Reactivity 2.2 — HL Flashcards
Reaction mechanism
A sequence of elementary steps by which a chemical reaction occurs.
Elementary steps
One step in a series of simple reactions that show the progress of a reaction at the molecular level. Also known as an elementray reaction.
Reaction intermediate
A reaction intermediate refers to a transient molecule formed during one stage of the reaction and used up in a subsequent stage.
Rate determining step
The slowest step of a chemical reaction that determines the rate at which the overall reaction proceeds.
How must reaction mechanisms be consistent?
Reaction mechanisms must be consistent with both stoichiometric data (the quantitative relationship between reactants and products) and kinetic data (the rates at which reactants transform into products).
What are intermediates in a reaction mechanism?
Species that are formed in one step of the reaction mechanism and consumed in the next. They are stable enough to be isolated from the reaction mixture.
What are transition states in a reaction mechanism?
Highly unstable species formed between two steps of the reaction mechanism, characterized by partial bond formation and breakage. They quickly revert to form products and are represented at the peaks in energy profile diagrams.
Where are transition states and intermediates located in an energy profile diagram?
Transition states are located at the peaks (highest energy points) and intermediates are found in the dips (lower energy points) of an energy profile diagram.
What does the molecularity of a reaction refer to?
The number of reactant particles taking part in the rate determining step of the reaction mechanism.
Unimolecular
A reaction or reaction step in which only one reactant species is taking part.
Bimolecular
A reaction or reaction step in which two reactant particles are taking part.
Termolecular
A reaction or reaction step where three reactant particles are taking part.
Rate expression
The mathematical expression that describes the relationship between the rate of a chemical reaction and the concentration of its reactants.
The Arrhenius factor
It accounts for the frequency and alignment of collisions. While it changes minimally with temperature, these variations are typically small. It is often regarded as a constant for all temperatures and is specific to each reaction.
