It is a white needle crystal or off-white powder with a slow-heating melting point of 168°C. It is soluble in alcohol and ether and can be sublimated. When exposed to air, it progressively turns red. It is synthesized by combining methyl salicylate and hydroxylamine hydrochloride with sodium hydroxide, followed by acidification.
Salicylhydroxamic acid is a collector with efficient chelating effect on rare metal oxide minerals. It is used in rare metal beneficiation and has the advantages of good selectivity and strong collecting power. Salicylhydroxamic acid is mainly used as a complexing agent or extractant for rare earth ore, copper oxide ore, lead-zinc oxide ore, gold ore, kaolin, etc., as well as organic synthesis intermediates.
Salicylhydroxamic acid has various applications, such as:
Synthesizing phenylboronic acid-based bioconjugates for chromatographic use.
Acting as a ligand to create complexes of Fe(III), Cu(II), Ni(II), and Zn(II).
Acting as a selective collector during the flotation technique for segregating oxide minerals.
The synthesis of salicylhydroxamic acid involved a two-step process. In the first step, methyl salicylate was prepared by esterifying salicylic acid with methanol using 28g (0.2 mol) of salicylic acid, 81 ml of methanol, and 8 ml of concentrated sulfuric acid. In the second step, hydroxylamine was coupled with the methyl salicylate. 13.9 g (0.2mol) of hydroxylamine was mixed with 200 ml of 10% sodium hydroxide solution and cooled. To this, 152.3g (0.1mol) of methyl salicylate was added in small portions with vigorous shaking after each addition to ensure complete dissolution. The mixture was allowed to stand for 36 hours, then acidified with 2M sulphuric acid and cooled. The precipitate was filtered, recrystallized from hot water containing a drop of acetic acid, recooled, and filtered. The yield of white precipitate collected and weighed was 14g of salicylhydroxamic acid.
Preparation and Characterization of Salicylhydroxamic acid and its Complexes with Iron (III), Cobalt (II) and Manganese (II)
ChEBI: Salicylhydroxamic acid is a hydroxamic acid that is N-hydroxybenzamide carrying a phenolic hydroxy group at position 2. It has a role as an antibacterial drug, a trypanocidal drug, an EC 3.5.1.5 (urease) inhibitor and an EC 1.11.2.2 (myeloperoxidase) inhibitor. It is a member of phenols and a hydroxamic acid.
General procedure for the synthesis of salicylhydroxamic acid from salicylaldehyde: To an aqueous solution (6 mL) containing AgNO3 (1.7 mg, 0.01 mmol, 1 mol%) was added vitamin K3 (2.6 mg, 0.015 mmol, 1.5 mol%) dissolved in ethanol (2 mL), followed by the addition of salicylaldehyde (1 mmol) dissolved in THF (2 mL). 1 mmol). Next, NH2OH-HCl (69 mg, 1 mmol) and Et3N (0.14 mL, 1 mmol) were added to the reaction mixture. The final solvent ratio was H2O:EtOH:THF = 3:1:1. The reaction mixture was stirred at room temperature for 30 min under visible light irradiation using a halogen lamp (HALOPAR 20 75 W 230 V 30-GU10; Osram, Italy). The reaction progress was monitored by TLC. After completion of the reaction, EtOAc (30 mL) was added for extraction. The aqueous layer was separated and concentrated under reduced pressure at 25 °C to obtain a pure sample containing silver nanoparticles, which was characterized by UV-Vis and TEM analysis. The organic phase was collected, dried with anhydrous MgSO4 and filtered. The solvent was evaporated under vacuum using a rotary evaporator and the residue was purified by a short silica gel column (eluent: hexane:EtOAc = 1:1) to afford salicylhydroxamic acid (2a-j) in 81-92% yield.
Crystallise the hydroxamic acid from acetic acid. [Beilstein 10 H 98.]
[1] Research on Chemical Intermediates, 2018, vol. 44, # 12, p. 7173 - 7186
