Carboxylic acids are compounds that contain the -COOH group.

Examples of carboxylic acids:


Salts of carboxylic acids are called carboxylate salts. The formation of carboxylate salts shows that carboxylic acids are acidic. A carboxylate salt is formed upon the removal of H from -COOH group, leaving -COO.

Physical properties of carboxylic acids

  • Carboxylic acids have higher melting and boiling points than the corresponding alcohols.
  • This is because in a pure carboxylic acid, hydrogen bonding can occur between two molecules of acid to produce a dimer.
  • This doubles the size of the molecule, making the van der Waals’ forces stronger. iii. Hence more energy is required to overcome these forces of attraction.
  1. Small carboxylic acids are soluble in water.
  • carboxylic acid is capable of forming hydrogen bond with water molecule.
  • However, the solubility decreases as the number of carbon atoms increases. This is because the presence of long hydrocarbon tail disrupts the effectiveness of hydrogen bonding.

Preparation of carboxylic acids

  • Oxidation of primary alcohol.
  • Oxidation of aldehyde.
  • Acidic/alkaline hydrolysis of nitrile.

Oxidation of primary alcohol and aldehyde

Acidic hydrolysis of nitrile:

  1. When nitrile is heated under reflux with a dilute acid such as dilute hydrochloric acid, carboxylic acid will be formed.
  2. Using ethanenitrile as an example, ethanoic acid is formed. CH3CN + 2H2O + H CH3COOH + NH4

Alkaline hydrolysis of nitrile:

  1. When nitrile is heated under reflux with an alkali such as sodium hydroxide, salt of carboxylic acid(carboxylate salt) is produced. Using ethanenitrile as an example, ethanoate ion is formed. CH3CN + 2H2O + OH CH3COO + NH3
  2. Ethanoate ion can be converted to ethanoic acid by the addition of acid. CH3COO + H CH3COOH

 

Reactions of Carboxylic Acids

Acidity of carboxylic acids

Carboxylic acids are acidic because they can donate a proton to form carboxylate ion and hydroxonium ion. The presence of hydroxonium ions makes the solution acidic.

RCOOH + H2O ⇌ RCOO + H3O

However, carboxylic acids are only weak acids. For instance ethanoic acid has a pH of about 2-3.

Reaction with bases

Since carboxylic acids are acids, they will react with a base such as sodium hydroxide to produce a carboxylate salt and water. This is a simple neutralisation reaction.

  • Take ethanoic acid and sodium hydroxide as an example: CH3COOH + NaOH CH3COONa + H2⁺ + OH H2O

 

Reaction with metals

Carboxylic acids will react with reactive metals such as sodium to produce a carboxylate salt and hydrogen gas.

  • Take ethanoic acid and sodium metal as an example:

2CH3COOH + 2Na 2CH3COONa + H2

 

Reaction with carbonates and hydrogen carbonates

Carboxylic acids will react with carbonates and hydrogen carbonates
to produce a carboxylate salt, carbon dioxide gas and water.

  • ethanoic acid and sodium carbonate

    2CH3COOH + Na2CO3 2CH3COONa + CO2 + H2O …and the ionic equation is: 2H + CO3² CO2 + H2O

  • This is a useful test to distinguish carboxylic acids from alcohols and phenols. This is because alcohols and phenols are not acidic enough to react with these.

 

Converting carboxylic acids to acyl chlorides

  • Acyl chlorides have the -OH in the -COOH group of the carboxylic acid replaced by chlorine.

  • ethanoic acid produce ethanoyl chloride.

  • Acyl chlorides are very reactive and can be used to produce a range of other organic compounds.

 

There are three methods to produce acyl chlorides from carboxylic acids:

i. Reaction with phosphorus(III) chloride, PCl3.

Using ethanoic acid, the equation is: 3CH3COOH + PCl3 3CH3COCl + H3PO4

ii. Reaction with phosphorus(V) chloride, PCl5  eg ethanoic acid, the equation is:

CH3COOH + PCl5 CH3COCl + POCl3 + HCl

iii. Reaction with thionyl chloride, SOCl2.

  • Take ethanoic acid as an example, the equation is:

CH3COOH + SOCl2 CH3COCl + SO2 + HCl

  • This method is generally preferred because SO2 and HCl are both gases, and can be separated from the mixture easily.

5 Comments

author

Options d’expédition discrète pour le theophylline en Belgique
theophylline : Le point sur les achats en ligne Acheter theophylline sans souci en France
theophylline en ligne en Suisse sans consultation préalable
quibron-t et pilule contraceptive : interactions possibles
Options d’achat de quibron-t en Italie
commander quibron-t à Monaco
theophylline sans ordonnance en Belgique
Informations sur l’achat sécurisé de theophylline
quibron-t disponible en vente en ligne theophylline en ligne : ce qu’il faut savoir avant d’acheter
theophylline en pharmacie en ligne : une solution pratique
Guide complet pour acheter quibron-t en ligne en France
où trouver theophylline en Suisse theophylline en Belgique: ce qu’il faut savoir avant
d’acheter
Acheter de la theophylline à prix abordable en ligne
Comparaison des prix du theophylline en ligne
theophylline à acheter en Europe quibron-t en ligne disponible 24/7
theophylline sans risque d’achat Acheter quibron-t sans
consultation médicale
commander quibron-t en ligne Acheter de la theophylline en ligne sans risque en Belgique
Options d’expédition discrète pour le quibron-t en Belgique quibron-t en stock permanent
theophylline en ligne : Ce que les consommateurs doivent savoir Achetez
quibron-t en ligne en toute sécurité en Belgique

Reply
author

Hello! Do you know if they make any plugins to help
with SEO? I’m trying to get my blog to rank for some targeted
keywords but I’m not seeing very good success.
If you know of any please share. Thank you!

Reply
author

This paragraph presents clear idea in support of the new people of blogging, that
truly how to do blogging and site-building.

Reply
author
Cedric
April 11, 2024

Pretty section of content. I just stumbled upon your web site and in accession capital to
assert that I get in fact enjoyed account your blog posts.
Any way I will be subscribing to your feeds and even I achievement you
access consistently rapidly.

Reply
author

It is appropriate time to make some plans for the long run and it’s time to be
happy. I have learn this submit and if I could I desire to
suggest you few fascinating things or advice.
Perhaps you could write next articles relating to this article.
I want to read even more things about it!

Reply

Leave a Reply

Your email address will not be published. Required fields are marked *