Advertisement

Reaction Kinetics, Mechanisms and Catalysis

, Volume 108, Issue 1, pp 91–105 | Cite as

Aminocarbene mechanism of the formation of a tertiary amine in nitrile hydrogenation on a palladium catalyst

  • Jiri Krupka
  • Jakub Drahonsky
  • Anna Hlavackova
Article

Abstract

The hydrogenation of an aliphatic nitrile, molecules of which do not bear hydrogen atoms on the α-carbon with respect to the nitrile group, has been studied to gain a deeper insight into the mechanism of the heterogeneously catalyzed hydrogenation of nitriles. Hydrogenations were performed in the liquid phase on a Pd/C catalyst at a reaction temperature of 110 °C and a hydrogen pressure of 5 MPa. In the hydrogenation of trimethylacetonitrile in the presence of a lower aliphatic N,N-dialkylamine (e.g., diethylamine), the formation of a mixed tertiary amine, dialkylneopentylamine, was observed. Experiments have shown that the disproportionation reactions of the amines present are not responsible for its formation. Since the corresponding enamine incorporating a double bond in the neopentyl chain cannot be derived from the dialkylneopentylamine, the formation of the dialkylneopentylamine cannot be explained in terms of the enamine theory of the formation of a tertiary amine during the hydrogenation of the nitrile. It has been proved experimentally that the entire process of tertiary amine formation by nitrile hydrogenation is generally reversible: butyronitrile results from a reverse process from tributylamine and ammonia on the surface of the metal catalyst. The combination of experimental facts thus obtained gives an indirect proof of the validity of the hypothesis that the aminocarbene mechanism is involved in the formation of secondary and tertiary amines by nitrile hydrogenation.

Keywords

Heterogeneous catalysis Nitrile hydrogenation Surface species Mechanism 

Notes

Acknowledgments

The study was financially supported by the Grant Agency of the Czech Republic (Project No. P106/10/P441).

References

  1. 1.
    Krupka J, Pasek J (2012) Nitrile hydrogenation on solid catalysts—new insights into reaction mechanism. Curr Org Chem 16:988CrossRefGoogle Scholar
  2. 2.
    Krupka J (2010) Mechanism of the heterogeneously catalyzed hydrogenation of nitriles. Chem Listy 104:709Google Scholar
  3. 3.
    Rylander PN, Hasbrouck L (1970) Hydrogenation of nitriles over platinum metals. Engelhard Ind Tech Bull 11:19Google Scholar
  4. 4.
    Tlusty T, Pasek J, Vonka P (2006) Gas phase amination of octan-1-ol over a Cu–Cr catalyst. React Kinet Catal Lett 88:371CrossRefGoogle Scholar
  5. 5.
    Volf J, Pasek J, Duraj M (1973) Disproportionation of diethylamine in the presence of cobalt and copper. Collect Czech Chem Commun 38:1038CrossRefGoogle Scholar
  6. 6.
    Krupka J, Patera J (2007) Catalytic and mechanistic aspects of the hydrogenation of N-substituted aliphatic aldimines over solid catalysts. Appl Catal A 330:96CrossRefGoogle Scholar
  7. 7.
    Petrisko M, Krupka J (2005) Isomerization of an imine intermediate in a reductive amination reaction over metal catalysts. Res Chem Intermed 31:769CrossRefGoogle Scholar
  8. 8.
    Sachtler WMH, Huang Y (2000) Metal/overlayer and encaged carbonyl cluster catalysis. Appl Catal A 191:35CrossRefGoogle Scholar
  9. 9.
    Bakker JJW, Neut AGVD, Kreutzer MT, Moulijn JA, Kapteijn F (2010) Catalyst performance changes induced by palladium phase transformation in the hydrogenation of benzonitrile. J Catal 274:176CrossRefGoogle Scholar
  10. 10.
    Von Braun J, Blessing G, Zobel F (1923) Catalytic hydrogenations under pressure in the presence of nickel salts. VI. Nitriles. Ber 36:1988Google Scholar
  11. 11.
    Volf J, Pasek J (1986) Hydrogenation of nitriles. Stud Surf Sci Catal 27:105CrossRefGoogle Scholar
  12. 12.
    Sivasankar N, Prins R (2006) Iminium cations as intermediates in the hydrodenitrogenation of alkylamines over sulfided NiMo/γ-Al2O3. Catal Today 116:542CrossRefGoogle Scholar
  13. 13.
    Greenfield H (1967) Catalytic hydrogenation of butyronitrile. Ind Eng Chem Prod Res Dev 6:142CrossRefGoogle Scholar

Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2012

Authors and Affiliations

  1. 1.Department of Organic Technology, Faculty of Chemical TechnologyInstitute of Chemical TechnologyPrague 6Czech Republic

Personalised recommendations