Ronald M. Jarret

ORDERED CONFORMATIONS IN BIS(AMINO ACID) DERIVATIVES OF 1,1'-FERROCENEDICARBOXYLIC ACID

Abstract Two bis(amino acid) derivatives of 1,1′-ferrocenedicarboxylic acid were characterized by IR, 1 H NMR and 13 C NMR spectroscopy. Each was found to adopt an ordered, intramolecularly hydrogen bonded conformation in CHCl 3 .

13C-13C Coupling in [1.1.1]Propellane

Abstract The C1–C2 coupling constant in [1.1.1]propellane is measured to be 9.9 ± .1 Hz. The CH bond is sp 2.1 and the CCH 2 bond is estimated to be sp 8.6 -sp 4.8 . The remaining orbital at each bridgehead carbon is sp 0.5 .

High resolution 13C-n.m.r. spectroscopy of ‘mixed linkage’ xylans

Three xylan fractions, obtained by stepwise precipitation with ethanol, were analysed by 75-MHz 13C-n.m.r. spectroscopy. Diad frequencies, determined from the C-2 resonances, show that the (1----3)-linkages are interspersed throughout the chain rather than grouped contiguously. This type of distribution is in agreement with a random coil conformation and with the constancy of the optical rotation in solvents of different ionic strength and chaotropic power. These diad frequencies were compared with the theoretical values calculated for a random distribution from the ratio of (1----4)-:(1----3)-linkages in the 1H-n.m.r. spectra, and from the methylation analysis for one of the fractions.

Use of various nuclei as probes in a new NMR method for obtaining proton/deuteron fractionation data

An extension to the new NMR spectroscopic method for rapidly and conveniently obtaining isotopic fractionation factors of substrates undergoing rapid proton-deuteron exchange, with solvent water (H/sub 2/O, HOD, D/sub 2/O), through the observation of /sup 13/C spectra is presented. The intrinsic isotope shift of nuclei near the sites of isotopic incorporation is the basis of this procedure, which has the unique capability of simultaneously measuring the exchange constants for isotopic exchange of several different groups in the same molecule. In this report, /sup 1/H, /sup 7/Li, /sup 11/B, /sup 14/N, /sup 17/O, /sup 19/F, /sup 23/Na, /sup 31/P, /sup 35/Cl, /sup 37/Cl, /sup 39/K, /sup 79/Br, /sup 81/Br, and /sup 127/I are examined and the utility of each as probes in the application of this technique is evaluated. A wider variety of compounds have thus been opened to experimental investigations, using this new method.

The High-Resolution 1H NMR Spectra and Conformations of N-Acetyl-α-D-Galactopyranosylamine Peracetate and 1,1-Bis(Acetamido)-1-Deoxy-D-Glucitol Peracetate in Aqueous Medium

Abstract In contrast with the spectra previously measured with lower resolution equipment, the 500-MHz 1H NMR spectra of 1,1-bis(acetamido)-1-deoxy-d-glucitol peracetate and N-acetyl-α-d-galactopyranosylamine peracetate in aqueous solution were amenable to full resolution. The former compound shows a “sickle” conformation produced by rotation of the C2-C3 bond out of the planar, zigzag arrangement, while the latter has a 4C1 conformation.