Fatty Acids and their Derivatives as Renewable Platform Molecules for the Chemical Industry.

Oils and fats of vegetable and animal origin remain an important renewable feedstock for the chemical industry. Their industrial use has increased during the last 10 years from 31 to 51 million tonnes annually. Remarkable achievements made in the field of oleochemistry in this timeframe are summarized herein, including the reduction of fatty esters to ethers, the selective oxidation and oxidative cleavage of C-C double bonds, the synthesis of alkyl-branched fatty compounds, the isomerizing hydroformylation and alkoxycarbonylation, and olefin metathesis. The use of oleochemicals for the synthesis of a great variety of polymeric materials has increased tremendously, too. In addition to lipases and phospholipases, other enzymes have found their way into biocatalytic oleochemistry. Important achievements have also generated new oil qualities in existing crop plants or by using microorganisms optimized by metabolic engineering.

"Carbon-Centered Radical Addition to O=C of Amides or Esters as a Route to C-O Bond Formations" Remains Elusive.

"Carbon-Centered Radical Addition to O=C of Amides or Esters as a Route to C-O Bond Formations" was recently claimed by Liu et al. and published in this journal. However, is there really experimental or computational evidence for this reaction? This question is discussed in more detail in this Correspondence article.

Renewable Polyethers via GaBr3 -Catalyzed Reduction of Polyesters.

Herein, a novel approach is reported for the synthesis of medium- and long-chain aliphatic polyethers 2 based on the GaBr3 -catalysed reduction of polyesters 1 with TMDS as the reducing agent. Thus, various linear and branched aliphatic polyesters 1 were prepared and systematically investigated for this reduction strategy, demonstrating the applicability and versatility of this new polyether synthesis protocol. Medium- and long-chain chain polyethers were obtained from the respective polyesters without or with minor chain degradation, whereas short-chain polyesters, such as poly-l-lactide 1 i and poly[(R)-3-hydroxybutanoate] 1 j, showed major chain degradation. In this way, previously unavailable and uncommon polyethers were obtained and studied.

Initiation of radical chain reactions of thiol compounds and alkenes without any added initiator: thiol-catalyzed cis/trans isomerization of methyl oleate.

A kinetic study of the dodecanethiol-catalyzed cis/trans isomerization of methyl oleate (cis-2) without added initiator was performed by focusing on the initiation of the radical chain reaction. The reaction orders of the rate of isomerization were 2 and 0.5 for 1 and cis-2, respectively, and an overall kinetic isotope effect k(H)/k(D) of 2.8 was found. The initiation was shown to be a complex reaction. The electron-donor/-acceptor (EDA) complex of dodecanethiol (1) and cis-2 formed in a pre-equilibrium reacts with thiol 1 to give a stearyl and a sulfuranyl radical through molecule-assisted homolysis (MAH) of the sulfur-hydrogen bond. Fragmentation of the latter gives the thiyl radical, which catalyzes the cis/trans isomerization. A computational study of the EDA complex, MAH reaction, and the sulfuranyl radical calculated that the activation energy of the isomerization was in good agreement with the experimental result of E(A)=82 kJ M(-1). Overall, the results may explain that the thermal generation of thiyl radicals without any initiator is responsible for many well-known thermally initiated addition reactions of thiol compounds to alkenes and their respective polymerizations and for the low shelf-life stability of cis-unsaturated thiol compounds and of mixtures of alkenes and thiol compounds.

Oils and fats as renewable raw materials in chemistry.

Oils and fats of vegetable and animal origin have been the most important renewable feedstock of the chemical industry in the past and in the present. A tremendous geographical and feedstock shift of oleochemical production has taken place from North America and Europe to southeast Asia and from tallow to palm oil. It will be important to introduce and to cultivate more and new oil plants containing fatty acids with interesting and desired properties for chemical utilization while simultaneously increasing the agricultural biodiversity. The problem of the industrial utilization of food plant oils has become more urgent with the development of the global biodiesel production. The remarkable advances made during the last decade in organic synthesis, catalysis, and biotechnology using plant oils and the basic oleochemicals derived from them will be reported, including, for example, ω-functionalization of fatty acids containing internal double bonds, application of the olefin metathesis reaction, and de novo synthesis of fatty acids from abundantly available renewable carbon sources.

ESIMS studies and calculations on alkali-metal adduct ions of ruthenium olefin metathesis catalysts and their catalytic activity in metathesis reactions.

