Hydrogenation of 2-butanone

Synthesis of 2-butanol by the nickel-catalyzed hydrogenation of 2-butanone ... 

Szollosi, G. and Bartok, M. Catalytic transfer hydrogenation of 2-butanone on MgO. New active surface sites generated by treatment with chloroform, Catal. Lett., 1999, 59, 179-185. 

A pure phenomenological model of such an intricate process, taking into account all possible reaction steps, is therefore a powerful tool for the scale up and the prediction of performances of trickle-bed reactors. Such a model (20 has proved to be able to correctly reproduce experimental data using only two adjustable parameters. It has been checked in several cases (hydrogenation of alphamethylstyrene (3J, hydrogenation of 2-butanone (, hydrorefining (J5) ), with more or less volatile liquid reactants and it appeared to be also useful to calculate a posteriori the extent of the different types of wetted catalyst area and their different effectiveness factor. 

Consider a sample of racemic 2-butanol at room temperature, prepared by hydrogenation of 2-butanone under achiral conditions. In contrast to cij-1,2-difluorocyclohexane and ethylmethylpropylamine, molecules of 2-butanoI show no evidence of enantiomerization on the leisurely time scale that is associated with optical rotation measurements or with the separation of enantiomers. Because the probability is exactly one half that any macroscopic sample has an odd number of molecules, there is an even... 

Lopez-Martinez, A., and Keane, M.A.( 2000) The gas phase hydrogenation of 2-butanone over supported nickel catdysts introduction of enantioselectivity, J. Mol. Catal. A Chem. 153, 257-266. 

Hydrogenation of ketones is less facile and less selective than the reduction of aldehydes. [H2Ru(TPPTS)4] proved to be an active catalyst in hydrogenation of 2-butanone, cyclohexanone, and benzylacetone (80 °C, 3.5 MPa H2) [34]. The same catalyst was also rather selective toward the formation of the saturated ketone in the hydrogenation of tr ns-4-hexen-3-one [Eq. (9)], yielding only 2-7% of 3-hexanol. Similar C=C/C=0 selectivity was found with the [(C5R5)RuCl(PTA)2j (R = H or CHj) catalysts, too [41]. 

Hydrogenation of 2-butanone forms racemic 2-butanol. Hydrogen adds to either face of the double bond. Addition of H2 to one face gives the (R) product, while addition to the other fece gives the (5) product. 

Modeling of a Trickle-Bed Reactor. The Hydrogenation of 2-Butanone on a Ruthenium Catalyst... 

Yet, till now, a quantitative treatment of these phenomena is lacking. In addition, several observations remain completely unexplained dry zones formation even with prewetted beds, stationnary operation slow settling, hysteresis... That is the reason why we have chosen to investigate the hydrogenation of 2-butanone into 2-butanol on a ruthenium supported catalyst. Indeed this chemical reaction can be studied over a large... 

Aldol reaction of the campholenic aldehyde with 2-butanone gives the intermediate ketones from condensation at both the methyl group and methylene group of 2-butanone (Fig. 6). Hydrogenation results in only one of the two products formed as having a typical sandalwood odor (160). 

Scheme 6 Complementary regioselectivities in direct aldol couplings of 2-butanone and corresponding hydrogen-mediated reductive aldol couplings of MVK...

Figure 5.15 The reaction of 2-butanone with hydrogen in the presence of a nickel catalyst. The reaction rate by path (a) is equal to that by path (b).

In reactions carried out for 24 h at room temperature, a 95% yield of cyclo-hexanol from cyclohexanone was obtained. Other ketones and aldehydes were also hydrogenated under identical conditions, but with slower rates (38% conversion for hydrogenation of 2-hexanone, 25% conversion of acetophenone, 45% for 3-methyl-2-butanone). Insertion of the C=0 bond of the ketone or aldehyde into the Cr-H bond was proposed as the first step, producing a chromium alk-oxide complex that reacts with acid to generate the alcohol product. The anionic chromium hydride [(COJsCrH]- is regenerated from the formate complex by... 

There are two types of a-hydrogens in 2-butanone, and either may enolize ... 

Predict the H-NMR spectrum of 2-butanone. Include the approximate chemical shift, multiplicity, and integral for each type of hydrogen. 

Flammable liquid. A very dangerous fire hazard when exposed to heat, flame, or oxidizers. Moderately explosive when exposed to heat or flame. Reacts with air to form dangerous peroxides. The presence of 2-butanone increases the reaction rate for peroxide formation. Hydrogen peroxide sharply reduces the autoignition temperature. Violent explosive reaction when heated with aluminum isopropoxide + crotonaldehyde + heat. Forms explosive mixtures with trinitromethane, hydrogen... 

Dimethylpropanoic acid is the best additive11. Thus, hydrogenation of 1-phenylethanone with the Raney nickel/tartaric acid/sodium bromide/2,2-dimethylpropanoic acid system gave (5>)-l-phenylethanol in 63%ee. 2-Butanone was reduced to (,V)-2-butanol in 49% ee, while the optical inductions in the hydrogenation of 2-alkanones, ranging from 2-pentanone to 2-hene-icosanone, were between 58 and 66% ee. 4-Phenyl-2-butanone was reduced to (S)-4-phenyl-2-butanol in 58% ee, while the best result was achieved with 3,3-dimethyl-2-butanone yielding (S)-3,3-dimethyl-2-butanol in 74% cc11. 

Notice that a DEPT NMR spectrum does not show a signal for a carbon that is not attached to a hydrogen. For example, the NMR spectrum of 2-butanone shows four signals because it has four nonequivalent carbons, whereas the DEPT NMR spectmm of 2-butanone shows only three signals because the carbonyl carbon is not bonded to a hydrogen, so it will not produce a signal. 

If an unsymmetrical ketone is used in this reaction, the problem is exacerbated. Reaction of 42 with sodium ethoxide, under thermodynamic control conditions, generates two different enolate anions. When reacted with an aldehyde with no a-hydrogens (benzaldehyde), two aldol products are formed (131 and 132). When 42 reacts with sodium ethoxide under thermodynamic conditions in the presence of an unsymmetrical ketone such as 2-butanone, the kinetic and thermodynamic enolates of both ketones are formed, which means that four different enolate anions are formed, and each one reacts with two different ketones. Therefore, the attempted mixed aldol condensation of 2-butanone and 42, therefore, produces eight different aldol products. 

There are three different kinds of hydrogens in 2-butanone two different methyl groups and the methylene group. These protons are marked in the figinre. 

Using a condensed reaction form, treatment of 2-butanone with NaBI leads to 2-butanol, and the first step delivers the hydrogen marked in blue in the illustration, whereas aqueous ammonium chloride (a weakly acidic solution) is the second step that delivers the hydrogen marked in red. Sodium borohydride reduces both ketones and aldehydes. Indeed, the reduction of an aldehyde with NaBH4 is somewhat easier than the similar reduction of a ketone. Aldehydes are easier to reduce than ketones because the carbonyl unit is less stericaUy hindered. 

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