
Chemists make first-ever ring of pure carbon - headalgorithm
https://www.nature.com/articles/d41586-019-02473-z
======
apo
> Gawel and his collaborators have now created and imaged the long-sought ring
> molecule carbon-18. Using standard ‘wet’ chemistry, his collaborator Lorel
> Scriven, an Oxford chemist, first synthesized molecules that included four-
> carbon squares coming off the ring with oxygen atoms attached to squares.
> The team then sent their samples to IBM laboratories in Zurich, Switzerland,
> where collaborators put the oxygen–carbon molecules on a layer of sodium
> chloride, inside a high-vacuum chamber. They manipulated the rings one at a
> time with electric currents (using an atomic-force microscope that can also
> act as a scanning-transmission microscope), to remove the extraneous,
> oxygen-containing parts. After much trial-and-error, micrograph scans
> revealed the 18-carbon structure. “I never thought I would see this,” says
> Scriven.

The molecule (an all-carbon cycle of 18 atoms) was prepared in a very unusual
way - by directly manipulating the atoms using an atomic force microscope.

In other words, each molecule is made individually. This is not the way that
chemists typically work, and will not result in quantities of material that
can be seen.

The abstract says nothing about chemical stability, but I suspect C-18 quite
unstable and may never be prepared in gram quantities.

Higher cycles containing more carbons may be more stable, but this is likely
to remain a curiosity for some time.

Still, this is a new kind of "allotrope" of carbon. The cyclic, relatively
rigid nature of the structure and the potential for electrons to circulate
under applied fields could lead to some unusual applications.

~~~
0xDEFC0DE
>In other words, each molecule is made individually. This is not the way that
chemists typically work, and will not result in quantities of material that
can be seen.

Is there not merit in doing it via this 'hard way' first before optimizing
stuff and finding a production pathway? (IANAchemist)

~~~
apo
It's not really a question of hard way vs easy way. It's more like the
difference between having a balloon filled with helium and making a single
helium atom in a collider. One you can buy at the grocery store, the other
requires a team of trained scientists and a facility full of equipment.

A milllimole (10^20 moleculess) is considered small scale by many chemists.
Working with a single molecule as described in the artice is just short of
science fiction, and hardly any chemists have ever done it. It requires one of
the most expensive instruments in the world.

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loa_in_
A short, straight to the point read. Fascinatingly the scan image appears to
have 9 vertices.

Nit: Article confusingly uses name carbon-18 to denote a molecule with 18
atoms of carbon. Carbon-18 suggests otherwise an isotope of carbon.

~~~
sp332
The notation is confusing, but I don't think it's that uncommon. For example a
buckyball is denoted Carbon-60.

~~~
thaumasiotes
Geez, I wonder how radioactive carbon with 54 neutrons would be.

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Lerc
The question that springs to my mind from this is 'could rings be
interlinked?'

I'm not very familiar with chemistry. Are there other instances where other
molecules can interlink in a way that, while not having bonds between them
cannot be separated without breaking the bonds of one or the other?

At the very least it's fun to imagine a form of ringmail made of these.

~~~
theideaofcoffee
Very much so. There are different synthetic methods that could be used to
create these so called “catenanes”, from a slapdash wait-and-see process where
the starting material is thrown together and by hope and statistics a product
comes out of the reaction with two interlocked rings. Otherwise one could
build up a reaction with a starting material in a shape that’s conducive to a
ring structure then attempt complexation/liganding etc etc finish and close
the rings so they interlock.

For some interesting reading in self-assembling structures see: Hao Li et al.
Quantitative self-assembly of a purely organic three-dimensional catenane in
water, Nature Chemistry (2015). DOI: 10.1038/nchem.2392

~~~
im3w1l
Would the rings tunnel through each other at a significant rate?

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tempguy9999
IANAChemist but

> ...showed that the 18-carbon rings had alternating triple and single bonds.

 _Stable_ alternating single/triple bonds? As in the bonds don't flicker
around? How is that even possible?

