Acetophenone

Acetophenone is defined as an organic compound that is used as an ingredient in perfumes and also as a chemical intermediate in the manufacture of resins, pharmaceuticals, flavoring agents, and also as a fo2wrm of tear gas. It has been used as a drug in sleep induction. The acetophenone formula or structural formula of acetophenone is given as \[C_{6}H_{5}COCH_{3}\].

This compound can be made from acetyl chloride and benzene, but it is most commonly made by oxidizing the ethylbenzene compound in the air.

Properties of Acetophenone

Pure acetophenone is defined as a colorless liquid. Acetophenone melting point is about 20.2 °C (68.4 °F) and acetophenone boiling point is about 202.4 °C (396.3 °F). It is slightly soluble only in water, but it is freely soluble in ethanol (otherwise in the ethyl alcohol), chloroform, and diethyl ether. Acetophenone molecular weight is 120.15 g/mol.

Natural Occurrence

Acetophenone takes place naturally in several foods, including cheese, apple, banana, apricot, cauliflower, and beef. Also, it is a castoreum component, which is the exudate from the castor sacs of the mature beaver.

Pharmacology

In the late 19th century and early 20th centuries, acetophenone was used for various medicinal uses. It was also marketed as an anticonvulsant and hypnotic under the brand name Hypnose. The typical dosage of this compound was 0.12 to 0.3 milliliters, and it was considered to contain superior sedative effects to both chloral and paraldehyde hydrate. Acetophenone, in humans, can be metabolized to carbonic acid, acetone, and benzoic acid. Hippuric acid is an indirect metabolite of acetophenone, and its presence in urine can be used to confirm acetophenone exposure, while other substances, such as toluene, can also cause hippuric acid in urine.

Production

Acetophenone is a by-product of the oxidation of ethylbenzene to ethylbenzene hydroperoxide, which can be recovered. Also, ethylbenzene hydroperoxide is given as an intermediate in the propylene oxide’s commercial production via the propylene process of oxide-styrene co-product. Primarily, ethylbenzene hydroperoxide can be converted to 1-phenyl ethanol (which is the α-methyl benzyl alcohol) in the process of having a small amount of acetophenone by-product. Acetophenone can be hydrogenated or recovered to 1-phenyl ethanol and then dehydrated to produce styrene.

Acetophenone Uses

Precursor to Resins

Commercially significant resins can be produced from the treatment of acetophenone with a base and formaldehyde. The resulting copolymers are traditionally represented using the formula \[\left ( (C_{6}H_{5}COCH)_{x}(CH_{2})_{x} \right )^{n}\], which is derived from the condensation of aldol. These substances are given as the components of inks and coatings. The hydrogenation of the aforementioned ketone-containing resins will result in modified acetophenone-formaldehyde resins. And, the resulting polyol can further be crosslinked with diisocyanates. Modified resins are found in inks, coatings, and adhesives.

Niche Uses

Acetophenone is used to produce fragrances that smell like plum, almond, jasmine, honeysuckle, and strawberry. It can also be used in chewing gums and listed as an approved excipient by the U.S. FDA.

Laboratory Reagent

In the instructional laboratories, acetophenone can be converted to styrene in a two-step method, which illustrates the reduction of carbonyls with the aid of hydride and the dehydration of alcohols, where the chemical reaction is provided below:

\[4C_{6}H_{5}C(O)CH_{3} NaBH_{4} + 4H_{2}O \rightarrow 4C_{6}H_{5}CH(OH) CH_{3} + NaOH + B(OH)_{3} \rightarrow C_{6}H_{5}CH = CH_{2}\]

A similar two-step process can be used industrially, but the reduction step is performed using hydrogenation over a copper catalyst. The chemical reaction for this is given below.

\[C_{6}H_{5}C(O)CH_{3} + H_{2} \rightarrow C_{6}H_{5}CH(OH) CH_{3}\]

The acetophenone compound is a common test substrate for asymmetric hydrogenation experiments because it is prochiral.

Drugs

Acetophenone is also used for the synthesis of several pharmaceuticals.

Dimethyl-amino-propiophenone is generated by a Mannich reaction between formaldehyde and dimethylamine. Usage of diethylamine instead gives the diethylamino analog.

Natural Occurrence

Acetophenone naturally takes place in several foods, including cheese, apple, banana, apricot, beef, and also cauliflower. It's also a member of the castoreum, which is the exudate from mature beaver castor sacs.

Reactivity of Acetophenone and Benzophenone

When we think about reactivity, here comes the picture that which type of reactivity or towards which reaction we are thinking about. Considering the electrophilic attack on the carbonyl group, we have to consider some things such that in the acetophenone compound, the +I effect of the methyl group & three hyper conjugative structures somewhat stabilizes the carbonyl carbon center. On the other side, the +R effect and +I effect of the phenyl group also stabilize the carbon center.

Here, considering the IR spectra of both of them:

• Benzophenone: C=O stretching frequency is \[1659 cm^{-1}\].

• Acetophenone: C=O stretching frequency is \[1690 cm^{-1}\].

It indicates that the partial single bond character because of the conjugation is greater for the Benzophenone compared to the Acetophenone. As a result, Acetophenone's reactivity is higher than that of Benzophenone.

Toxicity

The LD50 is given as 815 mg/kg (rats, oral). Currently, acetophenone is listed as a Group D carcinogen representing that; it does not produce any carcinogenic effects in humans.