Reimer Tiemann Reaction Mechanism

Riemer Tiemann’s Reaction is named after the pioneering discoveries of the 19th-century chemists Karl Riemer and Ferdinand Tiemann. Reimer-Tiemann reaction is a versatile and important reaction in organic chemistry, which is used for the introduction of carbonyl groups into aromatic compounds, making it a fundamental tool for the synthesis of various valuable organic molecules.

Reimer-Tiemann Reaction can be used to synthesize a variety of ortho-hydroxy benzaldehydes, which are important precursors to a variety of other products, such as pharmaceuticals, dyes, and flavorings. Let’s dig deeper into Riemer Tiemann’s reaction discovered by German scientists and explore its mechanism, applications, and more through this article.

What is Riemer Tiemann Reaction?

Reimer-Tiemann reaction is a chemical reaction used in organic chemistry for the synthesis of ortho-formyl substituted phenols from phenols. It involves the generation of an ortho-formyl substituted phenoxide from a phenol and subsequent reaction with a chloroform (CHCl₃) in the presence of a strong base such as sodium hydroxide (NaOH) or potassium hydroxide (KOH).

The general reaction equation for the Riemer-Tiemann reaction is donated as follows:

Phenol (C₆H₅OH) + Chloroform (CHCl₃) + Sodium Hydroxide (NaOH) → Salicylaldehyde

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Mechanism of Riemer Tiemann Reaction

The process of Riemer Tiemann’s reaction starts with the breakdown of chloroform by a strong base to create a chloroform carbanion. The primary reactive species in this reaction, dichlorocarbene, is produced as soon as this chloroform carbanion goes through alpha elimination.

Chloroform, a base, and an acid workup are used in the Reimer-Tiemann reaction, an organic chemical process that turns phenol into an ortho-hydroxy benzaldehyde. The chemical process that is employed to ortho-formylate phenols is another way to characterize this reaction.

The following steps can be used to explain the mechanism of the Reimer-Tiemann reaction:

Step 1: The chloroform carbanion is produced when the strongly basic aqueous hydroxide solution deprotonates the chloroform

CHCI₃ + OH^_ → CCI₃^–+ H2O

Step 2: Dichlorocarbene is the result of the easy alpha removal of this chloroform carbanion. The primary reactive species is dichlorocarbene, as was previously mentioned.

CCI₃^– →CCI₂ + Cl^–

Step 3: A negatively charged phenoxide is produced when the phenol reactant is deprotonated by the aqueous hydroxide.

C₆H₅OH + OH⁻ → C₆H₅O⁻ + H₂O

Step 4: Now that this negative charge has delocalized within the benzene ring, it has significantly increased its nucleophilicity.

Step 5: An intermediate dichloromethyl-substituted phenol is formed as a result of a nucleophilic attack on the dichlorocarbene.

C₆H₅O⁻ + CCl₂ → C₆H₄-CCl₂-OH

Step 6: The intended ortho-hydroxybenzaldehyde is ultimately formed by the basic hydrolysis of this intermediate.

C₆H₄-CCl₂-OH + OH⁻ → C₆H₄-CHO + 2 Cl⁻ + H2O

Difference of Riemer Tiemann Reaction With Other Reactions

Here are the brief differences between Riemer Tieman reaction with other famous reactions such as Gattermann reaction, Gattermann-Koch reaction, Vilsmeier-Haack reaction, and Duff reaction.

Reaction	Reagents	Conditions	Products
Riemer Tiemann Reaction	Chloroform (CHCI2) and Sodium Hydroxide (NaOH)	The process of reaction takes place under alkaline conditions and requires heating	Aromatic Aldehyde
Gattermann Reaction	Carbon Monoxide (CO), Hydrogen Chloride (HCI), Aluminimum Chloride (AICI2)	The process of reaction takes place under high pressure conditions and at elevated temp	Aromatic Aldehyde
Gatterman-Koch Reaction	Carbon Monoxide (CO), Hydrogen Chloride (HCI), Aluminimum Chloride (AICI2) Copper (I) Chloride (CuCI) promoter	The process of reaction takes place under high pressure conditions and at elevated temp	Aromatic Aldehyde
Vilsmeier-Haack Reaction	Phosphorus Oxychloride (POCI3) Amine, Dimethylformamide (DMF)	The process of reaction takes place under milder conditions compared to the above two reactions	Aromatic Aldehyde
Duff Reaction	Phosphorus Pentachloride (PCI5)	The process of reaction takes place under anydrous and inert atmosphere conditions	Aromatic Aldehyde

Variations of Riemer Tiemann Reaction

The Riemer Tiemann reaction can be varied in so many ways. Here are some of the most common variations include:

• Different Bases: The reaction can be carried out with number of different bases such as potassium hydroxide (KOH) or sodium hydroxide (NaOH). It can help in yielding of the reaction. For example, using potassium hydroxide instead of sodium hydroxide can improve the yield of salicylaldehyde.
• Different Haloforms: The Riemer Tiemann reaction can be carried out with haloforms such as Carbon Tetrachloride (CCI₄) or bromoform (CHBr₃)_. It produces different ortho – hydroxybenzalyde depending on the different types of holoforms used in the reaction.
• Different Solvents: The reaction can also be made possible with using water or ethanol. It can help in yielding of the reaction. For example, using ethanol or water instead can improve the yield of salicylaldehyde.

