1H Spin-spin Coupling Constants Research Articles

13C, 1H-Spin-Spin Kopplungskonstanten Teil III: Naphthalin / 13C, 1H Spin-Spin Coupling Constants Part III: Naphthalene

Abstract Using a newly developed technique that employs highly deuterated compounds and 2H broadband decoupling the 13C, 1H spin-spin coupling constants for naphthalene have been measured from the 13C NMR spectra of α-and β-H-[D7]naphthalene. A linear dependence of the 3J(13C, 1H) data on the central π-bond order is indicated.

13 C nuclear magnetic resonance study of five- and six-coordinated carbon in nonclassical organometallic compounds: Dimeric trialkyl-, tricyclopropyl-, and triarylaluminums and some nido and closo carboranes

A (13)C nuclear magnetic resonance spectroscopic study of dimeric trimethyl-, triethyl-, tricyclopropyl-, and triarylaluminums is reported. The five-coordinated bridging carbons are found consistently more shielded than the terminal carbons, in accordance with the increased p-character of the former. The nature of bridging two-electron three-centered Al-C-Al bonds is discussed. (13)C nuclear magnetic resonance shifts of several nido and closo carboranes containing five and six coordinated carbons and their (13)C-(1)H spin-spin coupling constants were also obtained. The relationship between the carbon chemical shifts and coordination number of the carbon atom is discussed. There is approximately a 20- to 40-ppm shielding of the (13)C chemical shifts of five- and six-coordinated carbons, compared with those of four valent carbons, with a simultaneous general increase of J(C-H) coupling constants.

A new technique for the exact determination of 13C 1H spin-spin coupling constants

A new technique for the exact determination of 13C 1H spin-spin coupling constants

Long range 13C 1H spin-spin coupling constants in amino acids. Conformational applications

Two-bond and three-bond 13Cz.sbnd; 1H spin coupling constants have been measured in a series of amino acids from their natural abundance 13C spectra. It is shown that by considering the 13CCCH coupling constants between the α-CO 2 − and the β-protons it is possible to obtain side-chain conformational information concerning the rotamer populations which is not available from studies of HH coupling constants alone. The potential usefulness of other 13C 1H coupling constants in conformational studies of amino acids and peptides is discussed.

Quantum mechanical calculations of P-C and P-H spin-spin coupling constants in model compounds and in nucleotides

Molecular orbital calculations of 31P–13C and 31P–1H spin-spin coupling constants are carried out for ethyl phosphate taken as model compound for nucleotides. The calculations are in good agreement with the conformational dependence of vicinal PC and PH couplings found experimentally. It is found that the two bonds POC coupling constant is determined essentially by the rotation angle about the PO bond and the four bonds POCCH couplings by the rotation angle about the CC bond. Applications to cyclic nucleotide monophosphates are described.

Mercury-proton spin-spin coupling constants of some methylmercury compounds

The 199Hg 1H spin-spin coupling constants for methylmercury salts of 36 organic acids, CH 3HgX (where X = OR −, SR − or OOCR −, were determined. A linear relationship between the coupling constants and the p K's of the monobasic parent acids was found. The magnitudes of the coupling constants are dependent on the type of basic site, decreasing in the order CH 3HgOR > CH 3HgOOR > CH 3HgSR, i.e., with increasing covalent character of the HgX bond. The anomalous behavior of some dibasic acid salts is discussed.

Phosphonic acids and esters–XVIII : Preparation of β,γ-unsaturated phosphonates by the stobbe condensation with diethyl β-carbethoxyethylphosphonate; stereochemical dependencies of homoallylic 31P 1H spin-spin coupling constants

The base catalyzed condensation of the title compound ( 4) with benzaldehyde and a variety of ketones follows a normal Stobbe course yielding β,γ-unsaturated phosphonates, i.e. ethyl hydrogen β-carbethoxy-γ-substituted allylphosphonates ( 5). Despite the unsymmetrical nature of 4, condensation is specific at the position adjacent to the carbethoxy function; neither the isomeric α,β-unsaturated phosphonates nor the dephosphonated (Wittig) products, β,γ-unsaturated carboxylates, are observed. The specificity presumably reflects the greater stabilization afforded an α-anion by a carbonyl function than by a dialkoxyphosphono function. Condensations with unsymmetrical carbonyl components (acetophenone, benzaldehyde) yield mixtures of cis- and trans- 5 in a nonstereoselective manner. Gross structures and stereochemical relationships were assigned on the basis of PMR spectroscopy. In 5 derived from acetophenone and acetone, a long-range (five bond) 31P 1H coupling is observed. Based upon studies of these and model compounds (dimethyl γ,γ-dimethylallylphosphonate), it was shown that the transoid 5J PH is of larger magnitude than the corresponding coupling involving cisoid geometry.