A suite of 3D NMR methods for characterizing complex hydrocarbon structure fragments

3D NMR Studies of C-Centered n-ad Structures in Poly(ethylene-co-n-butylacrylate-co-13C-carbon monoxide) (PolyEBC*)

“…3D HC A C X and HC A C X −HH−TOCSY NMR spectra were collected with a Nalorac 1 H/ 13 C/ 15 N 5 mm probe and z -axis pulse field gradient (PFG) accessory, operating at 120 °C. The details of the pulse sequence and parameter optimization procedure have been previously described . The 3D HC A C X NMR pulse sequence was used to correlate H A (2.0−3.0 ppm) proton resonances in f 3 , the 13 C A carbon resonances (39.0−46.0 ppm) in f 2 , and the 13 C CO (205.0−209.0 ppm) carbonyl resonances in f 1 .…”

“…The details of the pulse sequence and parameter optimization procedure have been previously described. 19 The 3D HC A C X NMR pulse sequence was used to correlate H A (2.0-3.0 ppm) proton resonances in f 3 , the 13 C A carbon resonances (39.0-46.0 ppm) in f 2 , and the 13 C CO (205.0-209.0 ppm) carbonyl resonances in f 1 . Spectral windows in the f 1 ( 13 C CO ), f 2 ( 13 C A ), and f 3 ( 1 H) dimensions were 1506, 3400, and 6746 Hz, respectively.…”

“…Recently a suite of 3D NMR experiments (HC A C X , HC A C X −HH−TOCSY and HC A C X −CC−TOCSY) was described which enables the assignment of resonances from backbone atoms in 13 C labeled hydrocarbon-based polymers. , These experiments offer a powerful alternative to the more conventional approach which relies on sequential assignments of polymers via 1D and 2D NMR experiments. The versatility of the triple-resonance 3D-NMR approach has been demonstrated using a sample of poly(ethylene- co - n -butyl acrylate- co -carbon monoxide) poly(EB*C) prepared from 1- 13 C- n -butyl acrylate (CH 2 CH− 13 CO 2 - n -C 4 H 9 ) to assign the resonances of B-centered n -ads …”

“…Of late, HXY (X ) 13 C, Y ) 15 N, 19 F, 29 Si, 31 P, 119 Sn) 3D NMR methods have been used to overcome the peak overlap problem by introducing a third frequency dimension and dispersing the overlapped peaks into a number of 2D planes in the 3D NMR spectra of complex polymeric systems. 16,17 Unfortunately, most of the synthetic polymers of research and commercial significance are hydrocarbon based and lack a suitable third NMR active nucleus (Y); hence HXY 3D-NMR methods are not suitable in systems such as poly(EBC).…”

Three-dimensional solution NMR spectroscopy of complex structures and mixtures

“…It is easy to envision the incorporation of CC or HH spin-locking sequences into the HCACX pulse sequence to form HCACX-CC-TOCSY and HCACX-HH-TOCSY sequences analogous to those used in the triple resonance experiments. 48 The former will produce spectra with correlations among C A /C B and H A /H B shifts in a 2D plane at the shift of C X in a structure fragment with isotopic labeling patterns shown in structure 11. The spectrum from the latter experiment will exhibit correlations between C A and H A /H B /H C /H BA /H CA in a 2D plane at the shift of C X .…”