Saccharin

Saccharin, an "artificial sweetener", is the trade name for the organic compound 1,1-dioxo-1,2-benzothiazol-3-one (also known as benzoic sulfimide). It has been used widely in the production of "diet" foods and drinks because it has effectively no food energy, it passes through the human digestive system without being digested. Saccharin was first discovered by accident in 1878 by Constantin Fahlberg when he was analysing the chemical compounds in coal tar and discovered a sweet-tasting substance on his hands.

Saccharin was produced from toluene in several steps:
1/ chlorosulfonic acid is used to produce two sulfonated isomers of toluene:

2/ The ortho isomer is then separated, and reacted with ammonia to produce the sulfonamide:

3/ The sulfonamide product above undergoes oxidation to produce the carboxylic acid which then cyclicizes to form saccharin:

Further Reading
Molecular Formula
Functional Groups
Structural Isomers - Alkanes
Structural Isomers - Alkenes


Suggested Study Questions

1. Write the molecular formula for
   • toluene
   • saccharin
2. For each of the 3 steps shown in the synthesis of saccharin, circle the site on the reactant molecule where the reaction takes place.
3. In step 3 the carboxylic acid is formed and then the molecule forms a ring (cyclicizes)
   • What functional group is present in a carboxylic acid?
   • Draw the probable structural formula for the carboxylic acid produced in step 3.
4. What functional group is present in an amide? 
5. Toluene is an aromatic compound. Aromatic compounds contain a substituted benzene ring (C₆H₆). Circle the benzene ring  on the structural formula of toluene.
6. Given the formula for chlorosulfonic acid in the article, write the formula for each of the following:
   • fluorosulfonic acid
   • bromosulfonic acid
7. Two structural isomers of  the sulfonated product are shown in step 1. A third structural isomer is also possible. Draw the structural formula of this other isomer.
8. If the para isomer from step 1 reacts with ammonia in a similar manner to the ortho isomer, give the structural formula likely for the compound formed during this reaction.
9. Why do you think the ortho isomer must be separated from the para isomer before step 2?