H-NMR Chemical Shifts

Figure 10.2-2. Calculatiorr of H NMR chemical shifts and coupling constants arrd simulation of the spectrum with HyperChem 7.

Figure 10.2-4. Prediction of h NMR chemical shifts with the upstream WWW version,...

Counterpropagation neural networks (CFG NN) were then used to establish relationships between protons and their H NMR chemical shifts. A detailed description of this method is given in the Tools Section 10,2.4.2,... 

Fast and accurate predictions of H NMR chemical shifts of organic compounds arc of great intcrc.st for automatic stnicturc elucidation, for the analysi.s of combinatorial libraries, and, of course, for assisting experimental chemists in the structural characterization of small data sets of compounds. 

A combination of physicochemical, topological, and geometric information is used to encode the environment of a proton, The geometric information is based on (local) proton radial distribution function (RDF) descriptors and characterizes the 3D environment of the proton. Counterpropagation neural networks established the relationship between protons and their h NMR chemical shifts (for details of neural networks, see Section 9,5). Four different types of protons were... 

The H NMR spectra of formic acid (HCO2H) maleic acid cis H02CCH=CHC02H) and malonic acid (HO2CCH2CO2H) are similar in that each is charactenzed by two singlets of equal intensity Match these compounds with the designations A B and C on the basis of the appro pnate H NMR chemical shift data... 

H-nmr chemical shifts of N-1—H and N-3—H signals have been used as a criterion for distinguishing between N-l-substituted and N-3-substituted hydantoin derivatives (22). They can often be related to electronic properties, and thus good linear correlations have been found between the shifts of N—H and Hammett parameters of the substituents attached to the aryl group of 5-arylmethylenehydantoins (23). 

Table 1. H-nmr Chemical Shifts for Indole and C-nmr Chemical Shifts for Indole...

Analytical and Test Methods. Most of the analytical and test methods described for THF and PTHF are appHcable to OX and POX with only minor modifications (346). Infrared and nmr are useful aids in the characterization of oxetanes and their polymers. The oxetane ring shows absorption between 960 and 980 cm , regardless of substituents on the ring (282). Dinitro oxetane (DNOX) has its absorption at 1000 cm . In addition, H-nmr chemical shifts for CH2 groups in OX and POX are typically at 4.0—4.8 5 and 3.5—4.7 5, respectively (6,347,348) C-nmr is especially useful for characterizing the microstmcture of polyoxetanes. 

Table 2. H-Nmr Chemical Shifts for Selected Pyrazolones and Pyrazolines ...

Table 4 H NMR Chemical Shifts of Isothiazoies and Isothiazole Cations...

H NMR Chemical Shifts and Coupling Constants of Isothiazoles (IS) with Exocyclic Conjugation X... 

The H NMR spectrum of thiirane 1-oxide is complex (AA BB ) at 60 MHz 24 lines are cfbserved consisting of two sets of 12 centered about a midpoint. The H NMR chemical shift in thiirane 1,1-dioxide is fairly sensitive to solvent variations partly because of the high dipole moment (4.4 D) of the sulfone. The benzene-induced shift, A5 (CeDe-CCLt), is large (-1.04 p.p.m.), as expected from the presence of a sulfone group. Oxygen-17 chemical shifts for thiirane 1-oxide and thiirane 1,1-oxide are -71 and +111 p.p.m. respectively, relative to H2O. 

H NMR, chemical shifts, 4, 557 in nematic phase microwave spectra, 4, 537 nitration, 4, 45-46, 49, 603 nitro... 

UV Spectra (Ethanol) and h NMR Chemical Shifts (DMSO) of the H-3 Proton OF Benzoisochalcogenazoles... 

Water was also investigated as a proton donor for the hydrogen bond with DMSO and other Lewis bases at infinite dilution detected by means of 1H NMR54-69. A comparison of the hydrogen bonding ability of DMSO in various other aprotic solvents was presented by Delpuech70 who measured the H-NMR chemical shift of CHC13. 

Similarly, the Kass determined by the H NMR chemical shift of CHC13 in the presence of sulphoxides can be correlated well with the association constants obtained both on the basis of the IR stretching shift (AvOH) of phenol in the presence of sulphoxide and also with the 19F NMR chemical shifts of p-fluorophenol (<5,F). 

Ashe has demonstrated that 1,2-azaborines can undergo electrophilic aromatic substitutions [86]. The H NMR chemical shifts of 1,2-azaborines are consistent... 