Electrospray ionization mass spectrometry (ESIMS) and subsequent tandem mass spectrometry (MS/MS) analyses were used to study some important metathesis reactions with the first-generation ruthenium catalyst 1, focusing on the ruthenium complex intermediates in the catalytic cycle. In situ cationization with alkali cations (Li(+), Na(+), K(+), and Cs(+)) using a microreactor coupled directly to the ESI ion source allowed mass spectrometric detection and characterization of the ruthenium species present in solution and particularly the catalytically active monophosphine-ruthenium intermediates present in equilibrium with the respective bisphosphine-ruthenium species in solution. Moreover, the intrinsic catalytic activity of the cationized monophosphine-ruthenium complex 1 aK(+) was directly demonstrated by gas-phase reactions with 1-butene or ethene to give the propylidene Ru species 3 aK(+) and the methylidene Ru species 4 aK(+), respectively. Ring-closing metathesis (RCM) reactions of 1,6-heptadiene (5), 1,7-octadiene (6) and 1,8-nonadiene (7) were studied in the presence of KCl and the ruthenium alkylidene intermediates 8, 9, and 10, respectively, were detected as cationized monophosphine and bisphosphine ruthenium complexes. Acyclic diene metathesis (ADMET) polymerization of 1,9-decadiene (14) and ring-opening metathesis polymerization (ROMP) of cyclooctene (18) were studied analogously, and the expected ruthenium alkylidene intermediates were directly intercepted from reaction solution and characterized unambiguously by their isotopic patterns and ESIMS/MS. ADMET polymerization was not observed for 1,5-hexadiene (22), but the formation of the intramolecularly stabilized monophosphine ruthenium complex 23 a was seen. The ratio of the signal intensities of the respective with potassium cationized monophosphine and bisphosphine alkylidene Ru species varied from [I(4a)]/[I(4)]=0.02 to [I(23a)]/[I(23)]=10.2 and proved to be a sensitive and quantitative probe for intramolecular pi-complex formation of the monophosphine-ruthenium species and of double bonds in the alkylidene chain. MS/MS spectra revealed the intrinsic metathesis catalytic activity of the potassium adduct ions of the ruthenium alkylidene intermediates 8 a, 9 a, 10 a, 15 a, and 19 a, but not 23 a by elimination of the respective cycloalkene in the second step of RCM. Computations were performed to provide information about the structures of the alkali metal adduct ions of catalyst 1 and the influence of the alkali metal ions on the energy profile in the catalytic cycle of the metathesis reaction.

Electron-transfer-catalyzed dimerization of trans-anethole: detection of the distonic tetramethylene radical cation intermediate by extractive electrospray ionization mass spectrometry.

The desolvating droplets of EESI were used as microreactor for the mass spectrometric study of short-lived transients of reactions in condensed liquid phase in the millisecond time region. The electron-transfer-catalyzed dimerization of trans-anethole was investigated and the intermediates in the radical cation chain reaction were isolated and characterized by MS-MS. The distonic tetramethylene radical cation 3(o)(*+) was detected as intermediate, and its cyclization to give the cyclobutane radical cation 3(c)(*+) was observed giving strong evidence that the reaction takes place stepwise.

ESI-MS study on the aldol reaction catalyzed by L-proline.

The aldol reaction catalyzed by L-proline has been monitored and the accepted mechanism confirmed by intercepting and characterizing, for the first time, all the proposed intermediates by ESI-MS/MS.

10 years after rio-concepts on the contribution of chemistry to a sustainable development.

The principles of the United Nations Conference on Environment and Development (UNCED), held in June 1992 in Rio de Janeiro, and Agenda 21, the comprehensive plan of action for the 21st century, adopted 10 years ago by more than 170 governments, address the pressing problems of today and also aim at preparing the world for the challenges of this century. The conservation and management of resources for development are the main focus of interest, to which the sciences will have to make a considerable contribution. Natural, economic, and social sciences will have to be integrated in order to achieve this aim. In their future programs, the associations of the chemical industries in Europe, Japan, and the USA have explicitly accepted their obligation to foster a sustainable development. In this review we investigate innovations in chemistry exemplarily for such a development with regard to their ecological, economical, and social dimensions from an integrated and interdisciplinary perspective. Since base chemicals are produced in large quantities and important product lines are synthesized from them, their resource-saving production is especially important for a sustainable development. This concept has been shown, amongst others, by the example of the syntheses of propylene oxide and adipic acid. In the long run, renewable resources that are catalytically processed could replace fossil raw materials. Separation methods existing today must be improved considerably to lower material and energy consumption. Chemistry might become the pioneer of an innovative energy technique. The design of chemical products should make possible a sustainable processing and recycling and should prevent their bio-accumulation. Methods and criteria to assess their contribution to a sustainable development are necessary. The time taken to introduce the new more sustainable processes and products has to be diminished by linking their development with operational innovation management and with efficient environmental-political control procedures.

