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A collection of high impact articles focusing on C-H activation, from the RSC’s Organic & Biomolecular Chemistry (OBC), Green Chemistry, ChemComm, RSC Advances, Chemical Science, Chem. Soc. Rev and Catalysis Science & Technology.
One of the simplest and most utilised chemical reactions is the burning of hydrocarbons and while combustion is an excellent way to exploit the energy content of this naturally occurring resource, there is a lot more we can do with the ‘inert’ C-H bond.
C-H activation allows us to convert cheaper hydrocarbon starting materials into more valuable and versatile products; leading to the development of a wide range of reagents and catalysts that activate C-H bonds. To keep you up to date with the latest developments in the field we have created this article collection, where all articles are free to download until 15th December.
Click here for the full list of free articles
Scientists in the US and Ireland have developed a new approach to quantitative resistive-pulse sensing, using a nanopipette-based sensor to selectively detect antibodies to peanut allergens (about 1% of Americans suffer from peanut allergies, they say).
Peanut allergens are glycoproteins, and these cause an immune response elevating IgE (Immunoglobulin E) antibody levels in people with a peanut allergy. The increased immunoglobulin levels can be measured by the nanopipette sensor and will help to detect the likelihood of severe allergy episodes.
The nanopipettes work by sensing an analyte as it enters their nanometre-sized pores. The particle must be small enough to fit through the hole, but large enough to cause a measurable change in the recorded ion current. This technique allows label-free detection of antibodies.
Read the ‘HOT’ article:
Resistive-Pulse Measurements with Nanopipettes: Detection of Au Nanoparticles and Nanoparticle-Bound Anti-peanut IgY
Y Wang et al, Chem. Sci., 2012, DOI: 10.1039/c2sc21502k
Fluorescence responses can be analysed using digital photography instead of spectroscopy, say scientists in Germany. The technology could eventually be integrated into smart phones.
Uwe Bunz and his colleagues from the University of Heidelberg used digital photography to study the optical changes occurring when different pyridine-substituted cruciform (cross-conjugated) fluorophores (XF) were subjected to protonation. They protonated the nitrogen on the pyridine and observed the colour changes of the XFs in the presence of carboxylic acids.
Instrument set-up for taking photographs of emission colour
The team extracted data from the photographs by transforming the red, green and blue (RGB) values into numerical values, a process that helps define the colour and removes brightness information. ‘The method is quick and inexpensive, and large data quantities can be stored and acquired in seconds,’ says Bunz.
See the Chemistry World article in full or read the paper from Chemical Science:
Digital photography for the analysis of fluorescence responses
Thimon Schwaebel , Oliver Trapp and Uwe H. F. Bunz
Chem. Sci., 2013, DOI: 10.1039/C2SC21412A
Potential energy surfaces of reactions are usually measured in the gas phase. However the vast majority of chemical reactions in the laboratory are conducted in solvent. What effect do these solvent molecules have on the potential energy surfaces that have been measured in the gas phase? Andrew Orr-Ewing and colleagues have been finding out.
They have used ultrafast time-resolved broadband infra-red absorption spectroscopy to study the reaction of chlorine atoms with hydrocarbons in chlorinated solvent.
Two timescales were found, which corresponded to prompt reaction of the chlorine atom with the hydrocarbon, which was most likely located in the immediate solvent shell, and a slower reaction following diffusion into the bulk solvent. The presence of solvent molecules also partially suppresses the presence of vibrationally excited products that occur when the exothermic reaction is sufficient to form vibrationally hot products.
This work extends previous experiments conducted with cyanide radicals in solvent and general conclusions on the effect of solvent molecules on the potential energy surface are now emerging.
To find out more, download the Chemical Science article today (free to access until the 7th of December 2012).
Catalytic aerobic production of imines en route to mild, green, and concise derivatizations of amines
Toshiaki Sonobe, Kounosuke Oisaki and Motomu Kanai
Chem. Sci., 2012,3, 3249-3255
DOI: 10.1039/C2SC20699D
Permuting Diels–Alder and Robinson annulation stereopatterns
Feng Peng, Mingji Dai, Angie R. Angeles and Samuel J. Danishefsky
Chem. Sci., 2012,3, 3076-3080
DOI: 10.1039/C2SC20868G
Diazo compounds as highly tunable reactants in 1,3-dipolar cycloaddition reactions with cycloalkynes
Nicholas A. McGrath and Ronald T. Raines
Chem. Sci., 2012,3, 3237-3240
DOI: 10.1039/C2SC20806G
Fusarisetin A: scalable total synthesis and related studies
Jing Xu, Eduardo J. E. Caro-Diaz, Michelle H. Lacoske, Chao-I. Hung, Colin Jamora and Emmanuel A. Theodorakis
Chem. Sci., 2012,3, 3378-3386
DOI: 10.1039/C2SC21308G
Rhodium(III)-catalyzed synthesis of phthalides by cascade addition and cyclization of benzimidates with aldehydes
Yajing Lian, Robert G. Bergman and Jonathan A. Ellman
Chem. Sci., 2012,3, 3088-3092
DOI: 10.1039/C2SC20835K
Copper-catalyzed decarboxylative C–N coupling for N-arylation
Yun Zhang, Sejal Patel and Nello Mainolfi
Chem. Sci., 2012,3, 3196-3199
DOI: 10.1039/C2SC20606D
Diastereoselective ring-rearrangement metathesis to set the stereochemistry of all-carbon quaternary centres
Jingwei Li and Daesung Lee
Chem. Sci., 2012,3, 3296-3301
DOI: 10.1039/C2SC20812A
Bis(benzimidazolium) axles and crown ether wheels: a versatile templating pair for the formation of [2]rotaxane molecular shuttles
Kelong Zhu, V. Nicholas Vukotic, Nadim Noujeim and Stephen J. Loeb
Chem. Sci., 2012,3, 3265-3271
DOI: 10.1039/C2SC20986A
A new and efficient way to make β-lactams, the key components of common antibiotics such as penicillin, has been developed by US scientists.
