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Chemistry for Life and Technology

Chemistry for Life and Technology – Can the linear become circular?

Dr. Michael Londesborough

Everything in our Universe has a direction, which we often refer to as “time”. But it’s really increasing entropy – a tendency to chaos.

Chemistry for Life and Technology

Consider an egg when we drop it- it breaks. The organised becomes chaotic and entropy increases. There is no way back for the egg- what has gone is gone. There are a billion ways for it to break, but only one configuration to be as a whole.

For the same reason, we only get older and never younger – the molecules that make us struggle to maintain their complexity, because there are so many mechanisms for decaying to ever simpler forms.  We buy expensive creams and remedies in an effort to slow entropy, but it is ultimately a losing game.  We must eventually submit to its dictates.

But what if we could take the linearity of entropy and chaos, and bend it into a rejuvenating circle of recycled order?

This planet can!  As a consequence, we live on it.

It’s because planet Earth’s chemistry is circular!

Imagine you are an atom of carbon.  You pop into existence in the centre of the Sun, where temperatures and pressures are so high that smaller nuclei of helium are forced to fuse into a new atom of carbon – you.  You spend hundreds of millions of years here, spinning with incredible frequencies.  Then a collapse in the equilibrium between the fierce emission of light from your star and its own gravity leads to the biggest explosion in the Universe, a supernova, and you go flying into space-time at incredible speeds. You move as part of a huge cloud of stellar debris, called a nebula, until you stumble across a section of space-time with the necessary geometry to precipitate your swirling congregation into a new planet.  As a carbon atom, you love oxygen, and there is plenty of it around.  You react with the oxygen, dissolve in the oceans of water molecules and precipitate out of solution as a calcium salt of the CO3¯ ion.  A new morsel of calcium carbonate.  Being denser than water, you fall to the ocean bottom and stay there for millennia until tectonic plate movements shift you upwards.  For thousands of years, you remain just below the surface, surrounded by three atoms of oxygen and a calcium ion.  You recall your exhilarating beginnings- the light, the changing scenery, the adventure. Yet now nothing changes. You begin to suffer from elemental depression.

Suddenly, you hear a distant knock, growing louder. You feel a shuddering, and then, after so many dark years, the caress of photons of light from the Sun on your face.  Looking up you see your liberator: a workman, called Joe, his pick-axe glinting in the sunshine.  After millions of years of nothing, you bathe your eyes in the wondrous blue of the sky, the wonderful white of the clouds, the glorious greens of the trees, and sweaty Joe who finally frees you from your calcium carbonate neighbours and shovels you into his wheel-barrow. He takes you to a near-by kiln and flings you into the fire-heated oven.  The heat is wonderful and sends your molecular bonds into new vibrational levels, like an arthritic old man suddenly being able to move it like Mick Jagger!  You keep vibrating and shaking until you kick off an atom of calcium and an atom of oxygen, and leave the chimney of the kiln as a new molecule of CO2, carbon dioxide.  You rise majestically into the air, gently rotating and wobbling with an ease you haven’t experienced for millions of years.  Can you feel the freedom?  The lightness of being? As an average molecule of carbon dioxide, you spend years in our planet’s atmosphere, circumnavigating the globe several times.  You’re an international traveller, flying over mountains and forests, deserts and oceans. 

As a molecule of carbon dioxide you are able to dissolve in water to form carbonic acid, which happily reconverts back to carbon dioxide and throws you once again into the air. A swooping bird breathes you into its lungs and you cross through its alveoli into its blood.  Molecules of haemoglobin attempt to capture you, but to no avail.  You remain as CO2, passing through the bird’s bloodstream before being breathed out again, this time over a vineyard on a pleasant summer’s day.  Air pressure pushes you down.  You brush against one of the vine leaves, entering nature’s green solar panel via pores (stomata) on its underside. Here you combine with other molecules of carbon dioxide and water, and in a moment of photochemical genius, photons of sunlight drive your conversion into a new molecule of glucose, C6H12O6. A barrage of photons, packets of electromagnetic energy, in combination with the incredible molecular infrastructure of the vine leaf, manage to roll back entropy, and squeeze into your new molecule of glucose energy from the Sun.  Light energy has become chemical energy, and you are its store!

After a long summer as part of a sugary solution inside a ripening grape, you are picked, crushed and once again changed, this time by microbes of yeast.  These tiny single-celled microorganisms process you into a new molecule of ethanol, CH3CH2OH – a key ingredient of ruby-red wine.  Bottled and matured in a dark and damp cellar. Then, with the pop of a cork, you are poured into a glass and slipped down the gullet of an enthusiastic wine-taster.  Flowing into her digestive tract you fall prey to her body’s capacity to deconstruct your molecule, reaping much of its internal molecular energy and, in doing so, increasing the entropy of the system and converting you back into a new molecule of CO2, as which, during a conversation a day or two after drinking you, she breathes out and you again float up into the air, your story ready to continue; a new cycle awaiting.

***

This is but one example of a myriad of possibilities that the circular chemistry of this planet offers carbon.  This process that can reverse entropy is photosynthesis – the conversion of carbon dioxide and water into hydrocarbons and oxygen. This is the chemical equivalent of transforming an elderly couple into a young pair.  A rejuvenation. A revitalisation.  A carbon renaissance.

As these molecules are full of energy, they are full of chemical potential.  We can do lots of chemistry with them.  They are our foods and clothing, medicines, fuels and materials.

Furthermore, this cycle produces no waste!  Any excess hydrocarbons buried under ground transform into fossil fuels of oil, coal and gas.  Ancient Sunshine stored in molecular form!  Molecules so precious that it is impossible to imagine life without them.

Here is the rub: There is not sufficient public understanding of the wonderful opportunities that hydrocarbons present us with, and as a result we under-value them.

What we do with our precious hydrocarbon resources is a key aspect of our global economy.  There are many choices:  not just fossil fuels but polymers, hydrogen, new materials, medicines.

Where there is energy and choice, moving in a circular motion, there is opportunity. Opportunity for you!