The LR COSY-45° spectrum and H-NMR chemical shifts of an isoprenyl coumarin are given below. Determine the long-range H/ H homonuclear correlations based on the long-range COSV45° spectrum. Demonstrate with reference to problem -5.15 how they can be helpful in interconnecting different spin systems ... 

The SECSY spectrum of an isoprenyl coumarin along with the H-NMR chemical shifts are shown. Determine the homonuclear shift correlations between various protons based on the SECSY spectrum. 

The one-bond HETCOR spectrum and C-NMR data of podophyllo-toxin are shown. The one-bond heteronuclear shift correlations can readily be made from the HETCOR spectrum by locating the posidons of the cross-peaks and the corresponding 5h and 8c chemical shift values. The H-NMR chemical shifts are labeled on the structure. Assign the C-NMR resonances to the various protonated carbons based on the heteronuclear correlations in the HETCOR spectrum. 

The HETCOR spectrum, C-NMR data, and H-NMR chemical shift assignments of buxoxybenzamine (C35H50N2O5) are presented below. Assign the C-NMR chemical shifts to the various protonated carbons using the HETCOR plot. 

The heteronuclear multiple-quantum coherence (HMQC) spectrum, H-NMR chemical shift assignments, and C-NMR data of podophyllo-toxin are shown. Determine the chemical shifts of various carbons and connected protons. The HMQC spectra provide information about the one-bond correlations of protons and attached carbons. These spectra are fairly straightforward to interpret The correlations are made by noting the position of each crossf)eak and identifying the corresponding 8h and 8c values. Based on this technique, interpret the following spectrum. 

The HMQC spectrum, H-NMR chemical shift assignments, and C-NMR data of vasicinone are shown. Consider the homonuclear correlations obtained from the COSY spectrum in Problem 5.14, and then determine the carbon framework of the spin systems. 

The NOESY spectrum and H-NMR chemical shift assignments of 7-hydroxyfrullanolide are shown. Interpret the NOESY spectrum. What conclusions can you draw about the stereochemistry at C-6 and C-10 ... 

The HMQC spectrum of podophyllotoxin shows heteronuclear crosspeaks for all 13 protonated carbons. Each cross-peak represents a one-bond correlation between the C nucleus and the attached proton. It also allows us to identify the pairs of geminally coupled protons, since both protons display cross-peaks with the same carbon. For instance, peaks A and B represent the one-bond correlations between protons at 8 4.10 and 4.50 with the carbon at 8 71.0 and thus represent a methylene group (C-15). Cross-peak D is due to the heteronuclear correlation between the C-4 proton at 8 4.70 and the carbon at 8 72.0, assignable to the oxygen-bearing benzylic C-4. Heteronuclear shift correlations between the aromatic protons and carbons are easily distinguishable as cross-peaks J-L, while I represents C/H interactions between the methylenedioxy protons (8 5.90) and the carbon at 8 101.5. The C-NMR and H-NMR chemical shift assignments based on the HMQC cross-peaks are summarized on the structure. 

Table 1.1 C H NMR chemical shifts of the carbenic carbon atom...

The H NMR shifts of the OH proton in several hydroxyl compounds such as PhOH and fluoroalcohols were measured in CCI4 or CH Clj in the presence of DMSO and other bases and compared to values obtained without bases. The H NMR chemical shifts (5 values) give a good linear relationship against the enthalpy values obtained by equation 2 or by calorimetry . In the case of PhOH as the donor, equation 8 is obtained... 

Purcell and coworkers obtained good correlations between the IR and H NMR methods by the use of 1,1,1,3,3,3-hexafluoropropanol and phenol as acids . Taddei and colleagues have reported that with CHCI3 as the donor, a free energy relationship is established between the association constants and the H NMR chemical shift values of CHCI3 in the presence of Lewis bases. However, a non-linear relationship has been observed for several other Lewis bases and CHCI3 by other authors . 

Thus, the enantiomeric contents in a pair of sulphoxides can be determined by the H NMR chemical shifts in the methine or methylene protons in the two diastereomeric complexes which are stabilized by the hydrogen bond between the hydroxyl and the sulphinyl groups (Scheme 13). Similarly, the enantiomeric purity and absolute configurations of chiral sulphinate ester can be determined by measuring the NMR shifts in the presence of the optically active alcohols. ... 

Table 4. H-NMR Chemical Shifts (8) of Methyl-Substituted Tetrazoliums 128 and 129 ...

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