We’re about to celebrate the most important day in the chemical calendar. We started these celebrations about 7 years ago and it’s become a bit of a tradition in our school – it’s Mole day ! Held annually on 23rd October, this year it’s great as it falls on the last Friday of term. It seems Mole day started in the U.S. in 1991 as a way of increasing pupils’ exposure to chemistry. So what’s a mole?! Yes, it’s a furry creature but also a really big number, and that’s really big with a capital B! Probably the hardest concept in chemistry is that atoms are really small and therefore the number of atoms needed to allow us to actually see stuff is really large – it allows us to link our microscopic (should that be nanoscopic ?) world with the macroscopic world we can see and feel. Enter 6.02 x 10ˆ23 (6 billion trillion) otherwise known as Avogadro’s number – that’s more than all the grains of sand on all the beaches in the World.
The word mole comes from the Latin for ‘heap’ so the easiest way to think of a mole is as quantity – just as 12 is a dozen, 6.02 x 10ˆ23 atoms are a mole. The mole allows chemists to translate reactions on an atomic scale to those done on the bench. So really it allows chemists to follow recipes and make stuff – everything in fact from aspirin to nylon tights, honeycomb to tippex. We do a variety of activities on Mole day – an assembly, ‘pin the nose on Avogadro’ , chemical bingo but our favourite is the Mole cake competition – our answer to The Great British Bake Off. The fun we’ve had over the years with everything from ‘Colin the caterpillar’, ‘the advocado’ and ‘the rat’ . It is a serious event run in Year 13, a sort of right of passage to A level, with specially chosen judges with a strict marking criteria – that’s taste, texture, decoration and mole relevance, and it’s usually mole relevance that is the deciding factor. So roll on this year’s Mole Day – piece of cake anyone?!
I’ve been building a library of science blogs to follow and here is a physics blog written by a colleague of mine – Wendy is very passionate about Physics and there are some great posts about diverse careers involving physics.
I also spotted this blogpost on Twitter about one of the periodic tables I had mentioned in a previous post. Turns out it is not as accurate as I thought- very interesting article, it’s worth a read !
Technology is a great thing and the introduction of mobile devices in the classroom has great advantages when teaching Chemistry. In practical work we constantly encourage our pupils to note down their observations, in particular things like colour changes, bubbles, precipitates … So a video clip of the experiment allows an observation to be recorded and stored for future reference. Recently my senior pupils have been introducing me to joys of SloMo and the attached clip just proves how powerful a recording can be. This is an A2 experiment preparing an Azo dye – prepare to be mesmerised !
Great to hear about this years Nobel prize for medicine. It was divided, one half jointly to William C. Campbell and Satoshi Ōmura “for their discoveries concerning a novel therapy against infections caused by roundworm parasites” and the other half to Youyou Tu “for her discoveries concerning a novel therapy against Malaria”. William C Campbell was born in Donegal and attended school in Belfast before heading abroad for his studies. As you are maybe aware Northern Ireland has its fair share of Nobel Peace Awards but it’s great to see science being acknowledged, we are the country that bore Thomas Andrews and William Thompson (Lord Kelvin) after all !
As term continues it is becoming harder to keep up with the posting. However, being in the thick of the classroom definitely gives me new ideas about posts to write. This week’s molecule is one that lingers in every school chemistry lab. And if you can smell it then you know it’s time to check the gas taps. I’ve a Year 8 class this year and one of the first lessons is using a Bunsen burner – who would have guessed learning to light a Bunsen burner could produce such excitement, it really is all down hill after that ! The molecule in question is methanethiol, also referred to as methyl mercaptan, and its put into gas so that we can smell and identify leaks. I read an interesting article that cites the New London gas disaster in the 1930s as the catalyst for gas odorisation. A School board in Texas were tapping gas from a gas line and an undetected build up of this odourless natural gas caused an explosion killing 295 students and teachers.
The term mercaptan comes from the Latin to mean ‘captures mercury’ as the thiol group interacts strongly with mercury. This molecule is very similar to methanol with the only difference being a sulfur atom instead of an oxygen atom with the SH group being referred to as the thiol. The difference one atom makes is astounding – the lack of hydrogen bonding between the molecules means that methanethiol is a gas whereas methanol is a liquid and of course there is that smell.
Now if you smell gas but know there is no gas taps around have a look in the fruit bowl ! You might find a Durian which is probably the whiffiest fruit around. It is found in South East Asia and is renowned for its smell and this can be traced to amongst other chemicals the mercaptans. Mercaptans can be found everywhere, in our urine, skunk spray and even in the production of beer and wine. There was a mercaptan leak from a factory in France in 2013. Winds carried the smell over the English Channel and as you can imagine as well as an outcry there were some very witty observations made. Not often would you find a link to a red top on a science blog but this definitely made me giggle ! http://www.mirror.co.uk/news/weird-news/uk-hit-by-french-gas-leak-1549236
Although methyl mercaptan is found in our bodies in high concentrations it is also highly toxic. In November 2014 10 tonnes leaked from DuPont chemical plant in Texas, killing four workers and injuring 15.
