Consider the following statements; Acetophenone can be prepared by a. Oxidation of 1 -phenylethanol b. Reaction of benzaldehyde with methyl magnesium bromide c. Friedal Crafts reaction of benzene with acetyl chloride d. Distillation of calcium benzoate Which of the above statements are correct? (a) a and \(\mathrm{c}\) (b) c and \(\mathrm{d}\) (c) \(\mathrm{b}\) and \(\mathrm{c}\) (d) a and d

In organic chemistry, the oxidation of alcohols is a fundamental transformation. Specifically, the oxidation of 1-phenylethanol pertains to the process where this secondary alcohol is transformed into a ketone.

The structure of 1-phenylethanol includes a phenyl group (a benzene ring) attached to a carbon with a hydroxyl (-OH) group. Oxidation, in this case, involves the removal of hydrogen atoms and the formation of a double bond between the carbon of the hydroxyl group and an oxygen atom, resulting in a carbonyl group (C=O). The reagents commonly used for this oxidation can vary, including chromium (VI) compounds, such as chromic acid (H₂CrO₄), or milder agents like Dess-Martin periodinane.

The product of this oxidation is acetophenone, a ketone where the carbonyl group is flanked by a phenyl group and a methyl group. Acetophenone is used in various applications such as fragrances and as a precursor for other chemical syntheses. While this reaction is efficient, care must be taken to avoid over-oxidation which could potentially lead to the formation of a carboxylic acid instead.

Friedel-Crafts acylation is a powerful method for introducing acyl groups into aromatic rings, typically benzene or its derivatives. This reaction is named after Charles Friedel and James Crafts who first reported it in 1877.

An acyl chloride like acetyl chloride is a common acylating agent used in the reaction. The process involves generating a strong electrophile by reacting the acyl chloride with a Lewis acid catalyst like aluminum chloride (AlCl₃). This activated complex then attaches to the benzene ring, forming a bond between the aromatic carbon and the carbonyl carbon of the acyl group.

Key Steps in Friedel-Crafts Acylation

• Generation of an acylium ion from the acyl chloride and the Lewis acid.
• Electrophilic attack of the acylium ion on the aromatic ring.
• Re-establishment of aromaticity through deprotonation.

The result is a ketone, specifically acetophenone when using acetyl chloride and benzene. This reaction not only introduces a functional group but also retains the aromatic stability of the benzene ring, making it an ideal method for synthesizing aromatic ketones.

Ketones are a group of organic compounds characterized by the presence of a carbonyl group (C=O) bounded to two carbon atoms. They play a vital role in biochemistry and are also important in industry as solvents and intermediates for the synthesis of various materials.

General Pathways for Ketone Formation

• Oxidation of secondary alcohols, as discussed before with 1-phenylethanol.
• Acyl chloride reactions with aromatic rings via Friedel-Crafts acylation.
• Keto-enol tautomerism, where enols rearrange to form ketones.
• Through the reaction of nitriles with Grignard reagents, followed by hydrolytic workup.

The synthesis of ketones like acetophenone can be achieved through different synthetic routes, each with its own set of conditions and necessary reagents. The choice of method depends on factors such as the starting materials' availability, the desired yield, and specificity of the ketone to be synthesized. Understanding these processes allows chemists to synthesize a wide range of ketone compounds efficiently and selectively.