Kinetics and thermodynamic studies on chloroformates

The purpose of this study is to explore the nature of the reactions of n-propyl and benzyl chloroformates with tetra-n-butylammonium nitrate in actonitrile as a reaction medium. A thermodynamic investigation associated with the enthalpy of formation and vaporization of these chloroformates has also been undertaken. The reaction kinetics were determined at various concentrations of chloroformates and tetra-n-butyl-ammonium nitrate at different temperatures. The reactions have been found to be second-order and to follow pseudo-first-order rate coefficients proportional to the nitrate ion concentration. The changes in entropies, deltaS+/-, ranged from -59.5 for n-C3H7OCOCl to -14.5J mol-1 deg-1 for C6H5CH2OCOCl, which indicates that the reaction proceeded by a bimolecular SN2 mechanism. The studies give evidence that the rate-determining step is the initial reaction between the chloroformates and NO-3 to give nitratocarbonate via a tetrahedral intermediate. The expected products, nitrate ester and carbon dioxide, are obtained in maximum yields of 18-20% and 61% respectively. Addition of pyridine or tetra-n-butylammonium perchlorate, has little effect on the yield of nitrate ester product. The tetra-n-butylammonium chloride product is more reactive towards both n-propyl and benzyl chloroformates than the corresponding nitrate. The enthalpies of solution of n-propyl and benzyl chloroformates in sodium hydroxide (1 mol dm -3 ) have been measured over a range of concentrations at 298. 15 K, using a solution reaction calorimeter. The variation with the concentration of the enthalpy of hydrolysis was not significant over the concentration ranges studied deltaHthetaf (C3H7OCOCl, 1) = -524.396 +/- 0.767 kj mol-1 for 5791 <n < 19593 and deltaHtheta(C6H5CH2OCOCl, 1) = -375. 244 +/- 1.088 kJ mol-1 for 36804 < n < 52495. Enthalpies of vaporization have been obtained from measurements of vapour pressure over the temperature range 293. 13 to 306. 30 K, deltaHthetav (n-C3H7OCOCl, 298. 15 K) = 40. 676 +/- 0. 450, and 293. 770 to 302. 34 K, deltaHthetav (C6H5CH2 OCOC1, 298. 15K) = 38. 527 +/- 0. 1 10 Kj mol -1. Enthalpies of vaporization were also obtained using a vaporization calorimeter, giving deltaHthetav (n-C3H 7OCOCl, 298. 15 K ) = 40. 742 + 0. 403 kj mol -1. These values of deltaHthetav, obtained from the vapour pressure measurements, are combined with the enthalpies of formation of deltaHthetaf (1) values to give enthalpies of formation in the gaseous state at 298. 15 K viz., deltaHthetaf (n-C3H7OCOCl, g) = -483.720 +/- 0. 864 kj mol deltaHthetaf (C6H5CH2OCOCl, g) = -336.717 + 1.094 kJ mol<p

Overexpression of a Bacillus subilis amylase in E.coli and application in bread making

Bacterial alpha-amylases (EC3.2.1.1) have potential use in wide number of industrial applications such as textile, paper, detergent, food, fermentation and pharmaceutical industries. Recombinant DNA technology for amylase production involves the selection of an amylase gene, its insertion into an appropriate vector system, transformation in an efficient bacterial system to produce high amount of recombinant protein. In this context, the aim of this work is the overexpression of an α-amylase gene from Bacillus subtilis US572 in E.coli strain, the characterization of the recombinant enzyme and test the effect of different quantities added of amylase on wheat flours and bread characterization

Structure/function/properties relationships and application of a GH11 xylanase

Xylanases are hemicellulolytic enzymes, which are responsible for the degradation of the heteroxylans constituting the lignocellulosic plant cell wall. Due to their variety, xylanases have been classified in glycoside hydrolase families GH5, GH8, GH10, GH11, GH30 and GH43 in the CAZy database. In this work, we focus on GH11 family, which is one of the best characterized GH families with bacterial and fungal members. GH11 xylanases have for a long time been used as biotechnological tools in various industrial applications and represent in addition promising candidates for future other uses

