Parr hydrogenator

The most common low pressure reactor is the Parr hydrogenator shown in Fig. 6.5. This system is composed of a reaction bottle that is coimected to a gas reservoir that has a capacity of about four liters. Two versions of the apparatus are commercially available a standard model that takes 250 mL and 500 mL reaction bottles and that can be used to pressures up to about 60 psig and a larger size that uses 1 liter and 2 liter bottles that have about a 40 psig pressure limit. The bottles are coimected to the gas reservoir by a tube inserted through a rubber stopper in the mouth of the bottle. The common black rubber stoppers may contain catalyst poisons that can be extracted into the reaction mixture by some solvents. The use of neoprene stoppers will minimize this problem. 

Special reactor bottles having working volumes of 1 mL to 1000 mL are also available. As depicted in Fig. 6.6, these bottles have threaded Teflon adapters to hold the hydrogen inlet tube so catalyst contamination by the reactor is virtually eliminated. The smaller bottles, which have working volumes between 1 mL and 20 mL, use a spacer to secure them into the shaker assembly (Fig. 6.6a). Those with capacities of 20 mL to 200 mL (Fig. 6.6b) fit directly into the shaker assembly of the smaller Parr apparatus while 500 mL and 1000 mL vessels of this type (Fig. 6.6c) are available for the larger unit. 

Gas-liquid mass transport limitation can be a problem with reactions run in the larger reactor bottles using the standard shaking speed for agitation. This can 

As with any catalytic reactor, the catalyst is first placed in the reaction bottle and the liquid substrate or solution carefully added to it. The bottle is placed in a protective shield, placed in the rocking cradle and connected to the gas reservoir. The bottle is alternately pressurized from the reservoir, isolated from the reservoir, and vented, several times to remove the air in the reaction system. The reaction bottle is then shaken by means of a motor driven eccentric. If needed the reactor can be heated by a controlled heating jacket. 

The progress of the reaction is monitored by the drop in the pressure of the system. With the standard apparatus having the reactor open to the reservoir, a 0.1 mole of gas uptake corresponds to approximately an 8 psig pressure drop. To detect smaller quantities of gas uptake, the reactor can be isolated from the reservoir so the gauge reads only the pressure of the gas in the reactor bottle. With a half full 500 mL reactor bottle a 0.1 mole gas uptake corresponds to about a 150 psig pressure drop. Approximate pressure drops for other volumes and quantities of gas consumed are easily calculated using the ideal gas law. 

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Hydrogenation of 2- (4-oxo-4//-pyrido[l, 2-n]pyrimidin-2-yl)oxymethyl -4-isopropyl-6-alkoxysaccharins 134 over 10% Pd/C catalyst at 50 psi Parr hydrogenator yielded 6,7,8,9-tetrahydro derivatives 135... 

Apparatus for carrying out hydrogenation at several atmospheres can be constructed readily (1,78,93), but there seems little point in this exercise since good commercial equipment is available. The most commonly used commercial low-pressure equipment is the Parr hydrogenator (manufactured by Parr Instrument Co., Moline, Illinois). This equipment (Fig. 1) has withstood the test of time it was first described in 1922 and offered commercially in 1926. It comes in two sizes one for 500-ml reactor bottles and one for 1000-and 2000-ml reactor bottles. Specially made smaller bottles, down to 50 ml, can be used also but require special holders to compensate for differences in bottle heights. Shaker bottles should not be more than half full to ensure good mixing, a consideration in selection of bottle size. 

L-(-)-7-benzyloxycarbonylamino-o -hydroxybutyrylI -6 -carbobenzoxykanamycin A was dissolved in 40 ml of 50% aqueous dioxane and a small amount of insoluble material was removed by filtration. To the filtrate was added 0.8 ml of glacial acetic acid and 1 gram of 10% palladium-on-charcoal and the mixture was hydrogenated at room temperature for 24 hours in a Parr hydrogenation apparatus. The reaction mixture was filtered to remove the palladium catalyst and the filtrate was evaporated to dryness in vacuo. 

The flask of a Parr hydrogenation apparatus was charged with 10,5 g of 3,3-diphenylpropyl-amine, 7.7 g of cyclohexylacetone, 50 ml methanol and 150 mg of platinum dioxide. Hydrogen at a pressure of 3 atmospheres was introduced and the mixture stirred. Upon absorption of the theoretical amount of hydrogen, stirring is discontinued, the catalyst is filtered off and the solution is evaporated to dryness. The residue is taken up with ether and the hydrochloride is precipitated with HCI in alcoholic solution. The product, as collected on a filter and washed with ether, is recrystallized from isopropanol. Yield 17 g (92.5% of theory). 

Examples Reaction mixtures include 10% Pd/C in THF—water at 50 psi H2 in a Parr hydrogenation apparatus for 1 hour,228 5% Pd/C in EtOH229 at... 

