Calculation for C19H12O6S + 2H2O = 7·92% S.
These analyses show with but little doubt that the substance has the composition indicated above i.e. C19H12O6S + 2H2O. The reaction therefore which takes place between ortho-sulpho benzoic acid and resorcin from its analogy to that taking place between phthalic anhydride and resorcin may be represented thus, as shown by Baeyer in his second paper (Ann. 202. S. 43)
Representing the formation of the anhydride as the first action.
| COOH | CO | |||||
| ╱ | ╱ | ╲ | ||||
| C6H4 | = C6H4 | O + H2O | ||||
| ╲ | ╲ | ╱ | ||||
| SO2OH (o) | SO2 |
and the action of resorcin on this anhydride thus.
| O | ||||||||||
| ╱ | ╲ | |||||||||
| (HO)H4C6 | C6H4(OH) | |||||||||
| ╲ | ╱ | |||||||||
| CO | OH | C | ||||||||
| ╱ | ╲ | ╱ | ╱ | ╲ | ||||||
| C6H4 | O + C6H4 | = | C6H4 | O + 2H2O. | ||||||
| ╲ | ╱ | ╲ | ╲ | ╱ | ||||||
| SO2 | OH (m) | SO2 |
The substance thus formed would naturally receive the name Sulphonfluoresceïn from its analogy with Fluoresceïn.
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| Sulphonfluoresceïn. | Fluoresceïn. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Properties of S.fluoresceïn.
This compound shows a marked similarity to the fluoresceïn described by Baeyer as would naturally be expected from its great similarity of composition and constitution, but it also shows decided differences which may be attributed to the replacement of CO by SO2.