A. Lunghi

The N⋯I Intermolecular Interaction as a General Protocol for the Formation of Perfluorocarbon–Hydrocarbon Supramolecular Architectures 1

Abstract The formation of infinite 1D networks where diiodoperfluorocarbons are halogen bonded to di-nitrogen substituted hydrocarbons is described. The N⋯I non-covalent interaction is specific, directional, and strong enough to effectively overcome the low affinity between perfluorocarbon and hydrocarbon modules and to drive their self-assembly in the solid and liquid phase. Several analytical techniques are used to identify and characterise the electron donation from nitrogen to iodine atoms. The effectiveness of the interaction is largely independent from the overall structure of the involved modules. Indeed, supramolecular architectures have been obtained starting from diiodoperfluoroalkanes and -arenes (electron poor motifs) as well as from pyridine derivatives and di- or trialkylamines (electron rich motifs). The halogen bonding can thus begin to be considered as a first choice intermolecular interaction in crystal engineering.

Perfluorocarbon—hydrocarbon self assembling. Thermal and vibrational analyses of one-dimensional networks formed by α,ω-diiodoperfluoroalkanes with K.2.2. and K.2.2.2.

Abstract When perfluorocarbon diiodides 1 and hydrocarbon diamines 2,3 are co-crystallised from chloroform a donor-acceptor interaction between the nitrogen atoms of 1 and the iodine atoms of 2, 3 lead to the formation of infinite one-dimensional coordination networks 4 and 5 . Thermal and infrared analyses of these adducts are reported. Nitrogen-iodine interaction is proposed as a non-covalent bonding strong enough to drive the formation of co-crystals between fluorocarbon and hydrocarbon derivatives.

Emulsion polymerization of vinyl acetate: safe optimization of a hazardous complex process.

Fast and exothermic discontinuous emulsion polymerization processes are particularly difficult to optimize from both safety and productivity point of view because of the occurrence of side undesired reactions (e.g. chain transfer to monomer, backbiting, propagation of tertiary radicals, termination by disproportion, etc.) and the hazards of boiling phenomena and stable foam formation under atmospheric pressure. Moreover, the relevant number of loading, heating and cooling steps, required before starting the monomer addition (that is, the desired reaction), makes a strict product quality reproducibility very difficult to obtain. Under these operating conditions, it is necessary to employ a suitable combined theoretical and experimental procedure able to detect the optimum process dosing time at both the laboratory and the industrial scale. In this work, it is shown how to use the topological criterion theory together with proper adiabatic calorimeter and RC1 experimental data to safely optimize the synthesis of polyvinyl acetate through the radical emulsion polymerization of vinyl acetate by the means of an indirectly cooled isoperibolic semibatch reactor.

Hazardous N-containing system: thermochemical and computational evaluation of the intrinsic molecular reactivity of some aryl azides and diazides

The exothermic decompositions of the tosyl azide 1, five substituted aryl monoazides 2––6 and two diazides: 1-azido-4-(4-azidophenoxy)benzene 7 and 1-azido-4-[(4-azidophenyl)sulfanyl]benzene 8 were studied experimentally using DSC, weight loss TGA-FTIR and C80-FTIR techniques, and theoretically using the CHETAH software. Numerical modelling and electron impact mass spectrometry (EI-MS) were also performed to investigate the nature of the intrinsic molecular reactivity of azides 1––8, and the possible early stage rate-controlling of an oxidative self-heating process. Significant data were obtained in the instances of 4-methylbenzenesulfonyl azide 1, 4-azido-1,1′-biphenyl-2,2-azido-1,1′-biphenyl 3 and 1-azido-2-(trifluoromethyl)benzene 6. The most likely decomposition pathways of the azides are proposed to explain the observed thermal behavior.

Hydroxyurea explosion: a thermoanalytical and calorimetric study

Abstract An accident occurred during a production process of hydroxyurea. Several thermoanalytical techniques were used in order to understand the reason for the accident, even utilising a simulation program. Thermogravimetric analysis and Fourier transform infra-red spectroscopy were performed to identify the decomposition products according to European Directive 96/82/EC, the so-called Seveso II.

Explosion during distillation in a solvent recovery plant

Abstract Calorimetric and thermoanalytical methods were used to understand the reason why, during a distillation process, an explosion occurred in a solvent recovery plant. A sample of unreacted residue of the explosion was analysed by differential scanning calorimetry (DSC), thermogravimetry (TG), heat flux calorimetry and adiabatic calorimetry (ARC). The thermal stability of the residue was detected and the mechanism of the decomposition was deduced.