Question

MCAT Tutorial: Acid Halides & Anhydrides

Answer 1

\({\bf{Basic~Definition}}\) a carboxylic acid derivative with a halogen atom attached to the carbonyl carbon

Properties: easily hydrolyzed. often used as intermediates.

Synthesis: react carboyxlic acid with SOCl2 in a basic solvent. SN2.

Answer 2

\({\bf{Reactions}}\)

- Friedel-Crafts Acylation: makes alkyl aryl ketones via reaction of acid chloride with AlCl3

- Hydrolysis with H2O and pyridine to make carboxylic acid

- Formation of Anhydride via reaction with carboxylate salt

- Formation of amides by reacting acid chlorides with ammonia (requires 2 units)
> first NH3 attacks the carbonyl carbon
> second NH3 is base and reacts with the HCl and forms salt

Answer 3

\({\bf{Anhydrides}}\)



Two types: symmetric (like the one pictured above) and mixed anhydrides (made from two different carboxylic acid)

Nomenclature:

symmetric: replace acid suffix with anhydride
mixed: take the names of the acids used to derive the anhydride, alphabetize them, list them in order, then write anhydride

Answer 4

Properties: easily hydrolyzed but less reactive than acid chlorides. used as intermediates/reagents for acylation.

Synthesis: acid chloride + carboxylate salt

Aromatic anhydrides: heat dicarboxylic acid at high temp. forms five membered anhydride ring with the hydroxyl groups converted to a oxygen that is continuous with the five membered ring.

Answer 5

Other Synthesis Reactions:

1. hydrolyze to carboxylic acid
> symmetric: produces two units of same acid
> mixed: 1:1 mix of parent acids

2. react with alcohol to produce ester + carboxylic acid (not easily separated)
3. react with ammonia to produce amine (same rules regarding which unit of ammonia does what)

Answer 6

Anyway, that's the end of my tutorial, I hope it was a helpful resource. Source material is the 2nd Edition Barron's Prep book for the new MCAT