Addition reaction

The chemical addition ( from Latin: addere = add ), also referred to as addition reaction or addition reaction, is one of the typical reactions in organic chemistry. In this reaction, at least two molecules are combined into one, wherein one or more multiple bonds are split. The atom economy of the addition reactions is consistently excellent.

Addition is the reverse of the removal, the molecules are cleaved from a molecule in which, for example, the formation of multiple bonds.

When the addition is ( alkene and alkyne ), carboxylic acid derivative, aldehyde or ketone, for example, to an unsaturated hydrocarbon with cleavage of a symmetric ( for example, HH, FF) or unbalanced ( for example, H -Cl) adsorbed molecule to an atom bond with a double or triple bond.

A special form of addition is the polyaddition in the run consecutively and several additions to the formation of larger chain-like molecules - lead, which are possibly linked spatially - to macromolecules.

  • 3.1 Proof of multiple bonds
  • 3.2 types of addition reactions
  • 3.3 further reactions of organic chemistry
  • 3.4 other applications

Example hydrocarbons

For those not used by the carbon atoms electron pairs form the alkenes and alkynes double and triple bonds. You are now stable, but do not have the maximum number attached to each carbon atom of hydrogen atoms. They are therefore referred to as unsaturated.

Unsaturated hydrocarbons are stable but energetically less favorable than saturated hydrocarbons. Therefore, it is quite possible that multiple bonds of unsaturated hydrocarbons with the removal of a π - bond (see double bond and covalent bond ) in the next lower level to convert, for example, an alkene into an alkane.

Addition of hydrogen to an alkyne

The addition of hydrogen is also referred to as hydrogenation. For the reaction, a catalyst is used usually as a heterogeneous catalyst herein is suitable palladium ( dispersed on activated carbon Pd / C ), which accepts the activation of the hydrogen when it is bound to the metal surface. In Heterogeneous Catalysis preferentially or exclusively a cis alkene.

Addition of hydrogen chloride to an alkene

Example aldehydes ( acetalization )

Aldehydes react - usually acid catalysis - with alcohols to form hemiacetals, which can then react with another molecule of the elimination of water to the acetals.

Applications

Evidence of multiple bonds

Addition reaction can be detected multiple bonds in molecules of organic substances with bromine: This usually reddish- brown, dissolved in water, bromine ( " bromine water " ), discolour, since the bromine splits the multiple bonds and attaches itself and thus loses its color.

Both reactions proceed so long as, attached all the bromine molecules to either or no more multiple bonds are present (in the case of the detection reaction is not desired). The positive result of the detection is a colorless solution in the ideal case. Normally, however, the solution has a slightly yellowish tint by virtually unavoidable impurities.

Types of addition reactions

  • Electrophilic Addition
  • Nucleophilic Addition
  • Radical Addition

Further reactions of organic chemistry

  • Substitution
  • Elimination
  • Rearrangement
  • Condensation reaction

Other applications

  • Plastics manufacturing
  • Hydrogenation
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