Ketones can be understood as an organic compound with a carbonyl group, where one carbon atom is bonded to an oxygen atom, whereas the other bonds are hydrocarbon radicals. The compounds have significant physiological properties and are used for medical purposes. Anti-inflammatory agents have ketone groups. Ketones are the building blocks of paints, solvents, lacquers, and textiles. Several manufacturing explosives are made up of ketones. Ketone is also used in the application of the hydraulic agents and preservation and tanning. In no small measure, the ketone is one of the most significant compounds for the growing industrial sector.
Structure of Ketones
A carbonyl group (C=O) has two R groups attached to it, and the R group needs to have at least one molecule of carbon compound. It is the R group that determines the type of ketone. Furthermore, the molecular formula of the same is represented as RCOR.
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Ketone Reactions
Ketones are considered to be one of the most reactive compounds in chemistry. Still, in comparison to the aldehydes, the ketones are less responsive and reactive. Ketones and aldehydes are similar, considering the carbonyl group forming the base of any chemical activity. The ketones have uneven electronic distribution, which is responsible for its polar nature. The unequal distribution is responsible for the carbon atoms having a positive charge.
In the case of the secondary alcohol, ketone preparation is possible with oxidation, resulting in the formation of ketonic compounds. However, in the case of ketones, they do not go through any further process of oxidation similar to that of the aldehydes.
The oxidation of secondary alcohol results in the forming of several oxidizing agents, including chromic acid, potassium permanganate pyridinium chlorochromate, and manganese dioxide.
Identifying Ketones
It is effortless to locate a ketone merely from the chemical word. In case the name of the chemical term ends with a suffice "one," then the compound has the presence of ketone in it.
To identify the ketone from its physical properties, you need to check the solution's water solubility and the boiling point. If it is a keystone, then the water solubility will be very high, and a boiling point will be high. When a solution has the presence of ketone, it can be marked by the charge of the molecules.
In case the solution has a high polarity that is the characteristic of electron hogging, it is considered to be very attractive relatively.
Preparation of Ketones
Several methods of Preparation of Ketones are widely practised in the chemical laboratories and on an industrial scale. Some of the methods have been listed down below:
Preparation of Ketones From Nitriles
Ketones under this process can be obtained by treating the nitriles with the Grignard reagent. After the solution is prepared, it needs to undergo hydrolysis to form the final product, ketone.
For example: When Magnesium is made to react with nitrile with an aqueous acid, then ketone is formed along with Ammonia and Magnesium salt is the residual. Some bonds are formed while some are broken in this chemical process of preparation of ketone from nitrates.
Preparation of Ketones by Dehydrogenation of Alcohols
In case, two hydrogen molecules are removed from the concerned alcohol molecule, then the dehydrogenation process of alcohol occurs. During the oxidation process, the C-O and the O-H strong bonds are broken down to form merely C=O bonds. Thus, to produce ketones, secondary alcohol must go through the process of dehydrogenation.
However, in the case of the tertiary alcohols after the oxidation process, the dehydrogenation must be altered with dehydration. Thus, when it comes to tertiary alcohol, alkalines are used for manufacturing.
Example: When n-Propyl alcohol undergoes an oxidation reaction under copper solution then Propionaldehyde is formed and hydrogen gas is released.
Preparation of Ketones from Acyl Chlorides
In case, the acyl chlorides are treated with as strong metal halide and then the Grignard reagent is made to react, ketones are formed. For example cadmium chloride when made to react with the reactive reagent, then the dialkyl cadmium is a solution obtained. The result formed then is prepared to act with acyl chlorides to create ketones. However, if you consider using Rosenmund's Reaction for the same, then the ketone will not be formed.
Ketones Preparation From Benzene and Substituted Benzenes to Form Aromatic Ketones
Aromatic ketone formation is a straightforward process with the help of benzenes and substituted benzenes. In chemistry, this is supposed to be the best-suited method to prepare aromatic ketone. In the technique, the benzene is treated with acid chloride to obtain ketone. Such a reaction is only possible in the presence of a catalyst such as an anhydrous aluminium chloride, which is a Lewis acid.
FAQs on Ketone Preparation
1. How to Identify if a Substance is a Ketone?
In chemistry, the iodoform test is used to identify if a substance is having traces of ketone. It also helps to detect the presence of an alpha-methyl group. Alpha methyl group refers to any functional group which is attached to the carbon element. In the iodoform test, drops of iodine solution are added to an alcohol liquid, and the sodium hydroxide solution is used to absorb the iodine colour. If the result is positive, then yellow precipitates of triiodomethane appear in the solution. Along with the pale complexion, an antiseptic pungent smell is released. The following substances which have been tested positive are Ethanol, Methyl ketones, and Acetaldehyde.
2. What is a Schiff Agent?
The Schiff agent in chemistry caters to testing the presence of a ketonic group. The agent is also used to differentiate between the acetone solution and the acetaldehyde solution. When sulfur dioxide gas passes through the chemical solution of p-rosaniline hydrochloride, then a Schiff agent is formed. It helps to oxidize the aldehyde solution, and the pink colour appears to detect ketones. The aliphatic ketones can be time-consuming to make the pink colour bloom in the solution, marking the presence of a ketonic group. On the other hand, the aromatic ketone solution never reacts, and there is no change in colour.