A new chiral thiohydantoin catalyst is used for the stereoselective iodoamination of alkenes. N-iodosuccinimide as the source of the electrophilic iodine is activated by catalytic amounts of different additives which also influence the regioselectivity of some cyclizations.
A novel and eco-friendly procedure for durable wood protection applying covalently bound organic insecticides is presented. Biological tests confirmed the effectiveness of the method, which also reduces the environmental impact.
For a durable improvement of the hydrophobization properties of wood Scots pine (Pinus sylvestris L.) sapwood veneer chips were covalently modified with surfactant-like p-alkylated benzoates and a corresponding 4-cyanophenyl derivative. These esterification reactions of wood hydroxyl groups at varied temperatures and different reaction times afforded weight percent gains (WPG) ranging from 8 to 44% and quantities of covalently bonded organomaterials (QCO) of 0.3–2.6 mmol per gram, respectively. The successful covalent attachment of the functional precursors was proven by attenuated total reflection-infrared spectroscopy (ATR-IR), while the improvement of hydrophobicity was demonstrated by resulting contact angles (CAs) in a range from 113 to 150°.
Chemical modification
of wood applying benzotriazolyl-activated
carboxylic acids has proven to be a versatile method for the durable
functionalization of its lignocellulosic biopolymers. Through this
process, the material properties of wood can be influenced and specifically
optimized. To check the scope and limitations of this modification
method, various benzamide derivatives with electron-withdrawing (EWG)
or electron-donating (EDG) functional groups in different positions
of the aromatic ring were synthesized and applied for covalent modification
of Scots pine (
Pinus sylvestris
L.)
sapwood in this study. The bonded amounts of substances (up to 2.20
mmol) were compared with the reactivity constants of the Hammett equation,
revealing a significant correlation between the modification efficiency
and the theoretical reactivity constants of the corresponding aromatic
substitution pattern. The successful covalent attachment of the respective
substituted benzamides was proven by attenuated total reflection infrared
(ATR-IR) spectroscopy, while the stability of the newly formed ester
bond was proven in a standardized leaching test.
Long-flying sparks are an essential part of several pyrotechnic
effects. Unfortunately, and in contrast to colored flames, the color
space of sparks is basically limited to the black body curve. With
low-boiling-point metals, vapor-phase combustion and bright colorful
flashes are achievable. Since 1999, alloys of rare-earth elements
have been proposed for colorful spark generation. To the best of our
knowledge, here, we present the first investigation of such alloys
to change the color of sparks beyond the black body limit. Alloys
consisting of >65 at. % of a brightly emitting and low-boiling-point
metal and a carrier metal allow achieving long-flying deeply colored
sparks. Besides the color, branching of sparks is crucial for the
visual appearance. Rare-earth metals were found to promote branching
of different alloys. Finally, fountains ejecting golden/green sparks
based on a stable eutectic Yb–Cu alloy and continuously branching
sparks based on Nd
2
Fe
14
B are presented.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.