Chemistry of Cooking

Question 1

What does cooking do to proteins?

Answer 1

Causes proteins to denature

Question 2

Many flavour molecules are…

Answer 2

Aldehydes or ketones

Question 3

What functional group do aldehydes and ketones contain?

Answer 3

Carbonyl c—o

Question 4

What is the carbonyl group structure?

Answer 4

C double bond O

Question 5

In aldehydes where is the carbonyl group?

Answer 5

On an end carbon

Question 6

In ketones where is the carbonyl group?

Answer 6

Joined to two other carbons

Question 7

What can aldehydes and ketones be distinguished by?

Answer 7

Acidified potassium dichromate, fehlig’s solution or Tollen’s reagent

Question 8

Is the carbonyl functional group polar or non polar?

Answer 8

Polar

Question 9

What does the polarity of the carbonyl functional group lead to?

Answer 9

Permanent dipole- permanent dipole attractions between molecules

Question 10

Describe the boiling points of aldehydes and ketones in comparison to their equivalent alcohols

Answer 10

Much lower boiling points than the equivalent alcohols which have hydrogen bonding

Question 11

Describe the water solubility of aldehydes and ketones

Answer 11

Low molecular mass aldehydes and ketones are water soluble due to hydrogen bonds forming between the carbonyl group and the water molecules

Question 12

Describe the volatility of aldehydes and ketones

Answer 12

Low molecular mass aldehydes and ketones are very volatile

Question 13

Describe the colour change in acidified potassium dichromate

Answer 13

Orange dichromate ions are reduced to green chromium (iii) ions

Question 14

Describe the colour change in Fehlig’s solution

Answer 14

Blue copper (ii) ions are reduced to give a precipitate of red/brown copper (I) oxide

Question 15

Describe the colour change in Tollens’ reagent

Answer 15

Colourless silver (I) ions are reduced to the metal leaving w thin layer of silver metal on the test tube. ‘Silver mirror test’