Applications of Riemer Tiemann Reaction

Riemer Tiemann reaction has a wide range of applications in industry and research. Here are some of the applications of the Reimer Tiemann reaction:

• The Riemer Tiemann reaction is a process used to create aromatic aldehydes. It’s a helpful way to add the chemical group called the formyl group (-CHO) to a specific spot on a phenol ring.
• The Riemer Tiemann reaction helps make the building blocks for various compounds, including pharmaceuticals, agrochemicals, and materials.
• The Riemer Tiemann reaction also helps in producing products of ortho-hydroxy benzaldehydes such as dyes and pigments.
• This reaction is also used in producing Vanillin which is used in various products of fragrances such as perfumes, scents, deodorants, etc.

Read More,

• Preparation of Alcohal
• Preparation of Ethers
• Preparation of Phenols

Sample Questions on Reimer Tiemann Reaction

Question 1: What is the primary reagent used in the Riemer-Tiemann reaction?

Answer:

The primary reagent used in the Reimer-Tiemann reaction is chloroform (CHCl₃) along with a strong base, typically sodium hydroxide (NaOH) or potassium hydroxide (KOH).

Question 2: How does the Riemer-Tiemann reaction differ from the Gattermann reaction?

Answer:

The Riemer-Tiemann reaction is specifically used for the introduction of the formyl group (-CHO) at the ortho position of a phenol ring. In contrast, the Gattermann reaction involves the introduction of a formyl group to aromatic compounds in general, including benzene.

Question 3: Brielfy explain the mechanism of Riemer-Tiemann reaction.

Answer:

The following steps can be used to explain the mechanism of the Reimer-Tiemann reaction:

Step 1: Chloroform carbanion is generated by deprotonation with aqueous hydroxide.

Step 2: Dichlorocarbene is produced by removing an alpha hydrogen from chloroform carbanion.

Step 3: Phenoxide is formed when phenol is deprotonated by aqueous hydroxide.

Step 4: The negative charge on phenoxide becomes more nucleophilic due to delocalization within the benzene ring.

Step 5: Dichloromethyl-substituted phenol is created through a nucleophilic attack on dichlorocarbene.

Step 6: The final product, ortho-hydroxybenzaldehyde, is achieved by the basic hydrolysis of this intermediate.

Question 4: What is the primary purpose of Riemer-Tiemann reaction in organic chemistry?

Answer:

The primary purpose of Riemer-Tiemann reaction in organic chemistry is the synthesis of salicylaldehydes. It has various applications in industry of pharmaceuticals, fragrances, dyes, etc.

Question 5: What are some common applications of Riemer-Tiemann reaction?

Answer:

The chemical reaction has its usage in various products such as fragrances, flavor compounds in the food, synethsis of pharmaceuticals, dyes, colorants and more.

Question 6: Explain Riemer-Tiemann reaction.

Answer:

The Reimer-Tiemann reaction is a chemical reaction used in organic chemistry for the synthesis of ortho-formyl substituted phenols from phenols. It involves the generation of an ortho-formyl substituted phenoxide from a phenol and subsequent reaction with a chloroform (CHCl₃) in the presence of a strong base such as sodium hydroxide (NaOH) or potassium hydroxide (KOH).

Riemer Tiemann Reaction – FAQs

1. Explain Riemer Tiemann Reaction in Organic Chemistry.

The Riemer-Tiemann reaction in organic chemistry used for the synthesis of ortho-formyl substituted phenols from phenols. It involves the generation of an ortho-formyl substituted phenoxide from a phenol and subsequent reaction with a chloroform (CHCl₃) in the presence of a strong base such as sodium hydroxide (NaOH) or potassium hydroxide (KOH).

2. Why Chloroform is used in Riemer Tiemann Reaction?

The chlorform is used in the chemical reaction because of the presence of (KOH) that undergoes de-hydrohaolgentation (loss of H+ and CI-) to form the dichlorocarbene.

3. Is Riemer-Tiemann Reaction a Electrophilic Substitution?

Yes, the Riemer-Tiemann reaction is an electrophilic substitution.

4. What is the Riemer-Tiemann Reaction on Ether?

This chemical reaction cannot be performed on ethers. It is used to convert phenols to ortho-hydroxy benzaldehydes using chloroform which is a base and an acid workup.

5. What is the Temperature of Riemer Tiemann Reaction?

The reaction is basically carried out on a temperation of 70-105°C.