The Call of the Void

Apparently, I experience ‘High Place Phenomenon’.

As a climbing instructor, I’m used to people saying “I can’t go any further – I’m afraid of heights.”

And I always say, “So am I.”

Of course I am. Everyone is. We just develop strategies for managing that fear, and some manage it better than others. The first time I climb somewhere new, I can feel the fear eating away at me, like a voice in my head saying “Oh god, oh god, oh god.” My strategy is just to get to the top and get it finished – and once I’ve done that, going up again has lost its dauntingness.

It can even feel exciting. I’ve oftentimes sat on the edge of a ledge preparing to belay and realised how easily I could unclip and jump to my death. The thought of the rush of the world shooting past, the feeling of somehow having triumphed over my survival instincts and beaten nature, the sense of freedom, power, and the excitement tremble through me. I’m drugged up on adrenalin. My fingers move instinctively with the rope – and it’s a good job they do, because my mind is addled.
 

Looking down from above. Image © Thing We Don’t Know.

Does this sound familiar? 30% of people experience it at least once. The French call it l’appel du vide – the call of the void – and that is exactly what it feels like to me. A beckoning. As though someone were on my left shoulder... whispering, “Do it!”

Carbon-Based Hydrogen Bonding

Many chemists will be shocked to discover that carbon-based hydrogens can hydrogen bond. Weakly. But actually.

If you're not a chemist you're probably thinking that doesn't sound like much of a surprise... A hydrogen can hydrogen bond? Who've thunk it? And that is the first condition for hydrogen bonding – having a hydrogen.

However, until the discovery of the carbon-based hydrogen bond between acetone and halogenated hydrocarbons in 1937, it was believed that that the hydrogen could only make these bonds when attached to something very electronegative – electron-loving.

Why is this?

Electronegative atoms are electron-greedy and pull the electrons in a bond towards themselves. The electrons are shared unequally, leaving the electronegative atom a bit negative and whatever it’s bonded to a bit positive. We call this bond polar, because it has two differently charged ends, like a magnet. And, just like with two magnets, when the positive end of one comes near the negative end of the other, they bond. All polar molecules do this; we call it permanent dipole bonding. But hydrogens do it with an aggressive zeal that marks them out as unique.

Hydrogen bonds form between the slightly positive hydrogen atoms and slightly negative oxygen atoms in water molecules. Image via Wikipedia Commons.

There are three elements considered electronegative enough to polarise a hydrogen: fluorine, oxygen and nitrogen. Fluorine is the most electronegative element in the periodic table, given the Pauling electronegativity value (a made up scale we use to compare electronegativity values) 4. Oxygen is just behind it, with an electronegativity value 3.5, and nitrogen is 3. In contrast, hydrogen has an electronegativity value of 2.1, which means the difference between it and fluorine is 1.9 – considered enough to make a bond polar. But carbon is not very electronegative, and the difference between it and hydrogen is 0.4, surely too little to create polar bonds?

Apparently not.