|Preparation of Polyphosphoric acid(s)||Bookmark|
Edit: Title Change
Found by Billy Boy
Acetic Anhydride from peracetic acid!
The following text was taken from book titled Industrial Chemicals, which is all about industrial processes for making chemicals for organic industry. I cant remember name of the author, but I have copied few pages from it and re-written them:
ACETIC ANHYDRIDE (CH3CO)2O
CH3CHO + O2 ----> CH3COOOH (peracetic acid!)
CH3COOOH + CH3CHO ----> (CH3CO)2O + H2O
Basis -1 ton acetic anhydride:
Acetaldehyde 2400 lbs Diluent 3300 lbs
Catalyst 2 lbs Air variable
Air is bubbled trough liquid acetaldehyde in a reactor in the presence of 2% (based on the weight of acetaldehyde) catalyst, such as a mixture of copper and cobalt acetates or manganese acetate, wich prevents the formation of explosive amounts of peracetic acid. Approximately 1.4 parts of acetic acid per part of acetaldehyde is present as a diluent to promote acetic anhydride formation. Methyl or ethyl acetate, triacetin, or benzene may also be used as diluents, and the last is generally utilized in conjuction with acetic acid as a withdrawing agent in subsequent vacuum distilation to allow separation of the reaction mixture from water at lower temperatures.
The reactor is maintained at a temperature of 50-60 °C, and the pressure is approx. 60 psi. The overhead from the crude vacuum coulumn is fractionated in a aldehyde column, yielding acetaldehyde for recycle as the overhead and water and diluent as bottoms. The diluent is returned to reactor after the water is separated.
The dehydrated mixture of acetic anhydride and acetic acid from the bottom of the crude vacuum column is separated by distillation. Acetic acid is removed as overhead, and the acetic anhydride is withdrawn from a bottom plate. The catalyst is taken from the bottom to be re-used. The acetic anhydride may be further purified by vacuum distillation.
Variations of this process involve type and amount of diluent, and several stages in reactor (with oxygen injection in each stage) under milder reaction conditions.
Present trends are away from air and toward oxygen. In one continuous process using ethyl acetate as diluent and a catalyst concentration of 1% (cobalt acetate and copper acetate in a weight ratio 2:1), the reaction is carried out at 50°C and 45 psi. Oxygen is injected at various points along the path of liquid travel, with overall oxygen supply limited to 1-2% excess. Under these conditions, 95% conversations of acetaldehyde are obrained. Both acetic anhydride and acetic acid are produced in a 50:50 weight ratio.
The same process carried out in the absence of diluent gives a higher oxidation rate but yields a lower acetic anhydride-acetic acid ratio(ca. 2:3)
Now the most interesting part of this process is when the peracetic acid reacts with acetaldehyde to form acetic anhydride + water
CH3COOOH + CH3CHO ===> (CH3CO)2O + H2O
We know that peracetic acid can be made with CH3COOH + H2O2 + H2SO4 so I propose next:
1. React CH3COOH + H2O2 + H2SO4 to get 15% solution of CH3COOOH in acetic acid (wich also acts as a diluent for next step)
2. React acetaldehyde with our 15% solution of CH3COOOH to get acetic anhydride (with a higher molar ratio of acetaldehyde to insure higher conversation of peracetic to anhydride)
Now, I know they operate this process @45-60 psi but IMO this is just to promote CH3CHO + O2
===> CH3COOOH convertion.
I bet you 10$ if we react acetaldehyde with peracetic acid at atmospheric pressure we should get some acetic anhydride. Even if the yield would be some 30-50% it is still dirt cheap process, and MOST OF ALL totally OTC!
The only real problem I see here is that if we make peracetic acid via H2O2/CH3COOH we can only get something like 15% solution, can this be too diluted for step no.2?
Suggestions for acetaldeyde by PolytheneSam:
Maybe this would work for
EtOH --> CH3CHO
Note the use of the Cr redox couple.
