Acid anhydrides give off RCOOH Acyl chlorides are much more reactive than carboxylic acids CH3 C O W + :X-+ :W-Explaining reactivity Many of the reactions of the carboxylic acid derivatives follow the pattern below with an attack by an nucleophile. Carboxylic acid - Carboxylic acid - Reduction: Although carboxylic acids are more difficult to reduce than aldehydes and ketones, there are several agents that accomplish this reduction, the most important being lithium aluminum hydride (LiAlH4) and borane (BH3).
You didn't finish your question. That's because the leaving group of an acid chloride is the conjugate base of a much stronger acid than all of the other derivatives (Cl- is the conjugate base of HCl, a stronger acid than for example, a carboxlyic acid).
Acyl chlorides mostly give off HCl. Aldehydes are more reactive than ketones (chapter 17) as they are less hindered and the alkyl group in the ketone is a weak electron donor.
This is due to the electronegative group, such as chlorine, polarizing the carbonyl group more strongly than an alkoxy group (ester) or an amino group (amide). Note: If you are want the mechanism for this reaction , you will find it by following this link to another part of the site dealing with nucleophilic addition-elimination reactions. The reaction is usually extremely vigorous at room temperature. Carboxylic acid derivatives react tend to react via nucleophilic acyl substitution where the group on the acyl unit, R-C=O undergoes substitution: Study Tip: Note that unlike aldehydes and ketones , this reactivity of carboxylic acids retains the carbonyl group, C=O . Since acyl chlorides are more reactive than esters, isolation of the ketone intermediate formed in their reactions with organometallic reagents becomes an attractive possibility.
Adding an acyl chloride to water produces the corresponding carboxylic acid together with steamy acidic fumes of hydrogen chloride. Under the reaction condition s the carboxylic acid will deprotonate to give the carboxylate which is a very poor electrophile (after all, it has a negative charge !) The business end of an acyl halide, #RC(=O)X (X=Cl, Br)#, contains a reactive #sp_2# hybridized carbon, and a potential leaving group in the chloride ion. The product is a primary alcohol (RCOOH → RCH2OH). so the ester is more reactive than the acid. Thus, acid chlorides are more reactive than anhydrides, which are more reactive than esters, which are more reactive than amides. . To achieve this selectivity we need to convert the highly reactive Grignard and lithium reagents to less nucleophilic species. Where –W: and :W-can be –Cl and Cl-(acyl chlorides) I'm assuming you're asking why they're more reactive than other carboxylic acid derivatives?