This section introduces several common representations to depict organic molecules.
- Thermodynamics how far a reaction proceeds, while kinetics describes how quickly it proceeds.
- A reaction coordinate diagram shows how the free Energy changes as a reaction progresses from reactant(s) to product(s).
- A transition state is the highest energy point on a reaction coordinate diagram.
- The free energy of activation is the difference in Gibbs free energy between the reactant(s) and transition state.
- Collision theory states that chemical reactions occur when reactants collide with the correct orientation and sufficient kinetic energy.
- Reaction rates tend to increase with increasing temperature, pressure and concentration.
- A catalyst provides an alternate reaction pathway with lower activation energy, thus increasing the rate of the reaction.
- A rate law shows how the rate of a reaction relates to the concentration(s) of the reactant(s) via a proportionality constant called the rate constant, k.
- The order of a reaction is the sum of the exponent terms in the rate law.
- A rate law can be experimentally determined by measuring how the initial reaction rate changes when the concentration of reactants is changed.
- An elementary reaction occurs in a single step (with a single transition state), whereas an overall reaction occurs via two or more steps.
- The molecularity of an elementary reaction is equal to the number of reactants.
- The Law of Mass Action states that the rate of an elementary reaction is directly proportional to the concentrations of the reactants.
- An integrated rate law shows how the concentration of a reactant changes over time.
- Elementary reactions of the type A→B have integrated rate laws in the form [A]=-kt+ln[A]0, where [A]0 is the concentration of A at time t=0.
- Elementary reactions of the type 2A→B have integrated rate laws in the form 1/[A]=kt+1/[A]0, where [A]0 is the concentration of A at time t=0.
- The half life of a reaction is the time, t, that it takes for the concentration of the reactant, [A], to reach half its initial concentration.
This section explores how the activation energy and free energy of activation affect the reaction rate.
- The activation energy is the difference in potential energy between the transition state and the reactant(s)
- The Arrhenius equation describes the relationship between the rate constant, k, and the activation energy, Ea
- The free energy of activation is the difference in free energy between the transition state and the reactant(s)
- The Eyring equation describes the relationship between the rate constant, k, and the free energy of activation, ΔG°‡.
This section introduces how to predict rate laws for multistep reactions.
- The rate determining step is the slowest step in the reaction, which controls the rate of the overall reaction.
- When the first step of a 2-step reaction is slow, the overall rate is equal to the rate of the first step.
- Rate laws can only include reactants, products, and/or catalysts, not intermediates.
- In the steady state approximation, we assume that the concentration of intermediate is small and constant.
- The Michaelis-Menton equation, used in biochemistry, is an application of the steady state approximation.
- If the rate law of a predicted mechanism matches the experimental rate law, the mechanism is supported (but not proven).
- If the rate law of a predicted mechanism does not match the experimental rate law, the mechanism is incorrected.