1,720,996 research outputs found
Isosorbide as biobased platform chemical: Recent advances
No full textD-sorbitol and isosorbide have been indicated by the US Department of Energy among the 15 target molecules of special interest for biorefinery development. This minireview reports on isosorbide conversion into potential substitutes of petrochemicals. In the last two years, investigations on the peculiar reactivity of isosorbide have been focused on preparation of green solvents, biobased monomers for polymerization reactions, functional materials, synthesis of pharmaceuticals, surfactants, novel organocatalysts, potential flame retardants, and cross-linking agents
Organic carbonates as green media: from laboratory syntheses to industrial applications
No full textThe research on greener solvents is of paramount importance for achieving sustainable processes. To replace traditional hazardous media, green solvents must display negligible environmental effects and biological degradability while being available on a large scale and exhibiting comparable or even superior performances than the currently employed media. In this scenario, organic carbonates (OCs) are among the most prominent candidates as they are commercially available at a reasonable price and offer a broad range of tunable proprieties, making them usable in a wide range of applications. Based on this premise, this review focuses on the use of OCs as green media ranging from laboratory synthetic approaches to industrial applications. According to our literature screening covering the last 40 years, organic carbonates have mostly been investigated as electrolyte solvents (23%), media in organic synthesis (21%) and solvents for the extraction of compounds from different biological and non-biological matrices (13%). Besides, OCs have applications in several other fields spanning from analytical chemistry and biological/biochemical fields to the restoration of ancient artifacts. Most of the OCs used in these applications are dialkyl carbonates (DACs), such as dimethyl carbonate (DMC), propylene carbonate (PC) and ethylene carbonate (EC), which are commercially available at low cost. However, owing to their simple synthetic procedures, new custom-made organic carbonates have been synthetized and used for membrane casting, preparation of polymers and plasticizers, surface modification of materials and as electrolytes in Li-ion batteries. Organic carbonates go beyond simply replacing toxic solvents; they offer an opportunity to transform a variety of processes into sustainable processes. From enhancing the performance of batteries and advancing materials science to driving innovations in green chemistry and improving industrial sustainability, their potential is vast. The adoption of organic carbonates as green media is likely to have far-reaching effects, making them valuable tools for researchers and industries aiming to develop more sustainable processes
Acid catalyzed synthesis of dimethyl isosorbide via dimethyl carbonate chemistry
Full text linkDimethyl isosorbide (DMI) is a bio-based solvent that can be used as green alternative for conventional dipolar
media (dimethyl sulfoxide, dimethylformamide, and dimethylacetamide). The main synthetic procedures to DMI
reported in the literature are based on the methylation of isosorbide employing different alkylating agents
including toxic halogen compounds such as alkyl halides. A more sustainable alternative would be to employ
dimethyl carbonate (DMC), a well-known green reagent and solvent, considered one of the most promising
methylating agents for its good biodegradability and low toxicity. Indeed, in recent years, DMC-promoted
methylation of isosorbide has been extensively exploited although mostly in the presence of a base or an
amphoteric catalyst. In this work, we report for the first time a comprehensive investigation on the synthesis of
DMI via DMC chemistry promoted by heterogeneous acid catalyst (Amberlyst-36 and Purolite CT275DR). Re-
action conditions were optimized and then applied for the methylation of isosorbide and its epimers, isoidide and
isomannide. Considerations on the related reaction mechanism were reported highlighting the difference in the
preferred reaction pathways among this new synthetic approach and the previously reported base-catalyzed
procedures
Recommended from our members
Catechol-based macrocyclic aromatic ether-sulfones: Synthesis, characterization and ring-opening polymerization
