Carboxylic Acids Part 1

Carboxylic acid general formula

C_nH_2nO₂

What are the 4 carboxylic acids derivatives?

• Esters

• Acyl chlorides

• Acid anhydrides

• Amides

What is the suffix used when naming carboxylic acids?

-anoic acid

What is the suffix used when naming acyl chlorides?

-oyl chloride

What is the suffix used when naming amides?

-anamide

What is the suffix used when naming esters?

alkyl alk-anoate

What is the suffix used when naming acid anhydrides?

-oic anhydride

Carboxylic acid displayed formula

Ester displayed formula

Acyl chloride displayed formula

Acid anhydride displayed formula

Amide displayed formula

Acid definition

A substance that donates H⁺ ions

Why do carboxylic acids have relatively high melting and boiling points?

Hydrogen bonds

acid + base →

salt + water

acid + carbonate →

salt + water + carbon dioxide

acid + metal →

salt + hydrogen

Ester general formula

C_nH_2nO₂

What are 3 properties of esters?

• Sweet-smelling

• Due to not forming hydrogen bonds:

  • Lower boiling points than carboxylic acids

  • Less soluble in water than carboxylic acids

What are 4 uses of esters?

• Perfumes

• Food flavourings

• Solvents

• Plasticisers (Allow materials to become flexible and smooth)

What are the 3 methods and equations of preparing esters?

• Carboxylic acid + Alcohol → Ester + Water

• Acid anhydride + Alcohol → Ester + Carboxylic acid

• Acyl Chloride + Alcohol → Ester + Hydrochloric acid

Condition and catalyst for Carboxylic acid + Alcohol → Ester + Water 

Catalyst: conc H₂SO₄

Condition: Heat (140^oC-180^oC)

Conditions for Acid anhydride + Alcohol → Ester + Carboxylic acid

Gently warm

Conditions for Acyl Chloride + Alcohol → Ester + Hydrochloric acid

Room temperature

Condensation reaction

A chemical reaction which two molecules are joined together with the elimination of a water molecule

What are the 3 laboratory methods of preparing esters involving condensation reactions?

• From a carboxylic acid and an alcohol

• From an acid anhydride and an alcohol

• From an acyl chloride and an alcohol

What is an ester prepared from?

• 2-hydroxybenzoic acid (salicylic acid)

• Ethanoic anhydride

Why are esters prepared with Ethanoic anhydride as opposed to Ethanoyl chloride (3 reasons)

• Less corrosive

• It does not react with water as readily

• It is safer as the by-product of its reaction is ethanoic acid (weak acid) rather than HCl (strong acid)

Hydrolysis

Breaking of a bond using water

What is the general equation for Acid hydrolysis of esters?

RCOOR’ + H₂O ⇌ RCOOH + R’OH

What are the products and conditions for acid hydrolysis of esters?

Products

• Carboxylic acid

• Alcohol

Conditions

• Reflux with dilute H₂SO₄ or dilute HCl

What is the general equation for Alkaline hydrolysis of esters?

RCOOR’ + NaOH → RCOO^-Na⁺ + R’OH

What are the products and conditions for alkaline hydrolysis of esters?

Products

• Carboxylate salt

• Alcohol

Conditions

• Reflux with dilute NaOH_(aq) or dilute KOH_(aq)

Where do triglycerides occur naturally?

• Animal fats

• Vegetable oils

What is a triglyceride?

A triester of glycerol and 3 fatty acids

What is a fatty acid?

A long chain carboxylic acid

What is the difference between a fat and oil? What is the difference between the triglycerides in fats and oils?

• A fat is a solid at room temperature whereas an oil is a liquid at room temperature

• Triglycerides found in fats often contain saturated fatty acids, whereas triglycerides found in oil often contain unsaturated fatty acids

Hydrolysis

The breaking of a bond using water

What conditions can triglycerides be hydrolysed in and why?

• Alkaline conditions

• Contain ester groups

What are the conditions and products of hydrolysing a triglyceride with NaOH?

Products

• Glycerol

• Sodium salt

Conditions

• Reflux

What are sodium salts formed in the hydrolysis of esters used as?

Soaps

Biodiesel

Mixture of methyl esters of long chain carboxylic acids

What is the name of the process where biodiesel is produced from triglycerides?

Transesterification

What are the reactants and catalyst in transesterification?

Reactants

• Vegetable oils

• Methanol

Catalyst

• KOH