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Competition experiment between SN2 and E2. With ethyl bromide, the reaction product is predominantly the substitution product. As steric hindrance around the electrophilic center increases, as with isobutyl bromide, substitution is disfavored and elimination is the predominant reaction. Other factors favoring elimination are the strength of the ...
Nucleophilic substitution at sp 3 centres can proceed by the stereospecific S N 2 mechanism, causing only inversion, or by the non-specific S N 1 mechanism, the outcome of which can show a modest selectivity for inversion, depending on the reactants and the reaction conditions to which the mechanism does not refer.
An example of modest stereoselectivity is the dehydrohalogenation of 2-iodobutane which yields 60% trans-2-butene and 20% cis-2-butene. [5] Since alkene geometric isomers are also classified as diastereomers, this reaction would also be called diastereoselective.
[1] [2] Stereocenters are also referred to as stereogenic centers. A stereocenter is geometrically defined as a point (location) in a molecule; a stereocenter is usually but not always a specific atom, often carbon. [2] [3] Stereocenters can exist on chiral or achiral molecules; stereocenters can contain single bonds or double bonds. [1]
In chemistry, pyramidal inversion (also umbrella inversion) is a fluxional process in compounds with a pyramidal molecule, such as ammonia (NH 3) "turns inside out". [1] [2] It is a rapid oscillation of the atom and substituents, the molecule or ion passing through a planar transition state. [3]
[4] [5] Diastereoselectivity is the preference for the formation of one or more than one diastereomer over the other in an organic reaction . In general, stereoselectivity is attributed to torsional and steric interactions in the stereocenter resulting from electrophiles approaching the stereocenter in reaction.
In quantum mechanics, a Slater determinant is an expression that describes the wave function of a multi-fermionic system. It satisfies anti-symmetry requirements, and consequently the Pauli principle, by changing sign upon exchange of two fermions. [1]
A typical value for K E is 0.0202 dm 3 mol −1 for neutral particles at a distance of 200 pm. [9] The result of the rate law is that at high concentrations of Y, the rate approximates k[M] tot while at low concentrations the result is kK E [M] tot [Y].