Full text linkCyclocondensation between 4,4`-bis(4-chlorobenzenesulfonyl)biphenyl and catechol, with subsequent chromatographic separation of the reaction products, led to the isolation of four novel ether-sulfone macrocycles (cyclic dimer, -trimer, -tetramer and -pentamer). Similarly, cyclocondensation of catechol with a novel seven-ring diketone/disulfone monomer allowed the isolation of the two new aromatic ether-ketone-sulfone macrocycles, a cyclic monomer and a cyclic dimer. Transannular shielding and deshielding effects in the cyclic monomer produce substantial chemical shift differences for chemically equivalent protons in the 1H NMR spectra of the cyclic monomer and -dimer. Fluoride-initiated ring-opening polymerization of the ether-sulfone cyclic trimer affords a novel, high-molecular weight poly(ether-sulfone)
Dimethyl isosorbide via organocatalyst N-methyl pyrrolidine: scaling up, purification and concurrent reaction pathways
No full textDimethyl isosorbide (DMI) is a well-known bio-based green replacement for conventional dipolar solvents such as dimethyl sulfoxide and dimethylformamide. The synthesis of DMI mainly relies on the etherification of the bio-based platform chemical isosorbide in the presence of basic or acid catalysts and by employing different alkylating agents. Among them, dimethyl carbonate (DMC) is considered one of the most promising for its good biodegradability and low toxicity. In this work, we report on a comprehensive investigation on high yielding methylation of isosorbide via DMC chemistry promoted by nitrogen organocatalyst N-methyl pyrrolidine (NMPy). Reaction conditions were optimized and then efficiently applied for the methylation of isosorbide epimers, isoidide and isomannide, and for some preliminary scale-up tests (up to 10 grams of isosorbide). The purification of DMI from the reaction mixture was achieved by both column chromatography and distillation at reduced pressure. NMPy demonstrated to be an excellent catalyst also for the one-pot conversion of d-sorbitol into DMI. Furthermore, for the first time, all seven methyl and methoxycarbonyl intermediates observed in the etherification of isosorbide were synthetised, isolated and fully characterised. This has provided an insight on the concurrent reaction pathways leading to DMI and on the role played by NMPy in the methylation of isosorbide. Finally, the reaction mechanisms for the methylation, methoxycarbonylation and decarboxylation promoted by NMPy partaking in the conversion of isosorbide into DMI via DMC chemistry have been proposed
Unravelling the crystal and molecular structure of a 1,3-linked aromatic poly(ether-ketone)
Full text linkHighly-oriented fibres of the aromatic polyetherketone [-O(1,4-Ar)CO(1,3-Ar)CO(1,4-Ar)-]n (Ar = phenylene) obtained by nucleophilic polycondensation of F(1,4-Ar)CO(1,3-Ar)CO(1,4-Ar)F with HO(1,4-Ar)CO(1,3-Ar)CO(1,4-Ar)OH afford, after annealing, very well-resolved X-ray fibre patterns. The new diffraction data are used to test two different published models for the crystal and molecular structure of this polymer, both based on a three-ring crystallographic repeat, and it is shown by diffraction-modelling that neither of these structures is compatible with the new fibre-data. In contrast, we report a novel structure, based on a six-ring crystallographic repeat, that gives a simulated fibre-diffraction pattern in very good agreement with the experimental pattern. Crystal data for the new structure are: orthorhombic, space group Pcam, a = 7.67, b = 6.13, c = 29.72 Å, two chains per cell, V = 1397 Å3 ρ = 1.43. Unusually, the two chains in the unit cell are related by an a-glide, meaning that the carbonyl groups in the two chains are aligned anti-parallel rather than having the more generally found parallel arrangement resulting from the presence of a b-glide. The new structure is shown to be fully compatible with previously published X-ray powder and electron diffraction data
Synthesis of 2,5-furandicarboxylic acid dimethyl ester from galactaric acid via dimethyl carbonate chemistry
Full text linkA convenient and simple procedure for the one-pot synthesis of 2,5-furandicarboxylic acid dimethyl ester (FDME) from galactaric (mucic) acid via dimethyl carbonate (DMC) chemistry is presented. Optimization of the reaction conditions showed that when galactaric acid was reacted with DMC in the presence of Amberlyst-36 for 2 hours at 200 °C, FDME formed as the main product. The compound was isolated as a pure crystalline powder in 70% yield using a simple custom-made purification protocol. The reaction intermediates of this one-pot procedure were identified and a possible reaction mechanism was proposed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
