Monday, 3 December 2012

Chemical of the Week: Olympicene

Welcome to another instalment of Chemical of the Week.

This week, we shall have a very brief look at an interesting organic compound.

Let's say that you have an important event coming up, and you would like to commemorate it. You could conceivably make big signs or host a big event, or you could do what Graham Richards and Antony Williams did. With the upcoming 2012 London Olympics coming up, they considered the possibility both synthesising an interesting organic molecule and recreating the Olympic rings on the smallest-of-small scales.

The structure of olympicene.

Going forward a couple of years to 2012, the synthesis was complete, and the first sample of olympicene was prepared. As you can see, the structure of olympicene does indeed bear a striking resemblance to the Olympic rings. More incredible is that by using a technique known as atomic force microscopy, it was possible for scientists to image a single molecule of olympicene, yielding the following picture:

To put this into some perspective, the above molecule is 1.2 nanometres wide. Another way of considering this is that a human hair is approximately 100 micrometres wide (though this does vary considerably). Consequently, a human hair is, by my calculations, 83,333 times wider than a molecule of olympicene.

It is truly incredible that not only are we able to synthesise a wide variety of organic molecules. It is even more incredible, in my mind, that we currently have the technology to image these molecules, and that their structures are as predicted.

If you wish to read more about olympicene and the journey from concept to creation, I highly recommend the post on the ChemConnector blog. As an added bonus, the author, Antony Williams, was one of the two persons who first pondered the existence and synthesis of olympicene.

Until next time,

Monday, 26 November 2012

Chemical of the Week: Solid Oxygen

Last week, we had a look at dicyanoacetylene, a highly reactive chemical found in our very own solar system, in the atmosphere of Saturn's moon Titan. This week, we will look at the curious case of a synthetic chemical formed under crushing pressures right here on Earth.

Oxygen. We all know it, and for better or worse, love it. After all, oxygen makes up approximately 21% of our atmosphere. Aside from being a rather useful chemical, it gives us something to breathe other than that oh-so-common nitrogen that those nitrogen-fixing microorganisms and symbiotic plants allegedly rave about.

Clover. Thanks to the diazotrophic rhizobia in its root nodules, it now has a thing for nitrogen. 

In our common experience, oxygen is either a simple diatomic gas, or found cloistered away in minerals, oxides and the like. In terms of oxygen in its gaseous state, what happens when it is subjected to freezing temperatures? As with many other gases, oxygen will condense to form a liquid, and when cooled further, form a solid. In the case of oxygen, it has a melting point of -218.79°C, and a boiling point is at -182.95°C, so we rarely encounter diatomic oxygen in anything but its gaseous state.

Now, as I mentioned above oxygen freezes at -218.79°C to form solid oxygen, though this is only the beginning of our story. By changing the temperature of solid oxygen, and by subjecting it to different pressures, it undergoes phase transitions to form different phases of solid oxygen. That is to say, changing the temperatures and pressures solid oxygen to will generally still leave us with solid oxygen, but these disparate phases will have different physical properties.

In the article "Solid Oxygen", by Freiman and Jodi (2004), it is noted that "the existence of six solid-state phases is established unambiguously". Accordingly, these six different phases of solid oxygen are the:

  • α phase
  • β phase
  • γ phase
  • δ phase
  • ε phase: "red oxygen", the phase we are interested in at the moment.
  • ζ phase: a truly fascinating phase, where solid oxygen becomes metallic

Of these different phases, today we shall first focus on the ε phase, also known as "red oxygen". Why is it called "red oxygen"? Well, liquid oxygen and three of the phases of solid oxygen (α, β and γ phases) are various shades of blue in colour. In contrast, the ε (epsilon) phase of solid oxygen is dark red in colour, hence the name "red oxygen".

A sample of cryogenic liquid oxygen displays its charming blue colouration.
Maybe it's cold?