PolytheneSam: "Re: potassium dichromate" (Acquisition Forum)
|HI acid via tetralin/decalin||Bookmark|
Found by Ballzofsteel
HI via tetralin/decalin
Reference: Patent US5693306
Procedure for HI acid via tetralin/decalin:
Flaky solid iodine of 40 g was dissolved in tetrahydronaphthalene of 160 g charged in a flask of 500 ml at 40.degree. C. to prepare a tetrahydronaphthalene solution of iodine. A flask of 500 ml was charged with tetrahydronaphthalene of 40 g and heated to 200.degree. C. while stirring. The iodine solution prepared above was continuously added thereto over a period of 2 hours while maintaining the above temperature to react them. Crude hydrogen iodide gas generated as the reaction went on was introduced into a 10% sodium hydroxide aqueous solution of 1 liter to absorb the whole amount thereof. A weight change in this aqueous solution was measured with the lapse of time, and the end point of the first reaction was set at the point where the change thereof was not observed. The yield of the crude hydrogen iodide was 94.6%, and the purity thereof was 99.5% or more. The concentrations of organic components and water contained therein were 200 ppm and 30 ppm, respectively. The concentrations of tetrahydronaphthalene and naphthalene contained in the liquid remaining after the reaction were 94.1% and 5.2%, respectively. The results thereof are summarized in Table 2 and Table 3
|HI acid via ascorbic acid and iodine||Bookmark|
Found by WizardX
HI from I2 + Ascorbic acid
Ascorbic Acid C6H8O6
MW= 176.12 grams/mole
MP: 190-192 *C
pH = 3 (@5mg/ml concentration)
pH = 2 (@50mg/ml concentration)
Redox potential at first stage is pH 5.0 is E = +0.127 Volts.
One grams dissolves in 3 mls of water.
Possesses relatively strong reducing powers, decolourizes many dyes.
Aqueous solutions are rapidly oxidized by air. The reaction is accelerated by alkalies, iron and copper.
Making HI from I2 and Ascorbic Acid.
C6H8O6 Ascorbic acid.
C6H6O6 Dehydroascorbic acid.
C6H8O6 ==>> C6H6O6 + 2H(+) + 2e E = +0.127 Volts
I2 + 2e ==>> 2I(-) E = +0.540 Volts
C6H8O6 + I2 ==>> C6H6O6 + 2H(+) + 2I(-) E = +0.667 Volts
The above reaction is used in analytical chemistry to determine quantitatively the amount of ascorbic acid.
In basic form: C6H8O6 + I2 ==>> C6H6O6 + 2HI
In a 50 ml flask, fill with 50 mls of demineralised water and add an iodine crystal. Stopper with rubber stopper. Iodine solubility in water is 0.0013 moles in 1Lt at 25 oC
Reaction Test Flask.
In a 50 ml flask, fill with 50 mls of 1M Ascorbic Acid solution (176.12 grams in 1 Lt of demineralised water) and add an iodine crystal of equal size as the Control. Stopper with rubber stopper.
Observe that happens.
57% HI SOLUTION (HYDRIODIC ACID)
BP: 125.5-126.5 *C/760mmHg
D= 1.70 gr/ml : 55-57% w/w HI is 0.936 to 0.99 grams of HI per ml.
If 57% w/w HI solution has a boiling point of 125.5-126.5 oC/760mmHg at which it form a azeotropic solution. Then lowering the pressure will lower the boiling point temperature and thus you can use azeotropic distillation for removal of the HI from the dehydroascorbic acid + HI solution.
At room temperature the reaction of HI with the hydroxy group of the glycol, [-C(-OH)-C(-OH) ]functional group on the dehydrascorbic acid is very slow. Refluxing is required to iodinate or reduce to -CH2CH3.
Therefore, by using flash azeotropic distillation (380-570mmHg), the reaction between the dehydrascorbic acid + HI can be minimized.
|Preparation of Pure Anhydrous HI in GAA||Bookmark|
Preparation of Pure Anhydrous HI in GAA
Reference Cited: Org. Proc. Res. Dev., 1 (1), 88-89, 1997.
Preparation of Pure Anhydrous Solutions of Hydrogen Iodide in Acetic Acid
Discussion of the Process:
The presence of molecular iodine in anhydrous solutions of hydrogen iodide in acetic acid gives rise to unstable impurities during the hydriodination of isolated double bonds. This can be overcome by using aqueous hydriodic acid, as the source of hydrogen iodide, from which the iodine has been removed by washing with a solution of an organic soluble ion exchange resin.
