The antioxidant activity, in terms of radical scavenging capacity, of altogether 15 different lignans was measured by monitoring the scavenging of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). The effect of differences in skeletal arrangement or the degree of oxidation of the lignans was investigated in a structure-activity relationship study. A large variety in the radical scavenging capacities of the different lignans was observed and related to some structural features. Lignans with catechol (3,4-dihydroxyphenyl) moieties exhibited the highest radical scavenging capacity, while the corresponding guaiacyl (3-methoxy-4-hydroxyphenyl) lignans showed a slightly weaker scavenging capacity. In addition, the butanediol structure was found to enhance the activity, whereas a higher degree of oxidation at the benzylic positions decreased the activity. Additionally, the readily available lignans (-)-secoisolariciresinol, a mixture of hydroxymatairesinol epimers and (-)-matairesinol were studied in more detail, including kinetic measurements and identification of oxidation products in the reactions with DPPH and ABAP (2,2-azobis(2-methylpropionamidine) dihydrochloride. The identification of reaction products, by GC-MS, HPLC-MS and NMR spectroscopy, showed that dimerisation of the two aromatic moieties was the major radical termination reaction. Also, the formation of adducts was a predominant reaction in the experiments with ABAP. The kinetic data obtained from the reactions between the lignans and DPPH indicated a complex reaction mechanism.

Epoxidation of cottonseed oil by peroxyformic acid (PFA) was studied in a semibatch calorimeter. This liquid-liquid reaction system is composed of different exothermic steps. Thus, a kinetic modeling strategy to diminish the number of parameters to estimate was developed by investigating each reaction system: PFA synthesis and decomposition, ringopening and epoxidation. A thermal study was conducted by determining heat capacity of the different organic species, and by analyzing the evolution of global heat-transfer coefficient with the reaction extent. The epoxidation reaction was performed in a semibatch reactor under isoperibolic mode within an initial temperature range of 50-708C, an organic phase of 30-34 wt %, a formic acid molar flow rate of 0.02-0.05 mol/min and an addition time of 25-50 min. The interfacial mass transfer was supposed to be faster than the intrinsic reaction kinetics suppressing the use of mass transfer correlation. Nonlinear regression was used to estimate the kinetic and thermal parameters. The kinetic parameters of epoxidation of the three different fatty acids, namely oleic, linoleic, and its intermediate were estimated. The reaction enthalpy of epoxidation was estimated to 2230 6 3.8 kJ/mol, and the reaction enthalpy of ring-opening was measured to be 290 kJ/mol by Tian-Calvet calorimeter.Kinetic modeling of vegetable oils epoxidation by peroxycarboxylic acids formed in situ in batch and semibatch reactor system has been described by several research groups. This system is complex due to the presence of several consecutive steps. Different approaches have been done such as:Taking into account mass transfer parameters using different correlations or by estimating them, this model is called two-phase kinetic model. Frequently, only carboxylic and peroxycarboxylic acids mass-transfer coefficients were taken into account. [24][25][26] Pseudohomogeneous model by assuming fast mass transfer compared to reaction kinetics, this leads to a simplification of the mass balance equations. [27][28][29][30][31][32] Establishing the mass balance only on the organic phase and assuming steady-state approach on peroxycarboxylic acids formation. 13,[33][34][35][36][37][38][39][40] The advantage of that approach is that graphical method can be used to determine epoxidation rate constants, but one neglects ring-opening reaction. This model is called homogeneous model.Some authors have focused their study only on the ringopening reactions system in batch or semibatch reactor. One can distinguish the two following approaches:Only considering the organic phase and using a pseudofirst-order approach. 41-43 Figure 1. Simplified mechanism of the Prileschajew oxidation of vegetable oils.

Direct catalytic valorization of bioethanol to 1-butanol over different alumina supported catalysts was studied. Thirteen (13) heterogeneous catalysts were screened in search for the optimal material composition for direct one-pot conversion of ethanol to 1-butanol. For the most promising catalyst, a 25% ethanol conversion with 80% selectivity (among liquid carbon products) to 1-butanol could be reached at 250 °C. Additionally, the reaction kinetics and mechanisms were further investigated upon use of the most suitable catalyst candidate. OPEN ACCESSCatalysts 2012, 2 69

The migration of acetyl, pivaloyl, and benzoyl protective groups and their relative stabilities at variable pH for a series of beta- d-galactopyranoses were studied by NMR spectroscopy. The clockwise and counterclockwise migration rates for the different ester groups were accurately determined by use of a kinetic model. The results presented provide new insights into the acid and base stabilities of commonly used ester protecting groups and the phenomenon of acyl group migration and may prove useful in the planning of synthesis strategies.