Hydrogenation apparatus

The use of more complex or more costly articles of equipment, such as catalytic hydrogenation apparatus, autoclaves, polari-meters, ultraviolet absorption spectrometers, etc., has not been described, because the type of such apparatus employed indifferent laboratories varies considerably, and students must be taught the use of their own laboratory equipment. 

Place a solution of 10 -4 g. of benzalacetophenone, m.p. 57° (Section IV,130) in 75 ml. of pure ethyl acetate (Section 11,47,15) in the reaction bottle of the catalytic hydrogenation apparatus and add 0 2 g. of Adams platinum oxide catalyst (for full experimental details, see Section 111,150). Displace the air with hydrogen, and shake the mixture with hydrogen until 0 05 mol is absorbed (10-25 minutes). Filter oflF the platinum, and remove the ethyl acetate by distillation. RecrystaUise the residual benzylacetophenone from about 12 ml. of alcohol. The yield of pure product, m.p. 73°, is 9 g. 

A suitable apparatus is the Aminco high-pressure hydrogenation apparatus, manufactured by the American Instrument Company, Silver Springs, Maryland. 

The technique of catalytic hydrogenation can be applied almost universally to unsaturated systems, and therein lies its chief advantage (7). By appropriate selection of catalyst, pressure, and temperature, a remarkable variety of substrates can be made to undergo hydrogenation, many of them under hydrogen pressure not exceeding 50 psi (see Appendix 3 for description and use of low-pressure hydrogenation apparatus). 

Fig. A3.9. Low-pressure hydrogenation apparatus (Parr Instrument Company).

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. 

In a stainless steel hydrogenation bottle were placed 17.6 g (0.1 mol) of 4-(p-methoxyphenyl)-3-buten-2-one, 80 ml of ethyl acetate, and 1 g of Raney nickel catalyst. The hydrogenation bottle was attached to a Paar low-pressure hydrogenation apparatus and the solution was hydrogenated under an initial hydrogen pressure of 50 psi. The hydrogenation was carried out at room temperature and after about 12 hours one equivalent of hydrogen had been absorbed. The catalyst was filtered from the reduction mixture and 18.1 g (0.1 mol) of homoveratrylamine were added to the reduction mixture. 

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). 

The production of tetracycline by catalytic dechlorination is described in U.S. Patent 2,699,054 as follows Pure chlortetracycline (4.8 grams) was suspended in 100 ml of methanol and sufficient anhydrous dioxane was added to completely dissolve the product. To the solution was added 0.5 gram of 5% palladium-on-charcoal catalyst. The mixture was placed in a conventional hydrogenation apparatus and subjected to a pressure of 50 psi of hydrogen while being agitated. 

B. Sodium 2-aminobenzenesulfinate. 2-Nitrobenzenesulfinic acid (3.74 g., 0.020 mole) is suspended in 10 ml. of water, and sufficient 1AT NaOH (about 20 ml.) is added to the well-stirred mixture to dissolve the acid and bring the pH to 9. Palladium oxide (0.2-1.0 g., Note 9) is suspended in 20 ml. of water in a 200-ml. glass hydrogenation bottle. The bottle is attached to a hydrogenation apparatus such as that of Adams and Voorhees,2 and the suspension is shaken with hydrogen under a pressure of... 

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... 

The bottle is connected to the hydrogenation apparatus and alternately evacuated and filled with hydrogen twice. Hydrogen is then admitted to the system until the pressure gauge reads 40 lb. The shaker is started, and the pressure drops to the theoretical value for absorption of 0.6 mole in 15-20 minutes beyond this point shaking causes no further absorption of hydrogen (Note 2). The bottle is removed and the nickel catalyst is allowed to settle. The tetrahydropyrane is decanted, but enough... 

Low-pressure hydrogenation apparatus fitted with a gas burette system to measure the hydrogen consumed1361... 

The Schlenk tube was connected to a low-pressure hydrogenation apparatus fitted with a gas burette system to measure the hydrogen consumed. The Schlenk tube was flushed through three cycles (reduced pressure/ hydrogen) and then placed under an atmospheric pressure of hydrogen. The burette was filled with 200 mL of hydrogen. 

Note that, in contrast, the reactions using [(COD) Rh ((S, S)Me-BPE)] or [(COD)Rh((R, R) Me-DuPHOS)] complexes can be performed at atmospheric pressure of hydrogen which avoids the use of heavy-duty hydrogenation apparatus. 

C. [18]Annulene. In a 300-ml. conical flask fitted with a side arm (with a closed stopcock) and a 3.5-cm. Teflon -coated magnetic stirring bar is placed 1 g. of a 10% palladium-calcium carbonate catalyst (Note 20) and 30 ml. of benzene (Note 10). The flask is attached to an atmospheric pressure hydrogenation apparatus, and the air in the system is replaced by hydrogen by evacuating the flask and refilling with hydrogen three times. The catalyst suspension is stirred until no more gas is absorbed. One-third (390 mg., determined spectroscopically)... 

Without any idea of what hydrogenation apparatus should look like, carrying out the process would be rather difficult. Along with the pictures are general instructions for proper procedure. If you are following a specific formula then you may need to change things around to produce the desired product. 

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