A Facile Route to Prepare Organic/Inorganic Hybrid Nanomaterials by ‘Click Chemistry’

An organosilane with an alkyne group at the non‐condensable end, [(2‐propynylcarbamate)propyl]triethoxysilane, has been synthesized. Condensation of this organosilane with tetraethoxysilane can be achieved by a co‐condensation strategy to produce silica nanoparticles with surface alkyne functionality. The size and uniformity of size distribution of the silica nanoparticles are influenced by varying the concentration of the added organosilane. The alkyne‐functionalized silica nanoparticles are coupled directly with azide‐modified polymers by ‘click chemistry’ to yield organic–inorganic hybrid nanomaterials.

     

Perkin’s and Caro’s Mauveine in Queen Victoria’s Lilac Postage Stamps: A Chemical Analysis

Mauveine, a chemical icon, is no longer commercially available. If nowadays one wanted to have a sample of the original Perkin, or Caro, mauveine, and see its colour, where would one find it? The answer is on UK Victorian 6d postage stamps from 1867–1880. This was found from a comparison with historical samples of mauveine, from both William Perkin and a Heinrich Caro sample (here analysed for the first time). These have distinctly different compositions and this was used to identify the origin of mauveine in the postage stamps, with evidence found for mauveine made by both Perkin’s and Caro’s synthesis.     

Heuristic Chemistry—Elimination Reactions

Besides additions and substitutions, elimination reactions play a fundamental role in organic synthesis. However, conceptual reviews of known 1,x‐elimination patterns that go beyond the typical olefin‐forming 1,2‐eliminations are scarce. To develop a broader understanding of elimination reactions, we follow a heuristic approach and deduce recurrent reaction patterns from traditional and specific elimination reactions. Our work demonstrates that 1,x‐elimination reactions and their outcomes can be easily rationalized by defined mnemonic categories.     

Genetically Encoded Click Chemistry†

Genetically encoded click chemistry (GECC) refers to a category of peptide/protein reactions that can spontaneously form covalent linkages with high efficiency and selectivity under mild physiological conditions. The emergence of powerful SpyTag/SpyCatcher chemistry, a prototype of GECC, has opened the door to new fields such as in cellulo protein topology engineering and design of synthetic organelles. The continuing developments of GECC will surely provide great opportunities for future materials science and synthetic biology and open up a new avenue to information‐coded chemical reactions.     

Assessment and application of Marfey’s reagent and analogs in enantioseparation: a decade’s perspective

Of the various methods available for high‐performance liquid chromatography separation of enantiomers (of e.g. amino acids and amino group containing compounds) by the pre‐column derivatization approach, use of Marfey’s reagent has been most successful with continued application since its introduction in 1984. The reagent is prepared from difluoro dinitro benzene by nucleophilic substitution of one of its F atoms by l‐ alanine amide. There is flexibility to prepare several chiral variants (by substituting the F atom with different chiral auxiliaries) and to tailor the hydrophobicity and resolution, ultimately, of the diastereomeric derivatives. The present paper assesses and reviews applications of Marfey’s reagent and its chiral variants (i.e. other FDNP reagents) for enantioseparation of certain amino group containing drugs/amino acids, and to provide some case studies on enantiomeric separations that are important for the pharmaceutical industry. Various explanations for separation mechanism and elution order using FDNP reagents are included and the question of the configuration of the corresponding enantiomer using an indirect approach has also been addressed.     

Nitrogen Analogues of Thiele’s Hydrocarbon

A series of bis[N,N‐di‐(4‐methoxylphenyl)amino]arene dications 1 ²⁺– 3 ²⁺ have been synthesized and characterized. Their electronic structures were investigated by various experiments assisted by theoretical calculations. It was found that they are singlets in the ground state and that their diradical character is dependent on the bridging moiety. 3 ²⁺ has a smaller singlet–triplet energy gap and its excited triplet state is thermally readily accessible. The work provides a nitrogen analogue of Thiele’s hydrocarbon with considerable diradical character.     

