A silanone

24 June 2019 - Orgo

In chemistry silicon to oxygen chemical bonds are nothing special, just look at siloxanes. But whereas a single bond is common, a double bond would require some counseling between the two. In a so-called silanone R(R)Si=0 a large difference in electronegativity is in the way and orbital mixing is generally considered just not that good. But an impossible bond to one sometimes means an excellent research opportunity to another. In this case Kobayashi et al. report (DOI) they have cracked it and made an actual stable and uncoordinated silanone. The new silanone is an improvement from an earlier prototype synthesized in 2015 that was stable at -80°C for several hours at best. The strategy is one of kinetic stabilization and in the 2015 effort a cyclic silanone was handled 4 bulky substituents (SiMe2iPr) but apparently not bulky and certainly not inert enough as an isomerization reaction takes place.
In the 2019 iteration the 4 bulky groups are 1,3-di-tert-butylaryls that do the job much better. In the final reaction step the precursor was a silylene (the silicone carbene analogue) and the oxidizing agent nitrous oxide. Measured Si=O length 1.518 A compared to 1.63 A for a single Si-0 bond. The introduction of the aryls had one distinct disadvantage that of overcrowding the spectroscopy. The compound is stable at RT but heating resulted in head-to-tail dimerisation.

New in ethanol oxidation

12 June 2019 - Catalysis

Liang et al. report a direct 12-electron ethanol oxidation with a new type of catalyst system. Ethanol fuel cells have a lot of advantages: high energy content, non-toxic, fuel readily available, light-weight but are not exactly commerce-ready: the only cell found available in a shop is a fuel cell science kit. The Nissan car ethanol fuel cell reforms ethanol to hydrogen first. Other cars with fuel cells use methanol or hydrogen.
Back to the science report: direct 12e oxidation means CH3CH2OH + 3H2O => 2CO2 + 12H+ + 12e-. The catalyst is core/shell Au@PtIr/C which means the core is made up of a gold supported by carbon nanoparticle with the shell a monolayer of platinum and iridium. Because Pt and Ir are sitting directly on the gold lattice, their mutual orientation is not ideal and hence the reactivity. The analytic toolbox has the following: energy-dispersive X-ray spectroscopy exposes the individual Pt and Ir atoms in a 2D map and cyclic voltammetry gives a peak current of 58 Ampere per mg, a lot more than that measured for for Au@Pt/C (no Ir) and Au@Ir/C (no Pt). A 2017 record by another team for Pd40Ni43P17 with almost 5 A/mg was smashed.(Chen et al. DOI). Infrared reflection absorption spectroscopy (IRRAS, alkaline, in-situ) allowed the team to look around for reaction intermediates. As they did find carbon dioxide (and as secondary reaction product carbonate) but not carbon monoxide - a catalyst poison - they conclude the reaction path is truly a 12 electron one with the carbon carbon bond broken in step 1.

Antimonene 2.0

10 June 2019 - Chemical Zoo

In a next iteration on the graphene theme, Peng et al. report on a new synthesis of antimonene. (DOI). In an ideal world antimonene is a single two-dimensional layer of antimony hexagons but in the harsh laboratory reality layers stick together to form multilayers and instead of one smooth layer you end up with a collection of ugly shards.
Antimonene was first reported in 2016 by Ares et al. (DOI) and produced by sonification / exfoliation of antimony in 4:1 isopropanol/water. Key characteristics: flake dimensions 1-3 square micrometers and flake height: a mixture of 4 nm multiples.
The new method is a controlled reduction of antimony trichloride - dodecylthiol with oleylamine/octadecene at 300°C and production collection by centrifugation. Key characteristics: hexagonal crystals 0.5 - 1.5 micrometer in size and heights ranging from 5 to 30 nanometre depending on the annealing time.
By comparison the same reaction with antimony oleate yields antimony oxide and the reaction with antimony acetate yields not rhombohedral antimony but tetrahedral antimony. It is suspected that clorine atoms cover the nanosheet plane, preventing tetrahedral growth, meanwhile the dodecylthiol groups occupy the edges.

Shell publicity stunt

08 June 2019 - PR

Very recently this blog (based in The Netherlands) had the opportunity to tank gasoline at a Shell station that had on offer a brand new product: carbon dioxide compensation. And very affordable: on one litre of E95 at 1,71 euro it costs just one cent. Shell's carbon footprint is a hot topic, the Dutch environmental organisation Milieudefensie is suing the company. (link) They argue that although Shell claims to support the 2016 Paris Agreement they continue with their large-scale oil and gas production. (link) They demand that the company abandons all oil and gas.

The court case has yet to start but it seems the company has already made it void with the introduction of the 'Go Well' campaign last month (link). The one cent compensates not only the one litre of gasoline itself but also it's production. The compensation is by way of forest protection projects one in Cordillera Azul National Park and on in Katingan Mentaya in Indonesia.

The one cent does not seem a lot. To check, if 1 litre emits 2.7 kilogram of carbon dioxide (source) and one carbon credit is equal to 1000 Kg we only have to find the current price paid for one carbon credit. Easier said than done, this blog time boxed the internet search to one hour but came up empty handed. It is not like finding the current Shell share price (under a second). If the businessinsider website (link) is to be believed then 24 Euro for one carbon credit (CO2 European Emission Allowance) translates to 6,5 cents which makes one cent not enough. As no one is disputing the one cent the blog must be missing a point.

One cent is then a tiny amount especially considering that the 1,71 Euro litre price is built up with 61% in taxes. The same litre in neighbouring (less tax-crazy) Belgium a week later was 1,43 Euro. The Dutch government could increase the taxes by one cent in the blink of an eye and every car in the country is covered.

And how have the environmental organisations responded? There is no paper trail but statements picked up from Milieudefensie and Greenpeace on radio and television summarise as 'is not going to be enough, just stop the production'. Keep in mind though that the compensation scheme now adopted by Shell is the very same as the ones popular with green people for offsetting their carbon footprint.


Side note on the Milieudefensie claims: the Wikipedia page on the Paris agreement only mentions countries as signatories and not companies, it mentions the goal of limiting the global temperature increase to 1.5 degrees but not that it has been agreed to keep coal and oil in the ground.