Analysis coursework

Question 1

DNP derivative test -

How would melting point of derivative different if recrystallisation was not carried out?

Answer 1

The melting point is lower

Melting point range is wider

Question 2

How can compounds be identified through the melting points of the derivatives?

Answer 2

By comparing them with known melting points of derivatives of compounds they are looking for

Question 3

Observation for positive reaction with sodium hydrogen carbonate

Answer 3

Effervescence (due to carboxylic acid)

Question 4

Why is it important to only add a few drops of acidified potassium dichromate when testing compounds?

Answer 4

Excess orange reagent would make it hard to see the colour change from orange to green

Question 5

Two compounds with same functional groups - can infrared spec. be used to differentiate? [2]

Answer 5

They contain the same functional groups so will have the same absorptions
However the the spectrum in the fingerprint region may be used against known spectra as a means of identification

Question 6

Two esters with same functional group and Mr, can mass spec. be used to differentiate? [2]

Answer 6

Have same molecular mass so M+ ion will be at same m/z value
(Fragmentation pattern will differ (dependent) but will be difficult to interpret)
Best to compare with library spec.

Question 7

Points to mention when asked if two compounds can be differentiated using H NMR

Answer 7

Number of peaks
Chemical shift/type of environment
Number of peaks in each region
Areas under each peak