Graphene Oxides Prepared by Hummers’, Hofmann’s,and Staudenmaier’s Methods: Dramatic Influences on Heavy‐Metal‐Ion Adsorption

Graphene oxide (GO), an up‐and‐coming material rich in oxygenated groups, shows much promise in pollution management. GO is synthesised using several synthetic routes, and the adsorption behaviour of GO is investigated to establish its ability to remove the heavy‐metal pollutants of lead and cadmium ions. The GO is synthesised by Hummers’ (HU), Hofmann’s (HO) and Staudenmaier’s (ST) methodologies. Characterisation of GO is performed before and after adsorption experiments to investigate the structure–function relationship by using Fourier‐transform infrared spectroscopy and X‐ray photoelectron spectroscopy. Scanning electron microscopy coupled with elemental detection spectroscopy is used to investigate morphological changes and heavy‐metal content in the adsorbed GO. The filtrate, collected after adsorption, is analysed by inductively coupled plasma mass spectrometry, through which the efficiency and adsorption capacity of each GO for heavy‐metal‐ion removal is obtained. Spectroscopic analysis and characterisation reveal that the three types of GO have different compositions of oxygenated carbon functionalities. The trend in the affinity towards both Pb^II and Cd^II is HU GO>HO GO>ST GO. A direct correlation between the number of carboxyl groups present and the amount of heavy‐metal ions adsorbed is established. The highest efficiency and highest adsorption capacity of heavy‐metal ions is achieved with HU, in which the relative abundance of carboxyl groups is highest. The embedded systematic study reveals that carboxyl groups are the principal functionality responsible for heavy‐metal‐ion removal in GO. The choice of synthesis methodology for GO has a profound influence on heavy‐metal‐ion adsorption. A further enrichment of the carboxyl groups in GO will serve to enhance the role of GO as an adsorbent for environmental clean‐up.     

Cluster Beam Chemistry—from Atoms to Solids

How do the properties of a solid gradually evolve as atoms are brought together to form increasingly larger units? In order to answer this question one must study aggregates of atoms too large to be called molecules but still too small to have even the structure of a crystal. Recent advances in both theory and experiment have made possible some first explorations in this long neglected but fascinating field of study. This review will emphasize the generation, growth, and properties of homo- and heteronuclear clusters in the vapor phase, particular attention being paid to mass spectrometric investigations.     

Perspectives in Chemistry—Steps towards Complex Matter

Chemistry is progressively unraveling the processes that underlie the evolution of matter towards states of higher complexity and the generation of novel features along the way by self‐organization under the pressure of information. Chemistry has evolved from molecular to supramolecular to become adaptive chemistry by way of constitutional dynamics, which allow for adaptation, through component selection in an equilibrating set. Dynamic systems can be represented by weighted dynamic networks that define the agonistic and antagonistic relationships between the different constituents linked through component exchange. Such networks can be switched through amplification/up‐regulation of the best adapted/fittest constituent(s) in a dynamic set. Accessing higher level functions such as training, learning, and decision making represent future lines of development for adaptive chemical systems.     

Laser Chemistry–What is Its Current Status?

In recent years, various methods have been developed to observe and to influence the course of chemical reactions using laser radiation. By selectively increasing the translational, rotational, and vibrational energies and by controlling the relative orientation of the reaction partners with tunable infrared and UV lasers, direct insight can be gained into the molecular course of the breaking and re-forming of chemical bonds. Examples for the application of lasers include the synthesis of monomers such as vinyl chloride and polymers such as polyethylene, the synthesis of biologically active substances such as vitamin D₃, the separation of isotopes, the removal of impurities, the production of catalysts, glasses, and ceramics, and the deposition and ablation of material on surfaces. Finally, several applications of lasers in medicine are discussed.