Chemistry - 4CH1 PearsonEdexcel

Esters

Overview

Esters are the molecules behind many of the pleasant smells in everyday life. From the fruity aroma of pear drops to the floral notes in perfume, esters give products their distinctive scent. They form when an alcohol meets a carboxylic acid, linking two earlier topics in the organic chemistry section into one elegant reaction.

In this lesson you will learn how esters are formed, how to name them, how to write structural and displayed formulae for ethyl ethanoate, and how to prepare a sample of an ester in the laboratory. You will also discover the wide range of uses esters have in the food and fragrance industries.

Objectives

know that esters contain the functional group
know that ethyl ethanoate is the ester produced when ethanol and ethanoic acid react in the presence of an acid catalyst
understand how to write the structural and displayed formulae of ethyl ethanoate
understand how to write the structural and displayed formulae of an ester, given the name or formula of the alcohol and carboxylic acid from which it is formed and vice versa
know that esters are volatile compounds with distinctive smells and are used as food flavourings and in perfumes
practical: prepare a sample of an ester such as ethyl ethanoate

Lesson Note

Walk past a bakery and the sweet smell is partly esters. Open a pack of boiled sweets and the fruity flavours are synthetic esters. The scent industry alone uses hundreds of different esters to replicate natural aromas. What makes them special is that they can be made from just two simple starting materials: an alcohol and a carboxylic acid.

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Lesson Evaluation

Congratulations on completing the lesson on Esters. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.

You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.

Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.

Which functional group is present in esters? A) -OH B) -COOH C) -COO- D) C=C Answer: C
What is the catalyst used in esterification? A) Phosphoric acid B) Concentrated sulfuric acid C) Aluminium oxide D) Iron Answer: B
The ester formed from methanol and ethanoic acid is called: A) Ethyl methanoate B) Methyl ethanoate C) Methanol ethanoate D) Ethanoic methanol Answer: B
Esters are typically: A) Odourless solids B) Volatile with fruity smells C) Strong acids D) Insoluble in all solvents Answer: B
What small molecule is produced alongside the ester in esterification? A) Hydrogen B) Carbon dioxide C) Water D) Oxygen Answer: C