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.

transition would be of the "normal" helix-to-coil variety, and hence increasing inert diluent concentration would increase Te.) Whether such a maximum can actually be observed within the accessible temperature and solute solubility range, however, would depend on the thermodynamic parameters for the particular system under investigation.In terms of the overall transition parameters, AHvh and

A transient intermediate (Amax 340 nm), detected during the fast polymerizaton of styrene by HC10, in CH,Cl, a t -8O0, is tentatively interpreted as the polystyryl carbenium ion, and apparent rate constants derived.

A transient spectrum of S2 which has been observed before only in emission and assigned to the b1Δu → x1Δg transition has been detected in flashed H2S2, H2S, COS, CS2, and SPF3 indicating the presence of S2(x1Δg) molecules in these systems. By detailed kinetic studies S2(x1Δg) has been shown to arise from the self and cross disproportionation reactions of the SH and S2H radicals and from the abstractive attack of S(1D) atoms on COS and SPF3. The recombination reaction of S(3P) atoms in the presence of CO2 also produces S2(x1Δg).