Pulp of high cellulose content, also known as dissolving pulp, is needed for many purposes, including the production of cellulosic fibers and films. Paper-grade pulp, which is rich in hemicellulose, could be a cheap source but must be refined. Hitherto, hemicellulose extraction procedures suffered from a loss of cellulose and the non-recoverability of unaltered hemicelluloses. Herein, an environmentally benign fractionation concept is presented, using mixtures of a cosolvent (water, ethanol, or acetone) and the cellulose dissolving ionic liquid 1-ethyl-3-methylimidazolium acetate (EMIM OAc). This cosolvent addition was monitored using Kamlet-Taft parameters, and appropriate stirring conditions (3 h at 60 °C) were maintained. This allowed the fractionation of a paper-grade kraft pulp into a separated cellulose and a regenerated hemicellulose fraction. Both of these exhibited high levels of purity, without any yield losses or depolymerization. Thus, this process represents an ecologically and economically efficient alternative in producing dissolving pulp of highest purity.
Methylated ferrocenes are useful building blocks for
novel materials in molecular
electronics with advantageous properties in comparison to normal
ferrocene derivatives. The
presence of nine, eight, or five methyl substituents leads to (i) a
decrease in oxidation
potential, (ii) amplified donor capacity with correspondingly increased
stability of the
ferrocenium salts, and, most significantly, (iii) increased solubility.
A modular synthetic
approach based on standard Wittig chemistry affords π-conjugated
soluble nona-, octa-, and
pentamethylated biferrocenes, bridged by up to five
vinylene−phenylene subunits. These
biferrocenes with spacers are “molecular wires” with a
metal-to-metal distance of up to 40
Å and an effective conjugation pathway of up to 50 Å.
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