Ketone: Structure, Properties, and Reactions

Ketone is any of a family of organic compounds and is distinguished by the presence of a carbonyl group, where the carbon atom is covalently bound to an oxygen atom. The rest of the two bonds are to other hydrocarbon radicals (R) or carbon atoms:

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Structure of Ketone

The structure of Ketone can be represented as follows:

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Properties of Ketone

Ketone compounds contain important physiological properties. They are found in many sugars and medicinal compound use, including synthetic and natural steroid hormones. The anti-inflammatory agent molecules cortisone contain 3 ketone groups.

In industry, only a small ketone count is manufactured on a large scale. They are synthesized by a wide range of methods, and because of their relative stability, high reactivity, and ease of preparation, they are said as nearly ideal chemical intermediates. Several complex organic compounds can be synthesized using ketones as building blocks. Mosty, in a wide range, they are used as solvents, especially in industries such as manufacturing lacquers, explosives, textiles, and paints. Also, ketones are used as preservatives in hydraulic fluids and tanning.

Acetone (CH3COCH3) is the most important ketone, where a liquid with a sweetish odour. Acetone among the only organic compounds, which are infinitely soluble in water (it means soluble in all proportions); it also dissolves other organic compounds. Due to this reason—and because of its low boiling point (56 °C), which makes it easy to remove by the process of evaporation, when no longer wanted—it is the essential industrial solvents being used in the products such as varnishes, paints, coatings, nail-polish removers, and resins.

Nomenclature of Ketones

The IUPAC - International Union of Pure & Applied Chemistry name of a ketone can be derived by selecting the parent as the longest chain of carbon atoms, which have the carbonyl group. The parent chain can be numbered from the end that produces the carbonyl-carbon, which is the smaller number. The ‘-e’ suffix of the parent alkane can be changed to ‘-one’ to represent that it is a ketone compound.

For example, (CH3)2 (CH3CH2COCH2CH) is named as 5-methyl-3-hexanone. The longest chain has 6 carbon atoms, and the carbon numbering must begin at the end, which gives the smaller number to the carbonyl carbon. The carbonyl group lies on carbon 3, and the methyl group lies on carbon 5. In cyclic ketones, atom numbering of the ring begins with carbonyl-carbon as number 1. The common names for ketones can be derived by naming every carbon group bonded to the carbon as a separate term followed by the term “ketone.”

CH3COCH3, the simplest ketone, whose IUPAC name is given as 2-propanone, is almost always referred to by its common name, acetone, which has derived from the fact and was first prepared by heating the acetic acid’s calcium salt.

Reactions of Ketone

Ketones are the highly reactive ones, although less compared to aldehydes, to which they are related closely. Much of their chemical activity obtains from the carbonyl group nature. Ketones readily undergo various chemical reactions. A primary reason is, the carbonyl group is highly polar; it means it contains an uneven electron distribution. This results in the carbon atom, a partial positive charge, by making it susceptible to attack by nucleophiles, which are the species, attracted to positively charged centers. The typical reactions are given as nucleophilic addition and oxidation-reduction. Also, the polarity of the carbonyl group affects the ketone’s physical properties.

Secondary alcohols oxidize to ketones (R2CHOH → R2CO) easily. The reaction is halted at the ketone stage due to ketones are normally resistant to further oxidation. Secondary alcohol oxidation to a ketone is accomplished by several oxidizing agents, most often pyridinium chlorochromate (PCC), chromic acid (H2CrO4), manganese dioxide (MnO2), or potassium permanganate (KMnO4).

The aromatic hydrocarbon treatment with an anhydride or acyl halide in the presence of a catalyst composed of a Lewis acid (it means a compound that is capable of accepting an electron pair), and aluminium chloride (AlCl3), resulting in either a diaryl ketone or aryl alkyl (ArH → ArCOR or ArCOAr′). Here, Ar represents an aromatic ring, and the reaction is called Friedel-Crafts acylation.

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Nitriles (RCN) reacts with the reagents of Grignard to produce ketones by following the hydrolysis (RCN + R′MgX → RCOR′).

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Ketones possessing α-hydrogens are often made to undergo aldol reactions (which are also known as aldol condensation) by certain technique’s use. The reaction can be often used to close the rings, wherein the case one carbon provides the carbonyl group and the other provides the carbon with an α-hydrogen. The synthesis of 2-cyclohexenone is an example. In this specific example, the aldol product undergoes a loss of H2O to yield an α, β-unsaturated ketone.

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Toxicity

Although it is not easy to generalize the toxicity of that kind of broad class compounds, in general, simple ketones are not highly toxic ones. This characteristic is a reason for their popularity, the same as solvents. The exceptions to this specific rule are the unsaturated ketones like methyl vinyl ketone having LD50 of 7 mg/kg (oral).