Unlike the α, β and γ phases of solid oxygen, the ε phase does not require freezing temperatures to form. Instead, it simply requires the application of pressure. Lots of pressure. In fact, to form the ε phase, you need to subject liquid or solid oxygen to more than 10 gigapascals (GPa) of pressure. In this phase, "red oxygen" is made up of four pairs of diatomic oxygen molecules in rhomboid cluster, forming an Ocrystal structure. Previous theoretical work expected some manner of O4 molecule to form, with no-one predicting the formation of an O8 rhombohedral unit.

The mysterious crystal structure of solid oxygen in the ε phase.
Note the four O2 molecules connected by the shorter bonds.

Depending on your point of reference and your knowledge of air pressure, and pressure in general, it may be hard to fathom the unbelievably crushing pressures needed to form the ε phase of solid oxygen. 

To put this into perspective, we need to define what a pascal is. In relation to atmospheric pressure, a pascal is a unit of measurement derived by the Système international d'unités, and one atmosphere is equivalent to  1.01325 ×105 pascals. 

Taking this one step further, the pressure required to form the ε phase of solid oxygen is equivalent to a wee bit over 98,692 atmospheres.


Going back to the list of the phases of solid oxygen, the final, ζ (zeta) phase was given a very brief description of "where solid oxygen becomes metallic". I cannot simply leave it at that. The ζ phase forms when solid oxygen is subjected to more than 96 GPa of pressure whilst at room temperature. Once again putting this pressure into perspective, 96 GPa is equivalent to 947,446.34 atmospheres. We may well have thought that the ε phase exists under incredible conditions, but the ζ phase truly takes the cake (if one assumes solid oxygen is partial to cake).

To understand how the metallic phase of solid oxygen is formed, we need to look at the work of Akahama et. al. (1995). Here, liquid oxygen was placed in a diamond anvil cell, and whilst at room temperature, the sample of liquid oxygen was placed under increasing pressure, up to 116 GPa. The different phases of solid oxygen encountered were analysed by x-ray diffraction and synchrotron radiation. It was found that visual observation of the ζ phase yielded something rather fascinating:

"From visual observation under a metallurgical microscope, we saw that the appearance of the oxygen sample became as shiny as the metal gasket after the structural transition at 96 GPa"

In other words, not only can solid oxygen adopt a variety of colours, including blue, pink, orange and red, the ζ phase has a metallic lustre.

Pictured: The metal ζ phase of solid oxygen

The amazing properties of the ζ phase doesn't end here. In Letters to NatureShimizu et. al. (1998) report another remarkable piece of information with regards to metallic oxygen. When the metallic ζ phase is cooled to below 0.6 K (-272.55°C), the electrical resistance of solid oxygen rapidly drops, and in turn, the ζ phase exhibits superconductivity!

Superconductivity of the metallic ζ phase was confirmed at the above reported temperature, by subjecting the sample to a 0.0225 tesla magnetic field. The sample of metallic oxygen expelled the applied magnetic field, or alternately, the sample exhibited the Meissner effect, and thus its status as a superconducting material was proved.

In closing, it is amazing to see how a fairly common chemical can have so many amazing properties and phases.

Now off to contemplate how much a diamond anvil cell costs,

Sunday, 25 November 2012

A Musical Interlude: Bjӧrk - Mutual Core

A friend of mine recently forwarded this brilliant Icelandic songstress, Björk. Though only marginally related to my general topics of chemistry and toxicology, this song (and music video) is too good to pass up. It is ostensibly science-related, with its talk of plate tectonics, volcanism and the like.

So without any further delay, I present Björk, with her recent song, "Mutual Core".

Though a bit trippy, I hope you enjoyed it.

Until next time,

Thursday, 22 November 2012

On Drugs and Fish: Contamination of Aquatic Environments and Drug Detection

I happened across an interesting article in Nature the other morning, titled "Human drugs make fish flounder". It explores the effects of two drugs, the antidepressant fluoxetine, and a sex hormone, estradiol.

At first glance it may seem odd to be concerned about the effect of human medications on aquatic wildlife. After all, fish are not typically known for travelling down to the local pharmacy. Rather, this article highlights a significant issue relating to the impact of humans and their behaviours on local ecosystems. A veritable cornucopia of drugs and drug metabolites are excreted via our urine and faeces, and though wastewater and sewage is typically treated,  these compounds end up in local waterways, and the aquatic homes of a range of fauna. The end result of this type of chemical pollution is not good, to say the least.

