Rhubarb Connection and Other Revelations: The Everyday World of Metal Ions - Softcover

Öhrström, Lars; Covès, Jacques

Softcover

ISBN 10: 1788010949 ISBN 13: 9781788010948

Publisher: Royal Society of Chemistry, 2018

Synopsis

Pink warships that vanish at dusk, urinary maladies of an emperor, and a gold test for cocaine – behold the chemistry of metal ions as never before.

In this book you will learn about the sarcophagus molecule, the Chen-Kao test, and how murderers can be caught blue-handed with the wonders of glowing luminol. You will also meet the hidden chemistry of metal ions in everyday life, from the clever modern devices that measure blood-sugar levels, to the leather on your shoes and chewing gum stuck to their soles.

Expect to encounter a fair share of heroes and villains, real and fictional, scientist and layperson. Such characters include an ex-MI5 employee running a hospital ward in London amid falling German V1 rockets, a notorious racing cyclist, a proud butler and the lady who first proposed nuclear fission (it’s not who you think it is).

With engaging, humorous and intelligent prose, the reader will discover the fascinating back-stories of chemical discoveries and inventions where metal ions have played a major role.

Featuring a foreword by popular science communicator Dr Raychelle Burks of St. Edward's University, Texas.

About this title

From the Back Cover

Pink warships that vanish at dusk, urinary maladies of an emperor, and a gold test for cocaine - behold the chemistry of metal ions as never before.

In this book you will learn about the sarcophagus molecule, the Chen-Kao test, and how murderers can be caught blue-handed with the wonders of glowing luminol. You will also meet the hidden chemistry of metal ions in everyday life, from the clever modern devices that measure blood-sugar levels, to the leather on your shoes and chewing gum stuck to their soles.

Expect to encounter a fair share of heroes and villains, real and fictional, scientist and layperson. Such characters include an ex-MI5 employee running a hospital ward in London amid falling German V1 rockets, a notorious racing cyclist, a proud butler and the lady who first proposed nuclear fission (it's not who you think it is).

With engaging, humorous and intelligent prose, the reader will discover the fascinating back-stories of chemical discoveries and inventions where metal ions have played a major role.

From the Inside Flap

Pink warships that vanish at dusk, urinary maladies of an emperor, and a gold test for cocaine behold the chemistry of metal ions as never before.

In this book you will learn about the sarcophagus molecule, the Chen-Kao test, and how murderers can be caught blue-handed with the wonders of glowing luminol. You will also meet the hidden chemistry of metal ions in everyday life, from the clever modern devices that measure blood-sugar levels, to the leather on your shoes and chewing gum stuck to their soles.

Expect to encounter a fair share of heroes and villains, real and fictional, scientist and layperson. Such characters include an ex-MI5 employee running a hospital ward in London amid falling German V1 rockets, a notorious racing cyclist, a proud butler and the lady who first proposed nuclear fission (it s not who you think it is).

With engaging, humorous and intelligent prose, the reader will discover the fascinating back-stories of chemical discoveries and inventions where metal ions have played a major role.

Excerpt. © Reprinted by permission. All rights reserved.

The Rhubarb Connection and Other Revelations

The Everyday World of Metal Ions

By Lars Öhrström, Jacques Covès

The Royal Society of Chemistry

Copyright © 2019 Lars Öhrström and Jacques Covès
All rights reserved.

ISBN: 978-1-78801-094-8

Contents

Foreword, 
About the Authors, 
Acknowledgements, 
Overture, 
Chapter 1 Fantastic Metal Ions and How to Catch Them, 
Chapter 2 Rhubarb, an Emperor and the Butler's Pride, 
Chapter 3 Mining, Magnets and Making New Elements, 
Chapter 4 On Poisoning, Self-poisoning and the Euro, 
Chapter 5 Down to Earth Chemistry, 
Chapter 6 Chemicals from Trees and How the Pacific Yew Was Saved, 
Chapter 7 Molecules and Murderers – The Art of Detection and Measuring, 
Chapter 8 Metal Medications and Metals Versus Medicines, 
Chapter 9 Blood, Iron and Body Metals, 
Chapter 10 Vanishing Warships and Sugary Gold, 
Appendix, 
Bibliography, 
Subject Index, 

