The Reimer-Tiemann reaction is a chemical reaction

Chemical reaction

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

 used for the ortho-formylation

Formylation reaction

A formylation reaction in organic chemistry is the catch-all name for any organic reaction in which an organic compound is functionalized with a formyl group .Aromatic formylation reactions via electrophilic aromatic substitution include:...

 of phenol

Phenol

Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...

s. The reaction was discovered by Karl Ludwig Reimer and Ferdinand Tiemann

Ferdinand Tiemann

Johann Karl Wilhelm Ferdinand Tiemann was a German chemist and together with Reimer discoverer of the Reimer-Tiemann reaction.Beginning in 1866, Tiemann studied pharmacy at the TU Braunschweig where he graduated in 1869...

. In the simplest case, the product is salicylaldehyde

Salicylaldehyde

Salicylaldehyde is the chemical compound with the formula C6H4CHO-2-OH. Along with 3-hydroxybenzaldehyde and 4-hydroxybenzaldehyde, it is one of the three isomers of hydroxybenzaldehyde. This colorless oily liquid has a bitter almond odor at higher concentration and a characteristic buckwheat...

:

Chloroform

Chloroform

Chloroform is an organic compound with formula CHCl3. It is one of the four chloromethanes. The colorless, sweet-smelling, dense liquid is a trihalomethane, and is considered somewhat hazardous...

 (1) reacts with strong base to form the chloroform carbanion (2), which will quickly alpha-eliminate to give dichlorocarbene

Dichlorocarbene

Dichlorocarbene is a carbene commonly encountered in organic chemistry. This reactive intermediate with chemical formula CCl2 is easily available by reaction of chloroform and a base such as potassium t-butoxide or sodium hydroxide dissolved in water...

(3). Dichlorocarbene will react in the ortho-position of the phenate (5) to give dichloromethyl substituted phenol (7).