Bromobenzoic acids
| Bromobenzoic acids | ||||||
| Surname | 2-bromobenzoic acid | 3-bromobenzoic acid | 4-bromobenzoic acid | |||
| other names | o -bromobenzoic acid | m -bromo benzoic acid | p -bromobenzoic acid | |||
| Structural formula |
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| CAS number | 88-65-3 | 585-76-2 | 586-76-5 | |||
| PubChem | 6940 | 11456 | 11464 | |||
| Molecular formula | C 7 H 5 BrO 2 | |||||
| Molar mass | 201.03 g mol −1 | |||||
| Physical state | firmly | |||||
| Brief description | crystalline solids | |||||
| Melting point | 147-150 ° C | 155-158 ° C | 254-256 ° C | |||
| boiling point | - | - | - | |||
| pK s value | 2.85 | 3.81 | 3.97 | |||
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GHS labeling |
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| H and P phrases | 302-315-319-335 | 315-319-335 | 302-315-319-335 | |||
| no EUH phrases | no EUH phrases | no EUH phrases | ||||
| 261-305 + 351 + 338 | 261-305 + 351 + 338 | 261-305 + 351 + 338 | ||||
In chemistry , the bromobenzoic acids form a group of substances that are derived from both benzoic acid and bromobenzene . The structure consists of a benzene ring with an attached carboxy group (–COOH) and bromine (–Br) as substituents . Their different arrangement results in three constitutional isomers with the empirical formula C 7 H 5 BrO 2 .
properties
The bromobenzoic acids are crystalline solids. The melting points differ significantly. The 4-bromobenzoic acid, which has the highest symmetry, has the highest melting point. The bromobenzoic acids have a higher acidity than benzoic acid due to the −I effect of the bromine substituent. The p K s values are therefore correspondingly lower (benzoic acid: 4.20).
o -Bromobenzoic acid crystallizes in the monoclinic crystal system in the space group C 2 / c (space group no. 15) with the lattice parameters a = 1482 pm , b = 2590 pm, c = 2590 pm and β = 118.25 °. In the unit cell there are eight formula units .
m -Bromobenzoic acid also crystallizes in the monoclinic crystal system in the space group P 2 1 / a (No. 14, position 3) with the lattice parameters a = 2599 pm, b = 473 pm, c = 607 pm and β = 102 °.
Also p- bromobenzoic acid crystallizes in the monoclinic crystal system in the space group P 2 1 / a (No. 14, position 3) with the lattice parameters a = 2959 pm, b = 615 pm, c = 398 pm and β = 95.5 °. There are 4 formula units in the unit cell.
Individual evidence
- ↑ a b Data sheet 2-Bromobenzoic acid from Sigma-Aldrich , accessed on November 3, 2016 ( PDF ).
- ↑ a b Data sheet 3-Bromobenzoic acid from Sigma-Aldrich , accessed on April 26, 2011 ( PDF ).
- ↑ a b Data sheet 4-Bromobenzoic acid from Sigma-Aldrich , accessed on November 3, 2016 ( PDF ).
- ↑ a b CRC Handbook of Tables for Organic Compound Identification , Third Edition, 1984, ISBN 0-8493-0303-6 .
- ^ G. Ferguson, GA Sim: "X-ray studies of molecular overcrowding. III. The crystal and molecular structure of o-bromobenzoic acid", in: Acta Cryst. , 1962 , 15 , pp. 346-350; doi : 10.1107 / S0365110X62000857 .
- ↑ N. Tanaka, T. Ashida, Y. Sasada, M. Kakudo: "The Crystal Structure of m-Bromobenzoic Acid", in: Bulletin of the Chemical Society of Japan , 1967 , 40 (11), p. 2717; doi : 10.1246 / bcsj.40.2717 .
- ↑ K. Ohkura, S. Kashino, M. Haisa: "The Crystal and Molecular Structure of p-Bromobenzoic Acid" in Bulletin of the Chemical Society of Japan , 1972 , 45 (8), pp. 2651-2652; doi : 10.1246 / bcsj.45.2651 .