507 research outputs found
voce Formaggi
No full textLa voce contiene una sintesi della normativa in materia di formaggi, con riferimenti storici, giurisprudenziali e bibliografici
Synthesis of Water-soluble Triazole Ligands and Application of Their Metal Complexes in Biphasic Hydrogenations of C=C and C=O
No full textAbstract:
Homogenous catalysis is a powerful tool for organic synthesis but its success in industrial application is limited because of difficult catalyst separation and reuse. To overcome these issues, the use of biphasic catalysis is at present of great interest because the catalyst is confined in one of the two-phases and the product in the other phase allowing for a prompt recovery of the product and an easy recycle of the catalyst. In particular, the development of water soluble catalysts for aqueous/organic biphasic reactions is increasingly attractive [1]. Our research group has been involved in the synthesis of triazolyl ligands by taking advantage of the copper-catalyzed azide-alkyne [3+2] cyclization [2]. Recently, we have synthesized a small library of N-N or N-S ligands which have been employed in Suzuki-Miyaura reactions [3,4]. In this work, we wish to present our studies on biphasic (water/toluene) catalytic hydrogenation of C=O and C=C (Schemes 3 & 4) double bonds using a water soluble triazole ligand in combination with Ruthenium and Iridium.
[1] (a) Cornils B.; Herrmann W. A.; Horvath I. T.; Leitner W.; Mecking S.; Olivier-Bourbigou H.; Vogt (Eds.) D. Multiphase Homogeneous Catalysis, Wiley-VCH, Weinheim, 2005. (b) Joo F. Aqueous Organometallic Catalysis, Kluwer Acad. Publ. Dordrecht, 2001. [2] V. V. Rostovtsev, L.G. Green, V.V. Fokin, K.B. Sharpless, Angew. Chem., Int. Ed. 2002, 41, 2596. [3] Amadio E.; Scrivanti A.; Chessa G.; Matteoli U.; Beghetto V.; Bertoldini M.; Rancan M.; Venzo A.; Bertani R. J. Org. Chem. 2012, 716, 193. [4] Amadio E.; Bertoldini M.; Scrivanti A.; Chessa G.; Beghetto V.; Matteoli U.; Bertani R.; Dolmella A. Inorg. Chim. Acta 2011, 370, 388
Disruption of Hyperion and Origin of Titan's atmospheres
No full textTwo peculiar features of the Saturnian satellite system, that is, the dense, N2-dominated atmosphere of Titan, and the very irregular shape of Hyperion, are probably related to each other. Numerical integrations show that most fragments ejected after the catastrophic breakup of a presumably larger and nearly-spherical proto-Hyperion fell onto Titan over a time scale of 103 yr, at impact speeds <4 km/s. Such impacts resulted into accretion of the constituent volatile materials into Titan's atmosphere. If proto- Hyperion was ≍1000 km in diameter, the entire current atmosphere may have been generated by this impact shower. Even for a smaller total mass of the impactors, any pre-existing atmosphere must have been chemically reprocessed, producing large amounts of N2 by shock effects. Impacts by proto-Hyperion fragments are also likely to have formed giant impact basins on Titan's surface
Cento anni della Rivista di Diritto Agrario. Una breve antologia per riflettere sul futuro
No full textAsymmetric hydrogenation by an in situ prepared (S)-BINAP–Ru(II) catalytic system
No full textA catalytic system obtained by in situ mixing [RuCl2(benzene)]2 and (S)-BINAP has been tested in the asymmetric hydrogenation of various substrates. The best results have been obtained working in methanol: excellent optical purities were achieved in the reduction of substrates such as tiglic acid (83%), geraniol (97%) and methyl 3-oxobutanoate (95%). Some investigations on the nature of the catalyst have been carried out
La difesa del suolo e i contratti di fiume
No full textIl lavoro affronta, da un lato, il tema della difesa del suolo, ripercorrendone l'evoluzione normativa, dall'altro lato il tema dei contratti di fiume, analizzandone l'origine e l'evoluzion
Il vincolo idrogeologico
No full textIl lavoro affronta il tema del vincolo idrogeologico, analizzandone oggetto, finalità, procedimento di imposizione e conseguenze
- …
