Nitrile function as a probe of cis/trans stereochemistry: carbon-13 NMR studies of poly(bicyclobutane-1-carbonitrile) and related model compounds

Abstract

To better understand the stereochemistry of poly (bicyclobutane-1-carbonitrile) (PBBC), 13C NMR studies were performed for a series of 3-substituted cyclobutanes. Of particular interest were the syntheses and NMR assignments for the two dimers (cis-and irans-3-(l-cyanocyclobutyl)cyclobutane-l-carbonitrile) and the four trimers. In all of the molecules studied, substituents at C3, which were cis to the nitrile, led to 13C NMR shifts of the nitrile that were 1-1.5 ppm to high field of those for the trans isomer; therefore the nitrile chemical shift is a very useful probe of cis/trans stereochemistry in cyclobutanecarbonitriles. Using data for cyclobutanecarbonitrile and the two dimers, we obtained additivity relationships; the calculated 13C resonances

Site-Specific Spectroscopic Reporters of the Local Electric Field, Hydration, Structure, and Dynamics of Biomolecules

“…133 Similarly, the chemical shift of the nitrile nitrogen ( 15 N) is found to be sensitive to solvent, 47,48 with the relation that the chemical shift decreases with increasing solvent acceptor number. In addition, Brewer and coworkers 134 have recently shown, using 15 N-labeled 2'-azido-2'-deoxyuridine as an example, that the chemical shift of azide is also sensitive to its environment.…”

Bicyclobutanes and cyclobutenes: Unusual carbocyclic monomers

“…Barfield and his colleagues44–46 carefully analyzed the NMR spectra of the free‐radical polymers. Both the bicyclobutane nitrile and ester polymers were characterized.…”

2‐(3‐Phenyl‐3‐methylcyclobutyl)‐2‐hydroxyethyl methacrylate and acrylonitrile copolymers: Synthesis, characterization, determination of monomer reactivity ratios, and investigation of their antifungal effects

“…6,7 However, polymers with structures including small strained carbon rings, such as cyclobutane, have been of interest to polymer chemists. Thus, there are many reports concerning polymers having cyclobutane rings, such as poly(1-cyanobicyclobutane), 8,9 linear polyesters of gem-dicyanocyclobutane, 10 and 2-hydroxyethyl methacrylate containing a cyclobutane ring. 11,12 There have been no reports of copolymerization of any monomer containing both the cyclobutane ring and the hydroxyethyl group, which can have interesting properties.…”