1\. Surely the bonds can't stay in the same place

2\. Surely they would 'nebulise'/spread out/whatever the right term is, over
the ring

3\. if 2. doesn't apply, why on earth is it more energetically favourable to
have a very high energy (ok, my assumption) triple bond next to a much lower
energy (ditto) single bond, and for it not to immediately snap into a pair of
double bonds?

Given my n00b level of teh chemistry, what is going on here?

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kortex
These alkyne (C≡C) bonds are indeed strained and unstable, but there is an
energy barrier to jumping to alkane (C-C) or alkene (C=C). Otherwise, polyynes
like Ichthyothereol [1] would not be stable.

Resonance is not possible with this configuration because the orbitals are not
symmetric. Benzene is often drawn with alternating alkane and -ene bonds, ⌬.
It's not obvious, but benzene is radially symmetric in its electronic
configuration. Each carbon has p-orbitals pointing vertically from the disc,
forming a cloud, rather than discrete pi bonds between neighbors, and the
electrons can "skate around the ring".

The first bond between carbons is always sigma. In alkenes, there is one sigma
bond, in -ynes, there are two pi's at 90 degrees to each other. I'm a bit
fuzzy on my o-chem, but iirc there is an energy gap between this configuration
and cumulene C=C=C, which makes spontaneous transition unlikely.

In this c18 cycloalkyne, the p-orbitals are further strained into a bent cross
shape if looking toroidally. This makes for an even bigger difference in
energy levels, which means it can't flip to alkene or even swap positions.

[https://en.m.wikipedia.org/wiki/Ichthyothereol](https://en.m.wikipedia.org/wiki/Ichthyothereol)

~~~
tempguy9999
OMG which part of "I Is A N00b" did I not make clear? :-)

The role of spdf and sigma/pi electrons, I'm aware of these things but don't
have a mental model for them. And "p-orbitals pointing vertically from the
disc"??.

That was brutal but you've given me a lot to aim for so I'll get to reading
this afternoon - thanks!

~~~
logfromblammo
In order for a pi-bond to easily flip parallel to a different sigma-bond,
there has to be some factor making the other end of the new bond more
positive, or the other end of the existing bond more negative. And pi-bonds
basically occupy two side slots. You can think of them as left&right for one
slot and top&bottom for the other.

Aromaticity is basically alternating single and double bonds. So when one pi-
bond flips to the next bond down the chain (preferably into the same slot, but
not necessarily--molecules can twist and flex), you get two single bonds in a
row on one side, and two double bonds in a row on the other. Ordinarily, this
would be a strong incentive to flip back to the way it was before, but if a
double bond further down the chain can be flipped, it might propagate further
down. In a ring, like benzene or a phenyl group, that wave of bond-flipping
can just chase its own tail forever. In a polymer, it can go all the way down
to the end of the (long) molecule before bouncing back.

When you have alternating single and triple bonds, that triple bond uses up
both mutually-perpendicular slots for the side bonds. No other pi-bond can
flip over next to the adjacent sigma-bond, because the bonds on the other side
just bounce it right back, like having Manute Bol and Hakeem Olajuwon on
either side of the paint when the second forward of your high school junior
varsity basketball team tries to go around to one side or the other to score a
new pi-bond. It's just not going to happen, unless you pump Jeremy Cohen full
of so much cocaine, amphetamines, and sugar that he can charge into a gigantic
center and somehow bounce _the defender_ into the top row of the bleachers.

~~~
tempguy9999
Oh my. I had no idea of "pi-bonds basically occupy two side slots" or "uses up
both mutually-perpendicular slots for the side bonds". This geometry aspect is
completely new.

I'll have a goggle but if you have any introductory resources for this, that
would be very helpful. Books, sites, appropriate terms to search for I may not
know, anything for a beginner just to get started, I'd appreciate it. Thanks.

~~~
logfromblammo
Electrons around an atom occupy certain probability functions that correspond
to the electron's energy level. The most basic and lowest energy of these at a
given tier of orbital distance is nested spherical shells (s). Next is 3
different 2-lobed dumbbell shapes (p), oriented mutually perpendicularly (px,
py, pz).

