Answer the question on basis of passage given below:

Alcohols and phenol are formed when a hydrogen atom in a hydrocarbon, aliphatic and aromatic respectively, is replaced by -OH group. The substitution of a hydrogen atom in a hydrocarbon by an alkoxy or aryloxy group forms ethers.

Alcohols and phenol consist of two part, an alkyl/aryl group and a hydroxyl group. The properties of alcohols and phenols are primarily due to the hydroxyl group. The nature of alkyl and aryl groups simply modify these properties. Alcohol react both as nucleophiles and electrophiles whereas in phenols, the reactions that take place on the aromatic ring are electrophilic subtitution reactions.

Name the given reaction:

Reimer-Tiemann reaction

The correct answer is option 3. Reimer-Tiemann reaction.

The Reimer-Tiemann reaction is a type of substitution reaction named after two chemists Karl Reimer and Ferdinand Tiemann. The reaction is employed for the ortho-formylation of \(C_6H_5OH\) (phenols).

Reimer-Tiemann reaction is a chemical reaction used for producing phenolic aldehydes under the action of chloroform and caustic alkaline on phenol in industries. Reimer-Tiemann reaction is an aromatic substitution reaction with great industrial importance.

The Reimer-Tiemann response uses a dichlorocarbene precursor patch similar as chloroform, an alkali hydroxide, and a protic detergent to convert a phenol to an ortho-formyl phenol. The first step removes the hydrogen from chloroform, generating a trichlorocarban ion which loses a \(Cl^+\) to shape dichlorocarbene. Phenol is too deprotonated by the base which is used as a reagents such as \(NaOH\) or \(KOH\), which helps in delocalizing the electrons into the ortho position of the ring, which attack the carbene. The internal proton is transferred, and release of a chloride ion forms a \(C-C\) double bond. Hydroxide adds to it, performing in the release of the last chloride ion. Tautomerization produces the final product.

Mechanism:

It involves electrophilic substitution of the aromatic nucleus, the electrophilic being dichlorocarbene \(:CCl_2\) (Carbon has only a sextet of electron) formed by the action of strong alkali on chloroform.