Benzonitrile, hydrogenations

The Payne epoxidation with benzonitrile/ hydrogen peroxide is also an efficient epoxidation process. It is often the method of choice for industrial batch-type applications, but on a small scale the need for continuous pH control is inconvenient. 

Methylenecyclohexane oxide has been prepared by the oxidation of methylenecyclohexane with benzonitrile-hydrogen peroxide or with peracetic acid by treatment of 1-chlorocyclo-hexylmethanol with aqueous potassium hydroxide and by the reaction of dimethylsulfonium methylide with cyclohexanone. This reaction illustrates a general method for the conversion of ketones and aldehydes into oxiranes using the methylene-transfer reagent dimethyloxosulfonium methylide. The yields of oxiranes are usually high, and the crude products, in most cases, are of sufficient purity to be used in subsequent reactions (e.g., rearrangement to aldehydes) without further purification. 

Figure 4. The effects of NH3 and modifiers on Benzonitrile hydrogenation over Ni.

Imines 337 were converted to oxaziridines 338 in good to excellent yields (60-90%) using a benzonitrile-hydrogen peroxide oxidizing system (Table 27) <2001SC263>. Commercial aqueous hydrogen peroxide (35%) can be used successfully in this reaction. Nonracemic oxaziridines were obtained when chiral imines were used. 

No evidence was found for benzonitrile hydrogenation and the measured concentration of benzonitrile in solution was found to be constant throughout these experiments. 

Benzonitrile hydrogenated ca. 5 hrs. with Raney-Ni in tetrahydrofuran-water-sulfuric acid at room temp, and atmospheric pressure benzaldehyde. Y 79%. - The presence of nitriles prevents the dissolution of Raney-Ni in acidic media. P. Tinapp, Ang. Gh. 80, 152 (1968). 

Uses. The principal use of adiponitrile is for hydrogenation to hexamethylene diamine leading to nylon-6,6. However, as a result of BASE s new adiponitrile-to-caprolactam process, a significant fraction of ADN produced may find its way into nylon-6 production. Adipoquanamine, which is prepared by the reaction of adiponitrile with dicyandiamide [461-58-5] (cyanoguanidine), may have uses in melamine—urea amino resins (qv) (see "Benzonitrile, Uses"). Its typical Hquid nitrile properties suggest its use as an extractant for aromatic hydrocarbons. 

In benzonitrile both types of processes occur in parallel with similar efficiencies. In hydrogen-donating solvents (toluene, ether, dioxane, ethanol), hydrogen abstraction processes prevail [toluene (114) -> (123)]. 

Interestingly, benzonitrile oxide does not react with thiirene dioxide 19b even in boiling benzene, whereas the electron-rich diene l-piperidino-2-methyl-l, 3-pentadiene (177) does react under the same reaction conditions to give the expected six-membered [4 + 2] cycloadduct 178, accompanied by sulfur dioxide extrusion and 1,3-hydrogen shift to form the conjugated system 179175 (equation 70). 

The strategy of introducing water as second phase has been used by Greenfield for obtaining higher yields of dibenzylamine (>97%) by hydrogenation of benzonitrile. In this case, water seems to prevent poisoning of the catalyst (Doraiswamy and Sharma, 1984). 

Similarly, reactions which are substantially enhanced by the use of PTC can be carried out even with reduced use of PTC with substantial enhanced rates of reaction as has been demonstrated by Sivakumar and Pandit (2000) in the case of conversion of benzamide to benzonitrile. In the case of A-alkylation of diphenylamine with benzyl bromide, in the presence of KOH as the anion source and PEG methyl ether as the PTC, some improvement in the rate has been observed. (Cains et al., 1998). Metal catalysed hydrogenations, such as those based on Ni, Pd/C, and Ru/C also benefit from ultra-sound. 

The Influence of FT on the Hydrogenation of Benzonitrile. Figure 57.18 displays the reaction scheme for the hydrogenation of benzonitrile (BN) to benzylimine (Bl), benzylamine (BA), dibenzylimine (DBI) and dibenzylamine (DBA). This reaction proceeds stepwise proceeds stepwise from BN to BI and from Bl to BA however,... 

Parker37 defined class 4 as solvents "which cannot donate suitable labile hydrogen atoms to form strong hydrogen bonds with an appropriate species and proposed the designation dipolar aprotic solvents he extended their range down to s > 15 and quoted as examples acetone, acetonitrile, benzonitrile, dimethylformamide, dimethyl sulphoxide, nitrobenzene, nitromethane (41.8) and sulfolane (tetramethylene sulphone) (44), where e varies from 21 to 46.5, and the dipole moment p from 2.7 to 4.7 debye. 

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