Chapter 20 Nitrogen compounds

Question 1

Production of Amines

Answer 1

-Amines are compounds with the amine (-NH2) functional group

• The halogen atom in halogenoalkanes is more electronegative than the carbon atom it is bonded to
• The halogen, therefore, draws electron density from the C-X bond (where X is the halogen) towards itself
• The carbon, therefore, has a partial positive charge and the halogen itself has a partial negative charge
• The lone pair of electrons on the nitrogen atom (in NH3) acts as a nucleophile and attacks the partial positively charged carbon
• As a result of this nucleophilic attack, the C-X bond is broken and the halogen is substituted by an amine group

Question 2

how are amines produced

Answer 2

-They can be produced as a result of nucleophilic substitution reactions of halogenoalkanes when they are heated under pressure with ethanolic ammonia (NH3 in ethanol)

Question 3

Production of Nitriles

Answer 3

• Nitriles are compounds with a -CN functional group

- They can be prepared from the nucleophilic substitution of halogenoalkanes

Question 4

Reaction with KCN

Answer 4

• The nucleophile in this reaction is the cyanide, CN– ion
• Ethanolic solution of potassium cyanide (KCN in ethanol) is heated under reflux with the halogenoalkane
• The product is a nitrile

Question 5

Production of Hydroxynitriles

Answer 5

• Hydroxynitriles are compounds with both a hydroxy (-OH) and cyanide (-CN) functional group
• They can be prepared from the nucleophilic addition of aldehydes and ketones

Question 6

Reaction with HCN

Answer 6

• The nucleophilic addition of hydrogen cyanide to carbonyl compounds is a two-step process
• In step 1, the cyanide ion attacks the carbonyl carbon to form a negatively charged intermediate
• In step 2, the negatively charged oxygen atom in the reactive intermediate quickly reacts with aqueous H+ (either from HCN, water or dilute acid) to form a 2-hydroxynitrile

Question 7

Hydrolysis of Nitriles

Answer 7

Nitriles are hydrolysed by either dilute acid or dilute alkali followed by acidification to give a carboxylic acid
–Hydrolysis is the breakdown of a compound using water

Question 8

Hydrolysis of nitriles

Answer 8

-Nitriles are hydrolysed by either dilute acid or dilute alkali followed by acidification

• –Hydrolysis by dilute acid results in the formation of a carboxylic acid and ammonium salt
• –Hydrolysis by dilute alkali results in the formation of a sodium carboxylate salt and ammonia; Acidification is required to change the carboxylate ion into a carboxylic acid

-The -CN group at the end of the hydrocarbon chain is converted to a -COOH group