Simulation of carbon-13 nuclear magnetic resonance spectra of alkyl-substituted cyclohexanones and decalones

Simulation of carbon-13 nuclear magnetic resonance spectra of linear cyclic aromatic compounds

“…Four approaches can be used to simulate or model chemical shifts in aromatic compounds; (1) the direct calculation of chemical shifts based on the theoretical principles of magnetic shielding (1-8), (2) the calculation of chemical shifts based on substituent effects (9), (3) the derivation of empirical models that relate structural characteristics to chemical shifts (10)(11)(12)(13)(14)(15)(16)(17)(18), and (4) the retrieval of chemical shifts from a spectral database in which each stored chemical shift is indexed to an encoded representation of the corresponding carbon atom environment (19). Each of these methods has limitations.…”

Automated model selection for the simulation of carbon-13 nuclear magnetic resonance spectra of cyclopentanones and cycloheptanones

“…Scheme 1 involves subsetting by location. In previous studies involving the carbonyl moiety, subsetting by location was found to be successful in generating high-quality models with sound predictive ability (3,10). In these studies, subsets were divided into carbonyl carbons, carbons located one bond from the carbonyl, carbons located two bonds from the carbonyl, etc.…”

“…The creation of a spectral simulation database containing predictive equations for prior simulation studies was recently reported (3). Prior to this study, the database consisted of 66 regression models capable of simulating 13C NMR spectra of linear and branched alkanes (4), cycloalkanes (5), cyclohexanols and decalols (6), hydroxysteroids (7), cyclopentanes and cyclopentanols (8), norbornanols (9), cyclohexanones and decalones (10), piperidines (11), polychlorinated biphenyls (12), alkyl-substituted benzenes and polyaromatics (13), ketosteroids (3), and quinolines and isoquinolines (14). A complete summary of the current model database is shown in supplemental material Table VII.…”

“…Previous reports from this laboratory described imaging of surfaces by employing the feedback 1 Current address: Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125. mode, where the steady-state tip current, iT, controlled by an electrochemical reaction at the tip electrode, is a function of the solution composition, tip-substrate distance, d, and the nature of the substrate itself. The measurement of ¿r can thus provide information about the topography of the sample surface as well as its electrical and chemical properties; electrodes (e.g., minigrids and interdigitated electrode arrays) (6)(7)(8), polymer and oxide films on electrode (7,9), and biological materials (10) have been imaged. Thus SECM allows, at least in favorable circumstances, analysis of surface features with high spatial resolution.…”

Carbon-13 nuclear magnetic resonance spectrum simulation

“…Because fewer than eight observations were not sufficient to generate statistically valid regression models, the average chemical shift of each atom subset was used in place of traditional regression equations. tertiary carbons (36) 20 tertiary and quaternary side chain carbons (13) tertiary with -OH (11) 21 secondary carbons (21) quaternary carbons (13) 22 tertiary carbons with attached -OH (32) Norbornan-2-ols primary carbons (50) 28 tertiary carbons with attached -OH (30) secondary carbons (95) 29 quaternary carbons (17) tertiary carbons without attached -OH (82) tertiary/quaternary carbons 2 or more bonds from carbonyl (43) primary carbons 2 or more bonds from carbonyl (46) 69 Each compound class was studied independently, and a standard set of procedures was followed in order to develop the regression models. The methodology used to develop these linear mathematical models has been described previously18 and, therefore, will only be briefly reviewed here.…”