Question

(a) Explain the chemical principles behind one type of chromatography (b) Sketch the expected 13C NMR, 'H NMR and major features of the IR spectra of:

Answer 1

Let’s take an example of column chromatography.

In column chromatography, compounds are separated on the basis of difference in adsorption of compound to the adsorbent. Compounds moves through the column at different rate and later collected into separate fractions. Molecules polarity is the key factor for the separation used in column chromatography.

IR data

1100 cm-1 indicates presence of C-O stretch

2900 cm-1 indicates presence of aliphatic C-H stretch

3200 cm-1 indicates presence of O-H stretch

1H NMR data

4.3 (bs, 1H) alcoholic OH proton

3.5 (t, 2H) CH2 attached to CH2

1.9 (q, 2H) CH2 attached CH2 and CH

1.4 (m, 1H) CH attached to two CH3 and CH2

1.0 (d, 6H) two CH3 attached to CH

¹³C NMR data:

60 ppm presence of aliphatic carbon attached to electronegative atom

42 ppm presence of aliphatic carbon nearer to CH2O

25 ppm presence of aliphatic carbon

24 ppm presence of aliphatic carbon