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In chemistry, racemization is a conversion, by heat or by chemical reaction, of an optically active compound into a racemic (optically inactive) form. This creates a 1:1 molar ratio of enantiomers and is referred to as a racemic mixture (i.e. contain equal amount of (+) and (−) forms).
The D- and L- prefixes describe the molecule as a whole, as do the (+) and (−) prefixes for optical rotation. In contrast, the ( R )- and ( S )- prefixes from the Cahn–Ingold–Prelog priority rules characterize the absolute configuration of each specific chiral stereocenter with the molecule, rather than a property of the molecule as a whole.
In chemistry, a concerted reaction is a chemical reaction in which all bond breaking and bond making occurs in a single step. Reactive intermediates or other unstable high energy intermediates are not involved. [1] [2] Concerted reaction rates tend not to depend on solvent polarity ruling out large buildup of charge in the transition state.
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 ...
Two enantiomers of a generic amino acid at the stereocenter. In stereochemistry, a stereocenter of a molecule is an atom (center), axis or plane that is the focus of stereoisomerism; that is, when having at least three different groups bound to the stereocenter, interchanging any two different groups creates a new stereoisomer.
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.
Aprotic solvents do not add protons (H + ions) into solution; if protons were present in S N 2 reactions, they would react with the nucleophile and severely limit the reaction rate. Since this reaction occurs in one step, steric effects drive the reaction speed. In the intermediate step, the nucleophile is 185 degrees from the leaving group and ...
In particular, if the stereocenters are configured in such a way that the molecule can take a conformation having a plane of symmetry or an inversion point, then the molecule is achiral and is known as a meso compound. Molecules with chirality arising from one or more stereocenters are classified as possessing central chirality.