The spherical mode (s) and the dumbbell-shaped modes (px, py, pz) can also
hybridize when each has a single electron in it. Those hybrid modes can point
lobes out in different directions. A stable mode can hold up to 2 electrons,
each spinning in opposite directions.

When an electron probability function of one atom overlaps with that of an
adjacent atom, their functions can further hybridize into a bonding function.
(They can also hybridize into anti-bonding functions, but ignore that for
now.)

When the bonding function puts the electron pair mostly along the line
connecting the centers of the bound atoms, that's a sigma bond. It's the
lowest-energy kind of bond, so it always (aka exceedingly rare exceptions)
happens before any other kind of bond.

In a carbon triple bond, the spherical orbital (s) will hybridize with just
one of the dumbbell orbitals (p), forming one function (spx+) that mostly
occupies one lobe of the former dumbbell, and one that mostly occupies the
other (spx-). These two will then form direct sigma bonds with atoms on either
side, separated by 180 degrees. That leaves the other two dumbbell modes (py,
pz), mutually perpendicular to the two hybrids. Those can align with the
parallel dumbbell modes of the adjacent atom and create bonding functions
where the electron positions sort of average out to between the two bound
atoms, but mostly occupy places that do not overlap with the sigma bond. Those
are pi bonds. They happen between two aligned p orbitals. (There is another
kind of indirect bond, a delta bond, that happens between two aligned d
orbitals, which have more complex shapes. Those would be the fourth bond in a
quadruple bond.)

When those carbons are triple-bonded, their p-orbital atoms are leaning toward
the adjacent bound atom. It's much harder for the atom on the opposite side to
get their attention to maybe participate in a pi bond on that side.

If you look at the bond through a microscope, you're just going to see a big
blob of electron probability between the nuclei, with 6 electrons somewhere in
it most of the time, where the triple bond is. It's not organized into
discrete spaces for each separate bond. It only has separate slots when you
look at the mathematical model.

I don't have any specific resources, other than any modern chemistry textbook
you can find. Possible search terms "electron orbitals", "bonding orbitals"

~~~
tempguy9999
I do recognise spdf and the orbitals, I didn't realise the clouds interacted
(well duh!), and that's the clearest description of pi and sigma bonds I've
come across. That was brilliant, thanks!

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dlivingston
> Elusive 18-atom ‘cyclocarbon’ could be a step towards molecule-scale
> transistors.

Can someone 'in the know' on semiconductor device fabrication expand on this
more?

~~~
analog31
The press release always mentions the cool new technology _du jour_ as a
possible spinoff of the discovery. Today, it's transistors.

When the Superconducting Super Collider was proposed, the newspapers said that
research done at the SSC would lead to breakthroughs in computer graphics and
flat panel displays.

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ChuckMcM
This is really cool. Both the action of assembling it and how they imaged it.

One of the amazing things about carbon is that it can lots of interesting
things (conductor, insulator, semi-conductor, Etc) with no added elements,
just different bonding and structures. Further, it is an excellent thermal
conductor. As a result it has the potential to be the material that replaces
silicon in computer chips on a very large scale.

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Endy
Can we draw carbon out of the atmosphere to make this?

~~~
Filligree
We can draw carbon from the atmosphere, sure. It's an inefficient process
costing a lot of energy, but given they're making the final rings molecule by
molecule, it isn't as if we'd need a lot.

...for the purposes of scrubbing CO2 from the air? There's absolutely no
reason we'd use _this_ as the final product. Graphite or diamond would do the
trick just as well, and either is cheap to make.

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logfromblammo
Should've called it a cyclyne.

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jldugger
so basically benzene without the hydrogen?

~~~
logfromblammo
No. Benzene is an aromatic ring. It has C-C=C sequences that easily flip to
C=C-C, making electrons in the ring highly mobile. A C≡C-C sequence does not
easily flip to C=C=C, or vice versa. Those electrons are a lot less mobile.

Also, alternating single and double bonds leave a bonding site on each carbon
for a functional group. Alternating single and triple bonds use up all four
(easy) carbon bonds, and you can't cram another bond in there without an
insanely powerful acid.

