INTRODUCTION
Carboxylic acid is a type of organic acid that contains a carboxyl functional group (-COOH) consisting of a carbonyl group (C=O) and a hydroxyl group (-OH) bonded to the same carbon atom. The general formula for a carboxylic acid is RCOOH, where R is an alkyl or aryl group.
Carboxylic acids are found in many naturally occurring substances, including fatty acids, amino acids, and acetic acid, which is the main component of vinegar. They have a sour taste and are often used as flavoring agents in food and beverages.
Quizzes
Watch the video below taking keen concern on chemical formulas and chemical symbols and in groups discuss questions below.
1. Give the general formula of a carboxylic
2. what do R used in the formula stands for
3. Give some examples of natural extracts of carboxylic acids and the uses.
4. Ethanedioic acid has higher boiling point than ethanoic acid. Explain.
NOMENCLATURE
In naming of carboxylic acids by IUPAC system, the suffix „e‟ in alkane is replaced with„oic acid‟ to lead alkanoic acid and is derived from the name of the longest carbon chain
that contains the carboxyl group. However, the „e‟ is retained in dicarboxylic acids and
other polyfunctional acids.
HCOOH-Methanoic acid
CH3CO2H -Ethanoic acid
CH3CH2CO2H -Propanoic acid
The chain is numbered, beginning with the carbon atom of the carboxylic group. If the
carboxylic acid contains a carbon-carbon double or triple bond, change of infix from „an‟
to „en‟ and „yn‟ to indicate the presence of multiple bond. The location of the multiple
bond is indicated by a number with reference to the carboxyl group.
CH3CH=CHCO2H-2-Butenoic acid
CH2=CHCH2CO2H-3-Butenoic acid
There are branched and cyclic carboxylic acids
Branched carboxylic acids:
1. 2-methylbutanoic acid: CH3CH(CH3)CH2COOH
2. 3-methylhexanoic acid: CH3(CH2)3CH(CH3)COOH
3. 2,2-dimethylpropanoic acid: (CH3)2CHCOOH
4. 4-methylpentanoic acid: CH3(CH2)2CH(CH3)CH2COOH
5. 3,3-dimethylbutanoic acid: (CH3)2CHCH2COOH
Cyclic carboxylic acids:
1. 2-cyclopentylacetic acid: C10H16O2
2. 1,4-cyclohexanedicarboxylic acid: C8H12O4
3. 2-norbornanecarboxylic acid: C9H12O2
4. 1,3-cyclopentanedicarboxylic acid: C7H10O4
Quiz
Watch the video below taking into account the chemical formulas and answer questions that follow in groups
1. Briefly describe the steps taken to name any given carboxylic acid.
2. Draw the structures of the following;
a)4,5-diethyoct-3-enoic acid
b)3-phenyl pentatonic acid
c)2-ethyl-3-hydroxy-1-methylbut-2-enoic acid
(i)
3-methylbut-2-enoic acid
(ii)
(Z)-3-Phenyl-2-pentenoic acid
(iii)
2-(N-Methylamino)propanoic acid
PHYSICAL PROPERTIES
1. Solubility: Carboxylic acids are soluble in water due to their ability to form hydrogen bonds with water molecules. However, as the size of the hydrocarbon chain attached to the -COOH group increases, the solubility of carboxylic acids in water decreases.
2.Boiling point: Carboxylic acids have higher boiling points than alcohols and ethers of comparable molecular weight due to the presence of intermolecular hydrogen bonding between -COOH groups.
3. Odor: Many carboxylic acids have strong, unpleasant odors. For example, formic acid has a pungent odor, while butyric acid has a rancid odor.
4. Acidity: Carboxylic acids are weak acids and can donate a proton (H+) to a base to form a carboxylate ion (-COO-). The acidity of carboxylic acids increases with the presence of electron-withdrawing groups attached to the -COOH group.
