alkyl halide
an organic halide in which the halogen atom is bonded to an alkyl carbon
alkenyl halide
an organic halide in which the halogen atom is bonded to an alkene carbon
aryl halide
an organic halide in which the halogen atom is attached to an aromatic ring, such as a benzene ring
phenyl halide
an organic halide in which the halogen atom is bonded to a benzene ring. It's a specific type of aryl halide
nucleophile substitution reaction
A reaction initiated by a nucleophile (a neutral or negative species with an unshared electron pair) in which the nucleophile reacts with a substrate to replace a substituent (called the leaving group) that departs with an unshared electron pair.
nucleophile
a Lewis base, an electron pair donor that seeks a positive center in a molecule.
leaving group
the substituent that departs from the substrate in a nucleophilic substitution reaction.
substrate
the molecule or ion that undergoes reaction
kinetics
a term that refers to rates of reactions
bimolecular
a reaction whose rate-determining step involves two initially separate species.
molecularity
the number of species involved in a single step of a reaction (usually the rate-determining step)
SN2 reaction
Literally, substitution nucleophilic bimolecular. A bimolecular nucleophile attacks a carbon bearing a leaving group from the back side, causing an inversion of configuration at this carbon and displacement of the leaving group.
inversion
At a tetrahedral atom, the process whereby one group is relaced by another bonded 180 degree oppposite to the original group. The other groups at the tetrahedral atom "turns inside out." When a chirality center undergoes configuration inversion, its (R,S)
transition state
A state on a potential energy diagram corresponding to an energy maximum. Maximum potential energy; another term used is the activated complex
concerted reaction
A reaction where bond forming and bond breaking occur simultaneously through a single transition state.
exergonic
A reaction that proceeds with a negative free-energy charge.
endergonic
A reaction that proceeds with a positive free-energy change
free-energy diagram
A plot of free-energy changes that take place during a reaction versus the reaction coordinate. It displays free-energy changes as a function of changes in bond orders and distances as reactants proceed through the transition state to become products.
reaction coordinate
The abscissa in a potential energy diagram that represents the progress of the reaction. It represents the changes in bond orders and bond distances that must take place as reactants are converted to products
free energy of activation (delta G)
The difference between the transition state and the reactants.
stereochemistry
Chemical studies that take into account the spatial aspects of molecules
unimolecular
a reaction whose rate-determining step involves only one species
SN1 reaction
Literally, substitution nucleophilic unimolecular. A multistep nucleophilic substitution in which the leaving group departs in a unimolecular step before the attack of the nucleophile. The rate equation is first order in substrate but zero order in the at
rate-determining step
If a reaction takes place in a series of steps, and if the first step is intrinsically slower than all of the others, then the rate of the overall reaction will be the same as the rate of this slow step
intermediates
A transient species that exists between reactants and products in a state corresponding to a local energy minimum on a potential energy diagram.
hyper-conjugation
Electron delocalization (via orbital overlap) from a filled bonding orbital to an adjacent unfilled orbital. Hyperconjugation generally has a stabilizing effect.
racemization
A reaction that transforms an optically active compound into a racemic form. Takes place whenever a reaction causes chiral molecules to be converted to an achiral intermediate.
solvolysis reaction
Literally, cleavage by the solvent. A nucleophilic substitution reaction in which the nucleophile is a molecule of the solvent.
steric effect
An effect on relative reaction rates caused by the space-filling properties of those parts of a molecule attached at or near the reacting site.
steric hindrance
An effect on relative reaction rates caused when the spatial arrangement of atoms or groups at or near the reacting site hinders or retards a reaction.
Hammond-Leffler postulate
A postulate stating that the structure and geometry of the transition state of a given step will show a greater resemblance to the reactants or products of that step depending on which is closer to the transition state in energy. This means that the trans
polar aprotic solvents
A polar solvent that does not have a hydrogen atom attached to an electronegative element. They do NOT hydrogen bond with a Lewis base.
polar protic solvents
A polar solvent that has at least one hydrogen atom bonded to an electronegative element. These hydrogen atoms of the solvent can form hydrogen bonds with a Lewis base.
solvent effects
An effect on relative rates of reaction caused by the solvent. For example, the use of a polar solvent will increase the rate of reaction of an alkyl halide in an SN1 reaction.
dielectric constant
A measure of a solvent's ability to insulate opposite charges from each other. Measures a solvent's polarity. Solvents with high __________ are better solvents for ions than are solvents with low __________
polarizability
The susceptibility of the electron cloud of an uncharged molecule to distortion by the influence of an electric charge.
functional group interconversion
a process that converts one functional group into another
inversion of configuration
At a tetrahedral atom, the process whereby one group is replaced by another bonded 180 degree opposite to the original group. The other groups at the tetrahedral atom "turns inside out." When a chirality center undergoes configuration inversion, its (R,S)
elimination reaction
A reaction that results in the loss of two groups from the substrate and the formation of a pi bond. The most common elimination is a 1,2 elimination or Beta elimination, in which the two groups are lost from adjacent atoms.
dehydrohalogenation
An elimination reaction that results in the loss of HX from adjacent carbons of the substrate and the formation of a pi bond.
E2 reaction
A bimolecular 1,2 elimination in which, in a single step, a base removes a proton and a leaving group departs from the substrate, resulting in the formation of a pi bond
E1 reaction
A unimolecular elimination in which, in a slow, rate-determining step, a leaving group departs from the substrate to form a carbocation. The carbocation then in a fast step loses a proton with the resulting formation of a pi bond.