5
$\begingroup$

This question arose from my previous question: Can benzyne be trapped inside a polycyclic hydrocarbon?. While dodecahedrane was too small to fit an anthranilate ion or even a benzyne ion, there are lots of other cage molecules, notably fullerenes. Unfortunately fullerenes themselves have partial double bond characters in them, making them liable to undergo a Diels-Alder reaction with benzyne.

However, if it were possible to "saturate" the fullerene, it could serve as a molecular container to hold the benzyne molecule.

Is it possible to saturated fullerenes? After being saturated, can we use it as a molecular container?

Improve this question
$\endgroup$
3

1 Answer 1

Reset to default
8
$\begingroup$

I'm limiting my answer to $\ce{C60}$-fullerene, but the same idea applies to the higher fullerenes as well.

In short, it's not possible to fully hydrogenate $\ce{C60}$ to $\ce{C60H60}$. This is a result of the bond strain that would result upon hydrogenation, as the addition of hydrogen across an alkene in $\ce{C60}$ produces carbon atoms that would optimally be tetrahedral with angles near $109.5^\circ$, while the bond angles in $\ce{C60}$ are $108^\circ$ and $120^\circ$ for the pentagonal and hexagonal rings, respectively.

Partial hydrogenation of $\ce{C60}$ with zinc and hydrochloric acid has been done to form $\ce{C60H36}$,1 but this compound degrades quickly in the presence of oxygen to form hydroxylated groups; degradation of the fullerene cage and formation of ketones also occurs. Efforts to hydrogenate further under high pressure hydrogenation conditions results in complete breakdown of the fullerene cage, with pretty interesting results, including ejection of carbon atoms and $\ce{C2}$ loss, producing hydrogenated species with fewer than 60 carbon atoms.2 Collapse of the fullerene cage was also noted, forming hydrogenated compounds with 25 - 45 carbon atoms.

  1. Cataldo, Franco. Fullerenes, Nanotubes and Carbon Nanostructures 2003, 11 (4), 295-316. DOI: 10.1081/FST-120025852

  2. Talyzin, Alexandr V., Yury O. Tsybin, Jeremiah M. Purcell, Tanner M. Schaub, Yury M. Shulga, Dag Noréus, Toyoto Sato, Andrzej Dzwilewski, Bertil Sundqvist, and Alan G. Marshall. J. Phys. Chem. A 2006, 110 (27), 8528–8534. DOI: 10.1021/jp0557971

Improve this answer
$\endgroup$
2
  • $\begingroup$ Wait a minute. A hexagon in a flat surface would have a 120° angle, but a hexagon in a curved surface should have an angle less than 120°, no? $\endgroup$
    – Pritt says Reinstate Monica
    Commented May 30, 2017 at 13:19
  • 1
    $\begingroup$ @PrittBalagopal The hexagons and pentagons themselves remain flat and regular; it's the junctions between them that gives curvature to the fullerenes. Note that at a vertex in a repeating hexagonal tessalation on a flat surface, the angle sum at the vertices is 360º. However, in a truncated icosahedron (the shape of $\ce{C60}$), two regular hexagonal faces and a regular pentagonal face form each vertex, giving an angle sum of 348º; this leads to the intrinsic curvature. $\endgroup$
    – JSK
    Commented May 30, 2017 at 14:36

Not the answer you're looking for? Browse other questions tagged or ask your own question.