CHAPTER 1

Fantastic Metal Ions and How to Catch Them

In the Periodic Table of Elements there are 92 naturally occurring building blocks of our world and most of them are metals. Some give us power, other give us wealth, and a fair number just keeps us and all other living beings on this planet alive and well. This book is about how to catch them, put them in the right places, make them do good things and sometimes to remove them from places where they might do harm.

1.1 The Tarnished Platinum Cyclist

Before starting in earnest we need to sort out some basic stuff, and we do this together with a rather questionable character, a young American who in July 1996, with the breath-taking speed of a racer cyclist, was on his way to Aix-les-Bains in south-east France. For the last few years, he had been pedalling himself into the world cycling elite, and now he could perhaps make his breakthrough in this, possibly the world's toughest athletic competition, the Tour de France. However, he did not make it to Aix, and a few months later it did not look like he would ever make it anywhere else on two wheels either. Lance Armstrong received frightening information from his doctors: he had testicular cancer and it had already spread to his lungs, abdomen and brain. He was given a less than 50% chance of survival.

Followers of Le Tour and, indeed, sports in general, all know how it ended. Armstrong recovered and went on to win a record-breaking seven consecutive Tour de France competitions from 1999–2005. Only to be disgraced and have them taken away years later when the long controversy of his alleged use of banned performance enhancing compounds finally reached the end of the road.

Why are we telling you this you wonder? Because what saved his life from the cancer was not only his tough physique and possibly some luck, but a very simple compound that is an easy first example of the type of chemistry that we will discuss in this book, the blockbuster drug cisplatin. (To be clear, cisplatin is not a performance enhancing drug.)

Discovered by serendipity and then developed by much hard work by Barnett Rosenberg, Loretta Vancamp and co-workers at Michigan State University some 30 years earlier, it has a fascinating history of its own. Right now, however, we are concerned only with its simple components, two molecules of ammonia, two chloride ions and one platinum atom in the form of the ion with charge plus two, and how they stick together to form this amazing drug molecule, formally named cis-diamminodichloroplatinum(ii).

That is a bit of a mouthful, but start by noting that ammonia has the formula NH3 and is the same molecule that we find in some cleaning agents, that the chloride ion has charge minus one and is identical to the chloride ion in table salt, NaCl, and that platinum atoms are also found in catalytic converters for cars, but this one has two electrons removed to give the 2+ ion. Figure 1.1 represents how we like to picture the cisplatin molecule.

Now, in your mind remove the bonds between Pt (platinum) and N (nitrogen), and between Pt and Cl (chlorine), and you will find five detached units, one metal ion and four other units that we call ligands because they can bind to a metal ion. We will talk a lot about these ligands, so take note of this term.

But do not fear, we will not pepper the text with unnecessary jargon. We do need to name things to be able to talk about them though, imagine the sport pages without naming the individual footballers? Full of "this fellow", "that fellow" and "the other fellow". That would really be confusing! But this is a trap popular science occasionally falls into, sometimes to the extent of making the text unintelligible to layperson and specialist alike.

Back to cisplatin, which unfortunately will not cure all cancers, and sometimes a cancer may also develop resistance against this drug. Then the doctor might suggest an alternative platinum-based drug, for example oxaliplatin (trade name elotaxin) which you can see in Figure 1.2.

If you now remove the bonds between the metal and the ligands you will see that we are now left with two ligands instead of four, and one metal ion. This is because each ligand now binds to platinum 2+ with two atoms each, and Pt2+ still prefers having four bonds arranged in a flat "square planar" geometry.

