ALCOHOLS AND OXIDATION

Question 1

What is the name of this alcohol?

Answer 1

Pentan-2-ol

Question 2

what is the general formula of alcohols?

Answer 2

C_nH_2n+1OH

Question 3

Alcohol can be subdivided into 3 categories

Answer 3

primary / secondary / tertiary

Question 4

How to recognise a primary alcohol.

Answer 4

The –OH is attached to a C which is attached to only one other carbon atom.
Position: at the end of the carbon chain.

Question 5

How to recognise a secondary alcohol

Answer 5

The –OH is attached to a C which is attached to 2 other carbon atoms.
Position: join to an intermediate carbon atom.

Question 6

How to recognise a tertiary alcohol

Answer 6

The –OH is attached to a C which is attached to 3 other carbon atoms.
Position: Joined to an intermediate C which also has a branched attached.

Question 7

what is the polarity of alcohols?

Answer 7

they are polar because of the OH results in hydrogen bonding high bp and viscosity

Question 8

What happens to the BP and MP of alcohols as the number of OH increases?

Answer 8

The MP and BP increase as more hydrogen bonds can be formed between molecules.

Question 9

what do alcohols dissolve in?

Answer 9

polar liquids such as water

but not in non-polar liquids like hydrocarbons.

Question 10

What happens to the MP and BP of alcohols as the number of carbon atoms increase.

Answer 10

More intermolecular forces = MP and BP increase

Question 11

What happens to the solubility of alcohols in water as the number of carbon atoms increase

Answer 11

Less soluble as makes hydrogen bonding with the -OH group but the rest of the chain made of carbon and hydrogen is non-polar and therefore won’t dissolve in water.

Question 12

primary, secondary or tertiary alcohols?

Answer 12

Secondary

Question 13

primary, secondary or tertiary alcohols?

Answer 13

primary

Question 14

primary, secondary or tertiary alcohols?

Answer 14

Tertiary

Question 15

Primary alcohols can be oxidised to

Answer 15

Aldehyles then carboxylic acids

Question 16

Secondary alcohols can be oxidised to

Answer 16

ketones

Question 17

Tertiary alcohol get oxidise to

Answer 17

NOTHING, tertiary alcohols don’t get oxidised.

Question 18

What is the functional group of aldehyde?

Answer 18

C=O

Carbonyl group

Question 19

What are the oxidising agent used to oxidise primary alcohols to aldehydes then carboxylic acids or secondary alcohols to ketone?

give the result of the reaction

Answer 19

Hot copper oxide (black) become brown solid when it has oxidised an alcohols (itself get reduced, it is an oxidising agent)

Acidified dichromate (orange) become blue when it has oxidised an alcohols (itself get reduced, it is an oxidising agent)

Question 20

Acidified dicrhomate solution can be used to identify between aldehydes and ketones.

What are the other two oxidising agent that can be use for that purpose?

(give results of the reaction/colour change)

Answer 20

Blue Fehling’s solution forms a brick red precipitate

and

Colourless Tollen’s reagent forms a silver mirror.

Question 21

What happen to the O:H ratio as an oxidation takes place?

Answer 21

O:H ratio increase

either number of Oxygen increases or number of hydrogen decreases

Question 22

What happen to the O:H ratio as a reduction takes place?

Answer 22

O:H ratio decreases

Either number of oxygen decreases of number of hydrogen increases

Question 23

Solution A and B were reacted with Blue Fehlings solution.

Solution A stayed blue

Solution B formed a red brick precipitate

Which solution is an aldehyde and which one is a ketone?

Answer 23

Aldehyde can get oxidised further to carboxylic acid, therefore B is the aldehyde as it has been oxidised by the oxidising agent.

Reaction A, did not get oxidised further, therefore it is a ketone.