What is Acetophenone Definition Formula Preparation and Uses
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.
FAQs on Acetophenone Structure Properties and Reactions
1. What is acetophenone in chemistry?
Acetophenone is an aromatic ketone with the molecular formula C8H8O and the structure C6H5COCH3. It consists of a benzene ring attached to a carbonyl group (–CO–) and a methyl group. Key points about acetophenone include:
- IUPAC name: 1-phenylethanone
- Functional group: ketone (carbonyl group, C=O)
- Class: aromatic compound
- Commonly used in organic synthesis and fragrances
It is one of the simplest and most important aromatic ketones studied in organic chemistry.
2. What is the chemical formula and structure of acetophenone?
The chemical formula of acetophenone is C8H8O, and its structural formula is C6H5COCH3. Structurally, it contains:
- A benzene ring (C6H5–)
- A carbonyl group (C=O)
- A methyl group (–CH3) attached to the carbonyl carbon
The carbonyl carbon is bonded to both the aromatic ring and the methyl group, making it a typical example of an aromatic ketone.
3. How is acetophenone prepared in the laboratory?
Acetophenone is commonly prepared by the Friedel–Crafts acylation of benzene using acetyl chloride in the presence of a Lewis acid catalyst. The balanced reaction is:
C6H6 + CH3COCl → C6H5COCH3 + HCl (in the presence of AlCl3)
- Reagents: benzene and acetyl chloride (CH3COCl)
- Catalyst: AlCl3
- Reaction type: electrophilic aromatic substitution
This method introduces an acyl group (–COCH3) onto the benzene ring to form acetophenone.
4. What are the physical properties of acetophenone?
Acetophenone is a colorless liquid with a characteristic sweet odor and moderate boiling point. Its key physical properties are:
- Molecular formula: C8H8O
- Molar mass: approximately 120.15 g mol-1
- Boiling point: about 202°C
- Slightly soluble in water but soluble in organic solvents like ethanol and ether
Its aromatic ring and carbonyl group influence both its boiling point and solubility behavior.
5. What functional group is present in acetophenone?
Acetophenone contains a ketone functional group (carbonyl group, C=O) attached to an aromatic ring. Specifically:
- The carbonyl carbon is bonded to a phenyl group (C6H5–)
- And to a methyl group (–CH3)
Because the carbonyl carbon is bonded to two carbon atoms, it is classified as a ketone rather than an aldehyde.
6. What is the IUPAC name of acetophenone?
The IUPAC name of acetophenone is 1-phenylethanone. This name is derived as follows:
- Parent chain: ethanone (two-carbon ketone)
- Substituent at carbon-1: phenyl group
The carbonyl carbon is assigned position 1, and the phenyl substituent is attached to the same carbon, giving the name 1-phenylethanone.
7. How does acetophenone react with reducing agents?
Acetophenone is reduced to a secondary alcohol, 1-phenylethanol, when treated with common reducing agents. A typical reaction is:
C6H5COCH3 + 2[H] → C6H5CHOHCH3
- Reagents: NaBH4 or LiAlH4
- Reaction type: reduction of ketone to secondary alcohol
The carbonyl group (C=O) is converted into a hydroxyl group (–OH), forming 1-phenylethanol.
8. What is the difference between acetophenone and benzophenone?
The main difference between acetophenone and benzophenone is the groups attached to the carbonyl carbon. In:
- Acetophenone (C6H5COCH3), the carbonyl carbon is attached to one phenyl and one methyl group.
- Benzophenone (C6H5COC6H5), the carbonyl carbon is attached to two phenyl groups.
Both are aromatic ketones, but benzophenone is bulkier and has different physical and chemical properties due to the presence of two benzene rings.
9. What are the common uses of acetophenone?
Acetophenone is widely used as a fragrance ingredient and as an intermediate in organic synthesis. Its main uses include:
- Component in perfumes and flavorings
- Intermediate for pharmaceuticals and resins
- Starting material in the synthesis of other aromatic compounds
Its pleasant odor and reactive carbonyl group make it valuable in both industry and laboratory chemistry.
10. Does acetophenone undergo electrophilic substitution reactions?
Yes, acetophenone undergoes electrophilic aromatic substitution, but the carbonyl group deactivates the benzene ring and directs substitution to the meta position. Important points are:
- The –COCH3 group is electron-withdrawing
- It is a meta-directing group
- Reactions include nitration, sulfonation, and halogenation under suitable conditions
Thus, in reactions such as nitration, substitution mainly occurs at the meta position relative to the carbonyl group.
