Gattermann reaction

In Gattermann synthesis is a name reaction in organic chemistry, is used to synthesize aromatic aldehydes from phenols and other aromatics. It was named after the chemist Louis Goslar gate man ( 1860-1920 ). The Gatterman - synthesis can also be used to synthesize single hydrocarbon compounds, heterocyclic compounds such as furan, pyrrole and indole derivatives, and thiophene. Gattermann the synthesis is a variant of the Friedel-Crafts acylation.

Overview reaction

In the gate - man reaction aromatics react with hydrogen cyanide and hydrogen chloride in the presence of the catalyst zinc chloride ( ZnCl2 ) or aluminum chloride ( AlCl3 ) to formylated aromatics.

Mechanism

In the gate - man reaction is a Electrophilic aromatic substitution. The reactants hydrogen cyanide, hydrogen chloride and the aluminum chloride catalyst to react an electrophile which attacks the aromatics to form a cation - hexadienyl. This is rearomatized by deprotonation. Hydrolysis leads to formation of formylated aromatic. Used polyhydric phenols or phenol ethers, no catalyst is required.

Variants

Gate man -Adams reaction

The gate man -Adams reaction is a reaction names in organic chemistry. Today, most will not remember how worked in the gate man - reaction with free hydrocyanic acid. The gate man -Adams reaction describes the formation during synthesis. In this case, zinc (II ) cyanide, the hydrogen cyanide is released under the action of hydrogen chloride during the reaction. The activity of the resulting zinc (II ) chloride sufficient to act as a catalyst in the reaction with more reactive phenols. Upon reaction with sluggish phenols addition of aluminum chloride to be added as a catalyst.

Gate man - Koch reaction

The gate man - Koch synthesis is a name reaction in organic chemistry, which was named after the German chemists Ludwig gate man (1860-1920) and Julius Arnold Koch. It is the gate man synthesis similar. Here, aromatic compounds react with carbon monoxide and hydrogen chloride and the aluminum chloride catalyst or copper ( I) chloride to formylated aromatics.

Mechanism

The gate man - Koch reaction is an electrophilic aromatic substitution. The reactants carbon monoxide, hydrogen chloride and the aluminum chloride catalyst to react an electrophile which attacks the aromatics to form a cation - hexadienyl. This is rearomatized by deprotonation. Elimination of aluminum chloride gives the formylated aromatic. The mixture reacted under high pressure as the only stable at the temperature of liquid air formyl, so also arises here a formylated aromatic. The gate man - Koch synthesis must take place in the absence of water.