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These data show that I from the second method has two NMe proton peaks in a ratio of 1:2 a t 6 = 4.28 and 4.90 upfield from benzene. All the other spectra contain these two peaks in the same ratio, but other peaks are also present. In the spectra of crude products and in the 90 and 100 OC sublimate from both methods, another pair of peaks is located a t approxiinately 6 = 4.25 and 4.78 upfield from benzene and in the ratio of 1:2. These two closely spaced pairs suggest the presence of two forms of Be(NNIe2)2 of similar structure.If Be(N&11e~)~ were a cyclic trimer as suggested by Coates ( I ) , there should be two types of NhIe protons in a ratio of 1:1, that is, there should be 18 methyl protons bonded to terminal NMez groups and 18 protons on the bridging NA' Ie2 groups. Since the ratio of the two types of NMe protons is 1:2, a trimeric structure of the type is indicated to achieve a maxiinuin coordination for beryllium. The other form of Be(NMez)z may be another configuration of this trimer; for example, there may exist cis and trans forms for the terminal NMez groups.Only I of the second method appears to be a pure compound; hence, the molecular weight of this substance was the only one measured. The values 308 and 311 (calcd. 291.3 for Be(NMe2)z trirner) indicate this material is trimeric in freezing benzene; therefore, the form of Be(NMe2)2 obtained by sublimation a t 65 OC is more accurately represented by the structure shown above than by the cyclic form.

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ferred to the carbonyl group of these peptides. Instead, the pmr results suggest to these authors that the acid proton remains hydrogen bonded to the peptide carbonyl oxygen. As the concentration of acid increases, acid-polypeptide interaction and hydrogen binding without proton transfer increases. Intramolecular hydrogen bonding is, therefore, suppressed in favor of intermolecular hydrogen bonding between the acid and the polypeptide. This then is the driving force converting the polypeptide from the helical to the random coil form.The slight low-field shift and the small degree of line broadening of the I phenolic proton peak in the presence of poly-y-benzyl-L-glutamate and poly-L-methionine, respectively, encountered in the present studies also suggest that I hydrogen bonds to these polypeptides and that proton transfer does not occur. The pmr spectrum of poly-y-benzyl-L-glutamate was not altered in the presence of I. This indicates that either the low solubility or the moderate acid strength of I could not elicit peptide confirmational changes of the type previously reported for trifluoroacetic acid-polypeptide systems. 1, 2 3Hexachlorophene has now been shown to strongly hydrogen bond to polypeptides. The conclusions from the present investigations are useful in understanding the more complex interactions that occur between I and proteins.(23) J.Abstract: An experimental and theoretical study has been made of the secondary H/D kinetic isotope effect in the addition of S( 3P) atoms to ethylene. The values of the experimental kD/kH ratios were 1.14, 1.07, and 1.04 for the C2D4-C2Hl, CD2CHz-C2H4, and cis-CHDCHD-CzH4 reactant pairs, respectively. Calculation of the isotope effect was carried out within the framework of transition-state theory for two basic models of the transition state, a symmetrical ring and an asymmetrical ring-distorted structure. Either model can be made compatible with the experimental results by an appropriate and reasonable choice for the structural parameters of the transition state. Calculation of the isotope effect arising from each normal vibrational mode clearly shows that, contrary to current notions, the most important single factor inducing a secondary H/D isotope effect in addition reactions involving olefinic double bonds is not the out-of-plane bending motions of the CH bonds, but the gain in the isotopically sensitive vibrational degrees of freedom on going from reactant to activated complex. he addition of both lD2 excited and 3P ground-