MadSci Network: Chemistry
Query:

Re: The stability and bond length of carbon 60

Date: Sun Mar 14 14:42:36 2010
Posted By: Jerry Franzen, Chemistry Teacher
Area of science: Chemistry
ID: 1267537243.Ch
Message:

The values for the bond lengths as determined in the gas phase can be 
found at the following web site and at others.
 http://www.sciencemag.org/cgi/content/abstract/254/5030/410

"On the basis of this symmetry assumption, least-squares refinement of a 
model incorporating all possible interatomic distances led to the values of
(C1-C2) = 1.458(6) angstroms () for the thermal average bond length 
within the five-member ring (that is, for the bond fusing five- and six-
member rings) and rg(C1-C6) = 1.401(10)  for that connecting five-member 
rings (the bond fusing six-member rings). The weighted average of the two 
bond lengths and the difference between them are the values 1.439(2)  and 
0.057(6) , respectively. The diameter of the icosahedral sphere is 7.113
(10) . The uncertainties in parentheses are estimated 2 values."

All of the bonds in any 5 membered ring in the "buckyball" structure are 
equivalent and thus should be the same length - the 1.401 value.  If you 
check on the bonds in any 6 membered ring, they alternate between being 
common to a 5 membered ring (1.401) and being common to another 6 membered 
ring (1.439).  Even though there may be delocalization, there is not a 
hard and fast rule that would say that the bond lengths have to be the 
same value in the 6 membered ring.  Although this is may not be an exact 
analogy, I would not expect the length of the C-C bond common to both 
rings in indene would be the same as the lengths of the other C-C bonds in 
the 6 membered ring.  The fact that both values in the "buckyball" are 
between the usual values for a C-C (1.54 A) and the C=C (1.33 A) would 
seem to indicate that each has some degree of delocalization.

If this is not a convincing answer, get back to me at:
Dr. Jerry Franzen
jtfranzen@fuse.net




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