Of course, there is a name for this as well, but we are afraid you will not find the following very logical. We call a ligand that binds to a metal with more than one atom a chelating ligand, and this comes from the Greek for claw, and what the coiners of this term thought about was the claws of a lobster as the ligand clearly pinches the metal and holds it fast. Fair enough, you might think, but then we call a ligand that can make a chelate a multi-dentate ligand, thus a ligand with many teeth, we count one for each atom that binds to the metal. And now it gets weird, as it is not clear if a lobster even has teeth, and if it does, they are certainly not sitting in the claws but seem somewhat surprisingly to be found in the stomach.

But here we are, and a claw with many teeth, incongruous as it may sound, is good if you want to hold on to a metal ion or catch it before it does harm or disappears before you can do something useful with it.

1.2 Chelation Catches the Criminal

One standard use of this chelate effect, the way in which a multi-dentate ligand is much better at binding and "catching" a metal ion than two similarly looking but mono-dentate (and thus non-chelating) ligands, is in scene-of-crime forensic analysis. Lance Armstrong may have acted immorally, at least in the eyes of the sporting world, but he didn't wave guns around, and there were no bullets to look for.

However, at a crime scene where shooting is suspected, this is exactly what you are searching for, and if you find a bullet hole, you will also stand a good chance of finding the actual bullet that can then subsequently be tied to a certain weapon. In some cases, it is not obvious which holes are bullet holes and which are not. Or worse, in some cases, it might be hard to know which are new bullet holes and which are old. That is why a small attaché case with a bullet-hole-test-kit is always carried to the scene of crime. The ligands in the single-use vials will both catch the lead or copper ions present in the bullet traces left in the hole and give a distinct colouring that can be detected on the spot (see Figures 1.3 and 1.4).

Having said that, nothing is ever as simple as implied in the high-heeled-CSI shows on the telly. Ambiguous results, false positives and failure for the reagents to be specific enough, or to react with a low enough concentration of the suspected criminal residue, are some problems facing both the investigating officers and the chemist developing the methods.

1.3 What About the Metals?

So, multi-dentate ligands can catch metal ions, but there are so many different metals, are there no differences between them? Of course there are. Copper for example, likes sulfur (S) a lot, and it is not a coincidence that the Cu ion is detected with a sulfur containing ligand in the bullet-hole-test. Calcium ions (Ca) on the other hand, do not have much affinity, as we say, for ligands with sulfur, as their bonding atoms prefer oxygen, which is their natural surroundings in bones, teeth and marble for example. The metal ions also come in different sizes, the Li ion, very important in the treatment of some forms of bipolar disorder, is very small, 73 picometres, whereas the Pb ion, a rather nasty fellow, has almost twice this radius, 143 picometres, that is 0.000000000143 millimetres.

It will not be necessary to memorise the Periodic Table to follow the remainder of the book and for now, a quick look at Figure 1.5 will suffice.

There are so many metals, but still fewer than footballers in the Premier League. We will be mostly concerned with some of the "stars" such as gold (Au), but also lesser known metals, such as gadolinium (Gd) might find their way into the stories. We do not want to be biased though, every naturally occurring element is important in some way. As a student once said "all elements are created equal and should be treated with respect" (this particular chemistry class had been preceded by a diversity workshop).

One thing to take home from Figure 1.5 however, is that elements appearing in the same column tend to have similar properties, that is kind of why we call it the periodic table. Therefore, lithium and sodium will both form ions with the charge +1, calcium and strontium (Sr) will be 2+, and silver (Ag) and gold are noble metals, just to take a few examples.

On the side of the non-metals, we have the atoms that make up our ligands, and here we will be more restrictive. We will almost exclusively stick to carbon (C), hydrogen (H), oxygen (O), nitrogen (N), sulfur (S) and phosphorous (P), with the occasional chloride (Cl) or bromide (Br) ion making a guest appearance.

Now, this may have been a bit dry and reminded you of your school days. If so, rest assured that the rest of the book will contain more action. I'm sure you realise that to appreciate a game of football, you need to know the basic rules even though you might not grasp the finer details of the offside concept, and the same is true for chemistry.

