Benjamin P. Dailey

Bio: Benjamin P. Dailey is an academic researcher from Columbia University. The author has contributed to research in topics: Liquid crystal & Anisotropy. The author has an hindex of 18, co-authored 48 publications receiving 2186 citations.

NMR Determination of Deuterium Quadrupole Coupling Constants in Nematic Solutions

Abstract: The analysis of the NMR spectra of suitable nematic liquid‐crystal solutions appears to offer a convenient and desirable method for the determination of small nuclear quadrupole coupling constants for molecules in the liquid state. Nuclear quadrupole coupling constants have been determined for deuterium in the C–H bond of a number of small molecules. Assuming that the field gradient has axial symmetry, values of e2qQ/h along the bond axis are as follows: CH3CD3167± 18 kHzC3D6184± 20C2D2198± 7CH3C2D199.4± 2.0DCN199.0± 3.0. The results are discussed in terms of various theoretical calculations of the field gradient at the deuteron, and a compilation of some of the accurate experimentally determined deuterium coupling constants is presented.

Microwave Spectra and Structures of XYH3 Molecules

Abstract: Work on the microwave spectra of CH3Cl, SiH3Cl, GeH3Cl, CH3Br, SiH3Br, and GeH3Br, performed at this laboratory and others, is summarized, and preliminary reports of work at this laboratory are expanded. Structural parameters, dipole moments, and quadrupole coupling constants obtained from analysis of these spectra are tabulated and discussed, and a unified picture of the bonding in these series of molecules, based on the derived quantities, is presented.

15N magnetic shielding anisotropies in 15N15NO

Abstract: The 15N magnetic shielding anisotropies in nitrous oxide (15N15NO) have been determined using a pulsed FT NMR spectrometer. The shielding anisotropies obtained from the temperature dependence of the nematic phase chemical shifts are 512 ± 10 ppm (central 15N) and 369 ± 15 ppm (end 15N). The values obtained from the nematic‐isotropic phase difference method are 505 ± 10 ppm (central 15N) and 366 ± 10 ppm (end 15N). Theoretical estimates of the anisotropies from the so‐called atom dipole method are also reported. The indirect scalar coupling constant has been assigned to be negative. The signs of the 15N spin‐rotation constants are predicted to be positive.

The 1H and 31P N.M.R. spectra of phosphine in isotropic and nematic solvents

Abstract: The proton and 31P N.M.R. spectra of PH3 in various isotropic and liquid crystal solvents are discussed. Geometrical data and chemical shielding anisotropies for 1H and 31P are reported. The temperature dependence of the isotropic chemical shift and its influence on the evaluation of measurements in nematic solvents is discussed.

1,3-Dipolar Cycloadditions. Past and Future†

Abstract: In contrast to the very large number of special methods applicable to syntheses in the heterocyclic series, relatively few general methods are available. The 1,3-dipolar addition offers a remarkably wide range of utility in the synthesis of five-membered heterocycles. Here the “1,3-dipole”, which can only be represented by zwitterionic octet resonance structures, combines in a cycloaddition with a multiple bond system – the “dipolarophile” – to form an uncharged five-membered ring. Although numerous individual examples of this reaction were known, some even back in the nineteenth century, fruitful development of this synthetic principle has been achieved only in recent years.

Deuterium magnetic resonance: theory and application to lipid membranes.

Abstract: Proton and carbon-13 nmr spectra of unsonicated lipid bilayers and biological membranes are generally dominated by strong proton–proton and proton–carbon dipolar interactions. As a result the spectra contain a large number of overlapping resonances and are rather difficult to analyse. Nevertheless, important information on the structure and dynamic behaviour of lipid systems has been provided by these techniques (Wennerstrom & Lindblom, 1977).

1.3‐Dipolare Cycloadditionen Rückschau und Ausblick

Abstract: Einer sehr grosen Zahl spezieller Synthesewege in die heterocyclische in die Reihe steht ein nur bescheidener Satz an Aufbaumethoden von allgemeiner Verwendbarkeit gegenuber. Eine erstaunliche Anwendungsbreite bei der Synthese funfgliedriger Heterocyclen kommt der 1.3-Dipolaren Addition zu. Dabei vereinigt sich der nur mit zwitterionischen Oktett-Grenzformeln wiederzugebende „1.3-Dipol” mit einem Mehrfachbindungssystem, dem „Dipolarophil”, in einer Cycloaddition zum ladungsfreien funfgliedrigen Ring. Wenngleich die Kenntnis zahlreicher Einzelbeispiele bis ins vorige Jahrhundert zuruckreicht, gelangte das Syntheseprinzip erst in den letzten Jahren zu fruchtbarer Entfaltung.

A new criterion for the determination of molecular structures from ground state rotational constants

Abstract: Kraitchman has shown that a single isotopic substitution on an atom is sufficient to determine directly the coordinates of that atom with respect to the principal axes of the original molecule. Kraitchman's formulas represent exact solutions of the equations for the equilibrium moments of inertia. However, the effects of the zero‐point vibrations are such that the coordinates obtained by substitution from the ground state moments of inertia I0 are systematically less than r0. These coordinates have here been called r (substitution) or rs, and it is found that rs≃(r0+re)/2, and Is= ∑ imirsi2≃(I0+Ie)/2.In the usual method of solution, the coordinate of one atom is determined from the equation for I0, and therefore the difference I0—Is must be made up by this one coordinate. This introduces a large error in the structures normally determined from ground state constants, and results in variations of 0.01 A in structures determined from different sets of isotopic species. If instead, we obtain the structure on...