V Rutar

Utilization of selective spin flips for manipulated two-dimensional NMR spectroscopy

Abstract Efficiency of J -resolved two-dimensional 13 C NMR can be increased by selective flips which are accomplished on either distant or directly attached protons. Data sets are compressed and specialized measurements of J couplings are significantly faster.

Manipulated heteronuclear two-dimensional NMR bilinear pulses in the presence of strong coupling

Abstract Efficiency of heteronuclear 2-D NMR has been significantly increased by implementing bilinear pulses. Theoretical and experimental results confirm that the presence of 13C spin apparently eliminates effects of strong homonuclear coupling. On the other hand, spurious peaks can be detected when the difference between the chemical shifts of attached and distant protons approaches 1 2 1 J HC . Positions and intensities of responses are predictable, and accuracy of 1H chemical-shift measurements is not seriously hampered, if these effects are taken into consideration in the interpretation of results.Press, Inc.

Suppression of long-range couplings in heteronuclear two-dimensional J spectroscopy. Effects of nonuniform one-bond couplings

Abstract If long-range J couplings between 13 C and distant 1 H spins are suppressed by the selective reversal of directly attached protons, heteronuclear 2-D NMR can be used for quick determinations of CH m multiplicity and one-bond coupling constants C 1 J CH ). Theoretical and experimental analysis show that nonuniform values of 1 J CH may give rise to spurious peaks, but the reliability of the results is not affected.

Measurement of proton-proton geminal coupling constants via two-dimensional indirect J spectroscopy with selective spin flip

Description dune approche speciale facilitant la mesure directe des couplages gemines ( 2 J HH ), sans resoudre le modele de couplage homonucleaire complet

Effects of long-range and homonuclear couplings on bilinear rotation pulses

Abstract Suppression of long-range heteronuclear interactions in J-resolved 2D NMR facilitates separate measurements of one-bond coupling constants. Analysis of the pulse sequence describes the efficiency of bilinear rotation in the presence of long-range couplings. It also predicts intensities of possible spurious responses. Theoretical and experimental evidence confirm that long-range couplings do not represent a serious obstacle against routine applications of spin manipulations in heteronuclear 2D NMR.

Selective enhancement in polarization transfer nuclear magnetic resonance spectroscopy

Abstract A new pulse sequence for polarization transfer in NMR spectroscopy is proposed. It enables selective enhancements of multiplets and partial “editing” of coupled NMR spectra without any significant increase in time for data accumulation.

Influence of imperfect pulses on bilinear rotation in heteronuclear two-dimensional NMR spectroscopy

Clusters of bilinear rotation pulses selectively flip those protons which are attached to 13C spins. Misset 1H pulses give rise to intensity and phase distortions of expected signals, but the reliability of measurements of one-bond coupling constants is not seriously affected.

Indirect J spectroscopy using an extended DEPT pulse sequence

Abstract Indirect detection of homonuclear J couplings is accomplished by an extension of the DEPT pulse sequence. Measurement of coupling between chemically equivalent protons and simplification of spectra of CH2 groups are also discussed.

Cancellation of coupled and decoupled NMR signals of protonated carbons

Abstract A simple two-step pulse sequence ( π/2( 13 C )-τ-π/2( 1 H ), π( 13 C )-τ- acquire 13 C ) is used for selective cancellation of coupled and decoupled 13C signals of all protonated carbons. Adjustment of the evolution period τ ≈ 1 (2J) is not critical, therefore the sequence appears to be very suitable for generating subspectra of nonprotonated carbons.

Pulse sequence for the identification of particular spins in congested homonuclear coupling networks

Abstract Implementation of bilinear rotation pulses gives rise to useful spin manipulations in special homonuclear spin systems. If coupling constants J between neighboring spins are distinctively large and uniform, clusters 90° x - τ -180° y - τ -90° x with τ = 1 (2J) separately identify terminal spins in chains. Deviations from the anticipated coupling pattern produce mostly spurious cross peaks in 2D data sets, so that the main diagonal is very useful for the identification of particular spins in congested homonuclear spectra.