5. Melting point: Carboxylic acids have higher melting points than corresponding alcohols and ethers due to the presence of intermolecular hydrogen bonding
Quiz
Watch the video below and discuss the questions that follow and compare findings with other groups
1. Describe the physical properties of carboxylic acid
CHEMICAL PROPRTIES
Carboxylic acids are a class of organic compounds that contain a carboxyl functional group (-COOH) attached to an alkyl or aryl group. They have a number of important chemical properties, including:
1. Acidity: Carboxylic acids are weak acids, meaning they can donate a hydrogen ion (H+) in solution. The carboxyl group is acidic because the oxygen atom is highly electronegative and can pull electron density away from the hydrogen atom, making it easier to dissociate. The acidity of carboxylic acids can be increased by electron-withdrawing groups on the alkyl or aryl group, which make the carboxyl group more polar.
2. Reactivity with bases: Carboxylic acids react with bases to form carboxylate salts. The carboxylic acid donates a proton (H+) to the base, forming a carboxylate ion (-COO-). Carboxylate salts are often more water-soluble than the corresponding carboxylic acids.
3. Esterification: Carboxylic acids can react with alcohols in the presence of an acid catalyst to form esters. This reaction is important in the synthesis of many fragrances, flavors, and plasticizers.
4. Decarboxylation: Some carboxylic acids can undergo decarboxylation, a reaction in which the carboxyl group is removed as carbon dioxide (CO2) and a new functional group is formed.
Quizzes
Watch the video below and answer the questions that follow anx compare your answers with friends
1. How does the presence of a carboxylic acid functional group affect the acidity of a compound?
2. How do carboxylic acids react with metals, such as sodium or magnesium?
3. How do carboxylic acids undergo esterification reactions with alcohols?
4. How does the structure of a carboxylic acid affect its solubility in water?
5. How do carboxylic acids react with bases, such as sodium hydroxide or ammonia?
PREPARATION OF CARBOXYLIC ACIDS
1. By using primary Alcohols and Aldehyde
We will notice that the primary alcohol gets oxidised to carboxylic acid when oxidising agents are added, such as potassium permanganate (KMnO4), in an acidic, alkaline or neutral medium. By using a mild oxidising agent, we can get carboxylic acids from aldehydes.
2.From Alkylbenzenes
We can get aromatic carboxylic acids after vigorous oxidation of alkylbenzenes with chromic acid. Irrespective of the length of the chain, the whole side chain is oxidised to a carbonyl group. The oxidation of primary and secondary alkyl groups can be done in this manner while the tertiary group is
3. From Nitriles and Amides
Amides are prepared by the hydrolysis of nitriles and then converted to acids in the presence of catalysts (H+ or OH-1). In order to stop the reaction at the amide stage, mild reaction conditions are used.
4. By using Grignard Reagents
When Grignard reagent reacts with carbon dioxide, it forms salts of carboxylic acids which after some time gives corresponding carboxylic acid after the acidification with any mineral acid. We can prepare Grignard reagents as well as nitriles from alkyl halides. These methods are very useful for the conversion of alkyl halides into corresponding carboxylic acids which has one carbon atom more than what is present in alkyl halides.
5. By Acyl Halides and Anhydrides
When acid chloride is hydrolysed with water then carboxylic acid is produced and it is more readily hydrolysed with an aqueous base and gives corresponding carboxylic ions which on further acidification gives the carboxylic acid.
6. By using Esters
A carboxylic acid is produced after the acidic hydrolysis of esters and carboxylates are produced after the basic hydrolysis of an ester.
Qizzes
Watch the video below and in groups discuss the questions below and compare your answers with others
1. Describe the preparation of carboxylic acid using the oxidation of primary alcohols.
2. Explain the preparation of carboxylic acid from alkenes using KMnO4 as the oxidizing agent.
3. Describe the preparation of carboxylic acid from alkanes using the Kolbe’s electrolysis.
4. Explain the preparation of carboxylic acid from nitriles using the hydrolysis reaction
USES OF CARBOXYLIC ACIDS
1. Fatty acids that are essential to human beings are made up of carboxylic acids. Examples include omega-6 and omega-3 fatty acids.
2. Higher fatty acids are also used in the manufacture of soaps.
3. The production of soft drinks and many other food products involves the use of many carboxylic acids.
4. The manufacture of rubber involves the use of acetic acid as a coagulant.
5. Hexanedioic acid is used in the manufacture of nylon-6,6.
Carboxylic acids have numerous applications in the rubber, textile, and leather industries.
Below is a video showing the uses of carboxylic acids
EXCEPTIONAL BEAST 