I won't go into significant detail on this specific issue, as the article in Nature is rather informative in itself. In short, researchers at the University of Wisconsin-Milwaukee's Great Lakes Water Institute have studied the effects of fluoxetine on fathead minnows. By exposing this species of fish to different levels of fluoxetine, including concentrations that have been detected in wastewater, a series of significant effects were found.

Though females appear unaffected by the lowest concentration of fluoxetine tested, male fish were found to spend more time building their nests. Increasing the concentration of fluoxetine further, to 10 times the highest detected level in waterways, resulted in the male fish "[becoming] obsessive, to the point they're ignoring the females".

Depression in fish. Simultaneously adorable and so, so sad...
Image by Thezules
Further research was also done by Dan Rearick, an aquatic toxicologist from St Cloud State University in Minnesota. In this research, it was found that exposing the larvae of the fathead minnow to estradiol, an estrogenic sex hormone occasionally used in Hormone Replacement Therapy (HRT) had a negative effect on fish populations. Namely, larvae exposed to estradiol were ultimately less capable of escaping or eluding predators, as their reaction times to external stimulus had been significantly lessened.

Moving away from the effects of two specific drugs on a single species of fish, the fact that drugs and drug metabolites may be detected in the effluent from sewer systems may come as a surprise. So prevalent are these compounds in aquatic environments, they are considered emerging environmental contaminants. As a consequence, the detection of these compounds has some rather significant implications for humans.


Well, as most drugs and metabolites end up in the sewer system, this provides an excellent opportunity for chemists and toxicologists to analyse this effluent. Detection of these compounds may, in turn, allow for the analysis of drug use in local populations serviced by a section of the sewer system. Indeed, it is entirely possible to detect and compare illicit drug use in local populations through the collection and analysis of sewage, with the technique known as sewage epidemiology. As many drugs are metabolised to more polar compounds prior to excretion, much of this work revolves around the detection of drug metabolites, and using both their presence and relative concentrations to calculate drug consumption.

Though the following list is by no means exhaustive, it may provide you with a reasonable idea of the different drugs and respective metabolites reportedly detected in both wastewater and groundwater:

  • Amphetamine-type substances (amphetamine, methamphetamine, ecstasy)
  • Benzodiazepines (alprazolam, diazepam, lorazepam)
  • Cannabis
  • Cocaine
  • LSD
  • Opiates (heroin, morphine, methadone)

To date, a range of different populations and their apparent drug use/abuse has been studied. A quick read through peer-reviewed literature on this subject revealed the following areas that have been subjected to analysis via sewage epidemiology:

In addition to the above, a fascinating piece of research and collaboration, entitled "Comparing illicit drug use in 19 European cities through sewage analysis", sought to compare illicit drug abuse in a number of European cities. The range and number of cities selected in this study was rather impressive, and specifically sought to compare the usage rates of cannabis, cocaine and three amphetamine-type substances (amphetamine, methamphetamine, ecstasy). Perhaps the most incredible aspect of this manner of toxicological and chemical analysis is that this study allowed for the quantitative, non-intrusive and objective analysis of illicit drug use of approximately 15 million individuals, all over a one-week period.

An impressive feat, all things considered.
Image by Ssolbergj.

The general trends discovered in this work were quite fascinating. It would appear that cocaine use is more prevalent in more urbanised towns or cities within a set country. In terms of cannabis use, the data apparently indicated that the highest use was, unsurprisingly, in the Netherlands. In addition, the *ahem* highest reading recorded for cannabis use was in Amsterdam. Outside of the Netherlands, other high levels of cannabis use were detected in the Czech Republic, Spain, Italy and France. 