Genetic polymorphism of five genes associated with growth traits in goat

Genetic polymorphism studies in domestic animals aim at evaluating genetic variations within and across breeds mainly for conservation purposes. In this study, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) was used to detect polymorphisms of five candidate genes in four Egyptian and Saudi goat breeds (Barki, Zaribi, Ardi and Masri), to detect the genotype of GH, IGF1, POUIF1, MSTN and BMP15 genes in the goat breeds and their allele frequencies. Results of GH gene which encloses a Haelll endonuclease restriction site show four unique PCR-RFLP banding patterns (genotypes AA, AB, CC and CD). The frequencies of the A allele in the samples from the goat breeds varied from 0.410 to 0.620. While  IGF-1gene revealed three fragments after digestion with Haelll with genotype AA, AB and BB and the  frequencies of allele A varied from 0.432 to 0.731. Furthermore, PCR-RFLP of POUIF1 gene showed two  fragments after digestion by Pst1 endonuclease with genotype TT and CC and the frequencies of allele T varied from 0.250 to 0.840. The MSTN gene revealed three fragments after digestion with DraI with genotype AA, BB and AB and the frequencies of allele A varied from 0.240 to 0.630. Meanwhile, the BMP15 gene revealed one fragments of 112 bp for AA after digestion with Hinf1 enzyme.Key words: Goats, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), GH, IGF-1, POUIF1, MSTN, BMP-15

Draft genome sequence of Frankia sp. strain BMG5.23, a salt-tolerant nitrogen-fixing actinobacterium isolated from the root nodules of Casuarina glauca grown in Tunisia

Nitrogen-fixing actinobacteria of the genus Frankia are symbionts of woody dicotyledonous plants termed actinorhizal plants. We report here a 5.27-Mbp draft genome sequence for Frankia sp. strain BMG5.23, a salt-tolerant nitrogen-fixing actinobacterium isolated from root nodules of Casuarina glauca collected in Tunisia

Draft Genome Sequence of Frankia sp. Strain Thr, a Nitrogen-Fixing Actinobacterium Isolated from the Root Nodules of Casuarina cunninghamiana Grown in Egypt

Nitrogen-fixing actinobacteria of the genus Frankia are symbionts of woody dicotyledonous plants termed actinorhizal plants. We report here a 5.3-Mbp draft genome sequence for Frankia sp. stain Thr, a nitrogen-fixing actinobacterium isolated from root nodules of Casuarina cunninghamiana collected in Egypt

Studies on Arabic Dialectology and Sociolinguistics

This volume contains over fifty articles related to various fields of modern Arabic dialectology. All the articles are revised and enhanced versions of papers read on the 12th Conference of the Association Internationale de Dialectologie Arabe (AIDA) held in Marseille in June 2017. Since its first conference in Paris in 1993, AIDA members gather every two years in different country. The collection of the AIDA proceedings offer an updated insight of the development of the field. During the past few decadesthe the study of Arabic dialects has become an important branch of research covering a wide range of subjects from phonological analyses, morphosyntax, semantics to pragmatics, sociolinguistics, folk linguistics, studies on literacy and writings, cultural and artistic practices, etc. As many articles of this volume illustrate, the study of Arabic dialects explores different aspects of the languages and cultures of the contemporary Arab world. A remarkable feature is the growing and constant participation of young scholars from all around the globe

Raisonnement sous incertitude et en présence des préférences (application à la détection d'intrusions et à la corrélation d'alertes)

LENS-BU Sciences (624982102) / SudocLENS-CRIL (624982203) / SudocSudocFranceF

A Revised Qualitative Choice Logic for Handling Prioritized Preferences

International audienc

An alert correlation approach based on knowledge and preferences of security operator

International audienc