The team made the β-lactams from simple aldehydes via a multi-component catalytic asymmetric aziridination reaction. The reaction is high-yielding, stereospecific and diastereoselective. It should aid new drug discovery.
Read the Chemical Science article in full:
Multifaceted Interception of 2-Chloro-2-Oxoacetic Anhydrides: A Catalytic Asymmetric Synthesis of b-Lactams
L Huang et al.
Chem. Sci., 2012, DOI: 10.1039/c2sc21240d
Unlike conventional electromagnetic interactions, the chemical bond has not been quantified in strength by any known property of the participating species, until now.
Scientists in China say that bond energy (EAB), a quantitative measure of the bond strength, can be decoupled into two contributions of the participating reactants, which is a new principle.
The team verified their theory with more than 300 bonds, including covalent bonds in molecules and adsorption bonds on metal surfaces; this can be applied in a wide range of chemical reactions. Particularly, the characteristic complex quantity, termed ‘chemical amplitude’ can be used to describe accurately the chemical reactivity of both molecules and metal surfaces, which is an advantage when studying heterogeneous catalysis.
The work should allow scientists to make a direct evaluation of the bond energy and also reveal new aspects of the chemical interaction, they say.
Read this ‘HOT’ Chemical Science Edge Article:
Bond-Energy Decoupling: Principle and Application to Heterogeneous
Catalysis Bing Huang , Lin Zhuang , Li Xiao and Juntao Lu
Chem. Sci., 2012, DOI: 10.1039/C2SC21232C
US scientists have reported a new method to create antibody mimics that could be used to make new and improved therapeutics.
Fusion proteins contain segments derived from two or more different precursors. The proteins allow multiple biological functions to be combined in a single entity. The most successful fusion protein therapeutics contain the crystallisable fragment (Fc) region of antibodies. But they are not easy to make and modify. The team has come up with two strategies to modify antibody Fc fragments using chemical modification, leading to the creation of novel Fc-synthetic molecule hybrids.
The strategy also allows Fc domains to be used as building blocks that can be appended to virtually any class of synthetic molecules. This allows the pharmacokinetic improvements imparted by Fc to be used in many different drug delivery contexts, and could add potential immunological function to many different constructs.
Read the ‘HOT’ Chemical Science article today:
Synthetically Modified Fc Domains as Building Blocks for Immunotherapy Applications
C Netirojjanakul et al, Chem. Sci., 2012, DOI: 10.1039/c2sc21365f
A stimuli-responsive system that brings chemists one step closer to mimicking the complexity of biological networks has been developed by scientists in the UK, Australia and the US.
Biological systems are complicated as they can produce multiple responses to stimuli at the same time. The team says that the key to unravelling the origin of life may come from studying the complex interactions of molecules.
They have discovered a self-assembled cage molecule that consists of a system of interconverting diastereomers in solution. When anionic guest molecules are added, the system adapts, expressing a new combination of diastereomers that synergistically bind the guest molecules. Not only do the cage diastereomers interconvert, the volume of the individual cages adapts physically through the rotation of bonds, providing a tailored binding pocket for the guest lined with hydrogen-bond donors.
This two-fold adaptation is a feature of the responses to external stimuli displayed by biological systems, something that has not previously been observed in synthetic systems. Complex and functional synthetic systems of this type will lead to the design of more effective systems for host-guest recognition and the development of systems approaching the complexity of those that exist in nature.
Read the ‘HOT’ Chemical Science article today:
A Stimuli Responsive System of Self-Assembled Anion-Binding Fe4L68+ Cages
Jack Kay Clegg, Jonathan Cremers, Andrew J Hogben, Boris Breiner, Maarten M. J. Smulders, John D. Thoburn and Jonathan Nitschke
Chem. Sci., 2012, DOI: 10.1039/C2SC21486E
