What's Hot,What's Not: The Trends of the Past 20 Years in the Chemistry of Odorants

This review is the sequel to the 2000 report on the recent advances in the chemistry of odorants and it summarizes the developments in fragrance chemistry over the past 20 years. Following the olfactory spectrum set out in that report, trendsetting so‐called captive odorants (patent‐protected ingredients unavailable to the market) are presented according to the main odor families: “fruity”, “marine”, “green”, “floral”, “spicy”, “woody”, “amber”, and “musky”. The design of odorants, their chemical synthesis, and their use in modern perfumery are illustrated with prominent examples. Featured are new fruity odorants that provide signature in the top note, as well as precursor technology. In the green domain, focus is on leafy notes and green pear. New benzodioxepines and benzodioxoles have modernized the marine family and required a revision of the existing olfactophore models. The replacement of Lilial and Lyral kept the industry busy in the floral domain with a plethora of new “muguets”. There was continued activity in the domain of rose odorants, especially in the area of rose ketones. Biotechnology became significant, for example, with Clearwood and Ambrofix, and the principal odorants of vetiver oil in the woody family have been found. Fourth and fifth families of musk odorants were also discovered and populated. Thus, new avenues for further explorations into fragrance chemistry have been opened.     

Development of Magnesium Anode-Based Transient Primary Batteries

Biodegradable primary batteries, also known as transient batteries, are essential to realize autonomous biodegradable electronic devices with high performance and advanced functionality. In this work, magnesium, copper, iron, and zinc – metals that exist as trace elements in the human body – were tested as materials for biomedical transient electronic devices. Different full cell combinations of Mg and X (where X = Cu, Fe, and Zn and the anodized form of the metals) with phosphate buffered saline (PBS) as electrolyte were studied. To form the cathodes, metal foils were anodized galvanostatically at a current density of 2.0 mA cm⁻² for 30 mins. Electrochemical measurements were then conducted for each electrode combination to evaluate full cell battery performance. Results showed that the Mg−Cu_anodized chemistry has the highest power density at 0.99 mW/cm². Nominal operating voltages of 1.26 V for the first 0.50 h and 0.63 V for the next 3.7 h were observed for Mg−Cu_anodized which was discharged at a current density of 0.70 mA cm⁻². Among the materials tested, Mg−Cu_anodized exhibited the best discharge performance with an average specific capacity of 2.94 mAh cm⁻², which is comparable to previous reports on transient batteries.     

An Inexpensive Laser Raman Spectrometer Based on CCD Detection

We describe an inexpensive modular Raman spectrometer system that can be assembled from commercial components for under $5000. Three typical applications are presented: a demonstration of a vibrational isotope effect, a Raman polarization experiment, and a resonance Raman experiment. This spectrometer system should make it easier to include the important topic of Raman spectroscopy in the undergraduate physical and analytical chemistry laboratory curricula.     

Easy and efficient selenocyanation of imidazoheterocycles using triselenodicyanide

The regioselective selenocyanation of imidazoheterocycles using triselenodicyanide at room temperature is reported. The electrophilic aromatic substitution of a broad range of substrates is promoted by the triselenodicyanide obtained by oxidative coupling of malononitrile and selenium dioxide, under an air atmosphere. The major advantages of the presented method are an easy set-up, excellent yields, short reaction times, use of odorless and inexpensive reagents and easy purification of the final products.     

Synthesis and anti-leukaemic activity of pyrrolo[3,2,1-hi]indole-1,2-diones,pyrrolo[3,2,1-ij]quinoline-1,2-diones and other polycyclic isatin derivatives

To further expand the structure–cytotoxic activity relationships of isatin derivatives and to reduce flexibility in substituent groups at nitrogen, 20 analogues incorporating a ring system between the N1 and C7 atoms of isatin were prepared using a variety of synthetic strategies. This yielded pyrroloindole-, pyrroloquinoline-, pyrroloacridine-, pyrrolophenanthridine- and benzopyrrolophenanthridine-based systems with embedded isatin moieties, the latter possessing a novel carbon skeleton. These compounds were subsequently assessed for their in vitro cytotoxicity against human U937 lymphoma cells, with the brominated pyrroloacridine dione 27 showing the most promising activity (IC₅₀ 3.01 μM) after 24 h.     

Advances on the Determination of the Astatine Pourbaix Diagram: Predomination of AtO(OH)2− over At− in Basic Conditions

It is generally assumed that astatide (At^?) is the predominant astatine species in basic aqueous media. This assumption is questioned in non‐complexing and non‐reductive aqueous solutions by means of high‐pressure anion‐exchange chromatography. Contrary to what is usually believed, astatide is found to be a minor species at pH=11. A different species, which also bears a single negative charge, becomes predominant when the pH is increased beyond 7. Using competition experiments, an equilibrium constant value of 10^?6.9 has been determined for the formation of this species from AtO(OH) with the exchange of one proton. The identification of this species, AtO(OH)₂^?, is achieved through relativistic quantum mechanical calculations, which rule out the significant formation of the AtO₂^? species, while leading to a hydrolysis constant of AtO(OH) in excellent agreement with experiment when the AtO(OH)₂^? species is considered. Beyond the completion of the Pourbaix diagram of astatine, this new information is of interest for the development of ²¹¹At radiolabeling protocols.     

EXAFS investigations of the mechanism of facilitated ion transfer into a room-temperature ionic liquid

The Sr(II)-crown ether complexes formed in a room-temperature ionic liquid (RTIL), 1-methyl-3-pentylimidazolium bis[(trifluoromethyl)sulfonyl]amide, have been studied by X-ray absorption fine structure measurements at the Sr K-edge. When a Sr(NO(3))(2)-crown ether complex is directly dissolved in a water-saturated RTIL, both nitrate ligands and the crown ether coordinate the Sr, as observed in a conventional two-phase water-octanol system. When the cationic Sr-crown ether complex is created in a two-phase water-RTIL system, however, only cationic Sr-crown ether complexes are observed in the RTIL phase. This difference in the coordination complexes arises from differences in the mechanism of cation extraction between the RTIL and conventional molecular organic solvents, a finding with important implications for synthesis, catalysis, and ion separations using two-phase water-RTIL systems.