Moving on to the amphetamine-type substances, and in particular apparent methamphetamine use, it would appear that Finland, Norway and the Czech Republic collectively hold the dubious honour of having the highest methamphetamine usage rates in the cities studied. Meanwhile, for amphetamine, high apparent use rates were found in Northern Belgium and in the Netherlands. Ecstasy use, on the other had, was allegedly quite high in Eindhoven, Amsterdam and Utrecht (the Netherlands), and also in London (England). 

This method of assessing intra- and inter-community drug use may be considered rather contentious. On one hand, it allows for a non-intrusive method of assessing drug use, which may be of use for providing adequate health services and allow for the effective development of government policy. However, such techniques may also be construed as invasive. Indeed, some may well view with suspicion the position posed in an article by van Nuijs et. al., (2011), where the following point was made with respect to estimating drug consumption based on analysis of wastewater:

"The consumption of illicit drugs causes indisputable societal and economic damage. Therefore it is necessary to know their usage levels and trends for undertaking targeted actions to reduce their use... [and] could be used in routine drug monitoring campaigns"

That being said, Frost, Griffiths and Fanelli (2008), provide a fascinating editorial concerning detection of drugs of abuse in wastewater, and the ethical and political concerns therein. 

All in all, it is clear that the contamination of waterways with drugs and their respective metabolites may have a significant impact on aquatic wildlife. Though perhaps the fish are getting their own back, with it now possible to examine sewage and wastewater to monitor both licit and illicit drug use.

Until next time, 

Wednesday, 21 November 2012

The Wandering Rover: Big News From Mars?

A short piece to bring to your attention some interesting news from NASA. It appears that the most recent robotic wanderer on Mars, the Curiosity Rover, may have found something whilst analysing the chemical composition of Martian soil.

What did they find?

Well, at the moment the team over at NASA, and the Mars Science Laboratory, are only hinting at something potentially significant. A very recent article from NPR indicates that one of the instruments present on the rover, the Sample Analysis at Mars (SAM), has picked up some soil from the Martian surface, and may have detected something of note. To use the words of John Grotzinger, the principal investigator for the rover mission:

"This data is gonna be one for the history books. It's looking really good..."

Despite hinting at a potential groundbreaking discovery on Mars, no specific details have been released as yet. Though I'm sure those in the know at NASA may well be bursting at the seams to let us know what they have found, they are also being understandably cautious. As is so often the case with science, one needs to be sure of what they have, or have not, found. Indeed, it will apparently take several weeks until any findings, if there are any, are released.

A self-shot of the Curiosity Rover. No duck-face in sight, thankfully.
(Image courtesy of NASA)

Too often we can become excited by some breath-taking discovery, only to find that there is a simpler, more mundane, explanation available. It brings to mind the scientists over at CERN, where a a skeptical team working on the OPERA project were left scratching their heads after supposedly detecting subatomic particles, neutrinos, travelling slightly faster than the "universal speed-limit", the speed of light. As opposed to rushing to the media to capitalise on a truly remarkable discovery, they announced that they were understandably skeptical. As a consequence of this healthy skepticism, they attempted to verify the results whilst simultaneously asking other scientists to identify any potential flaws in their experimental design that may have given rise to an erroneous result.

Ultimately, it was found that the neutrinos detected by OPERA were not travelling faster than the speed of light, and were behaving as good neutrinos do. Instead of being embarrassed by rushing to let everyone know about something incredible, these scientists followed good practice and double-checked their data and, though not confirming any upheavals in the laws of physics, they set a fantastic example for all scientists.

Going back to the Curiosity Rover, and this recent hint of something newsworthy, it is nice to hear that NASA isn't overtly rushing to tell us what they allegedly have found. That being said, they are certainly building up an appreciable amount of hype over something they are currently looking into.

A few friends asked me what they may have found, and though I am no expert on the composition and chemistry of Martian soil, I gladly offered this comment:

"We won't know for sure until NASA issues an official press release, though it is fun to ponder. Evidence of past life? Complex molecules? Oil? A fat-free fudge cake that doesn't let you down in the flavor department like so many others? Only time will tell..."

