Printer vriendelijke versie

The curse of the illegal drug labs

29 April 2014 - Crime

drug lab source europol.PNGThe Netherlands have a dubious reputation when it comes to illegal drug labs. The phenomenon is nothing new (30 labs have been dismantled this year alone) but the labs nevertheless made the news this week because the general increase in chemical waste dumping and the discovery of two dead lab workers in their laboratory.

According to this 2011 EMCDDA/Europol report amphetamine in Europe is bigger than methamphetamine, The most popular production method is the Leuckart synthesis with benzyl methyl ketone (BMK). In the Netherlands the labs are increasingly professional with 30 to 50 liter reactors and a 20 - 50 Kg daily output of finished product. The chemical waste is a problem itself: up to 24 Kg for each kilo of product.

In recent years with availability of BMK more tightly controlled (no longer illegal imports from China) the labs have expanded to BMK synthesis itself. Since 2012 a popular precursor has been the then legal compound alpha-phenylacetoacetonitrile (APAAN). All it takes for conversion to BMK is sulfuric acid and water. In 2013 possession of the compound was made illegal so now according to one source the drug labs are in hot pursuit of new APAAN method (NOS)

The two bodies were found in a laboratory heavily filled with fumes. One of the victims apparently died wearing a gas mask.

Oil-water separation by GO

26 April 2014 - Biomimickry

Dong oil water separation 2014.PNGDong et al. report a novel way to separate oil and water using a wire mesh and graphene oxide (DOI). Graphene oxide (GO) is the reaction product of graphite and a strong oxidizing agent. Dong adopted a combination of sulfuric acid, sodium nitrate and hydrogen peroxide in water and noted that the resulting GO is very hydrophilic. A comparison was then made with the known oil-repellent properties of clam shells that exist thanks to a "layered arrangement of hydrophilic inorganic nanosheets and proteins into a bricks-and-mortar nanostructure". As GO can also be considered a multi-layer hydrophilic material it was put into practical use in this very way: a wire mesh (pore diameter 38 micron) was coated with GO multiple times and then a mixture of oil (hexane) and water was forced through it by just gravity. Results: almost 100% of the water passed through and almost 100% of the hexane was rejected. Top speed: 84 Liter per square meter per second.

Trivial: the research was funded by the "Western Light Talent Culture" Project and the "Top Hundred Talents" Program of the Chinese Academy of Sciences. Is the first project aimed at the not-so talented as opposed to the really talented in the second one?

Graphene by electrochemistry

25 April 2014 - Nanotech

graphene Parvez 2014.PNGA next step in graphene mass-production has been reported by Parvez et al. in JACS (DOI). Experimental electrochemical set-up: one graphite flake as working electrode and one platinum bar as reference electrode in a solution of ammonium sulfate and with a 10 volt direct current. Within minutes the graphite has exfoliated and dispersed up to a 75% yield. Filtration and washing do the rest. Product: graphene, in a 16 gram batch. Makes the Scotch tape method seem as awkward as a flint in fire-making.

Rationale according to the authors: reduction of water produces hydroxyl anions that eat away at the graphite edges, the graphene layers expand and sulfate ions can intercalate between the layers. In stage three oxygen gas and sulfur dioxide gas also formed in the electrolysis process agitate the layers even further and the whole thing comes apart. Dimensions: width between 5 and 44 micron, thickness on average 0.7 nanometers.

The material was field-tested in a supercapacitor set-up: graphene was dissolved in DMF and coated onto regular A4 paper. The resulting conductive sheet was coated with a poly(vinyl alcohol)/ sulfuric acid gel and after solidification two put together formed a working capacitor.

A solvent for tellurium

22 April 2014 - Inorgo

a solution of tellurium.PNGWebber et al. report a new method for the synthesis of tin telluride, a compound of some relevance as semiconductor (DOI). The avenue towards the new method was opened by the development of a new solvent system for elemental tellurium. The researchers note that tellurium has a poor solubility record but after collecting some clues from the literature they came up with a novel 1:4 mixture by volume of ethanethiol and ethylenediamine that at room temperature allows for up to 10% by weight in Te. Solubility in either solvent was zero and curiously, replacing ethanethiol by n-propanethiol also eradicated solubility.
Elemental tin was then be added at 60°C and is soluble only because tellurium is already present. The so-called Sn-Te ink was then stripped of solvent at 260°C to the final product.

The on-solvent reaction

04 April 2014 - Physical chemistry

Never expected to one day see mercury listed as an organic solvent but it has happened. Here is how. Sela & Vigalok have been investigating the on water reaction and are reporting about it here. In this type of reaction, water is added to an ordinary organic reaction forming an emulsion and thereby greatly increasing the reaction rate. One possible explanation is hydrogen bonding taking place at the water-organic solvent interface. But what if water is replaced by an entirely different nonsolvent? Sela & Vigalok examined a specific Passerini reaction, well known to benefit from on-water conditions. To their surprise other solvents worked just as well. Perfluorooctane performs better than water, mercury is comparable to water. Both solvents were selected working under the assumption that organic reactions are accelerated by solvents with a very low or very high Hildebrand parameter. More puzzling data. Adding up to three equivalents of water in addition to the nonsolvent also increases the reaction rate. Hydrogen bonding does matter but a water - organic interface apparently does not.

This molecule must be in so much pain

02 April 2014 - Orgo

biphenylophane nobusue 2014.PNGThis molecule must be in so much sprain. In alkynes the bond angles are usually 180° but here the diacetylene unit makes an angle of 160°. It was synthesised in a simple intramolecular acetylene coupling with copper acetate in a 52% yield. Degradation starts at 70°, triggered by benzyne formation in an intramolecular alkyne - diacetylene 4+2 cycloaddition. The molecule was reported by Shunpei Nobusue et al. in Organic Letters (DOI).