The reaction between propanoyl chloride and benzene is an example of acylation - AQA - A-Level Chemistry - Question 26 - 2019 - Paper 3

The acylation of benzene with propanoyl chloride involves the generation of a reactive acylium ion from propanoyl chloride. Upon mixing with aluminum chloride (a Lewis acid), it facilitates the electrophilic aromatic substitution. Therefore, the correct representation that shows an acylium ion interacting with benzene is option C. This option correctly depicts the addition of the acylium ion to the benzene ring, leading to the formation of the substituted product.