US Patent 4707294
Preparation of alcoholic Hydroxylamine Solution from Hydroxylammonium SulfateAbstract:Solid hydroxylammonium sulfate is reacted with an alcohol solution of an alkali metal hydroxide or alkoxide to produce an alcoholic hydroxylamine liquid phase and a sulfate-containing solid phase. The liquid phase may be used for further reactions such as oxidations, hydroxamic acid production or neutralization to other hydroxylammonium salts. The different bases behave differently with regard to suitable and preferable solvents and temperatures.
Notes on Reactants:
The concentration of the NaOH in methanol or ethanol is not critical, but it is preferred to operate as near to the solubility limit as possible without creating so viscous a solution as to make the agitation difficult.
NaOH in ethanol should be used at 10*C (no higher than 30*C, preferably below 20*C).
KOH in methanol IS NOT SUITABLE for this reaction. Extremely low yields result. However, KOH in ethanol is VERY suitable.Example 1:Hydroxylamine FreebaseA solution of methanolic NaOH was prepared by mixing NaOH (17.2g, 0.43mol) with absolute methanol (150ml) in a 250ml flask.
In the meantime, a 500ml, 3-neck flask was fitted with a thermometer, dropping funnel and N
2 inlet (inert atmosphere) and a mag. stirrer. Solid hydroxylamine sulfate (35g, 0.213mol) was placed in the flask with methanol (50ml) and the flask was placed in an ice-water bath over a stir plate. With vigorous stirring, the methanolic NaOH solution was added slowly (over 5 minutes) using the dropping funnel while keeping the reaction temperature below 10*C. After the addition was complete, stirring was continued for 1.5 hours with cooing (5-10*C). A white slurry formed and was filtered. The cake was washed with 25ml of methanol. The clear, colorless filtrate (pH 12.5) was analyzed for free hydroxylamine by mixing with known excess of MEK (40g) and adjusting the pH to 7 with conc. H
2SO
4 (2.5g). Methyl ethyl ketoxime formed was determined by GC to correspond to free hydroxylamine.
Yield: 87.4%The white filter cake (34.2g) of sodium sulfate by dissolving in water (150ml) and mixing the excess of MEK (40g) and titrating with 50% NaOH solution (3.9g) to pH 7. The amount of hydroxylamine sulfate left in the cake represented 11.4% of the total.
Example 8:Hydroxylamine freebaseThe experiment was conducted using the same equipment as Example 1. Sodium hydroxide (17.2g, 0.43mol) was dissolved in methanol (200ml) and the solution was placed in the 500 ml flask. With stirring and cooling (5-10*C) solid hydroxylamine sulfate was added using a spatula over 20 minutes. The mixture was then stirred for 1.5 hours more and the white slurry was filtered.
The filtrate on analysis in the usual manner showed 86.6% of the hydroxylamine. The solid on analysis was found to contain 10.4% of hydroxylamine sulfate that was started with. Example 11:Hydroxylamine freebaseSodium hydroxide pellets (17.2g, 0.43mol) were stirred over nearly two hours in a 500ml flask with absolute ethanol (200ml) till a clear solution was obtained. The solution was placed in a 250ml, 3-neck flask fitted with thermometer and a drying tube (Drierite TM was used). A stirring rod was placed in the solution along with hydroxylamine sulfate (35g, 0.213mol) and absolute ethanol (20ml). As the contents were stirring vigorously over the stir-plate with cooling in an ice-water bath (5-10*C), the ethanolic NaOH was added slowly over 10 minutes. The slurry was filtered and the cake washed with 25ml of absolute ethanol.
The white cake (38.6g) was analyzed in the usual manner and was found to contain hydroxylamine sulfate as 4.7% of the mass.
The clear filtrate was analyzed by GC after mixing with excess MEK (40g) and adjusting the pH to 7 with conc. Sulfuric acid. Yield: 88.3%Example 26:Hydroxylamine NitrateA solution of sodium methoxide in methanol produced by dissolving sodium (10g, 0.435mol) in methanol (150ml) was stirred with hydroxylamine sulfate (35g, 0.213mol) in an ice-water bath (5-10*C) for more than 2 hours. The slurry was filtered and the clear methanolic filtrate with cake-wash (pH 9.2) was mixed with conc. Sulfuric acid (0.8g) to pH 8.0. The thin white solid produced was filtered off and the clear filtrate was placed in a 500ml flask with a mag. stirrer. While cooling in ice-water and stirring, conc. Nitric acid (35.5g) was added til the pH was 2.8.
The clear methanolic solution of hydroxylamine nitrate (273.3ml) was found to contain 37.99g of the nitrate (13.9g/100ml). Yield: 92.7%Example 27:Hydroxylamine Phosphate:A solution of hydroxylamine sulfate (210g, 1.28mol) in methanol (228ml) at a concentration of 4.84g/100ml. The solution was placed into a 250ml 3-neck flask with a thermometer, stirrer and a dropping funnel. While stirring above an ice-water bath (5*C), 85% orthophosphoric acid (8.0g, 0.069mol) was added slowly til the pH of the solution went from 11.8 to 8.0. A white slurry is produced. Stirring at 5*C was continued for 15minutes more. Then, the solution was filtered and the solid weighed 11.8g. this was recrystallized from hot water the phosphate was collected.
Yield: 85.4% that had; MP: 175*CExample 28:Hydroxylamine OxalateA solution of hydroxylamine in methanol (680ml) as in Example 27 was used (pH 11.
. Conc. Sulfuric acid was added slowly to adjust the pH to 8.0 and the thin white precipitate formed was filtered off and the clear filtrate placed in a 1L flask with mag stirring. The flask was placed on an ice bath (5*C) and oxalic acid (45g, 0.5mol) was added dissolved in methanol (100Mml) slowly with cooling and stirring. The thick white slurry thus produced was filtered to give 84.8g of cake.
The cake was recrystallized from hot water to give the oxalate in 94.6% yield. It had; MP: 192*C (with decomp.)Example 29:Hydroxylamine FreebaseA 500ml, 3-neck flask was fitted with a thermometer, reflux-condensor and drying tube. Freshly cut sodium (10g, 0.435mol) was placed in the flask and absolute methanol (175ml) was carefully added with cooling. After the sodium was completely dissolved in methanol forming a clear solution of sodium methoxide, solid hydroxylamine sulfate (35g, 0.213mol) was added over 2 minutes. No significant heat was evolved. The mix was stirred with cooling (10*C) in ice-water bath with mag stirring for 1 hour. Subsequently, cooling was removed and vigorous stirring continued for 2 hours. By this point a slurry had formed and this was filtered and the cake washed using more methanol.
The total filtrate (162g) was analyzed potentiometrically and found to contain hydroxylamine corresponding to 87.5% yield. The filtrate was virtually water-free. Unused hydroxylamine sulfate amounted to 1.6%.References Cited:
US Patent 4551323
USSR 168305