GCSE Chemistry: C10 - Organic reactions

What are alcohols in water?

Alcohols are soluble in water and form neutral solutions.

How does the solubility of an alcohol change with the number of carbon atoms?

As the number of carbon atoms increases, the solubility of an alcohol decreases.

Describe what happens in the reaction between ethanol and sodium

- in the reaction of the alcohol ethanol with sodium, we see bubbles of hydrogen gas being produced

- we have also made the product sodium ethoxide

ethanol + sodium ----->

ethanol + sodium ----> sodium ethoxide + hydrogen

Show the general word equation for the reaction of an alcohol with sodium

alcohol + sodium -> sodium (prefix of alcohol)oxide + hydrogen

methanol + sodium ---->

methanol + sodium ----> sodium methoxide + hydrogen

propanol + sodium ---->

propanol + sodium -----> sodium propoxide + hydrogen

butanol + sodium ---->

butanol + sodium ----> sodium butoxide + hydrogen

Name a good example of an oxidising agent

A good example of an oxidising agent is acidified potassium dichromate.

Describe what happens when an alcohol reacts with an oxidising agent

- when an alcohol reacts with an oxidising agent, they produce a carboxylic acid and water

Show the general word equation for the reaction of an alcohol with an oxidising agent

alcohol + oxidising agent -----> carboxylic acid + water

ethanol + oxidising agent

ethanol + oxidising agent ----> ethanoic acid + water

methanol + oxidising agent

methanol + oxidising agent ----> methanoic acid + water

propanol + oxidising agent

propanol + oxidising agent -----> propanoic acid + water

butanol + oxidising agent

butanol + oxidising agent ----> butanoic acid + water

Describe what happens in the combustion of an alcohol

- alcohols release energy when combusted

- combusting an alcohol in air produces carbon dioxide and water

Show the general word equation for the combustion of an alcohol

alcohol + oxygen ----> carbon dioxide + water

The carboxylic acids are a ....

The carboxylic acids are a homologous series.

This means that carboxylic acids all have the same functional group.

What is the functional group of carboxylic acids?

Carboxylic acids have the functional group COOH.

Methanoic acid

Structural formula of methanoic acid

HCOOH

Ethanoic acid

Structural formula of ethanoic acid

CH₃COOH

Propanoic acid

Structural formula of propanoic acid

CH₃CH₂COOH

Butanoic acid

Structural formula of butanoic acid

CH₃CH₂CH₂COOH

In water, carboxylic acids are ...

In water, carboxylic acids are weak acids.

Describe what happens when the carboxylic acid ethanoic acid ionises

- when ethanoic acid ionises, the ethanoate ion and H⁺ hydrogen ions are produced

- this is a reversible reaction, so the ethanoate ion and H⁺ can recombine to form ethanoic acid

Ethanoate ion

Hydrogen ion

Why are carboxylic acids weak acids?

Because carboxylic acids only partially ionise in aqueous solution, they are weak acids.

What sort of pH do carboxylic acids have?

- as carboxylic acids are weak acids, this means that carboxylic acids have a higher pH than a stronger acid such as hydrochloric acid

- this is because, releasing H⁺ hydrogen ions in aqueous solution lowers the pH of an acid, but carboxylic acids only partially ionise as they are weak acids, and so this means that carboxylic acids have a high pH, as they release fewer H⁺ hydrogen ions in aqueous solution

Describe what happens in a reaction between ethanoic acid and sodium carbonate

- in the example of ethanoic acid reacting with sodium carbonate, we have made the salt sodium ethanoate, carbon dioxide gas and water

Show the general word equation for the reaction of a carboxylic acid with a metal carbonate

carboxylic acid +metal carbonate->salt +carbon dioxide+ water

The salt is ....

The salt is the positive ion from the metal carbonate, followed by the negative ion produced by the carboxylic acid.

Methanoic acid produces the negative ion

methanoate

Ethanoic acid produces the negative ion ....

ethanoate

Butanoic acid produces the negative ion ....

butanoate

Propanoic acid produces the negative ion ....

propanoate

Describe what happens in a reaction of a carboxylic acid with an alcohol

- When we react a carboxylic acid with an alcohol, we make a molecule called an ester, and water

What are esters and what are they used for?

Esters are really useful molecules, as they often have a pleasant smell, and so are used a lot in foods.

Give two properties of esters that make them suitable for use in perfumes

- esters have a pleasant smell

- esters are volatile

What is the name of the ester produced in the reaction between ethanoic acid and ethanol?

Ethyl ethanoate

Bonding diagrams to show: ethanoic acid + ethanol

Ethyl ethanoate

ethanoic acid + ethanol ----->

ethanoic acid + ethanol -----> ethyl ethanoate + water

In the reaction between ethanoic acid and ethanol, the ester ....

In the reaction between ethanoic acid and ethanol, the ester ethyl ethanoate is produced, as well as water.

What conditions are needed for the reaction between ethanoic acid and ethanol to produce ethyl ethanoate and water?

The reaction between ethanoic acid and ethanol requires sulfuric acid as a catalyst.

What is the functional group of an ester?

C=O-O

How is an ester named?

The first part of the name of an ester is the name of the alcohol but with the 'anol' suffix replaced by the suffix 'yl'.

The second part of the name of an ester is the negative ion produced by the carboxylic acid.

What does volatile mean?

Volatile means a substance evaporates into a gas easily.