In order to develop a practicable synthesis, a procedure for generating anhydrous hydrogen iodide in acetic acid was required. Procedures using molecular iodine (iodine/tetralin at reflux, iodine, and red phosphorus) or compressed hydrogen iodide all proved to be unacceptable. This was because the procedure either was time-consuming or presented safety, handling, or waste management concerns.
All these procedures had one additional and important shortcoming in the context of the proposed chemistry, namely, that traces of iodine, residual during the preparation of the hydrogen iodide, were not readily removable from the resulting solutions produced by passing the gas stream into glacial acetic acid.
The answer was to use analytical grade aqueous hydriodic acid as a readily available and cost effective source of hydrogen iodide. Hydriodic acid of accurately determined concentration was utilised, and all operations were carried out under an argon atmosphere. Traces of molecular iodine were removed by washing with a toluene solution of LA-2 ion exchange resin to produce a colourless and stable aqueous solution. The concentration of hydriodic acid was not affected by the washing process nor was its specific gravity, both of which needed to be accurately determined for the calculation of stoichiometric quantities. The anhydrous acetic acid solutions were prepared by adding the aqueous hydriodic acid to the appropriate quantity of degassed acetic anhydride, with control of the exotherm to below 55°C. The clear and colourless solution was then cooled to 20°C prior to the addition of a solution of alkene in glacial acetic acid. After completion of the required reaction period, the colourless reaction mixture was worked up by vacuum codistillation removal, using toluene, of the majority of the organic and inorganic acids, the product finally being extracted into toluene.
Into an argon-purged separation vessel fitted with a mechanical stirrer is placed hydriodic acid (2.165 L, specific gravity 1.91, 65.0% w/w). A solution of Amberlite LA-2 (0.395 kg) in toluene (5.0 L) is then added to the vessel, and the agitator is used to mix the layers for 2 min. After the layers are allowed to separate, the colourless hydriodic acid layer is run into an argon-purged holding vessel prior to returning to the separator for a single wash with a quantity of degassed toluene. For solutions heavily contaminated with molecular iodine, a second wash with the LA-2 resin solution is required.
Into an argon-purged reaction vessel is then placed acetic anhydride (6.94 L, 99.7%, 73.33 mol) which is vacuum degassed. Washed hydriodic acid (1.973 L, 19.15 mol of HI, 73.33 mol of H2O) is added to the mechanically stirred solution at such a rate that the temperature is maintained below 55°C by the use of external water cooling. If the temperature is allowed to rise above this limit, there is some loss of water vapour by entrainment, and this results in incomplete hydrolysis of the acetic anhydride.
The mixture is stirred for a further 60 min after completion of the addition of the aqueous acid and is then cooled to 20°C prior to the addition of a vacuum-degassed solution of alkene (4.822 mol) in glacial acetic acid (2.0 L) over a period of 10 min.
After completion of the addition, the mixture is stirred for a further 16 h prior to removal of the majority of the acetic acid by vacuum codistillation with 10 volumes of toluene (50 mmHg, <50°C). The dark residue is dissolved in toluene (14.0 L) and then transferred to a separating vessel followed by washing with a 5% solution of sodium thiosulphate (2.0 L) and then deionised water. The thiosulphate wash is first back-washed with a small quantity of toluene, which is combined with the main solution of product.
The organic solution is dried over magnesium sulphate and filtered through a short bed of 100-200 mesh Florisil prior to removal of the toluene under reduced pressure, to leave the product iodoalkene as a colourless to very pale yellow oil. Yield range: 90-97%.
|100% Nitric Acid||Bookmark|
Found by Rhodium
Preparation of 100% nitric acid
Reference Cited: J. Org. Chem. 25, 469-470 (1960)
Preparation of 100% nitric acid
Nitric acid (6.79 g.; 0.108 mole as 52.72 g. of a 12.88% solution) was carefully neutralized, with cooling, by addition of 4.32 g. (0.108 mole) of sodium hydroxide dissolved in the minimum amount of water. The water was removed by distillation and the dry salt was treated with concentrated sulfuric acid (18 ml, 0.32 mole).
