2-Amino-5-bromopyridine is an organic compound characterized by a pyridine ring substituted with an amino group and a bromine atom. Its molecular formula is C5H5BrN2, indicating the presence of five carbon atoms, five hydrogen atoms, one bromine atom, and two nitrogen atoms. The compound features a pyridine structure, which is a six-membered aromatic ring containing one nitrogen atom. The amino group (-NH2) is located at the 2-position, while the bromine atom is at the 5-position of the pyridine ring, influencing its reactivity and properties. 2-Amino-5-bromopyridine is typically a solid at room temperature and is soluble in polar solvents. It is used in various chemical syntheses, including the preparation of pharmaceuticals and agrochemicals. The presence of both the amino and bromine substituents allows for further functionalization, making it a versatile intermediate in organic synthesis. Safety precautions should be taken when handling this compound, as it may pose health risks if ingested or inhaled.

2-Amino-5-bromo-pyridine–4-hy-droxy-benzoic acid

We have recently reported the crystal structures of 2-amino-5-bromopyridine-benzoic acid, 2-amino-5-bromopyridinium 3-aminobenzoate and 2-amino-5-bromopyridinium hydrogen succinate from our laboratory. In continuation of our studies of pyridinium derivatives, the crystal structure determination of the title compound has been undertaken. A hot methanol solution (20 ml) of 2-amino-5-bromopyridine (43 mg, Aldrich) and 4-hydroxybenzoic acid (34 mg, Merck) were mixed and warmed over a heating hotplate magnetic stirrer for a few minutes. The resulting solution was allowed to cool slowly to room temperature and brown needles of (I) appeared after a few days.[1]

The asymmetric unit of the title compound consists of two crystallographically independent 2-amino-5-bromopyridine molecules (A and B) and two 4-hydroxybenzoic acid (A and B) with comparable geometries. The bond lengths (Allen et al., 1987) and angles in the title compound (Fig. 1) are within normal ranges and comparable with the related structures (Quah et al., 2010, 2008a, b). Each 2-amino-5-bromopyridine molecule is approximately planar, with a maximum deviation of 0.020 (8) ? for atom C4A in molecule A and 0.021 (8) ? for atom C1B in molecule B. In molecule A, the 2-amino-5-bromopyridine molecule is inclined at dihedral angle of 28.8 (3) and 55.7 (3)° with the C6A—C11A and C6B—C11B phenyl rings, respectively. The correspondence angles for molecule B are 45.6 (3) and 27.2 (3)°.

Normal coordinate analysis of 2-amino-5-bromopyridine

Aminopyridine and its derivatives are currently finding increasing applications for several reasons. At the outset, they represent a group of compounds used as reagents in analytical chemistry. Secondly, some of them show anesthetic properties and are used as drugs for certain brain diseases. Sasaki et al. recorded infrared and Raman spectra for iodine dichlorides and iodine dibromides of 2-, 3-and 4-aminopyridines in solids and they have also measured pyridine Raman spectra in methanol solutions. The spectra of 2-amino-5-bromopyridine is not reported and analysed in the literature. Hence this study has been undertaken to record and study the FTIR and laser Raman spectra of title compound and to assign the normal mode of vibrations on the basis of normal coordinate analysis.[2]

Wilson's F-G matrix method was used for the normal coordinate calculations. Assuming NH2 group as single mass point, the present molecule 2-amino-5-bromopyridine belongs to Cs point group symmetry. The molecule has 11 atoms and one expects 27 fundamental vibrations which fall into 19 in-plane vibrations of the a′ species and 8 out-of-plane vibrations of the a′′ species. The three hydrogen atoms left around the ring in 2-amino-5-bromopyridine give rise to three CH stretching, three CH in-plane bending and three CH out-of-plane bending vibrations. The heteroaromatic structure shows the presence of CH stretching vibrations in the region 3000–3100 cm?1 which is the characteristic region for ready identification of this structure. The bands at 1139, 1087 and 1025 cm?1 in 2-amino-5-bromopyridine are assigned to CH in-plane bending vibrations which belong to a′ species. These assignments are in agreement with values given in the literature.

References

[1]Quah CK, Hemamalini M, Fun HK. 2-Amino-5-bromo-pyridine-4-hy-droxy-benzoic acid (1/1). Acta Crystallogr Sect E Struct Rep Online. 2010 Jul 7;66(Pt 8):o1935-6. doi: 10.1107/S1600536810025924. PMID: 21588263; PMCID: PMC3007384.

[2]Sundaraganesan, N et al. “Vibrational spectra, assignments and normal coordinate analysis of 2-amino-5-bromopyridine.” Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy vol. 59,5 (2003): 1113-8. doi:10.1016/s1386-1425(02)00285-8