Carboxylic Acids & Derivatives

How are primary alcohols oxidised to carboxylic acids?

Primary alcohol is heated under reflux with acidified K2CrO7

The dichromate will change colour from orange to green

How do nitriles react to form carboxylic acids?

Nitriles react via hydrolysis to form carboxylic acids

Heat the nitrile under reflux with a strong acid catalyst:

CH3CN + 2H2O + HCl ——> CH3COOH + NH4Cl

How do carboxylic acids react with metals?

Carboxylic acids react with metals to form a salt and hydrogen gas

What is the chemical equation for the reaction of ethanoic acid with sodium?

2CH3COOH + 2Na ——> 2CH3COO-Na+ + H2

How do carboxylic acids react with carbonates?

Carboxylic acids react with carbonates to form a salt, carbon dioxide and water

What is the chemical equation for the reaction of ethanoic acid with sodium carbonate?

2CH3COOH + Na2CO3 ——> 2CH3COO-Na+ + CO2 + H2O

How do carboxylic acids react with alkalis?

Salt and water is formed

CH3COOH + NaOH ——> CH3COO-Na+ + H2O

How do alcohols react with carboxylic acids?

They form esters and heating is required with a sulfuric acid catalyst

How do carboxylic acids form alcohols?

Reduction with LiAlH4

How do carboxylic acids react to form acyl chlorides?

They react with SOCl2 to form an acyl chloride, SO2 and HCl

CH3COOH + SOCl2 ——> CH3COCl + SO2 + HCl

How is methanoic acid further oxidised?

It has an aldehyde functional group so it can be oxidised further by using Tollens’ reagent or Fehling’s solution. The products are CO2 and H2O

HCOOH + [O] ——> CO2 + H2O

How is ethandioic acids oxidised further?

It’s oxidised to carbon dioxide and water using warm acidified KMnO4

(COOH)2 + [O] ——> 2CO2 + H2O

State the relative acidities of carboxylic acids, alcohols and phenols

Carboxylic acids to Phenol to Alcohols, the acidity is decreasing

Explain the relative acidities of carboxylic acids

Carboxylic acids are the most acidic amongst alcohols and phenols since it has a delocalised pi system that develops over the -COO- group. This distributes the negative charge, making the carboxylate ion more stable

Why are phenols more acidic than alcohols?

The phenoxide ion is relatively stable. The lone pair on the oxygen is delocalised into the pi system so the negative charge is dispersed.

It is more likely to donate a hydrogen ion

Why are alcohols the least acidic in comparison to phenols and carboxylic acids?

It has a positive inductive effect. In the alkoxide ion, the alkyl groups push electron away from themselves, increasing the electron density of oxygen, making it more likely to bond to a hydrogen ion and reform an alcohol

What determines the acidity of chlorine substituted ethanoic acids?

Puling charge away from the -COO- end, this is done by adding a chlorine atom to the chain

Since chlorine is very electronegative it will have a tendency to attract electrons towards itself. The more chlorines bonded, the stronger the acid

How do acyl chlorides react with water?

Forms a carboxylic acid and HCl

Give the chemical equation for the hydrolysis of ethanoyl chloride?

CH3COCl + H2O ——> CH3COOH + HCl

How do acyl chlorides react with alcohols?

They form an ester and HCl

CH3COCl + CH3OH ——> CH3COOCH3 + HCl

How do acyl chlorides react with phenol?

Forms a phenyl ester and HCl. Takes place in the presence of a base

Phenol reacts with base to form phenoxide ion
CH3COCl + sodium phenoxide ——> Phenyl ethanoate + NaCl

How do acyl chlorides react with ammonia?

Forms a primary amide and HCl

CH3COCl + NH3 ——> CH3CONH2 + HCl

How do acyl chlorides react with a primary amine?

Forms a secondary amide and HCl

CH3COCl + CH3NH2 ——> CH3CONHCH3 + HCl

Compare the relative ease of hydrolysis of acyl chlorides and aryl chlorides

Acyl chlorides react vigorously with cold water to produce a carboxylic acid and hydrogen chloride gas

Alkyl chlorides have almost no reaction with water

Aryl chlorides have no reaction with water

How do esters undergo acid hydrolysis?

Heat the ester under reflux with dilute aqueous acid. A carboxylic acid and alcohol are formed.

The reaction is slow and reversible

How do esters undergo base hydrolysis?

Heat the ester under reflux dilute alkali. The salt of the carboxylic acid and alcohol. The reaction is one way and faster than acid hydrolysis

State the major commercial uses of esters

Perfumes

Solvents

Flavouring