Ruthenium ion catalysed C–C bond activation in lignin model compounds – towards lignin depolymerisation

Lignin is the most abundant renewable feedstock to produce aromatic chemicals, however its depolymerisation involves the breaking of several C–O and C–C inter-unit linkages that connect smaller aromatic units that are present in lignin. Several strategies have been reported for the cleavage of the C–O inter-unit linkages in lignin. However, till today, only a few methodologies have been reported for the effective breaking or the conversion of the recalcitrant C–C inter unit linkages in lignin. Here we report the ruthenium ion catalysed oxidative methodology as an effective system to activate or convert the most recalcitrant inter unit linkages such as β-5 and 5–5′ present in lignin. Initially, we used biphenyl as a model compound to study the effectiveness of the RICO methodology to activate the 5–5′ C–C linkage. After 4 h reaction at 22 °C, we achieved a 30% conversion with 75% selectivity towards benzoic acid and phenyl glyoxal as the minor product. To the best of our knowledge this is the first ever oxidative activation of the C–C bond that connects the two phenyl rings in biphenyl. DFT calculation revealed that the RuO4 forms a [3 + 2] adduct with one of the aromatic C–C bonds resulting in the opening of the phenyl ring. Biphenyl conversion could be increased by increasing the amount of oxidant; however, this is accompanied by a reduction in the carbon balance because of the formation of CO2 and other unknown products. We extended this RICO methodology for the oxidative depolymerisation of lignin model hexamer containing β-5, 5–5′ and β-O-4 linkages. Qualitative and quantitative analyses of the reaction mixture were done using 1H, 13C NMR spectroscopy methods along with GC-MS and Gel Permeation Chromatographic (GPC) methods. Advanced 2D NMR spectroscopic methods such as HSQC, HMBC and 31P NMR spectroscopy after phosphitylation of the mixture were employed to quantitatively analyse the conversion of the β-5, 5–5′ and β-O-4 linkages and to identify the products. After 30 min, >90% of the 5–5′ and linkages and >80% of the β-5′ are converted with this methodology. This is the first report on the conversion of the 5–5′ linkage in lignin model hexamer

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Absorption of low molecular weight penetrants by a thermoplastic polyimide

The response of a thermoplastic polyimide (TPI) to immersion in a range of solvents was investigated by a number of experimental techniques. The kinetics of solvent diffusion were determined by weight uptake and NMR imaging, the effect of absorbed solvent on thermal behaviour was investigated by dynamic mechanical analysis and differential scanning calorimetry and the morphology of TPI exposed to solvent was determined by wide-angle X-ray scattering. The tensile properties of amorphous and crystalline TPI were measured before and after exposure to solvent. Amorphous TPI absorbed significant quantities of some solvents that lowered the T-g, but none were sufficiently plasticising to induce crystallisation at room temperature. There was a direct correlation between the extent of solvent ingress and the environmental stress cracking behaviour of amorphous TPI. Crystalline TPI absorbed only small quantities of all the solvents used, but showed limited environmental stress cracking resistance. (C) 2000 Elsevier Science Ltd. All rights reserved

Anatomy of an Experimental Political Stock Market.

Results from the Iowa Political Stock Market are analyzed to ascertain how well markets work as aggregators of information. The authors find that the market worked extremely well, dominating opinion polls in forecasting the outcome of the 1988 presidential election, even though traders in the market exhibited substantial amounts of judgment biases. Their explanation is that judgment bias refers to average behavior, while in markets it is marginal traders who influence price. They present evidence that in this market a sufficient number of traders were free of judgment bias so that the market was able to work well. Copyright 1992 by American Economic Association.

Biocatalytic conversion of lignin model oligomer using a laccase-mediator system

The use of the laccase enzyme from the fungus Trametes versicolor, coupled with the mediator 1-hydroxybenzotriazole (1-HBT) has been shown to be effective for the biocatalytic conversion of a hexameric lignin model compound containing three of the most common linkages found in native lignin. Cleavage of the model takes place over a 24 hours period predominantly at the β-O-4 ether linkage to give a previously known β-5 dimer intermediate which in turn was rapidly consumed to further degradation products. There is also mass spectrometric evidence of repolymerisation of the β-5 dimer and other degradation intermediates to form higher oligomers. Mechanistic pathways to account for the major catalytic processes are proposed