Aldehydes & Ketones, Amines, Optical Isomerism

Question 1

Nucleophilic Addition ( addition of NaBH₄)

Answer 1

slightly acidic, aqueous
Reagent - NaBH
reaction -> REDUCTION
(does not work for carboxylic acids because needs a stronger reducing agent because it has OH & OR groups pushing electrons towards the carbon which makes it more stable)

Question 2

Nucleophilic Addition (addition of HCN)

Answer 2

• acidic conditions (for H⁺)
• aqueuous
  product: Hydroxynitriles
  reagent - KCN + dilute acid

Question 3

Reduction of Aldehydes and Ketones

Answer 3

Question 4

Formation of Racemic Mixtures of Carbonyl Compounds

Answer 4

• When aldehydes and unsymmetrical ketones react with Cyanide ( i.e KCN) followed by dilute acid, they form mixtures enantiomers.
• When there is an equal amount of emanations a racemic is formed.
• this is because the C=O group is planar so the :CN- ion can attack from either above or below the molecule.

Question 5

Making Esters

Answer 5

• Esters are formed by the reaction of a caboxylic acid and alcohol.
  e.g Ethanoic acid + ethanol ⇌ ethyl ethanoate + water
  ( CH₃COOH + CH₃CH₂OH ⇌ CH₃COOCH₂CH₃ + H₂O)
• the esters formed are less soluble in water than the carboxylic acid and alcohol, less dense and can be separated via funnel.

Question 6

Ester Hydrolysis

Answer 6

insert pic

• when an ester is heated under reflux with dilute acid, a carboxylic acid and alcohol are formed.
• the reaction is reversible and the yield of products is poor
• when an ester is heated under reflux with dilute alkali (e.g NaOH), an alcohol and carboxylate salt are formed.

Question 7

What is an ester link?

Answer 7

the formation of bonds between glycerol and fatty acids

Question 8

What caused the properties of soap?

Answer 8

• salt contains a hydrophobic ( fatty acid chain) end and a hydrophilic end (carboxylate ion).
• the hydrophobic end mixes with grease and the hydrophilic end mixes with water
• allowing for both the water and grease to be washed away together.

Question 9

What are the Acyl groups?

Answer 9

put pic

Question 10

Why are acid anhydrides less reactive than Acyl Chlorides?

Answer 10

• the ester group attached to the C is not as electronegative as the chloride group for an acyl chloride

Question 11

Polarisation of Acyl groups

Answer 11

• The oxygen atom is more electronegative than the carbon atom
• therefore permanent dipole-dipole forces in each acyl molecule
• the oxygen atom attracts the electron pair to itself more strongly, becoming more negative
• and the C atoms form delta positives
• the delta positive C is attacked by nucleophiles
• the degree of polarisation, hence the extent of nucleophilic attacks, depends on the groups around C atom in in the acyl group

Question 12

Products formed from Nucleophilic Addition Elimination

Answer 12

• ## the reactions with acyl chlorides occur at cold or room temperatures and are very vigorous/violent. The reactions with acid anhydrides are less vigorous and may need gentle heating.