Stereoselective and stereospecific reactions

chemistry presentation

1. STEREOSELECTIVE AND STEREOSPECIFIC REACTIONS…

2. STEREOISOMER… Two molecules are described as stereoisomers if they are made of the same atoms connected in the same sequence, but the atoms are positioned differently in space. The difference between stereoisomers can only be seen when the three-dimensional arrangement of the molecules is considered .

3. ENANTIOMERS… Enantiomers are chiral molecules that are mirror images of one another. Furthermore, the molecules are non-superimposable on one another. This means that the molecules cannot be placed on top of one another and give the same molecule.

4. STEREOSELECTIVE REACTIONS … STEREOSELECTIVE REACTIONS : A stereoselective process is one in which one stereoisomer predominates over another when two or more may be formed. If the products are enantiomers, the reaction is enantioselective; if they are diastereoisomers , the reaction is diastereoselective . Stereoselectivity is dominated by the structural features of the reactants .

5. Diastereoselective reactions … A diastereoselective reaction is one in which one diastereomer is formed in preference to another (or in which a subset of all possible diastereomers dominates the product mixture), establishing a preferred relative stereochemistry .

6. STEREOSPECIFIC REACTIONS …. TEREOSPECIFIC REACTIONS: A stereospecific reaction is one which, when carried out with stereoisomeric starting materials, gives a product from one reactant that is a stereoisomer of the product from the other. 'Stereospecific' relates to the mechanism of a reaction, the best-known example being the SN2 reaction, which always proceeds with inversion of stereochemistry at the reacting centre .

7. APPLICATIONS… STEREOSPECIFIC : Use of organo borane… Stereochemistry of hydroboration: Hydroboration can also be used to produce organo borane compounds which are chemical compounds which have carbon-boron bonds and are derivatives of BH3. These organoborane can be reacted with some reagents to give alkyl halides, alcohols, and amines which are quite useful . STEREOSELECTIVE : • Stereoselective biosynthesis… As an anti cancer agent … • Pinoresinol biosynthesis involved a protein called a dirigent protein . • It is useful in Anti-cancer causing agent and Hypoglycemia.

8. APPLICATIONS … STEREOSPECIFIC : Hydrogenation process… Hydrogenation is used to solidify, preserve or purify many products, raw materials, or ingredients. Ammonia, fuels (hydrocarbons), alcohols, polyols , various polymers and chemicals (hydrogen chloride and hydrogen peroxide ) harmaceuticals , margarine, are products treated using a hydrogenation process. STEREOSELECTIVE : iodine electrophiles in stereoselective reaction recent developments and synthetic application chalcoge electrophiles also play an important ole New synthetic applications using his methodology showing scope and listotons of iodine mediated promises within the context of other electrophile reactions are highlighted .

9. APPLICATIONS… STEREOSPECIFIC : Use of bromine water… One of the major uses of bromine is a water purifier/disinfectant, as an alternative to chlorine. Brominated compounds are used for water treatment in swimming pools and hot tubs and are also used to control algae and bacterial growth in industrial processes. STEREOSELECTIVE : Aspects of the chemistry of sulfimides ( sulfliminnes ) which are of important terioselective synthesis are reviewed The three principal sections cover bonding anden antiomerically entiched suifimides from choral and achiral starting materials configuration, preparation of and applications of chiral sulfimides in steriosele active synthesis, including reactions

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