Formation and nitration heats for 3-nitro-4-chloro- and 3,5-dinitro-4-chloro-benzotrifluoride. Dinitration reaction investigation

Although various authors have determined the heats of combustion of many halogen derivatives we still do not have at our disposal data concerning the 3-nitro-4-chlorobenzotrifluoride and the 3,5-dinitro-4-chlorobenzotrifluoride.The object of this study has been that of determining the thermochemical constants for the above mentioned compounds. The values of the heats of combustion and of formation have been determined experimentally and from them the heats of nitration. These data and those determined with Handrick's method (group's energy contribution) have been compared with the heats of reaction carrying the nitration into an adiabatic system.Afterwards it has been investigated how to get the maximum output for the dinitro production. Data and considerations are reported.     

Peptides adsorption on TiO2 and Au: Molecular organization investigated by NEXAFS, XPS and IR

We present a spectroscopic study of the structure of two peptides deposited on Au and TiO₂:

- PeptA, (EAK16-RGD) bringing the adhesive RGD sequence linked to EAK16;

- PeptB, having RGD linked to a “scrambled” sequence of the EAK16 peptide.

Previously reported NEXAFS investigations on thin films of the self-assembling peptide EAK16 deposited on Au and TiO₂, revealed molecular order and orientation for both substrates.IR spectra show a β-sheet conformation for PeptA and a random structure for PeptB. Angular-dependent NEXAFS measurements reveal an ordered structure with preferential molecular orientation only for PeptA. XPS analysis indicates that PeptA is adsorbed on TiO₂ in a larger amount than PeptB.     

Electrofluorination of uracil

In view of the importance of the medical applications of fluorinated uracil and derivatives, synthetic methods directed to obtain such compounds are of particular interest. Several aspects of the electrochemical fluorination of uracil in different experimental conditions will be discussed.     

Correlation between yield and operating conditions in the electrochemical fluorination of tripropylamine

Electrochemical fluorination of tripropylamine in anhydrous hydrogen fluoride was studied in order to verify the correlation between the operating conditions and the yield of the corresponding perfluoroamine. The parameters tested were: temperature, voltage, initial concentration of amine in the bath, constant concentration of amine in the bath and stirring effect. Experimental data show that temperature is the parameter exerting the most remarkable influence over perfluoroamine yield and by-products formation.     

Liquid-phase fluorination of aromatic compounds by elemental fluorine

The fluorination of aromatic compounds (benzene, toluene, phenol and benzoic acid) by elemental fluorine diluted with nitrogen has been investigated in various solvents (Freon 11, chloroform, methanol, trifluoroacetic acid, 2,2,2-trifluoroethanol, water) in order to define the influence of the experimental conditions on the reaction. Experiments have been carried out by varying the temperature, the substrate concentration in solution, the molar ratio of fluorine to substrate, and the concentration of fluorine in the fluorine/nitrogen mixture. In all cases, the effects on the yield of fluorinated products were studied. Monofluorinated compounds were mainly found in the reaction mixture, the isomers formed being in accord with the mechanism for electrophilic substitution. The highest yield of monofluorinated products was obtained with polar solvents and the following order was found: CFCl₃ < CHCl₃ < CH₃OH < CF₃CH₂OH < CF₃COOH. Interesting results were also found using particular additives (for instance, KOH or C₄F₉SO₃Na in methanol) or water as the solvent. A direct relationship was observed between the yield of monofluorinated compounds and the molar ratio of fluorine to substrate, which has to be less than one in order to obtain high yields. In contrast, low selectivity, expressed as the yield ratio of ortho to para (or meta) isomers, was found.     

Electrochemical fluorination of the n-methylmorpholine

The results of some researches as regards the possibility to carry out selective electrochemical fluorinations of organic compounds by use of organic solvents are reported.Various organic solvents (acetonitrile, 1,4-dioxane, N,N-dimethylformamide) have been employed in the electrochemical fluorination of the N-methylmorpholine (NMM), but the results have not been those expected. Because of strong interactions taken place within certain ratios solvent/HF, many difficulties have been got into as regards the conductivity.Better results were obtained working without the solvent and with a great concentration (40 %) of the NMM in hydrogen fluoride. In the experiments carried out, the electrochemical fluorination of the NMM appeared highly selective: at first it took place on the positions beside the oxygen atom, then on those beside the nitrogen atom and at last on the methylic group. A mechanism of the reaction is proposed.     

Depuration from SiF4 of industrial gaseous waste

The problem of wet treatment of gases containing fluorine compounds produced in industrial processes, with particular reference to the phosphatic fertilizers and ceramic industries, is here considered.With this purpose and also in view of the low limits imposed by law, the chemical-physical properties of the SiF₄ and HF absorption in H₂SiF₆ solutions are discussed. In connection with these properties and with fluorine content in the gases to be treated , several devices and plant schemes are examined, also considering the problem to dispose of liquids at high Fluorine concentration for its recoveryThe results obtained in some industrial plants are finally presented and discussed.     

The electrochemical fluorination of organic compounds: Further data in support of the ECbECn mechanism

Data in support of the four-stage mechanism EC_bEC_N result from the electrochemical fluorination of some acyl halides (benzoyl, n-butyryl and iso-butyryl, benzenesulphonyl and p-toluenesulphonyl chlorides) and amines (tripropylamine and N-methylmorpholine).     

The reactions of chlorine monofluoride with unsaturated compounds and the dehydrohalogenation of some of the derivatives

The reactions of chlorine monofluoride with benzene, toluene and nitrobenzene to give monochloro derivatives has been investigated and its addition reactions to various substituted olefins studied. The products from all these reactions are consistent with the participation of a chloronium ion as the reactive species, even in solvents of low dielectric constant. The chlorofluoro addition products formed from the olefins have been dehydrohalogenated and the mechanism of reactions discussed in terms of an E1 cb mechanism or paene-carbonium ion extreme.     

Electrochemical fluorination: state of the art and future tendences

A brief survey of the ECF process for the preparation of perfluorinated organo-compounds is given. The yield of perfluorinated products depends on the experimental conditions and on the nature of the starting material. Some useful rules are reported in order to optimise the ECF process. An improved operational technique allowed to obtain high yield of perfluorodimorpholinepropane (PFDMP) by simultaneous fluorination of dimorpholinepropane and N-methylmorpholine.