The reaction of C(60) with BH(3): tetrahydrofuran in toluene followed by hydrolysis yielded C(60)H(2). This product was separated by high-performance liquid chromatography and characterized as the addition product of H(2) to a 6,6-ring fusion (1alb isomer). The (1)H nuclear magnetic resonance (NMR) spectrum of the product remained a sharp singlet between -80 degrees and +100 degrees C, which suggests a static structure on the NMR time scale. Hydrolysis of the proposed borane addition product with acetic acid-d(1) or D(2)O yielded C(60)HD, and its (3)J(HD) coupling constant is consistent with vicinal addition. The observation of a single C(60)H(2) isomer is in complete agreement with earlier calculations that indicated that at most 2 of the 23 possible isomers of C(60) would be observable at equilibrium at room temperature. These results suggest that organoborane chemistry may be applied to further functionalization of fullerenes.

Equilibration of 1,9- and 7,8-C(70)H(2) has allowed the relative free energy of these isomers to be measured. These "simplest hydrocarbon derivatives of C(70)" are formed by hydroboration of C(70) at room temperature. Analysis of the platinum-catalyzed equilibration of these isomers yielded a relative free energy at 295 kelvin of 1.4 +/- 0.2 kilocalories per mole, with the 1,9 isomer being more stable. This value is in excellent agreement with the ab initio HF/6-31 G(*) calculated energy difference of 1.3 kilocalories per mole, whereas semiempirical calculations gave poor agreement.

COMMUNICATIONS[4] A. Schmidpeter. C. Weingand. A n g e~. .C k m . 1968,80, 234; Angrw. Chem. h i .onal" addition of the H, pairs, see Fig. 1 a) [XI Thc X-ray structure analysis gave a N-H bond length of 74.9(26) pm. C,,H, :

ABSTRACT:The room-temperature mechanical properties of a closed-cell, polyurethane encapsulant foam were measured as a function of foam density. Over the range of densities examined, the modulus could be described by a power-law relationship with respect to density. This power-law relationship was the same for both tension and compression testing. The basis for this power-law relationship is explained in terms of the elastic compliance of the cellular structure of the foam using a simple geometric model put forth by Gibson and Ashby. The elastic collapse stress, a property relevant to compression testing, also is found to exhibit a power-law relationship with respect to density. The density dependence of this property is also found in the work of Gibson and Ashby and is explained in terms of the Euler buckling of the struts that comprise the cellular structure. Energy absorption during deformation is also reported for both tension and compression testing.

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