Ketones - Carboxyl / Alfa Chemistry

Introduction

Ketones represent a class of compounds characterized by the presence of the carbonyl functional group. Distinguished from aldehydes by the direct bonding of the carbonyl carbon atoms to two hydrocarbon groups, ketones bear the general formula RC(=O)R', where R and R' denote either similar or dissimilar atoms or functional groups (Fig. 1).

Ketones find diverse applications across various industries due to their reactivity and versatility. They are commonly utilized as solvents, flavoring agents, pharmaceutical intermediates, and etc. Additionally, ketones serve as key components in polymer synthesis and analytical chemistry.

Alfa Chemistry stands as a reputable supplier offering a comprehensive range of organic compounds, including a diverse selection of high-quality ketones tailored to meet the varied application requirements of customers.

Fig. 1 Structure of acetone.

Classification of Ketones

Several methods are employed for categorizing ketones, including substituent-based classification, hydrocarbon group-based classification, and number of carbonyl groups-based classification, as listed below.

Based on the similarity of the substituents attached to the carbonyl group, ketones are classified as symmetrical or asymmetrical. Symmetrical ketones, exemplified by acetone and benzophenone, feature identical substituents, whereas asymmetric ketones like acetophenone possess dissimilar substituents.
Based on the nature of the hydrocarbon group within the molecule, ketones are further categorized into aliphatic ketones, aromatic ketones, and alicyclic ketones. Aliphatic ketones consist of aliphatic hydrocarbon groups, while aromatic ketones have the carbonyl group directly linked to an aromatic ring. Ketones wherein the carbonyl group resides within a ring structure are termed alicyclic ketones (Fig. 2).
Based on the number of carbonyl groups present in the molecule, ketones are also classified into mono- and diketones. Monoketones denote molecules with a single carbonyl group, while diketones contain two carbonyl groups. Diacetyl serves as a representative example of a diketone.

Fig. 2 Structures of aliphatic and aromatic ketones.

Representative Reactions

Ketones, owing to their unique chemical structure, participate in a variety of reactions, showcasing their versatility in organic synthesis. Here are three representative reactions of ketones.

Ketones Representative Reactions

Nucleophilic Addition Reaction: Ketones react with nucleophiles, forming tetrahedral intermediates followed by proton transfer to yield products. A prominent example is the Grignard reaction, in which a Grignard reagent (RMgX) is added to a ketone, forming a tertiary alcohol after acidic workup.
Oxidation Reaction: Ketones can be oxidized to yield carboxylic acids or other functional groups by strong oxidizing agents such as potassium permanganate (KMnO₄) or chromic acid (H₂CrO₄). During oxidation, the carbonyl carbon of the ketone gains oxygen, leading to the formation of carboxylic acid.

Catalytic Hydrogenation Reaction: In the presence of catalysts such as palladium on carbon (Pd/C) or Raney nickel (Ni), ketones can undergo catalytic hydrogenation, resulting in the formation of alcohol. A common industrial application of this reaction is to synthesize phenylethanol from acetophenone.

Applications

Ketones have a variety of uses in different fields due to their chemical properties and the variety of reactions they participate in. Here are some examples.

Flavoring Agents: Certain ketones contribute to the aroma and flavor profiles of foods and beverages. For instance, acetophenone is used as a flavoring agent in baked goods and beverages, adding a sweet, floral note.
Pharmaceutical Intermediates: Ketones serve as crucial intermediates in pharmaceutical synthesis. They are employed in the production of drugs and pharmaceutical compounds, contributing to the synthesis of antibiotics, analgesics, and other therapeutic agents.
Polymer Synthesis: Ketones play a role in polymer synthesis, particularly in the production of resins, plastics, and fibers. They are utilized as monomers or reactants in polymerization reactions, contributing to the formation of various polymeric materials with desirable properties.
Analytical Chemistry: Ketones are employed as analytical standards and reference materials in analytical chemistry techniques such as gas chromatography and mass spectrometry. They aid in the identification and quantification of ketone-containing compounds in complex mixtures.

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