The following two reactions are very similar. The only difference is that one adds a carbonyl to the bezene ring and the other adds a alkyl group. They share the same mechanism and similar reagents. Let's say we want to add a group R ( regardless a carbonyl or not) to the benzene ring. We would use silver chloride and the halide with the R group. There are more to talk about acylation . After the carbonyl R group is added, the carbonyl can be reduced and give a alkyl product. There is one limit in acylation , we cannot add a formyl halide to the reagent.