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α-carbon
The carbon adjacent to the leaving group .
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β-carbon
The carbon(s) adjacent to the α-carbon.
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β-hydrogen
The hydrogen(s) attached to the β-carbon.
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Aprotic
A solvent that is not a hydrogen bond donor.
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Leaving Group
The group that leaves in a substitution or elimination reaction.
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Nucleophile
A group characterized by it's SN2 reactivity. Good nucleophiles tend to be good bases, though they need not be. A nucleophile has a lone pair of electrons which makes up the business end of the molecule. See the nucleophilicity section.
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Protic
A solvent that is a hydrogen bond donor.
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Rate
The speed of a reaction. Often measured in moles per second.
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Rate law
A mathematical equation that relates the rate of a reaction to the concentration of its reactants. For a generic reaction:
X + Y → Z
The rate law is expressed as:rate = k [X] a [Y] b
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Rate-limiting step
The slowest step in a reaction that determines the overall rate.
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Reaction order
In the rate law, the value of "a" and "b" for reactants "X" and "Y," respectively. The overall order of a reaction is the sum of "a" and "b" and tells how many molecules of reactant are involved in the transition state of the rate-limiting step.
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Reaction intermediate
An intermediary molecule that accumulates in negligible quantities during a reaction.
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Transition state
An extremely unstable molecule that forms between the reactants and their intermediates/products. A transition state exists at the peaks of an energy diagram, in contrast to intermediates and products, which form in the troughs. The âá symbol and brackets denote a transition state structure. The number of reactant molecules present in the rate-limiting transition state is equal to the reaction order.
