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can someone please explain syn and anti elimination with example

can someone please explain syn and anti elimination with example

Grade:12

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Arun
25750 Points
4 years ago
Inorganic chemistry,syn and anti additionare different ways in which two substituents can be added to adouble bondortriple bond. This article will usecycloalkenesas examples.[1,2-disubstituted Cycloalkene undergoing syn and anti addition]Syn addition is the addition of twosubstituentsto the same side (orface) of adouble bondortriple bond, resulting in a decrease inbond orderbut an increase in number of substituents. Generally thesubstratewill be an alkene oralkyne. An example of syn addition would be the oxidation of analkeneto a diol via a suitable oxidizing agent such asOsmium tetroxideOsO4orPotassium permanganateKMnO4.Anti addition is in direct contrast to syn addition. In anti addition, two substituents are added to opposite sides (or faces) of a double bond or triple bond, once again resulting in a decrease in bond order but an increase in number of substituents. The classical example of this isbromination(anyhalogenation) of alkenes.Depending on the substrate double bond, addition can have different effects on the molecule. After addition to astraight-chainalkene such asC2H4, the resulting alkane will rapidly and freely rotate around its singlesigma bondunder normal conditions (i.e.room temperature). Thus whether substituents are added to the same side (syn) or opposite sides (anti) of a double can usually be ignored due to free rotation. However, ifchiralityor the specific absolute orientation of the substituents needs to be taken into account, knowing the type of addition is significant. Unlike straight-chain alkenes,cycloalkenesyn addition allows stable addition of substituents to the same side of the ring, where they remain together. The cyclic locked ring structure prevents free rotation.Syn elimination and anti elimination are the reverse processes of syn and anti addition. These result in a new double bond, such as inEi elimination.

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