Until next time,

Monday, 19 November 2012

Chemical of the Week: Dicyanoacetylene

Welcome to the first Chemical of the Week! This week, we shall have a brief look at compound composed entirely of carbon and nitrogen: dicyanoacetylene.

Dicyanoacetylene, or carbon subnitride, is a fairly interesting compound. Structurally, it is completely linear, thanks to its alternating triple bonds. Ciganek and Krespan (1968) report that dicyanoacetylene was first synthesised by the scientists Moureu and Bongrand in 1909 and was achieved by dehydrating the bisamide of acetylenedicarboxylic acid, also known as 2-butynediamide. Graupner and Saunders (2008) report that dicyanoacetylene can be produced by heating 2-butynediamide with phosphorous pentoxide under vacuum.

At the time, this compound has been noted for its high reactivity, an aspect which is not surprising when one considers the presence of two electron-withdrawing groups (EWG's) at the terminal ends of this molecule (specifically, two cyano groups). Due to the presence of these electron-withdrawing groups and their attachment to an acetylene backbone, dicyanoacetylene is a potent dienophile, and of particular use in the Diels-Alder reaction. Indeed, it is so reactive that it is capable of reacting with dienes that are considered, due to low reactivity, poor candidates for the Diels-Alder reaction.

Ah, the things chemists find fascinating... 

Aside from the work of Moureu and Bongrand, there have been numerous methods proposed for the synthesis of dicyanoacetylene, with five proposed by Ciganek and Krespan back in 1968. Two reactions of note were found capable of producing dicyanoacetylene: the heating of nitrogen gas at 2500°C over graphite; and the gas-phase pyrolysis of a chemical with a rather cool structure (below), 4,5-dicyano-1,3-dithiol-2-one.

Told you it was a cool structure!

Though I'm sure I could happily go on a tangent regarding 4,5-dicyano-1,3-dithiol-2-one, dicyanoacetylene has a few more fascinating bits of information up its sleeve. Due to the presence of three triple covalent bonds in its structure, dicyanoacetylene is thermodynamically unstable, and under the right conditions will explode to form carbon powder and nitrogen gas. As such, when exploring the heat of combustion of dicyanoacetylene, Armstrong and Marantz (1960) analysed the results of earlier experiments and proposed that dicyanoacetylene will burn in an oxygen atmosphere and produce a flame with a temperature in excess of 5000K (4726.85°C).

Let me repeat that.

In theory, dicyanoacetylene will burn in an oxygen atmosphere and produce a flame with a temperature greater than 4700°C.

In reality dicyanoacetylene doesn't disappoint. In an oxygen atmosphere, it burns with an intense blue-white flame with a temperature of 5260K (4986°C)!. That is a truly incredible temperature.

Even more remarkable was that the work of Kirshenbaum and Grosse (1956), who used the experimentally determined heat of combustion of dicyanoacetylene in oxygen, in combination with the enthalpy data for carbon monoxide and molecular nitrogen, to discover that burning dicyanoacetylene in an atmosphere of ozone will increase the heat of combustion. Indeed, burning dicyanoacetylene in an atmosphere of ozone (at standard atmospheric pressure) will produce a flame with a temperature of 5516K (5242.85°C).

At this point I am tempted to make a joke about dicyanoacetylene being hot stuff, but I fear I would be burned in the process...

Continuing on, this fascinating molecule has also been found in the atmosphere of Titan, the largest moon of Saturn. Yung (1987), proposed new chemical schemes for the formation of both cyanogen and dicyanoacetylene in order to explain data obtained by the infrared spectra obtained by the Voyager 1 spacecraft. Detection of dicyanoacetylene, and other compounds, is of importance as it gives important information regarding the atmospheric chemistry of Titan.

Titan: Known hideout for dicyanoacetylene.
(Photo courtesy of NASA)
Of particular note is that the abundance of dicyanoacetylene in Titan's atmosphere varies based on the season. According to Samuelson et. al. (1997), in the spring of the northern hemisphere, the stratosphere cools, allowing dicyanoacetylene vapour to condense out of the atmosphere into lower, cooler regions that will be protected by the shadow of the cloud layers above. In the upper stratosphere, the progression of the season means increasing levels of sunlight, which breaks down dicyanoacetylene in a photolytic process. All in all, these variations in the concentration of dicyanoacetylene in Titan's atmosphere gives us a remarkable means of studying the weather on Titan.

