Fenton’s Reagent Catalyzed Release of Carbon Monooxide from 1,3-Dihydroxy Acetone

Triose sugar, 1,3-dihydroxy acetone (DHA) on treatment with Fenton’s reagent releases CO under physiological conditions. The release of CO has been demonstrated by myoglobin assay and quantum chemical studies. The mechanistic study has been carried out using B3LYP/6-311++G­(d,p), M06-2X/6-311++G­(d,p) and CCSD­(T)//M06-2X/6-311++G­(d,p) level of theories in aqueous medium with dielectric constant of 78.39 by employing the polarized continuum model (PCM). The theoretical investigation shows that DHA breaks down completely into 2 equiv of CO, 1 equiv of CO₂, and 6 equiv of H₂O without formation of toxic metabolites. The activation barriers of some steps are as high as ∼50 kcal mol^–1 along with barrierless intermediate steps resulting from highly stabilized intermediates. The quantum tunneling mechanism of proton transfer steps has been confirmed through kinetic isotope effect study. The natural bond orbital analysis is consistent with the proposed mechanism. The present protocol does not require any photoactivation and thus it can serve as a promising alternative to transition metal CO-releasing molecules. The present work can initiate the study of carbohydrates as CO-releasing molecules for therapeutic applications and it could also be useful in generation of CO for laboratory applications

Pyrolysis of three different categories of automotive tyre wastes: Product yield analysis and characterization

Thermal pyrolysis of three automobile tyre waste (ATW’s) - light vehicle tyre (LVT), medium vehicle tyre (MVT) and heavy vehicle tyre (HVT), was investigated in a thermogravimetric analyser and a batch reactor. Such investigations on the effect of the fractions of natural and synthetic rubbers on product yield and the type of tyres on the pyrolysis process and products have not reported in the literature. The product yields were influenced strongly by the reactor temperature with higher temperature favouring the formation of more gases and more char being formed at lower temperatures. The range of degradation temperature was found to be the smallest for LVT as it contained mostly natural rubber (NR), while it was the largest for HVT due to the presence of NR and synthetic butyl rubber(SBR), having widely different degradation temperatures. In the batch reactor, maximum liquid yields of 51%, 45% and 63.5% were obtained for LVT, MVT and HVT at the optimum temperatures of 650 °C, 750 °C and 750 °C respectively at a heating rate of 20 °C/min. The oil obtained from LVT shows high aromatic content while the oil from MVT and HVT has a high presence of napthelinic component. The reactor pressure profile showed that the LVT started producing the non-condensable gaseous fraction earliest due to faster degradation. More secondary reactions for MVT generated more gases, leading to the highest final reactor pressure and high concentration of non condensable gases. Gas chromatographic (GC) analysis indicated that H2, CO, CO2, CH4, C2, C3H8 and C4 were the main gases obtained for all type of tyre wastes. Cracking of heavier hydrocarbons to the lighter ones and H2 was more dominant in MVT, while this was least prominent in HVT, producing less H2 and added oil. The activation energies for the pyrolysis reaction of LVT, MVT and HVT wastes were estimated to be 53.185, 62.489 and 64.574 kJ/mol respectively