Statement 1 Friedel-Crafts acylation reaction of benzene with acetyl chloride in presence of anhydrous \(\mathrm{AlCl}_{3}\) gives only acetophenone and not polysubstituted product. and Statement 2 Friedel-Crafts acylation is an electrophilic substitution reaction.

Electrophilic aromatic substitution (EAS) is a fundamental type of organic reaction where an atom, typically hydrogen, attached to an aromatic system, such as benzene, is replaced by an electrophile. The beauty of this reaction is that it retains the aromaticity of the benzene ring after the substitution process.

The process begins when the aromatic ring, rich in π-electrons, approaches a positively charged electrophile. A temporary complex is formed where the aromaticity of the ring is lost, leading to a carbocation intermediate. Subsequently, a base (usually the conjugate base of the electrophile or a solvent molecule) removes a proton from the sp³ hybridized carbon, restoring the aromaticity.

In the case of Friedel-Crafts acylation, the electrophile is an acylium ion. It's pertinent to recognize that the electrophilic species must be powerful enough to disrupt the stable π-system of benzene, and this is often achieved with the help of a Lewis acid catalyst.

A Lewis acid catalyst is a substance that can accept an electron pair. In the realm of organic chemistry, it plays an instrumental role in increasing the reactivity of certain electrophiles. A classic example is anhydrous aluminum chloride (\textbf{AlCl}\(_3\)), widely used in Friedel-Crafts acylation.

This catalyst coordinates with electron-rich atoms like chlorine, increasing the polarity of adjacent bonds and hence making the attached carbon more electrophilic. It's fascinating how \textbf{AlCl}\(_3\) not only enhances the electrophilicity of the acyl group but also maintains a stoichiometric balance by cycling back to its original form after each reaction cycle. This means that it is not consumed in the process, emphasizing its role as a true catalyst.

An acylium ion is a positively charged species (\textbf{R-CO}^+) and is the star electrophile in Friedel-Crafts acylation. It is formed when an acyl chloride reacts with a Lewis acid, such as \textbf{AlCl}\(_3\). The chloride leaves, and the resultant ion is immensely electrophilic, due to the stabilization of the positive charge by resonance within the carbonyl group.

The stability provided by resonance is a key principle as it allows the acylium ion to exist long enough to react with the benzene ring. This ion is so reactive because it seeks electrons to fill its positive charge, making it a perfect match for the electron-rich benzene ring in EAS.

Visualizing the mechanism of Friedel-Crafts acylation ensures a thorough understanding of this elegant process. It's a two-step reaction that starts with the generation of the acylium ion electrophile. The acyl chloride reacts with the Lewis acid catalyst, leading to the departure of the chloride ion and formation of the acylium ion.

Once the acylium ion is formed, it interacts with the benzene ring to create a sigma complex, which momentarily disrupts the ring's aromaticity. The key to the process is this complex's subsequent deprotonation, which restores aromaticity and yields the substituted product.

The beautiful simplicity of Friedel-Crafts acylation lies in its specificity. Since the introduced acyl group is electron-withdrawing, it deactivates the ring and prevents overreaction. Therefore, typically only one acyl group is introduced, avoiding polysubstitution and making the process highly controllable and predictable for synthesizing various aromatic ketones.