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In organic chemistry, syn-and anti-addition are different ways in which substituent molecules can be added to an alkene (R 2 C=CR 2) or alkyne (RC≡CR).The concepts of syn and anti addition are used to characterize the different reactions of organic chemistry by reflecting the stereochemistry of the products in a reaction.
Alkynes are capable of adding two equivalents of H 2, whereas an alkene adds only one equivalent. [12] Depending on catalysts and conditions, alkynes add one or two equivalents of hydrogen. Partial hydrogenation, stopping after the addition of only one equivalent to give the alkene, is usually more desirable since alkanes are less useful:
In organic chemistry, alkynylation is an addition reaction in which a terminal alkyne (−C≡CH) is added to a carbonyl group (C=O) to form an α-alkynyl alcohol (R 2 C(−OH)−C≡C−R). [1] [2] When the acetylide is formed from acetylene (HC≡CH), the reaction gives an α-ethynyl alcohol. This process is often referred to as ethynylation.
The Prins reaction is an organic reaction consisting of an electrophilic addition of an aldehyde or ketone to an alkene or alkyne followed by capture of a nucleophile or elimination of an H + ion. [ 1 ] [ 2 ] [ 3 ] The outcome of the reaction depends on reaction conditions.
The four main categories are (1) nucleophilic attack on an alkene alkyne, or allyl ligand and (2) insertion of the alkene into the metal-amide bond. [11] Generic catalytic cycles appear below. Mechanisms are supported by rate studies , isotopic labeling , and trapping of the proposed intermediates.
In organic chemistry, an addition reaction is an organic reaction in which two or more molecules combine to form a larger molecule called the adduct. [1] [2]An addition reaction is limited to chemical compounds that have multiple bonds.
The acidity of the terminal alkynyl proton allows the alkynylzinc compound to be generated in situ from the appropriate alkyne with an alkylzinc reagent or zinc triflate, Zn(OTf) 2. [1] The first example of catalytic asymmetric addition of alkynylzinc compounds to aldehydes was reported by KensÅ Soai and co-workers in 1990.
The Corey–Fuchs reaction, also known as the Ramirez–Corey–Fuchs reaction, is a series of chemical reactions designed to transform an aldehyde into an alkyne. The formation of the 1,1-dibromoolefins via phosphine-dibromomethylenes was originally discovered by Desai, McKelvie and Ramirez.