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Carboxylic acids contain COOH and are weak acids. They react with bases and carbonates to give salts; carbonate also releases carbon dioxide. An alcohol and a carboxylic acid form an ester in an acid-catalysed reversible reaction. Name an ester with the alcohol-derived alkyl group first and the acid-derived carboxylate part second. The ester linking oxygen and its attached carbon group come from the alcohol; tracing those atoms prevents reversed names and incorrect displayed formulae.
Video by Eliot Rintoul. The video’s own board label is retained; follow the specification reference and scope notes on this lesson for assessed content.
Viewing focus: Explain acid and ester reactions
After watching, attempt these questions before opening the answers. You can also use the written lesson below.
After watching 1: What forms when a carboxylic acid reacts with carbonate?
Salt, water and carbon dioxide. Acid–carbonate reactions release CO2.
After watching 2: Which mechanism describes an acyl chloride reacting with a nucleophile?
Nucleophilic addition–elimination. Addition is followed by loss of the leaving group.
What you'll be able to do
Carboxylic acids contain COOH and are weak acids. They react with bases and carbonates to give salts; carbonate also releases carbon dioxide. An alcohol and a carboxylic acid form an ester in an acid-catalysed reversible reaction. Name an ester with the alcohol-derived alkyl group first and the acid-derived carboxylate part second. The ester linking oxygen and its attached carbon group come from the alcohol; tracing those atoms prevents reversed names and incorrect displayed formulae.
Acyl chlorides react readily with water, alcohols, ammonia and amines. A nucleophile adds to the carbonyl carbon and an intermediate eliminates chloride, giving nucleophilic addition–elimination. With water the product is a carboxylic acid; with an alcohol an ester; with ammonia an amide. Acid anhydrides provide another acylating route and release a carboxylic acid rather than hydrogen chloride. Distinguish these reactions from nucleophilic addition to an aldehyde or ketone, where an appropriate leaving group is absent.
Acid hydrolysis of an ester is reversible and gives the carboxylic acid and alcohol. Alkaline hydrolysis gives a carboxylate salt and alcohol, making reversal under those alkaline conditions unfavourable. Acidifying the resulting salt liberates the carboxylic acid. Reflux often supplies heat while retaining volatile components. A synthesis evaluation should consider equilibrium yield, reagent hazards, purification and waste rather than choosing the most reactive reagent solely because it reacts rapidly.
Attempt these problems on paper before opening the worked reasoning. Explain your steps as well as giving a final answer.
Common mistakes to avoid
Key takeaways
Question 1: Give the organic product from ethanoyl chloride and ammonia.
Ethanamide, CH3CONH2.
Check the assessed scope and practical or mathematical requirements.
An external explanation or interactive activity to use alongside the lesson. It may include extension material.
Close the notes and answer from memory. Revisit any explanation you cannot yet reconstruct.
Test yourself
Answer a few questions, then review anything you missed.
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