Although the next chapter is going to be completely inorganic, save for some rhubarb, a lot of the stuff in this book relates to biochemistry and living organisms, from fascinating sea-snails to humans. Let us therefore finish by just showing a molecule you have in your body and that we will discuss further later on, the heme group in haemoglobin. This is an example of how efficiently some biological molecules trap metal ions in a perfect cavity between four nitrogen atoms arranged in a square with the metal at the centre.

The molecule works like a kind of a molecular lasso, but instead of a cow, we have trapped iron in the heme-molecule that is attached to our haemoglobin and without which we cannot breathe (Figure 1.6).

However, the oxalate ion in Figure 1.2 and the bullet-hole detection ligands in Figure 1.4 look more like pincers than lassos, but may be equally efficient, as we shall see in the next chapter.

CHAPTER 2

Rhubarb, an Emperor and the Butler's Pride

September 1870 had already started badly for Charles Louis Napoléon Bonaparte, and it was going to get worse. At Sedan, a small French town close to the Belgian border, the commander of the French army, Patrice de Mac-Mahon, was wounded and the sick and weak emperor, better known as Napoléon III and nephew of the great Corsican, had to surrender and give himself up as a prisoner to the invincible German duo, Helmuth von Moltke and Otto von Bismarck.

In the run-up to the battle of Sedan, the decisive battle of the Franco-Prussian war of 1870–1871, von Moltke had successfully engaged the French army by a classic pincer movement, attacking from two sides rather than in the centre. Urate ions, that have nothing to do with the element uranium, but are a product of the break-down of DNA, attack sodium ions, Na+, and calcium ions, Ca2+, in the same way. Two electron pairs on each of the negative oxygen and nitrogen atoms can bind, from two sides, to any metal ion that is in its way (Figure 2.1).

As long as these compounds float around dissolved in our bodily fluids they are not a problem, but when they become too concentrated and starts to add onto each other via a second pincher attack on the backside of the sodium ion, or the flat urate molecules start to stack one upon the other, we might have a problem. As now we will start to form particles, and just as a snowball, they will pick up more and more of the urate and chelate even more metal ions until the "stones" are so big that this becomes a very painful condition.

2.1 The Emperor's Stones

Such stones were something Napoléon III was all too familiar with, and during the battle of Sedan he was in terrible pain, owing to his stones (Figure 2.2). Was the war lost because of this? Probably not; it seems the war was lost as soon as it was declared because of the Prussian technical and organisational superiority.

However, the Emperor was not very keen to take up arms in the first place, with some of his advisors being the chief warmongers. How well he could resist and counteract them, while being beset by his bladder stones, is difficult to know.

It is easier to turn to the "stones" themselves, because these are susceptible to detailed methods of scientific interrogation such as X-ray crystallography. This is the supreme method we use to find out the detailed arrangement of atoms and molecules in solid materials and other chemical compounds, and these could be anything from metals to proteins or to somebody's kidney or bladder stones.

Surprisingly there are things we still do not know about the urate compounds, and detailed information is just emerging. Such as the structure of the first calcium compound reported by Janeth Presores, Jennifer Swift and co-workers in 2013, and the sodium urate structure found by analysing the stones coming from a 63 year old male. In the latter case, Dominique Bazin and his team noted that this solved a 150 year-old problem, but that they needed the most up-to date technology to do so, namely a large-scale facility known as a synchrotron. Somewhat confusingly these solid objects are known as "calculus" in medicine, not to be confused with the branch of mathematics that some people unfortunately seem to find equally painful, and that we might just need to avoid this painful condition.

(Continues...)

Excerpted from The Rhubarb Connection and Other Revelations by Lars Öhrström, Jacques Covès. Copyright © 2019 Lars Öhrström and Jacques Covès. Excerpted by permission of The Royal Society of Chemistry.
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Edition details

• Publisher: Royal Society of Chemistry
• Publication date: 2018
• Language: English
• ISBN 10: 1788010949
• ISBN 13: 9781788010948
• Binding: Paperback
• Edition number: 1
• Number of pages: 233