So why do thiols smell ? Why does methanethiol have such an distinctive smell compared to its analogue methanol when they only differ by one atom ? The first property that is essential for a molecule to have for us to smell it is to be a gas or volatile liquid but that’s not enough. It seems that we can smell these molecules as there is an interaction between the molecule and olfactory receptors in the nose. This is a complex process and the Nobel prize in medicine was awarded to Linda Buck and Richard Axel in 2004 for work in this field. Smells are so emotive and of course chemistry lies at the centre of this sense – while writing this post it reminded me of a book I read a few years back called Perfume by Patrick Suskind, one to recommend !
This is a post that I can take no credit for as it is my first guest post. It’s also the post I wish I had read before I started my chemistry degree as it would have crystallised the link between organic chemistry and natural products. As I say to pupils the link between the medicine men of the South American jungles and the drugs that we are prescribed is closer than we could ever realise, anyway over to the ‘organic chemist’ ……….
There’s a branch of organic chemistry that focusses on the synthesis of highly complex naturally occurring compounds. “Natural product synthesis” (as it’s referred to in the field) is a long established discipline that is both highly regarded and more recently somewhat divisive amongst organic chemists. It’s not unusual for the synthesis of a complex natural product to take several years – typically consuming one (or many) student’s entire PhD tenures (typically 4 years!).
Probably the most extreme example of human endeavour in the field of natural product synthesis is that of the synthesis of vitamin B12. This synthesis of this molecule took no less than 12 years and was accomplished collaboratively by 91 post-doctoral researchers and 12 PhD students from 19 different nations. Accomplishments such as this of course receive the accolades they deserve but there also exists a contrarian viewpoint that asks the general question, “why would anyone want to spend such much time, effort and money making molecules that generally have no current applications in the real world?” (There’s no need to make vitamin B12, it’s in our food!!). Parallel viewpoints like this can of course be expressed outside organic chemistry: “Why would any sane person ever want to climb Mt Everest?”; “Why did mankind think it necessary to spend billions of dollars putting men on the moon?”; “Why are we seriously considering sending humans to Mars given the cost and risks?” The argument to counter all of the above viewpoints (whilst difficult to justify before the completion of whatever heroic task is being undertaken) is that the things we learn from tackling the most difficult, complex, dangerous and costly problems often will have indirect benefits that will hopefully advance/sustain humankind (and our planet) in the decades and centuries to follow. For example, climbing Everest has taught us a lot about human endurance under extreme conditions and how sustained hypoxic (low oxygen) conditions affect human physiology (especially with respect to congestive heart failure and sleep apnea). These findings have then been applied in the real world.
As for natural product synthesis and those labs that specialize in this discipline, the direct and indirect benefits are multitude: not only do these labs offer an amazing environment in which the industrial and pharmaceutical chemists of the future learn their trades but new discoveries along the way lead to new general synthetic methodologies that benefit all of the organic chemistry community (and beyond…). Having a portion of academic organic chemistry research dedicated to natural product synthesis is on balance probably a good thing even if detractors think it outdated. The benefits of spending 10 years making “nobodycaresomycin A” might not be immediate but somewhere down the line a use for this product (or methods of making it) might be realized (and millions of Japanese sea slugs won’t suffer the fate of being squashed and extracted to isolate 0.5g of compound!).
No post about the synthesis of complex molecules would be complete without mention of a titan in this field, Robert Burns (RB) Woodward (1917-1979). Undoubtedly one of the greatest organic chemists of all time (some would argue the greatest) he forged the field of complex natural product synthesis at Harvard University and synthesized fantastically complex molecules including: vitamin B12, quinine, cholesterol, cortisone, strychnine, lysergic acid, reserpine, cephalosporin C and chlorophyll but to name a few. These achievements not only represent the pinnacles of synthetic methodology and practice but many are important molecules that have advanced human health immeasurably.
Not only a Nobel Prize winning chemist (in 1965) but Woodward was a true character to boot. An always dapper man his Thursday evening lectures were legendary – known to last for 3-4 hours at a time, chain-smoking cigarettes whilst drawing exquisitely beautiful complex structures from memory in coloured chalk (such were the epic nature of his lectures his students developed a measurement for the length of these sessions in units of so-called “milli-Woodwards”!). His lectures were characteristically clear, original and insightful – starting at the upper left hand corner of a large blackboard and finishing at the bottom right hand corner with precise logic. Understandably (and sadly) only parts of a few of his lectures were ever recorded for our enjoyment. He loved the colour blue – from his suits to his parking space being painted blue at Harvard (on which was parked his blue Mercedes…). He was very partial to Scotch or maybe a Daiquiri (usually ordered two at a time…).
Many have observed that his methodologies and syntheses have an element of artistic elegance to them in addition to stellar science. Such was Woodward’s breadth and depth of chemical expertise that he most likely would have obtained a second Nobel Prize in chemistry in 1981 had he been alive (the 1981 Nobel Prize was awarded for studies into the nature of chemical reactions). His contributions to organic chemistry (beyond the ability to purely make something) are important, vast and enduring. Woodward died in his sleep on 8 Jul 1962 (aged 62), no doubt deep in the dreams of his next synthetic adventure.
“A scientist has to work very hard to get to the point where he can be lucky.” – RB Woodward.