pair is distributed unequally.

Non-polar covalent bond

A bond formed when atoms share electrons equally due to equal electronegativities, typical in identical atoms like $H_2$, $O_2$, or $Cl_2$.

Ionic bond

A bond resulting from the transfer of electrons from a metal (forming a cation) to a non-metal (forming an anion), held together by opposite charge attraction.

Degree of ionicity

An expression of how ionic or covalent a bond is, depending mainly on the electronegativity difference between atoms.

Bond Angle

The angle between two bonds that share a common atom.

Bond length

The distance between the nuclei of two bonded atoms.

Bond Energy

The energy needed to break a bond or the energy released when a bond is formed.

Dipole moment

A measure of bond polarity that appears when charge is unequally distributed, calculated as the product of the separated charge and the distance between the center of charges.

Intramolecular forces

The forces that hold atoms together inside a molecule, such as covalent, ionic, and metallic bonds.

Intermolecular forces

Forces between separate molecules such as hydrogen bonds and Van der Waals forces; they are weaker than intramolecular forces.

Hydrogen bond

The attractive interaction of a hydrogen atom with a highly electronegative atom such as Oxygen ($O$), Nitrogen ($N$), or Fluorine ($F$).

Keesom Forces

Dipole-Dipole interactions resulting from electrostatic attractions between opposite poles of permanent dipoles in polar molecules.

Debye Force

Dipole-Induced Dipole interactions that occur when a polar molecule induces a dipole in a non-polar molecule.

London dispersion forces

Induced dipole-induced dipole interactions arising from temporary induced dipoles in all molecules due to electron shifts.

Inductive effect

The transmission of charge through $\sigma$-bonds due to electronegativity differences, leading to permanent polarization that decreases with distance.

Mesomeric effect

The way a substituent pulls or pushes electrons through a $\pi$ bond system using resonance; it only occurs in conjugated systems.

Addition reaction

A reaction where atoms or groups are added across a multiple bond, reducing bond multiplicity and increasing saturation.

Elimination reaction

A reaction in which atoms or groups are removed from a molecule, usually forming a multiple bond and releasing a small molecule such as $H_2$ or $H_2O$.

Substitution reaction

A reaction in which one atom or functional group in a molecule is replaced without changing the degree of saturation.

Reduction reaction

A reaction characterized by the gain of Hydrogen ($H$), loss of Oxygen ($O$), gain of electrons ($e^-$), or decrease in oxidation state.

Free radicals

Highly reactive and unstable species containing an unpaired electron.

Electrophiles

Electron-deficient, 'electron-loving' species that accept an electron pair; they can be positively charged or neutral.

Nucleophiles

Electron-rich, 'nucleus-loving' species that donate an electron pair.

Activation Energy ($E_a$)

The minimum energy required for a chemical reaction to occur, a concept introduced by Svante Arrhenius in 1889.

Transition State

The highest-energy unstable arrangement of atoms during a reaction formed when bonds are partially broken and formed.

Dynamic equilibrium

A state in a reversible reaction where the forward and reverse reaction rates are equal, and substances continue to react without a change in concentration.

Enthalpy ($\Delta H$)

The heat content of a system at constant pressure; a change represented by heat released (exothermic, $\Delta H < 0$) or absorbed (endothermic, $\Delta H > 0$) per mole.

Constitutional isomers

Isomers that have the same molecular formula but different connectivity of atoms, resulting in different structures and properties.

Stereoisomers

Isomers with the same molecular formula and connectivity but different spatial (3D) arrangement of atoms.

Optical isomerism

Molecules that are non-superimposable mirror images due to chirality and are capable of rotating plane-polarized light.

Dextrorotatory

An optically active substance that rotates plane-polarized light to the right ($+$).

Levorotatory

An optically active substance that rotates plane-polarized light to the left ($-$).

Racemic mixture

An optically inactive mixture containing equal amounts of both dextrorotatory and levorotatory enantiomers.

Newman projection

A structural formula technique that shows a molecule viewed along a carbon-carbon bond to emphasize conformations.

Diastereomers

Stereoisomers that are not mirror images of each other, involving molecules with more than one chiral center where only some centers differ.

Meso compound

A compound that has chiral centers but is optically inactive because it possesses an internal plane of symmetry.

Epimers

A special type of diastereomers that differ in configuration at only one chiral center while having the same connectivity otherwise.

Atropisomerism

A special case of restricted rotation around a single bond that cannot rotate freely, giving stable stereoisomers.

Akamptisomerism

A phenomenon involving the restricted bending of a bond angle.