Production, bleaching and characterization of pulp from Stipa tenacissima

Alfa grass pulping was successfully performed in hydro-organic acid medium under mild conditions (107°C, atmospheric pressure, cooking time: 3 h). Use of an acetic acid/formic acid/water mixture as pulping liquor was perfectly suitable for selective isolation of pulp, lignin, and hemicelluloses. The unbleached pulp obtained in good yield was first delignified by peroxyacids in organic acid medium and then bleached with hydrogen peroxide in a basic medium to give pulp offering good physico-chemical and mechanical characteristics

Synthesis of primary amines by one-pot reductive amination of aldehydes.

We report here a novel, one-pot, two-step reductive amination of aldehydes for the atom-economical synthesis of primary amines. The amination step has been carried out with hydroxylammonium chloride and does not require the use of a base. In the subsequent reduction step, a metal zinc/hydrochloride acid system has been used. This method is applicable to both aliphatic and aromatic aldehydes. The operational simplicity, the short reaction times, and the mild reaction conditions add to the value of this method as a practical alternative to the reductive amination of aldehydes. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications1 to view the free supplemental file

Role of end-groups and catalyst in polyester cyclodepolymerization and cycle-chain equilibria

International audienc

Synthèse de polymères de l'acide glycolique dans les liquides ioniques

Des poly(acide glycolique) (PGA) ont ŽtŽ synthŽtisŽs dans une sŽrie de liquides ioniques, milieux rŽactionnels utilisŽs en "chimie verte". Deux probl mes importants se posent : l'Žvaporation de l'acide glycolique qui limite le rendement de la rŽaction et la prŽcipitation du polym re en fin de rŽaction. Des PGA de DPn = 45 ont cependant ŽtŽ synthŽtisŽs avec un bon rendement par post-polycondensation d'oligom res du PGA dans BMIm+Tf2N-. L'Žtude cinŽtique de la polyestŽrification dans ces nouveaux milieux montre qu'elle suit un schŽma classique avec des constantes de vitesse du m me ordre de grandeur que celle des polyestŽrifications en masse. Des interactions prŽfŽrentielles entre le catalyseur organomŽtallique et les ions du liquide ionique semblent cependant limiter l'activitŽ catalytique. Des copolym re PGA-PCL ont ŽtŽ ensuite synthŽtisŽs dans BMIm+Tf2N- partir de caprolactone et d'oligo-PGA. Leur microstructure et leurs propriŽtŽs thermiques ont ŽtŽ ŽtudiŽes par RMN et DSC.PARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceTunisiaFRT

Quasi-alternating polyesteramides from \varepsilon-caprolactone and α-amino acids

International audienc

Random and quasi-alternating polyesteramides deriving from \varepsilon-caprolactone and β-alanine

International audienc

Random polyesteramides based on \varepsilon-caprolactone and glycine

International audienc

Structural Analysis of Alfa Grass (<i>Stipa tenacissima</i> L.) Lignin Obtained by Acetic Acid/Formic Acid Delignification

Alfa grass lignin obtained by the acetic acid/formic acid/water CIMV pulping process was characterized by FTIR and ¹H, ¹³C–¹H 2D HSQC, and ³¹P NMR spectroscopies. Lignin samples purified by further dissolution/precipitation or basic hydrolysis steps were also analyzed. The CIMV alfa lignin is a mixture of low molar mass compounds (<i>M</i>_n = 1500 g/mol) of <b>SGH</b> type with β-O-4 ether bonds as the major interunit linkage. The crude lignin contains fatty acids and residual polysaccharides. It also contains large amounts of acetate and hydroxycinnamates, mostly in the γ-position of β-O-4 interunit linkages. Although partial acetylation induced by the process cannot be excluded, the absence of aromatic acetates and acetylated polysaccharides in crude lignin demonstrates the mildness of the process. By combining smooth alkaline hydrolysis and dissolution/precipitation steps to the CIMV pulping, it is possible to produce a purified lignin with a composition and a structure quite analogous to that of the native polymer in the plant