Organic tests, organic synthesis and NMR spectroscpoy

Question 1

Whats the test for an alkene?

Answer 1

Add bromine water. It should go from orange to clear.

Question 2

What’s the test for a carbonyl group?

Answer 2

2,4- DNP (only works for aldehydes and ketones)

Question 3

What are the two tests for an aldehyde?

Answer 3

• Tollen’s reagent - will observe a silver mirror if present
• Fehling’s solution - Red precipitate should form

Question 4

What’s the test for a carboxylic acid?

Answer 4

NaHCO3 - fizzing from the CO2 being produced.

Question 5

Whats the test for a primary alcohol?

Answer 5

Distil with potassium dichromate (IV) and a moderate concentration of H2SO4

Should go from orange to green

Question 6

Whats the test for a secondary alcohol?

Answer 6

Distil with potassium dichromate (IV) and a moderate concentration of H2SO4

Orange to green

Question 7

Whats the test for a tertiary alcohol?

Answer 7

Distil with potassium dichromate (IV) and a moderate concentration of H2SO4

No aldehyde or ketone formed meaning no reaction

Question 8

How do you test for a phenol?

Answer 8

• Add a few drops of iron (III) chloride solution to the phenol in the water - Purple colour should form
• White fumes of 2,4,6-tribromophenol should be seen

Question 9

How would you test for a methyl group in alcohols, aldehydes or ketones?

Answer 9

NaOH is added to a solution of iodine in potassium iodide solution until most of the colour has gone. The organic compound is warmed with this solution - A yellow solid is formed with the smell of anti-septic. A yellow precipitate is also formed

Question 10

What gives off a sweet smell?

Answer 10

The presence of an ester group

Question 11

What do the peak areas tell you in proton NMR?

Answer 11

How many protons are on the carbon.

Question 12

What does a triplet, singlet and a doublet tell you?

Answer 12

How many protons are in the next carbon.

• Singlet = 0
• Doublet = 1
• Triplet = 2

Question 13

`Explain how a student can distingush between an aldehyde, ketone and a carboxylic acid.

Answer 13

• Add 2,4-DNP to the solutions. If it was either a ketone or an aldehyde, the mixture should go to turn yellow/orange.
• Then add Tollen’s reagent to distinguish whether or not if the mixutre was an aldehyde or not. If it was an aldehyde, the mixture should turn from orange/yellow and a silver mirror should form inside the test tube.