So there you have it. A fascinating molecule that burns at an incredible temperature, and is also found in the far-flung reaches of our very own solar system.

Until next time,

Wednesday, 14 November 2012

Further ponderings: legalisation of recreational marijuana in Colorado and Washington

One of my posts from a few days ago was in relation to the recent passing of two key amendments in Colorado and Washington, in relation to recreational marijuana use. At the time, I noted that I was curious to see the implications of the passing of these amendments, and the potential problem this may pose to Federal authorities in the United States. 

The reason that this may be problematic for Federal authorities is that since marijuana is classified as a Schedule 1 drug in the Comprehensive Drug Abuse Prevention and Control Act of 1970, it is illegal to possess, use, buy, sell, and/or cultivate marijuana. This stance, combined with failed attempts at rescheduling marijuana, does put Washington and Colorado at odds with the Federal government, and puts lawmakers in these two states into a tricky situation until the ramifications of these votes develop.

Map of current United States cannabis laws
Light Green: State with legal medical cannabis
Olive Green: State with decriminalized cannabis possession laws
Dark Green: State with both medical and decriminalization laws
Purple: State with legalized cannabis
(Map courtesy of Wikipedia)

It was brought to my attention that in March of 2009, Eric H. Holder Jr, current Attorney General of the United States, indicated that the Justice Department has no intentions to prosecute medical marijuana dispensaries in California and other states. In this regard, use of medical marijuana may seem to be on a sure footing in Colorado, Washington, and in any other states that have passed laws pertaining to this matter. What is not sure sure is whether this "tolerance" of the Justice Department and U.S. Government will extent to recent attempts to legalise the recreational use of cannabis. 

Indeed, this concept was the focus of an article by professor and former Federal prosecutor Mark Olser, published on the CNN website. Professor Olser expresses his view in a rather succinct, and perhaps even poetic, manner: 

"The residents of Colorado and Washington state have voted to legalize the recreational use of marijuana, and all hell is about to break loose -- at least ideologically"

Without delving into the conflict between State's rights and appeals from ethics and morality within an ideologically diverse nation such as the United States, it will be curious to see the broader implications of this vote. Already, four leaders from Latin American countries (Mexico, Belize, Honduras and Costa Rica) have claimed that the votes in Washington and Colorado state will have significant implications for current attempts to halt drug smuggling. Indeed, these votes may also even affect the stance of these nations with regards to the current War on Drugs.

Perhaps one of the more concerning news stories to come out in the days following the Colorado and Washington votes, and in relation to the Federal stance on possession and cultivation of marijuana, is the case against Chris Williams. Following the move by the state of Montana to legalise medical marijuana, Williams opened a marijuana grow-house. Due to Federal laws surrounding the cultivation of marijuana, as set out by the Controlled Substances Act of 1970, Williams faces a mandatory minimum jail sentence of 80 years. 

Though I would generally not desire to second-guess the Justice Department of the United States, this seems to be outrageously draconian. Though it is true that Williams turned down various plea bargains offered by the Justice Department, to me it seems that the application of the Controlled Substances Act of 1970 seems outdated, doubly so when contrasted with two states explicitly legalising cannabis for recreational purposes. Perhaps it is time the Drug Enforcement Agency (DEA) and other parties consider whether this act represents a legal anachronism in light of recent events and the comments of Attorney General Holder back in 2009.

As an aside, the issues of medical and recreational marijuana use in relation to the United States reminds me of one of my lecturers from undergraduate days. During our discussion of drug law in relation to the seeming aversion some countries and jurisdictions have towards harm minimisation, he vehemently declared that the current stance is "schizophrenic". No doubt that these are strong words, though perhaps not surprising when one reads of draconian sentences for actions that are ostensibly legal from an individual's position within a State's legislature. 

Until next time,