Chemical Properties of the Fullerenes
Abstract
The UV-visible absorption spectra of pure C60, C70, and C60O dissolved in toluene were used to perform multicomponent analysis of graphitic soot extracts and to assess the purity of fullerene samples. Diffuse-reflectance FTIR spectroscopy of 1-2 mg solid C60 and C70 samples was used to determine the fraction of hydrocarbon impurities at the level of 0.01 atom fraction H. Vacuum sublimation is the only way to produce C60 and C70 samples free of hydrocarbon impurities. The solubility of C60 and C70 in toluene was measured as a function of temperature for 25 deg C < T < 80 deg C, and for C60 in CS2 for 25 < T < 45 deg C. At 30 deg C, C60 is three times as soluble as C70, but both solubilities decrease with increasing temperature. This unusual temperature dependence, exhibited by virtually no other organic solids in organic solvents, is attributed to the formation of solvated fullerene solids. The heat of combustion of C60(cr) was determined with the NIST adiabatic bomb calorimeter, and used to determine the enthalpy of formation of C60, 2193 +/- 9.6 kJ/mol. The average strength of the carbon-carbon bonds in C60 is 453 kJ/mole. The absorption spectrum of C60 gas in equilibrium with the solid was recorded between 500 and 680 deg C. From the slope of the ln(P sub vap) vs 1/T plot, an enthalpy of sublimation for C60 of 159 kJ/mol was determined.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1993
- Accession Number
- ADA282730
Entities
People
- Allan L. Smith
Organizations
- Drexel University