MadSci Network: Chemistry

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

The values for the bond lengths as determined in the gas phase can be 
found at the following web site and at others.

"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

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