Ruthenium Olefin Metathesis Catalysts Bearing Carbohydrate-Based N-Heterocyclic Carbenes

Ru-based olefin metathesis catalysts containing carbohydrate-derived NHCs from glucose and galactose were synthesized and characterized by NMR spectroscopy. 2D-NMR spectroscopy revealed the presence of Ru−C (benzylidene) rotamers at room temperature, and the rate of rotation was measured using magnetization transfer and VT-NMR spectroscopy. The catalysts were found to be effective at ring-opening metathesis polymerization (ROMP), ring-closing metathesis (RCM), cross-metathesis (CM), and asymmetric ring-opening cross-metathesis (AROCM) and showed surprising selectivity in both CM and AROCM

A Tandem Approach to Photoactivated Olefin Metathesis: Combining a Photoacid Generator with an Acid Activated Catalyst

Combining an acid activated precatalyst with a photoacid generator (PAG) in the presence of ultraviolet light resulted in a highly efficient catalyst for olefin metathesis. The tandem system of precatalyst and PAG was capable of both ring closing metathesis (RCM) and ring opening metathesis polymerization (ROMP) in good to excellent conversion. Mechanistic investigations revealed that the catalytically active species is very similar to that of other well-known Ru-based catalysts

ANALYZING TRADE IMPLICATIONS OF U.S. BIOFUELS POLICIES IN A GENERAL EQUILIBRIUM FRAMEWORK

As the biofuels are emerging as promising alternative transportation fuels across the world, they also offer huge potential for international trade in biofuels. A number of trade barriers such as import tariffs and domestic support have limited the scope for trade in biofuels. The purpose of this study is to analyze the implications of U.S. biofuel mandates, subsidies and import tariffs on global trade and welfare. We utilize the GTAP-BIO model, which was developed as a customized version of the Global Trade Analysis Project (GTAP) model capable of analyzing domestic and trade policy issues associated with biofuels (Birur, 2010). We supplement this model with updated and detailed sectoral level information on feedstock crops, different types of first and second generation biofuels and their byproducts. This highly refined data base facilitates the model for simulating changes in cropping patterns at individual crop level, land use changes, commodity prices, etc. We analyze the following policy scenarios in this study: (a) implementation of volume requirements consistent with the U.S RFS2 volumes for the year 2022 relative to a starting point of the base year 2004, (b) reduction in the ethanol specific import tariff from 54 ¢/gallon to 45 ¢/gallon, so that there will be “parity” between the U.S. and exporting country’s ethanol price, (c) Complete removal of the U.S. ethanol blenders’ credit and import tariff on ethanol, (d) combined implementation of (a) and (c) policy scenarios. This paper offers insights regarding the prospective policy options that can affect potential trade in biofuels amongst the major producing countries, such as the extent to which a removal of U.S. import tariff on ethanol affects pasture and forest land conversion in Brazil.Biofuels, Computable General Equilibrium, land use change, Land Economics/Use, Resource /Energy Economics and Policy,

Cis-Selective Ring-Opening Metathesis Polymerization with Ruthenium Catalysts

Cis-selective ring-opening metathesis polymerization of several monocyclic alkenes as well as norbornene and oxanorbornene-type monomers using a C–H activated, ruthenium-based metathesis catalyst is reported. The cis content of the isolated polymers depended heavily on the monomer structure and temperature. A cis content as high as 96% could be obtained by lowering the temperature of the polymerization

Protonolysis of a Ruthenium–Carbene Bond and Applications in Olefin Metathesis

The synthesis of a ruthenium complex containing an N-heterocylic carbene (NHC) and a mesoionic carbene (MIC) is described wherein addition of a Brønsted acid results in protonolysis of the Ru–MIC bond to generate an extremely active metathesis catalyst. Mechanistic studies implicated a rate-determining protonation step in the generation of the metathesis-active species. The activity of the NHC/MIC catalyst was found to exceed those of current commercial ruthenium catalysts