Another Hydrogenation with Platinum Oxide. JACS, 55, 2694. This method is used to reduce those hydrox-mandelonitriles in the amphetamine section. It uses low pressure and can be used on about any reducible compound. It can also use palladium oxide as the catalyst. A solution of 35.8 g of phenyl-2-propanol in 250 ml of 80% ethanol containing 7.3 g of HCl is hydrogenated for 3 hours in a Parr hydrogenation bottle at 3,5kg/cm or 50 p.s.i, over 0,5 g of platinum oxide (or palladium oxide Raney nickel may also work) or an equimolar ratio of analog catalyst for about 3 hours. Filter off the catalyst and rinse with a little water to wash all the product from the catalyst. Dilute the filtrate to 1 liter of volume with water and extract twice with ether to remove any acid insoluble material. The ether extracts do not contain product. The aqueous layer is made alkaline with solid NaHCOs to a pH of 8-9 and the basic oil which separates is extracted with two 300 ml portions of ether. This ether solution is dried over MgS04, and filtered, then evaporated to remove the ether. To convert to the oxalate, add ether to the crude product and add to a solution of 9.6 g of oxalic acid dihydrate in a small volume of methanol. Give ample... 

A 600 mL Parr hydrogenation vessel equipped with an injection port with a rubber septum for the addition of the solvent via syringe, a pressure gauge, a tightly fitting removable internal glass liner, thermocouple and an overhead mechanical stirrer was assembled and pressure tested to 14 bar with N2 over... 

A solution of 3.5 g 2,3-methylenedioxy-6-nitro-beta-dimethylaminostryrene in 200 ml benzene was placed in a Parr hydrogenation bomb and treated with 0.35 g of 10% Pd / C. The mixture was shaken for 7 h under 3 atm H2. The catalyst was removed by filtration, and the filtrate was washed first with 2N H2S04, followed by aqueous NaHC03 and H20. This was dried and the solvent removed under vacuum to give 1.2 g (50%) of 4,5-methylenedioxyindole as a residue. After crystallization from benzene / petroleum ether, it had a mp 111 °C. Anal C,H,N. 

Ethyl-5-methyl-4-isoxazolylmethyl)cyclohexanone (27.6 g., 0.125 mole) is dissolved in 250 ml. of ethanol in a Parr hydrogenation bottle, and 20 g. of freshly prepared W-4 Raney nickel catalyst (Note 10) is added. Hydrogenation is started at an initial hydrogen pressure of 25 p.s.i. Cleavage of the isoxazole ring is complete after 6 hours, after which time the reaction is stopped and the solution is filtered free of catalyst (Note 11). The catalyst is washed with ether and with absolute ethanol, and the combined organic filtrates are concentrated with a rotary evaporator (Note 12). 

The flask of a Parr hydrogenation apparatus was charged with 10.5 g of 3,3-... 

A mixture of (R)-4-benzyl albuterol as a free base (3.2 g, 9.73 mmol) and 10% Pd/C (0.64 g) in 24 mL of ethanol (denatured with 5 vol % 2-propanol) is shaken on a Parr-hydrogenator under 50 psi of hydrogen at room temperature for 3 hours. The catalyst is removed by filtration and the filtrate is concentrated to ca. 9 mL in volume containing crude (R)-albuterol and treated with anhydrous HCI in ether (1.0 M, 9.5 mL, 0.98 eq) at 0°-5°C. After 30 min at room temperature, 9 mL of methyl t-butyl ether (MTBE) is added, the resulting mixture is stirred at room temperature for 30 min and at 0°-5°C for 2 hours. The white solid (R)-albuterol hydrochloride is collected by filtration and recrystallized from 25 mL of ethanol and 12.5 mL of MTBE to give pure (R)-albuterol hydrochloride (2.17 g, 80.9% yield, 99.6% purity), white powder. 

A solution of 3.5 g 2,3-methylenedioxy-6-nitro-beta-dimethyl-aminostryrene in 200 mL benzene was placed in a Parr hydrogenation bomb and treated with 0.35 g of 10% Pd/C. The mixture was shaken for 7 h under 3 atm H2. 

If the hydrogenation is carried out in a Parr hydrogenation apparatus at 40-60 lb. pressure, about 2 hours is required to complete the hydrogenation as described. The low boiling point of the ethylenimine makes it impossible to remove the air from the bottle by evacuation in the usual way prior to hydrogenation. Instead the bottle is filled with hydrogen to 15-20 lb. pressure, the pressure is released, and the process repeated. 

The Parr hydrogenation apparatus shakes the reaction vessel (containing the alkene and the solid catalyst), while a pressurized cylinder supplies hydrogen. 

Some hydrogenations require high pressures of hydrogen gas to get them to go at a reasonable rate. They are usually done in a sealed apparatus known as a Parr hydrogenator. 

Transfer a solution of the /V,AA-dibenzyl-1,7,10,16,-tetraoxa-4,13-diazacy-clooctadecane (10 g, 0.023 mol) in ethanol (100 mL) to a 500 mL hydrogenation bottle suitable for use in a low pressure Parr hydrogenation apparatus. Carefully add Pearlman s catalyst (1.0 g), connect the bottle to the hydrogenation apparatus and shake for 72 h under a hydrogen pressure of 2-3 atmospheres. Filter the mixture through a bed of Celite (c. 1 cm) on a... 

A mixture of 126 g. (1.50 moles) of dimethylaminoacetonitrile (p. 124) and 30 g. of Raney nickel catalyst [Org. Syntheses, 21, 15 (1940) ] is placed in a Parr hydrogenation bomb and a tated at around 1000 lb. hydrogen pressure and a temperature of 78°. The theoretical amount of hydrogen is absorbed in about 3 hours. The catalyst is removed by filtration, and the filtrate is fractionally distilled. There is obtained 62 g. (47%) of j8-dimethylaminoethylamine, boiling at 105-108° at atmospheric pressure. 

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