28.1 Carbon-carbon Bond Formation & 28.2 Preparation of an Organic Solid

Question 1

In what 2 ways can nitriles be formed? What mechanisms are these reactions examples of?

Answer 1

• Reacting haloalkanes with sodium/ potassium cyanide
• Nucleophilic substitution
• Reacting aldehydes/ ketones with hydrogen cyanide
• Nucleophilic addition

Question 2

Write the general equation for the reaction of haloalkanes to form nitriles, and give the reaction conditions.

Answer 2

• Haloalkane + NaCN -> nitrile + NaX
• In ethanol

Question 3

Write the general equation for the reaction of aldehydes/ ketones to form nitriles, and give the reaction conditions.

Answer 3

• Aldehyde/ ketone + HCN -> hydroxynitrile
• NaCN/ H2SO4

Question 4

What can nitriles react to form, and through which processes?

Answer 4

• Amines through reduction
• Carboxylic acids through acid hydrolysis

Question 5

Write the general equation for the reaction of nitriles to form amines, and give the reaction conditions.

Answer 5

• Nitrile + 2H2 -> amine
• Nickel catalyst

Question 6

Write the general equation for the reaction of nitriles to form carboxylic acids, and give the reaction conditions.

Answer 6

• Nitrile + 2H2O + HCl -> carboxylic acid + NH4Cl
• Heat and dilute hydrochloric acid

Question 7

What are 2 other examples of reactions that increase the length of the carbon chain?

Answer 7

• Alkylation and acylation of benzene

Question 8

What are the 3 stages of purifying an organic solid?

Answer 8

• Filtration under reduced pressure
• Recrystallisation
• Determining the melting point

Question 9

What does filtration under reduced pressure do?

Answer 9

• It separates the solid from the solvent or the liquid reaction mixture

Question 10

How does filtration under reduced pressure work?

Answer 10

• A Buchner flask is fitted with a Buchner funnel with filter paper
• Pressure is created through a vacuum pump that is connected to the flask through a side arm

Question 11

What does recrystallisation do?

Answer 11

• It removes impurities after filtration

Question 12

How does recrystallisation work?

Answer 12

• You choose a solvent that your solid will dissolve in when it’s hot, and the impurities will dissolve in when it’s cold
• Dissolve the impure solid in the minimum possible volume of hot solvent
• Cool, filter (under reduced pressure) and leave to dry

Question 13

What can melting points determine about substances? Give 2 details.

Answer 13

• How pure they are
• Pure samples will have a sharp melting point close to the literature value (impurities lower the melting point, and causes the substance to melt over a range of temperatures)

Question 14

What are 2 methods for determining melting points?

Answer 14

• Using electrically heated melting point apparatus
• Using an oil bath/ Thiele tube