6. Understanding Organic Reactions Flashcards
A reaction in which another atom or group of atoms replaces an atom or a group of atoms. This reaction involves σ bonds: one σ bond breaks and another is formed at the same atom.
Substitution Reaction
A chemical reaction in which elements of the starting material are “lost” and a π bond is formed.
Elimination Reaction
A reaction in which elements are added to a starting material. In this reaction, a π bond is broken and two σ bonds are formed.
Addition Reaction
A detailed description of how bonds are broken and formed as a starting material is converted to a product.
Reaction Mechanism
A reaction in which all bond forming and bond breaking occurs in one step.
Concerted Reaction
A high-energy unstable intermediate formed during the conversion of a stable starting material to a stable product.
Reactive Intermediate
The breaking of a covalent bond by equally dividing the electrons between the two atoms in the bond and generates uncharged radical intermediates.
Homolysis (Homolytic Cleavage)
The breaking of a covalent bond by unequally dividing the electrons between the two atoms in the bond and generates charged intermediates.
Heterolysis (Heterloytic Cleavage)
A half-headed curved arrow used in a reaction mechanism to denote the movement of a single electron.
Fishhook
An arrow used in a reaction mechanism to denote the movement of a pair of electrons.
Full-Headed Curved Arrow
A reactive intermediate with a single unpaired electron, formed by homolysis of a covalent bond.
Radical
The energy absorbed or released in a reaction and is symbolized by ΔH°
Enthalpy Change (Heat of Reaction)
A reaction in which the energy of the products is higher than the energy of the reactants. energy is absorbed and the ΔH° is a positive value.
Endothermic
A reaction in which the energy of the products is lower than the energy of the reactants. energy is released and the ΔH° is a negative value.
Exothermic
A study of the energy and equilibrium of a chemical reaction.
Thermodynamics
The study of chemical reaction rates.
Kinetics
A mathematical expression, denoted by the symbol Keq, which relates the amount of starting material and product at equilibrium. Keq = [products]/[starting materials].
Equilibrium Constant
The free energy of a molecule and is denoted by the symbol G°.
Gibbs Free Energy
The change in the amount of disorder between reactants and products in a reaction. The change is denoted by the symbol ΔS°. ΔS° = S°products − S°reactants.
Entropy Change
A schematic representation of the energy changes that take place as reactants are converted to products. It indicates how readily a reaction proceeds, how many steps are involved, and how the energies of the reactants, products, and intermediates compare.
Energy Diagram
The x axis in an energy diagram that represents the progress of a reaction as it proceeds from reactant to product.
Reaction Coordinate
An unstable energy maximum as a chemical reaction proceeds from reactants to products. The state is at the top of an energy “hill” and can never be isolated.
Transition State
symbolized by Ea, is the minimum amount of energy needed to break bonds in the reactants.
Energy of Activation
In a multistep reaction mechanism, the step with the highest-energy transition state.
Rate-Determining Step
An equation that shows the relationship between the rate of a reaction and the concentration of the reactants.
Rate Equation
A reaction in which the concentration of both reactants affects the reaction rate and both terms appear in the rate equation. Two reactants are involved in the only step or the rate-determining step.
Bimolecular Reaction
The sum of the exponents of the concentration terms in the rate equation of a reaction.
Order of a Rate Equation
A rate equation in which the reaction rate depends on the concentration of two reactants.
Second-Order Rate Equation
A reaction that has only one reactant involved in the rate-determining step, so the concentration of only one reactant appears in the rate equation.
Unimolecular Reaction
A rate equation in which the reaction rate depends on the concentration of only one reactant.
First-Order Rate Equation
A substance that speeds up the rate of a reaction, but is recovered unchanged at the end of the reaction and does not appear in the product.
Catalyst
The region of an enzyme that binds the substrate.
Active Site
An organic molecule that is transformed by the action of an enzyme.
Substrate
A structure having a substrate bonded to the active site of an enzyme.
Enzyme-Substrate Complex
