Characteristics NMR

Characteristic NMR shifts for 2-amino and 2-imino derivatives are given in Table V]-5. 

Recryst from benzene-hexane or toluene and has characteristic NMR and IR spectra. [Justus Liebigs Ann Chem 622 10 1959 J Org Chem 39 1311 1974.]... 

The immonium salts derived from 1-azabicycloalkanes have very characteristic NMR spectra (115,116), as illustrated by the spectrum of -indolizinium perchlorate. Assignments of the peaks at t = 5.85 and +... 

Tables 3.10 to 3.13 contain principal characteristic NMR parameters for different types of nitronates. In spite of evident differences in the structures of the model compounds used, their 11 and 13C NMR spectra have many common features.

Stabilization of the vinyl cations 8-10 by aryl substituents is important but even substituents without strong resonance effects provide adequate stabilization to allow the synthesis of persistent vinyl cations at ambient temperature. This is demonstrated by the synthesis and isolation of the salts of alkyl-substituted vinyl cations 19 and 20, and their characteristic NMR parameters are summarized in Table 1. 

The carbenes derived from six- [20-22] and seven-membered heterocycles [22-24, 70] of type 14 can be obtained both with an aliphatic or an aromatic backbone. The characteristic NMR resonances for the C2 carbon atoms in six-membered carbene heterocycles (8 236-248 ppm) [20, 21] have been recorded in the same range as the Ccarbene resonances for saturated imidazolidin-2-ylidenes of type 7. Dimerization to enetetramines occurs for some carbenes derived from a six-membered heterocycle [21] and this behavior is independent from the nature of the backbone (saturated or unsaturated), but depends strongly on the steric bulk of the N,N -substituents. 

Finally, an interesting temperature effect was observed in the spectra of a-(phenylthio)benzyUithium 3THF (3, Scheme l) . Differences exist in the C and Li CP/MAS spectra observed at 293 and 208 K, respectively, which indicate a phase transition. This was confirmed by differential scanning calorimetry (DSC), which yielded a transition temperature of 204-212 K. The most characteristic NMR parameters of the... 

TABLE 2.26. CHARACTERISTIC NMR RESONANCES FOR BICYCLIC NITROSO ACETALS... 

The presence of residual THF in the final product is easily detected by the characteristic NMR signals at 6 1.85 (4 H) and 3.75 (4 H). The checkers found GLC to be more convenient than 1H NMR for analysis at this point. Either a 6 x 2 mm glass column of 3% 0V-101 on MHP 80/100 with 30 nt/min He or a 15 m x 0.25 mm fused silica capillary column of DB-5 (cross-linked phenyl silicone) with 1 mL/min H2 proved sufficient to resolve butane, trimethylsilylacetylene, butyltrimethylsilane, THF, 1-chlorobutane, and b1s trimethylsilyl)acetylene. 

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