Solvent-Free Organic Syntheses.

Ecological points of view must nowadays be taken into consideration in the development of new syntheses and apportioned due importance in assessing the viability of a new synthesis. A crucial factor here is the need to restrict the use of ecologically harmful organic solvents. Examples are presented which show that solvent-free reactions are not only of interest from an environmental viewpoint, but also offer considerable advantages in terms of yield, selectivity, and simplicity of the reaction procedures.

Synthesis of ethers by GaBr3 -catalyzed reduction of carboxylic acid esters and lactones by siloxanes.

Ethers were synthesized by reduction of the respective esters catalyzed by gallium bromide (GaBr3 ) and using siloxanes, preferentially 1,1,3,3-tetramethyldisiloxane, as reductant. Methyl oleate, triglycerides, that is, tributyrine and glyceryl triundec-10-enoate as well as γ- and δ-lactones were converted into the respective ethers in high to moderate yields. γ-Lactones were reduced with high selectivity in the presence of a methyl ester functionality. The reduction has been carried out at room temperature or moderately elevated temperature of up to 60 °C using stoichiometric amounts of the reductant and 0.005-0.01 equiv of GaBr3 as catalyst per ester functionality without any solvent added. After a reaction time of 1-4 h the conversion of the substrate was 100 %. The product was separated from polymeric siloxanes formed as coupled product by simple distillation.

Sustainable global energy supply based on lignocellulosic biomass from afforestation of degraded areas.

An important aspect of present global energy scenarios is the assumption that the amount of biomass that can be grown on the available area is so limited that a scenario based on biomass as the major source of energy should be unrealistic. We have been investigating the question whether a Biomass Scenario may be realistic. We found that the global energy demand projected by the International Energy Agency in the Reference Scenario for the year 2030 could be provided sustainably and economically primarily from lignocellulosic biomass grown on areas which have been degraded by human activities in historical times. Moreover, other renewable energies will contribute to the energy mix. There would be no competition with increasing food demand for existing arable land. Afforestation of degraded areas and investment for energy and fuel usage of the biomass are not more expensive than investment in energy infrastructure necessary up to 2030 assumed in the fossil energy based Reference Scenario, probably much cheaper considering the additional advantages such as stopping the increase of and even slowly reducing the CO(2) content of the atmosphere, soil, and water conservation and desertification control. Most importantly, investment for a Biomass Scenario would be actually sustainable, in contrast to investment in energy-supply infrastructure of the Reference Scenario. Methods of afforestation of degraded areas, cultivation, and energetic usage of lignocellulosic biomass are available but have to be further improved. Afforestation can be started immediately, has an impact in some few years, and may be realized in some decades.

On-line monitoring of Brookhart polymerization by electrospray ionization mass spectrometry.

For the first time, an electrospray ionization (ESI) mass spectrometer coupled on-line with a microreactor permitted the fast screening of polymerization growth of alkenes in the liquid phase mediated by palladium Brookhart catalyst and allowed the direct mass spectrometric identification of alkyl chains still bonded to Pd. The method also allowed us to intercept the catalytically active cationic intermediates of the Brookhart polymerization of alkenes, and to prove on-line their catalytic activity through ion/molecule reactions. The technique is fast and sensitive, requires no sample preparation and manipulation, and is therefore suitable for the fast screening of catalyst/polymer growth by MS identification, with potential applications in areas such as new catalyst development, polymer chemistry, and product quality monitoring in manufacturing.

Plant oil renewable resources as green alternatives in polymer science.

The utilization of plant oil renewable resources as raw materials for monomers and polymers is discussed and reviewed. In an age of increasing oil prices, global warming and other environmental problems (e.g. waste) the change from fossil feedstock to renewable resources can considerably contribute to a sustainable development in the future. Especially plant derived fats and oils bear a large potential for the substitution of currently used petrochemicals, since monomers, fine chemicals and polymers can be derived from these resources in a straightforward fashion. The synthesis of monomers as well as polymers from plant fats and oils has already found some industrial application and recent developments in this field offer promising new opportunities, as is shown within this contribution. (138 references.)