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An sp 2-hybridized carbon atom, with re and si faces. In stereochemistry, prochiral molecules are those that can be converted from achiral to chiral in a single step. [1] [2] An achiral species which can be converted to a chiral in two steps is called proprochiral.
Electrophilic aromatic substitutions with prochiral carbon electrophiles have been adapted for asymmetric synthesis by switching to chiral Lewis acid catalysts especially in Friedel–Crafts type reactions. An early example concerns the addition of chloral to phenols catalyzed by aluminium chloride modified with (–)-menthol. [6]
The alkene is working as an electron donor and bromine as an electrophile. The three-membered bromonium ion 2 consisted of two carbon atoms and a bromine atom forms with a release of Br −. Attacking of bromide ion The bromonium ion is opened by the attack of Br − from the back side. This yields the vicinal dibromide with an antiperiplanar ...
In electrophilic substitution in aromatic compounds, an atom appended to the aromatic ring, usually hydrogen, is replaced by an electrophile.The most important reactions of this type that take place are aromatic nitration, aromatic halogenation, aromatic sulfonation and acylation and alkylating Friedel-Crafts reactions.
A nitrogen bound to both a good electrofuge and a good nucleofuge is known as a nitrenoid (for its resemblance to a nitrene). [2] Nitrenes lack a full octet of electrons are thus highly electrophilic; nitrenoids exhibit analogous behavior and are often good substrates for electrophilic amination reactions.
Enantioselective ketone reductions convert prochiral ketones into chiral, non-racemic alcohols and are used heavily for the synthesis of stereodefined alcohols. [1]Carbonyl reduction, the net addition of H 2 across a carbon-oxygen double bond, is an important way to prepare alcohols.
For example, carbon monoxide is a very weak Brønsted–Lowry base but it forms a strong adduct with BF 3. In another comparison of Lewis and Brønsted–Lowry acidity by Brown and Kanner, [ 19 ] 2,6-di- t -butylpyridine reacts to form the hydrochloride salt with HCl but does not react with BF 3 .
A carbon atom with a larger coefficient will be preferentially attacked, due to more favorable orbital overlap with the electrophile. [ 16 ] The perturbation of a conjugating electron-withdrawing or electron-donating group causes the π electron distribution on a benzene ring to resemble ( very slightly !) an electron-deficient benzyl cation or ...