The spectra of photoelectrons from elements in D-peniciiiamine and related compounds were measured. Binding energies and photoelectron widths recorded were for N, 0, C, K, S, and Zn electron energy levels. In D-peniciiiamine and other a-amlno acids, the nitrogen was found to exist as a zwitterion with a N(1s) blndlng energy >401 eV. in the sodium salt of D-penicillamine and the potassium salt of giycine the nitrogen was found to exist as a free amine with a N(1s) binding energy <400 eV. in the zinc penicillamine complex, a mixture of the free amine and zwitterion was observed. This zinc complex structure Is discussed in terms of surface bonding. Zlnc blndlng energy data are also dlscussed.
The preparation of several 2‐furyl‐, 2‐thienyl‐, benzyl‐, and allylsubstituted silanes is reported. Such derivatives, when treated with aziridine in the presence of a metal catalyst, afford good yields of silylaziridines and silyldiaziridines. A qualitative study of electronic and steric requirements of the displacement reaction is reported.
The compression of binary facsimile images has now become widespread and has led to the adoption of standard codes implemented in VLSI chips. In this paper, we reexamine the heuristic and formal basis for the techniques used in compressing such data. This leads us to suggest a decomposition into the successive operations of preprocessing, image segmentation or color shrinking, and modeling and coding of color blocks. Such a decomposition allows a reevaluation of the comparative performance of standard codes and leads us to propose a new simple code, the PCSE code, which, using preprocessing and color shrinking prior to encoding, outperforms the READ code by from 7 to 42% for the standard CCITT test images with a very small change in image quality.
Our initial investigations employed the 1, 3-dioxolane (2) and acetal (3) moieties as carbonyl blocking groups during n-butyllithium metalations of the heterocyclic nuclei o f thiophene and furan. Subsequently we became interested in the production of multiple anions from a hetcrocyclic substrate containing a "blocked" carbonyl group. Consequently, c~-(2-thienyl)acetaldehyde diethylacetal (I) with active hydrogens a t positions a and b was selected for reaction with n-butyllithium.ht1t.n treated with n-butyllithium 1 did not provide a stable didnion but instead was found t o undergo a unique elimination-substitution reaction. Treatment of the generated anion with an appropriate electrophile, trimethylchlorosilane or phenyldimethylchlorosilane, resulted in the production of [5-(trimethylsilyl)-2-thienyl]-P-vinylethyl ether (2) and [ 5-(phenyldimethylsilyl)-2-thienyl] -0vinylethyl ether (3) (Scheme I), respectively. Decomposition of the intermediate anion with water provided 78% of 2-thienyl-/.l-vinylethyI ether (4). 1 4Thus it is apparent that metalation provides for dianiorr formation which gives rise concomitantly or otherwise, t o both elimination and substitution products, where the elimination product is a result of the loss of ethoxide ion. Such was verified by the isolation of trimethylethoxysilane and phenyldimethylethoxysilane when a n excess of the electrophilic reagents trimethylchlorosilane and phenyldimethylchlorosilane, respectively, were employed.Although our previous experimental results (2,3) would indicate ring substitution in the 5-thienyl position, this was shown unequivocally to be the case by an unambiguous synthetic route (Scheme I1 and 111).
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