Structure Determination of Chloramphenicol or Chloromycetin

Structure Determination of Chloramphenicol or Chloromycetin

Structure Determination of Chloramphenicol or Chloromycetin

Synthesis of Chloramphenicol



Structure of chloramphenicol can be established on the basis of following chemical evidences-
1. Elemental analysis and molecular weight shows that the molecular formula of of chlorampheicol is C11H12O5N2Cl2.
2. Its absorption spectrum is similar to that of nitrobenzene.
3. The presence of a nitro group was confirmed by the reduction of chloramphenicol with tin and hydrochloric acid (Sn/HCl), followed by diazotization and then coupling to yield an orange precipitate with β-naphthol.
4. Chloramphenicol when reduced with palladium it gives a product which has an absorption spectrum very similar to that of para-toluidine and the resulting solution gives a positive test for ionic chlorine.
5. Hydrolysis in either acidic or alkaline medium, chloramphenicol produces dichloroacetic acid together with an optically active base C9H12O4N2.
C11H12O5N2Cl2 ---H3O+ ---> Cl2CHCOOH + C9H12O4N2
6. The resulting base was shown to contain a primary amino group, and on being treated with methyl dichloroacetate, the base regenerated chloramphenicol.
7. Chloramphenicol on treatment with acetic anhydride in pyridine is converted into a diacetyl derivative, whereas the base obtained from chloramphenicol yields a triacetyl derivative on similar treatment. This is suggesting that chloramphenicol probably contains two -OH groups.
8. When the chloramphenicol base is treated with periodic acid two molecules of the periodic acid are consumed with the formation of one molecule each of ammonia, formaldehyde and para-nitrobenzaldehyde respectively. However, these products may be accounted for provided the base is assumed to be 2-amino-1-p-nitrophenylpropane-1,3-diol.
chloramphenicol Base On the basis of above evidences we can write the structure of Chloramphenicol as-
Structure of chloramphenicol