Syn and anti addition

Syn and anti used in organic chemistry to

• To appoint in bridged bicyclic hydrocarbons, the relative position of two substituents each other and
• To describe in addition reactions the reaction course unique.

Syn-and anti - bicyclic hydrocarbon in

The syn-anti isomerism describes the relative position of a substituent is located at the third bridge a bicycle. This substituent can occupy two positions isomers, which are syn - or anti- in with the descriptors.

Syn it denotes that position, in which said substituent is on the side of the first bridge. As an anti refers to the opposite position of the substituent.

The ranking of the three bridges of a bicycle is carried out as follows:

Based on the two bridgehead atoms, the length of each bridge is determined first. The ranking then takes place according to the bridge length, and the longest is referred to as the first and the shortest as a third bridge. If two bridges have the same length, so the more highly substituted bridge is only ranked.

Syn-and anti - addition reactions

In addition reactions of the point of entry of the two substituents to be added will be described with the syn-anti notation.

As syn refers to those addition reaction in which occur both substituents on the same side of the alkene or alkyne. As is known that anti- addition reaction, wherein each substituent occurs on a different side of the alkene or alkyne.

In the case of addition reaction of alkynes syn addition to the formation of the corresponding ( Z)- isomers leads (obsolete and cis - isomers), and the anti -addition leads to the formation of the corresponding ( E) -isomer (trans -isomer ).

From addition reactions at the double bond of cycloalkenes resulting substituted cycloalkanes:

The addition reaction to the double bond of alkenes, leading to the corresponding substituted alkanes. Thus at a CC single bond a statement about syn or anti conformation can be taken to other positions in the formation of chiral products must vary accordingly substituted, so that a chiral product is obtained. Otherwise, the reaction products would be by rotation about the CC single bond interconvertible. A syn / anti distinction would thus be void.

Syn-and anti - elimination reactions in

In elimination reactions produced in organic chemistry from a CC single bond, a C = C double bond. Depends on the structure of the starting material, it can result in the formation of cis -or trans- stereoisomeric alkenes. It also has an influence of the reaction mechanism of the elimination reaction:

• In two-stage elimination reaction by the E1 mechanism, the stereochemistry of the alkene is determined only by the elimination of a proton from the carbenium ion progressively emerged.
• In two-stage elimination reaction after E1cb mechanism, the stereochemistry of the alkene is determined only by the elimination of a leaving group X from the carbanion progressively emerged.

• In an elimination reaction after the E2 mechanism no intermediate forms two single bonds ( sp3 from adjacent carbon atoms) are broken and formed in synchronism, the C = C double bond of an alkene. From the two sp3 carbon atoms arise sp2 -hybridized carbon atoms. To breaking σ bonds have to lie in a plane. This is only possible in a staggered anti arrangement or in an eclipsed syn arrangement. In the anti-elimination, the σ bonds to each other anti- periplanar.