Oxidation and the chemistry of cooking

Question 1

What are alcohols?

Answer 1

Carbon compounds that contain the hydroxyl functional group (-OH)

Question 2

Rules of naming alcohols?

Answer 2

• numbering from the side which gives the -OH the lowest number
• ensuring the -OH takes priority over any branches

Question 3

What is a primary alcohol?

Answer 3

When the carbon bonded to the hydroxyl group is bonded to a maximum of 1 other carbon

Question 4

What is a secondary alcohol?

Answer 4

When the carbon bonded to the hydroxyl group is bonded to 2 other carbons

Question 5

What is a tertiary alcohol?

Answer 5

When the carbon bonded to the hydroxyl group is bonded to 3 other carbons

Question 6

What does the boiling point of alcohols increase as they have more -OH groups?

Answer 6

Adding hydroxyl groups means the molecules are being held together by hydrogen bonding meaning much more energy has to be supplied to overcome the hydrogen bonding

Question 7

Name 2 suitable oxidising agents:

Answer 7

• Acidified potassium dichromate
• Hot copper (||) oxide

Question 8

When tertiary alcohols are oxidised what happens?

Answer 8

Tertiary alcohols do no undergo oxidation readily

Question 9

When primary alcohols are oxidised what happens?

Answer 9

They produce aldehydes

Question 10

When secondary alcohols are oxidised what happens?

Answer 10

They produce ketones

Question 11

How can aldehydes and keystones be identified?

Answer 11

By the presence of the carbon - oxygen double bond (carbonyl group)

Question 12

Where is the carbonyl group in an aldehyde?

Answer 12

At the end of the carbon chain and has a hydrogen atom attached to it

Question 13

Where is the carbonyl group in a ketone?

Answer 13

Joined to 2 other carbon atoms and does not have a hydrogen attached to it

Question 14

What takes priority when naming branches aldehydes and ketones?

Answer 14

The carbonyl functional group

Question 15

When naming a ketone what is it necessary to specify?

Answer 15

The number of the carbonyl group
E.g. the 3 in 4-methyloctan-3-one

Question 16

What are the 3 most common oxidising agents used to oxidise aldehydes?

Answer 16

Fellings solution, Tollens reagent and acidified potassium dichromate

Question 17

Can ketones oxidise?

Answer 17

No

Question 18

Can aldehydes oxidise?

Answer 18

Yes

Question 19

Colour change observed when using acidified potassium dichromate solution?

Answer 19

Orange to green

Question 20

Colour change observed when using Fehlings solution?

Answer 20

Blue to orange/red

Question 21

Colour change observed when using tollens reagent?

Answer 21

Colourless to silver

Question 22

Oxidation of primary alcohols:

Answer 22

Primary alcohols -> Aldehydes -> carboxylic acids

Question 23

Oxidation of secondary alcohols:

Answer 23

Secondary alcohol -> ketone

Question 24

Oxidation of tertiary alcohols:

Answer 24

Not readily oxidised

Question 25

Oxidation occurs when… (in relation to oxygen)

Answer 25

There is an increase in the oxygen to hydrogen ratio

Question 26

Reduction occurs when… (in relation to oxygen)

Answer 26

There is a decrease in the oxygen to hydrogen ratio

Question 27

When naming carboxylic acids ____________ takes priority

Answer 27

The carboxyl group