Dihydroxybenzoic acids
In chemistry, the dihydroxybenzoic acids form a group of aromatic compounds that are derived from both benzoic acid and dihydroxybenzenes . The structure consists of a benzene ring with an attached carboxy group (-COOH) and two hydroxyl groups (-OH) as substituents . Their different arrangement results in six constitutional isomers with the empirical formula C 7 H 6 O 4 .
| Dihydroxybenzoic acids | ||||||||||||
| Surname | 2,3-dihydroxybenzoic acid | 2,4-dihydroxybenzoic acid | 2,5-dihydroxybenzoic acid | 2,6-dihydroxybenzoic acid | 3,4-dihydroxybenzoic acid | 3,5-dihydroxybenzoic acid | ||||||
| other names | β-resorcylic acid |
Gentisic acid hydroquinonecarboxylic acid |
γ-resorcylic acid |
Protocatechuic acid |
α-resorcylic acid |
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| Structural formula |
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| CAS number | 303-38-8 | 89-86-1 | 490-79-9 | 303-07-1 | 99-50-3 | 99-10-5 | ||||||
| PubChem | 19th | 1491 | 3469 | 9338 | 72 | 7424 | ||||||
| Molecular formula | C 7 H 6 O 4 | |||||||||||
| Molar mass | 154.12 g mol −1 | |||||||||||
| Physical state | firmly | |||||||||||
| Melting point | 204-206 ° C | 208-211 ° C (dec.) | 203-207 ° C | 165 ° C (dec.) | 197-200 ° C (dec.) | 236-238 ° C (dec.) | ||||||
| pK s value (25 ° C) | 2.94 | 3.29 | 2.97 | 1.3 | 4.48 | 4.04 | ||||||
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GHS labeling |
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| H and P phrases | 315-319-335 | no H-phrases | 302-315-319-335 | no H-phrases | 315-319-335 | no H-phrases | ||||||
| no EUH phrases | no EUH phrases | no EUH phrases | no EUH phrases | no EUH phrases | no EUH phrases | |||||||
| 261-305 + 351 + 338 | no P-phrases | 261-305 + 351 + 338 | no P-phrases | 261-305 + 351 + 338 | no P-phrases | |||||||
Individual evidence
- ↑ a b Datasheet 2,3-Dihydroxybenzoic acid from Sigma-Aldrich , accessed on March 7, 2017 ( PDF ).
- ↑ a b data sheet 2,4-Dihydroxybenzoic acid from Sigma-Aldrich , accessed on March 7, 2017 ( PDF ).
- ↑ a b Data sheet 2,5-Dihydroxybenzoic acid from Sigma-Aldrich , accessed on March 7, 2017 ( PDF ).
- ↑ a b data sheet 2,6-dihydroxybenzoic acid from Sigma-Aldrich , accessed on March 7, 2017 ( PDF ).
- ↑ a b Data sheet 3,4-Dihydroxybenzoic acid from Sigma-Aldrich , accessed on March 7, 2017 ( PDF ).
- ↑ a b Data sheet 3,5-Dihydroxybenzoic acid from Sigma-Aldrich , accessed on March 7, 2017 ( PDF ).
- ^ A b c d D'Ans-Lax: Pocket book for chemists and physicists , 3rd edition, Volume 1, Springer-Verlag, Berlin-Göttingen-Heidelberg 1967 ( ChemieOnline - pK b and pK s values ).
- ^ A b D'Ans-Lax: Pocket book for chemists and physicists , 3rd edition, Volume 1, Springer-Verlag, Berlin-Göttingen-Heidelberg 1967 ( ChemieOnline - pK b and pK s values ).
Web links
2,3-dihydroxybenzoic acid
2,4-dihydroxybenzoic acid
2,5-dihydroxybenzoic acid
2,6-dihydroxybenzoic acid
3,4-dihydroxybenzoic acid
3,5-dihydroxybenzoic acid