Rapid Estimation of T₁ for Quantitative NMR

Abstract

Quantitative NMR spectroscopy (qNMR) is an essential tool in organic chemistry, with applications including reaction monitoring, mechanistic analysis, and purity determination. Establishing the correct acquisition rate for consecutive qNMR scans requires knowledge of the longitudinal relaxation time constants (T 1 ) for all of the nuclei being monitored. We report a simple method that is about 10-fold faster than the conventional inversion recovery technique for the estimation of T 1 .

Protodeboronation of (Hetero)Arylboronic Esters: Direct versus Prehydrolytic Pathways and Self-/Auto-Catalysis

“… a Analyzed by in situ and stopped-flow 19 F/ 1 H NMR spectroscopy using excess KOH at pH > 13, [H 2 O] = 27.75 M, with rate coefficients extracted by simulations referenced against k BA ; see SI. b Nominal half-lives based on reaction solely by irreversible pseudo-first-order direct protodeboronation ( k BE ) or hydrolysis ( k′ hyd ). Phenomenological stability depends on speciation ( k′ hyd ; K hyd ) and protodeboronation ( k BA ) rate.…”

“… a Analyzed by in situ and stopped-flow 19 F/ 1 H NMR spectroscopy using excess KOH at pH > 13, [H 2 O] = 27.75 M, with rate coefficients extracted by simulations referenced against k BA ; see SI. …”

“…The effect of pinacol esterification was explored for a range of (hetero)­aromatic systems (Table , entries 1–10), using in situ and stopped-flow 19 F/ 1 H NMR spectroscopy and kinetic simulation; see SI. The behavior was consistent across the series for all but one case (2-pyridyl, entry 10), which is discussed separately.…”

“… a Kinetics analyzed by in situ and stopped-flow 19 F NMR spectroscopy with rate coefficients extracted by simulation; see SI. …”

Mapping catalyst activation, turnover speciation and deactivation in Rh/PPh3-catalysed olefin hydroformylation

“…Note that the static 31 P{ 1 H} NMR calibration spectra should use inversegated decoupling to prevent signal enhancement through NOEs (Nuclear Overhauser effect). 34 To test the validity and accuracy of the two internal standards we compared the…”