Distillation at atmospheric pressure in the absence of sunlight gave 5.6g (0.089 mole) of 100% nitric acid, bp 80-83°C (82% recovery)
Potassium nitrate (14.2 g.; 0.07 mole) and 31.1 ml. (0.56 mole) of concentrated sulfuric acid gave, upon distillation, 7.1 g. of 100% bp 78-82°C (81% recovery).
Noted by Osmium:
The regularly available azeotropic HNO3 can be concentrated by distilling it from the same volume of H2SO4, preferably under a slight vacuum. I've done this big scale with 6L RB flasks and it worked great.
|Preparation of Nitric Acid||Bookmark|
Found by Hermanroempp
Preparation of Nitric Acid:
"To 25 ml of (cooled) concentrated sulfuric acid in a distillation flask add 30 g of previously dried potassium nitrate and a little bit of silver nitrate (swirling). Close with stopper and let sit for 1 hour (to complete conversion). Then distil carefully (I guess it means "slowly" here). The brown-yellow forerun is discarded, only the fraction in the distilling range from 83 to 85 °C is collected. The distillation is finished when red fumes begin to form in the condenser."
They also recommend vacuum distillation for the production of larger amounts of nitric acid in combination with full glass apparatus with ground glass joints. The joints are lubricated with sulfuric or phosphoric acid.
Boiling point of 100 % nitric acid: 83 °C (atmospheric pressure), 36-38 °C (26 mbar)- no specific yields given. However, the yield is presumed to be high.
Reference Cited and Translated:
Jander-Blasius: Lehrbuch der analytischen und praeparativen anorganischen Chemie", 12. ed., 1985, S. Hirzel Verlag, Stuttgart
|Preparation of Anhydrous Nitric acid in DCM||Bookmark|
Found by Rhodium
HNO3 in DCM
Pure dry HNO3 can be liberated from KNO3 with 96% H2SO4 directly into CH2Cl2 to yield solutions of variable concentration for use in a number of organic reactions. The present method efficiently replaces the employment of 100% HNO3 in some synthetic applications, avoiding the problems associated in storage and handling the acid.
Unless otherwise specified, finely powdered KNO3 (50.0 mmol) was treated with the appropriate amount of 96% H2SO4 (47.5 mmol) and the mixture stirred for 15 min at room temperature; CH2Cl2 (25.0 mL) was added to the homogeneous slurry so obtained and the mixture cooled at 0°C with vigorous stirring. A solution of the substrate 1 (5.0 mmol) in CH2Cl2 (8.0 mL) was added dropwise and the stirring continued at room temperature for the required time. The reaction mixture was then poured into 10% aqueous Na2SO4 (30 mL) and the separated organic phase washed with 10% aqueous Na2SO4 (2×20 mL), dried over anhydrous Na2SO4, concentrated to dryness and the products obtained conveniently purified.
Notes on Safety:
The HNO3 in DCM is not stable and they reference possible explosions but state that they had no such problems. Be careful and only make this reagent when you need it, and dispose of extra.
Reference: Tetrahedron Letters, Vol 42(7), 1387-1389 (2001)
|Nothing against Rhodium Post 227902||Bookmark|
Nothing against Rhodium
Post 227902 (foxy2: "Anhydrous HNO3 in DCM, Useful for 2-CN/nitrations", Chemistry Discourse)
Foxy is correct, it was from that post of his I took the procedure and put it on my page.
Aurelius: Isn't this compilation more suitable to be a Digest instead of a regular post? Also, I would think it would be better if you used that format, and linked to longer posts and only writing a little abstract of each instead of reposting them all. One of the advantages of making a digest is that you can edit and re-edit it indefinitely, and any reply to it (like foxys and mine here) wouldn't clutter it, and would end up in a separate attached thread.
Compilation of Preparation of Acid Reagents
Going to start another compilation.
Polyphosphoric Acid Preparation:
From Ulmann’s Encyclopedia of Industrial Chemistry
“Polyphosphoric acid can either be produced from wet phosphoric acid by evaporative concentration, or thermally by combustion of elemental phosphorus.
