Phenols - Carboxyl / Alfa Chemistry

Introduction

Phenols represent a crucial category of organic compounds characterized by the presence of an aromatic ring linked with a hydroxyl group, directly attached to a carbon atom within the ring structure (Fig. 1). These compounds play a pivotal role as organic chemical precursors, serving as fundamental materials in the synthesis of various essential substances. For instance, they serve as precursors in the manufacturing of plastics such as polycarbonates and epoxy resins. Additionally, they find utility in the synthesis of pharmaceuticals, including aspirin and antibiotics. Furthermore, phenols contribute significantly to the production of herbicides and pesticides.

Alfa Chemistry stands as a prominent supplier of chemicals, offering a comprehensive assortment of organic compounds, including a diverse range of high-quality phenols meticulously tailored to fulfill the distinct application needs of our customers.

Fig. 1 Structure of phenol.

Classification of Phenols

Phenols are categorized into two main groups: simple phenols and polyphenols, based on the number of phenol units present in the molecule.

Simple phenols: Simple phenols consist of one phenol unit in the molecule, with at least one hydroxyl group attached to an aromatic ring. Essentially, these are substituted phenol compounds with a general C6 skeleton representation. Notable examples of simple phenols include catechol, resorcinol, and phloroglucinol ^[1].
Polyphenols: Polyphenols constitute a diverse class of naturally occurring compounds containing more than one phenol unit in their molecular structure. This group encompasses various subclasses such as flavonoids (e.g., quercetin, kaempferol, catechins, and anthocyanins), polyphenolic amides (e.g., capsaicinoids and avenanthramides), resveratrol, ellagic acid, lignans, and others.

Fig. 2 Structures of simple phenol (e.g. guaiacol) and polyphenol (e.g. quercetin).

Representative Reactions

Phenols exhibit a wide range of reactions due to the presence of the hydroxyl group attached to the aromatic ring. Some representative reactions of phenols are listed below.

Phenols Representative Reactions

Electrophilic Aromatic Substitution: Phenols undergo substitution reactions where the hydroxyl group activates the aromatic ring towards electrophilic attack. For instance, phenols can react with acyl halides or anhydrides in the presence of an acid catalyst to form esters known as Fischer esterification.
Kolbe-Schmitt Reaction: Phenols can undergo a base-catalyzed reaction with carbon dioxide to form salicylic acid. This reaction is commonly known as the Kolbe-Schmitt reaction and is significant in the synthesis of aspirin.

Ether Formation: Phenols can undergo nucleophilic substitution reactions with alkyl halides or alkyl sulfonates to form ethers. This reaction, known as Williamson ether synthesis, involves the substitution of the hydroxyl group with an alkyl group.

Applications

Phenols find diverse applications across various industries due to their unique chemical properties. Here are some notable applications of phenols.

Plastics Industry: Phenols serve as important precursors in the production of plastics such as polycarbonates and epoxy resins. These plastics are widely used in automotive parts, electronic components, construction materials, and consumer goods.
Pharmaceutical Industry: Phenols are essential in the synthesis of pharmaceuticals. They serve as building blocks for various drugs, including aspirin, antibiotics, antiseptics, and analgesics. Additionally, phenolic compounds like resveratrol have gained attention of pharmacologist for their potential health benefits.
Agricultural Industry: Phenols can be used in the formulation of herbicides and pesticides to control pests and weeds in agriculture. They play a crucial role in improving crop yield and protecting plants from diseases.
Other Industries: Phenolic resins derived from phenols are widely used as adhesives and sealants in various industries, including construction, automotive, and aerospace. These resins offer excellent heat resistance, durability, and adhesive strength. Phenols are also used as natural food additives and preservatives to extend the shelf life of food products and maintain their quality.

Alfa Chemistry provides various phenols to our customers. We can also customize the synthesis according to customers' requirements. Please feel free to contact us for more information.

Reference:

Mamari, H. H. A. Phenolic compounds: classification, chemistry, and updated Techniques of analysis and synthesis. Phenolic Compounds - Chemistry, Synthesis, Diversity, Non-Conventional Industrial, Pharmaceutical and Therapeutic Applications. 2021.