The reactions with acyl chlorides and with acid anhydrides

That means that the lone pair is no longer fully available to combine with hydrogen ions.  The nitrogen is still the most electronegative atom in the molecule, and so the delocalised  electrons will be attracted towards it, but the electron density around the nitrogen is nothing  like it is in, say, an ammonia molecule. The other problem is that if the lone pair is used to join to a hydrogen ion, it is no longer  available to contribute to the delocalisation. That means that the delocalisation would have  to be disrupted if the phenylamine acts as a base. Delocalisation makes molecules more  stable, and so disrupting the delocalisation costs energy and won't happen easily. Taken together - the lack of intense charge around the nitrogen, and the need to break  some delocalisation - means that phenylamine is a very weak base indeed. The acylation of phenylamine The reactions with acyl chlorides and with acid anhydrides These are reactions in which the phenylamine acts as a nucleophile. There is no essential  difference between these reactions and the same reactions involving any other primary  amine. You will find a summary of the reactions below, but all the detailed explanations  are on other pages.

We'll take ethanoyl chloride as a typical acyl chloride, and ethanoic anhydride as a typical  acid anhydride. The important product of the reaction of phenylamine with either of these  is the same. Phenylamine reacts vigorously in the cold with ethanoyl chloride to give a mixture of solid  products - ideally white, but usually stained brownish. A mixture of N-phenylethanamide  (old name: acetanilide) and phenylammonium chloride is formed. The overall equation for the reaction is: With ethanoic anhydride, heat is needed. In this case, the products are a mixture of  N-phenylethanamide and phenylammonium ethanoate.

The main product molecule (the N-phenylethanamide) is often drawn looking like this: If you stop and think about it, this is obviously the same molecule as in the equation above, but it stresses the phenylamine part of it much more. Looking at it this way, notice that one of the hydrogens of the -NH2 group has been replaced by an acyl group - an alkyl group attached to a carbon-oxygen double bond. You can say that the phenylamine has been acylated or has undergone acylation. Because of the nature of this particular acyl group, it is also described as ethanoylation. The hydrogen is being replaced by an ethanoyl group, CH3CO-.