Wet phosphoric acid is concentrated by direct heating with hot gases in reactors lined with carbon bricks  or by indirect heating under vacuum . In the former process, the heating gas is usually injected below the acid surface.
Concentration of wet phosphoric acid also improves its transportability. Commercial wet phosphoric acid with ca. 50 % P2O5 contains relatively high concentrations of impurities, which deposit on pipes and containers unless during shipment and storage the acid is constantly agitated. Because polyphosphoric acid has a higher lime binding strength, the impurities are held in solution and cannot deposit.”
 W. C. Scott, G. G. Patterson, A. B. Phillips, Commer. Fert. 113 (1966) no. 2, 32 ff.
 W. E. Rushton, Phosphorus Potassium 1966 no. 23, 12.
Noted by PrimoPyro:
Polyphosphoric acid appears to have the curious characteristic of not tearing the shit out of arylalkyl ethers, such as methoxy substituted benzene rings, and methylenedioxybenzenes, etc.
Preparation of Polyphosphoric acid from commercial 85% H3PO4 and phosphoric anhydride (P2O5/P4O10):
Approximately 25 mL of PolyPhosphoric Acid is prepared by mixing 18 g P2O5 and 10 g 85% H3PO4. The reagents are stirred at ca. 100 oC under a dry atmosphere until a homogeneous, clear viscous liquid has formed. Typically this takes around 24 h. The use of higher temperatures usually results in the discoloration of the PPA, although its efficacy appears unaffected in such cases. Additionally, owing to the high viscosity of the medium, all PPA reactions require mechanical stirring.
Liebig's Ann 65 30, 387 (1845) & 118 99 (1861)
Ueber einige Metallverbindungen der Triphosphorsäure Rostock (1896)
Beitrag zur Kenntnis der Triphosphorsäure und ihrer Salze Berlin (1899)
Ueber die Einwirkung von Phenolen auf Pyro- und Orthophosphorsäurchlorid, Rostock (1896)
Ultraphosphate Leipzig (1912)
Stahl Eisen 28 675 (1908) & 31 2020 (1911)
Chem Ztg 47 195 (1923)
Zeit anorg Chem 12 444 (1896); 76 387 (1912); 77 1 (1912) & 78 95 (1912)
Compt Rend Trav Chim 19 (1849)
Jour Iron Steel Inst 84 ii, 126 (1911)
From the Merck Index:
7740. Polyphosphoric Acid.
Phospholeum; tetraphosphoric acid. May be prepd by heating H3PO4 with sufficient phosphoric anhydride to give the resulting product an 82-85% P2O5 content: Bell, Ind. Eng. Chem. 40, 1464 (1949); Van Wazer, Holst, J. Am. Chem. Soc. 72, 639 (1950); Kennard, Org. Chem. Bull. 29, no. 1 (1957). Consists of about 55% tripolyphosphoric acid, the remainder being H3PO4 and other polyphosphoric acids. Typical analysis: 83.0% P2O5; ortho equivalent 115.0%. Viscous liquid at room temps. Conveniently fluid at 60 deg. Solidifies to a glass at low temps. Sol in water with evolution of heat and hydrolysis to H3PO4. Caution: In strong concns moderately irritating to skin, mucous membranes.
USE: In organic synthesis for cyclizations and acylations.
|Ulmann's Polyphosphoric acid||Bookmark|
I've taken phosphoric acid and heated it (about 100ml for 1-1/2 days at 100-150*C) and a white solid has deposited on the bottom of the flask. a solid cake (not individual crystals) what is this solid? phosphates of some sort? perhaps a polyphosphoric acid of unknown MW?
|Wasn't pure phosphoric acid a solid?||Bookmark|
Wasn't pure phosphoric acid a solid?
For those about to synth,we salute you
|pyro/ortho-phosphoric acid mixture||Bookmark|
Pure (ortho-)phosphoric acid is a solid. but you can't obtain it simply by heating aq. phosphoric acid to 100°, because it polymerises to polyphosphoric acid. I have an article describing the lab method of obtaining 100% ortho-phosphoric acid. it's rather involved.
You probably got a mixture of ortho-phosphoric and pyrophosphoric acid.