18.3 Reduction Of Aldehydes And Ketones

Question 1

Chemical equation of reduction of aldehyde and ketone

Answer 1

Aldehyde plus reducing agent—> primary alchohol
Ketone plus reducing agent—> secondary alchohol

Question 2

What reducing agent used for reducing aldehyde or ketones are

Answer 2

Sodium tetrahydrioborate NaBH4
Lithium tetrahydridialuminatr LiAlH4 in dry ether

Question 3

Give an example of nucleophilic addition with aldehydes and ketones

Answer 3

They are both to undergo addition reactions with hydrogen cyanide, HCN

Question 4

How is hydrogen cyanide formed?

Answer 4

Bajaj reaction of potential cyanide with dilute sulphuric acid

Question 5

You can carry out the hydrolysis of nitro group by

Answer 5

Reflux with dilute hydrochloric acid
-C(|||) N +HCl+2H2O—> -COOH +NH4Cl

Question 6

Testing for aldehydes and ketones

Answer 6

Step 1 is to test for carbonyl acid
Step 2 is to distinguish between aldehydes and ketones

Question 7

How to test for carbonyl acid

Answer 7

The condensation reaction of an aldehyde or ketone with 2,4-dinitrophenylhydrazine

Question 8

How to distinguish between aldehydes and ketones

Answer 8

Aldehydes can be further oxidised to form carboxylic acids, but ketones cannot be oxidised easily. Therefore use Tollen’s reagent or Fehling’s solution

Question 9

What is the positive result for tollen’s reagent?

Answer 9

Silver atoms being formed inside the tube

Question 10

What is the positive result for fehling’s test

Answer 10

When he cheated the blue solution becomes orange

Question 11

What is infrared spectroscopy?

Answer 11

A technique for identifying compounds based on the change in vibrations of particular atoms when infrared radiation or specific frequencies is absorbed

Question 12

What is infrared spectroscopy?

Answer 12

The frequency of absorption of radiation which stimulates larger vibrations in bonds to allow the absorption of energy