Carboxylic Acids

L.O: To understand the structure of carboxylic acids

Thursday, April 20, 2023

RECAP: What do these terms mean? functional group homologous series organic molecule Alkane alcohol

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Where are carboxylic acids found?

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What are carboxylic acids?

Carboxylic acids contain a functional group of carbon, hydrogen and oxygen atoms arranged like this...

What do you think the carboxylic acid with three carbon atoms is called?

...which is written as –COOH.

methanoic acid (HCOOH) ethanoic acid (CH3COOH)

E.g.

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Naming carboxylic acids

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Making carboxylic acids

In fact, any carboxylic acid can be made by oxidizing the corresponding alcohol.

If you leave wine standing open to the air, oxygen from the air will oxidize the ethanol to ethanoic acid, forming vinegar.

Q) Which carboxylic acid is made when methanol is oxidized?A) Methanoic acid.

ethanoic acidoxygen waterethanol

+ +

How do carboxylic acids compare to other acids? Try reacting the carboxylic acid,

ethanoic acid with sodium carbonate. What do you observe?

How does this reaction compare to hydrochloric acid

Does universal indicator show us any differences?

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Properties of carboxylic acids

Carboxylic acids:

have relatively high melting and boiling points

are very soluble in water

are weak acids

have a characteristic smell!

Examples of everyday carboxylic acids include:

citric acid (found in citrus fruits)

lactic acid (found in tired muscles)

malic acid (found in sour and tart foods).

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Chemical properties of carboxylic acids

Carboxylic acids are typical weak acids.

What would happen if you added a few cm3 of dilute ethanoic acid to each of these substances?

A few drops of universal indicator.

3 cm3 sodium hydroxide solution.

Half a spatula of sodium carbonate.

A piece of magnesium ribbon.

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Reactions of carboxylic acids

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Reactions of carboxylic acids

Carboxylic acids react like any other type of acid, forming salts when they react with alkalis, carbonates and metals:

ethanoic acidsodium

ethanoatewatersodium

carbonate+ +

carbondioxide

+

2CH3COOH 2CH3COONa H2ONa2CO3+ +CO2+

ethanoic acidsodium

ethanoatehydrogensodium+ +

2CH3COOH 2CH3COONa H22Na+ +

ethanoic acidsodium

ethanoatewater

sodiumhydroxide

+ +

CH3COOH CH3COONa H2ONaOH+ +

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Reactions of carboxylic acids

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Reactions of carboxylic acids