On the stereospecifity of intrinsic 2H/1H NMR isotope effects on carbon-13 chemical shifts in cyclohexanes

Computation of Deuterium Isotope Perturbation of 13C NMR Chemical Shifts of Alkanes: A Local Mode Zero-Point Level Approach

“…Returning to the case of cyclohexane, comparison was made in the introductory example with a room temperature experiment. It is also possible to compare the computed results for the individual conformations with experimental results obtained at low temperature or for t-butyl-cyclohexane 15 with a single D at position 4 in either of the two locked axial or equatorial positions (Table 8). The low temperature experiment for C 6 H 11 D provides only the 1 ∆ values for which each of the computed values are about 10% too low as is their average.…”

Deuterium‐induced isotope effects on the 13C chemical shifts of α‐d‐glucose pentaacetate

“…The n Δ DHIECS values were measured under uniform conditions (see Experimental Section) and are also summarized in Table . According to the general trend, the 1‐3 Δ DHIECS values decrease when the number of bonds between the deuterium atom and the observed 13 C atom increases, while 4,5 Δ DHIECS values are exceptions to this tendency. The 1 Δ DHIECS values exhibit a negative sign and are in the range of −273 to −365 parts per billion (ppb = 10 –9 ) for monodeuterated pentaacetates, while for the dideuterated pentaacetate, the magnitude increased almost twice, to −543 ppb, keeping the direct proportionality between the shift magnitude and the number of substituted deuterium atoms .…”

“…The n Δ DHIECS values were determined as the chemical shift differences of the nondeuterated and the deuterated molecules: where n is the number of bonds between the site of deuteration and the observed carbon atom. The n Δ DHIECS values were measured under uniform conditions (see Experimental Section) and are also summarized in Table .…”

The Structure of the “Vibration Hole” around an Isotopic Substitution—Implications for the Calculation of Nuclear Magnetic Resonance (NMR) Isotopic Shifts

“…For cyclohexane, the chair conformer is considered with H/D substitutions for both an axial (ax) and an equatorial (eq) H atom, and the results were compared to the experimental data from Refs. [ 27 , 65 ]. As a complement, we used DD-VPT2 and loc-VPT2 to determine the NMR isotopic shifts for various single H/D substitutions in norbornane and adamantane.…”

“…Such isotope effects have been observed and investigated for global properties such as dipole moments [ 2 , 3 ] and polarizabilities [ 4 , 5 ] but are most interesting for atom-specific spectroscopic properties such as electron spin resonance (ESR) [ 6 , 7 ], spin rotation constants [ 8 , 9 ] and above all nuclear magnetic resonance (NMR) isotopic shifts, in particular on chemical shielding constants [ 10 , 11 , 12 , 13 , 14 , 15 ]. NMR isotopic shifts have been used to investigate inter- and intramolecular hydrogen bonds [ 14 , 15 , 16 , 17 , 18 , 19 , 20 ] and salt bridges [ 21 , 22 ] as well as the backbone conformation in proteins [ 23 , 24 , 25 ] and local stereochemistry [ 26 , 27 , 28 , 29 ].…”