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Ethers chemical shifts

C solid-state NMR has been applied to study 4-acetyl-, formyl- and carboxy-benzo-9-crown-3 ether.Chemical shift differences of ca. 8.5 ppm have been observed between the two aryl-O-C carbons and are explained using results of ab initio calculations previously performed on anisole. Chemical shift assignments have been verified by the use of selectively deuterated derivatives. [Pg.248]

Electric quadrupole coupling, 115-16,143,152 Electrostatic model, 278-80 Electrostriction, 269-70 Emission, spontaneous, 70-71 3 Enolization, 137-38 Ethers, chemical shifts, 250-52 [ 1, 2 -%]Ethylbenzene, 179-80 Ethyl 3 carboline-3-carboxylate, 182-83 Excess linewidth, 321,416-20,427-28,434-37 Exchange effects see Dynamic processes Exchange matrix see Statistical matrix... [Pg.536]

H NMR The chemical shift of the proton m the H—C—O—C unit of an ether is very similar to that of the proton m the H—C—OH unit of an alcohol A range of 8 3 2-4 0 IS typical The proton m the H—C—S—C unit of a sulfide appears at higher field than the corresponding proton of an ether because sulfur is less electronegative than oxygen... [Pg.690]

Section 16 18 An H—C—O—C structural unit m an ether resembles an H—C—O—H unit of an alcohol with respect to the C—O stretching frequency m its infrared spectrum and the H—C chemical shift m its H NMR spectrum Because sulfur is less electronegative than oxygen the H and chemical shifts of H—C—S—C units appear at higher field than those of H—C—O—C... [Pg.695]

In the chemical shift range for alkenes and aromatic and heteroaromatic compounds enol ether fragments (furan, pyrone, isoflavone, 195-200 Hz) ... [Pg.27]

The keto-carbonyl C signal at 5c = 200.9 would only fit the aflatoxins B, and M,. In the C NMR spectrum an enol ether-C// fragment can also be recognised from the chemical shift value of 5c = 145.8 and the typical one-bond coupling constant Jch = 196 Hz the proton involved appears at Sh = 72, as the CH COSY plot shows. The H triplet which belongs to it overlaps with a sing-... [Pg.218]

The order of enolate reactivity also depends on the metal cation which is present. The general order is BrMg < Li < Na < K. This order, too, is in the order of greater dissociation of the enolate-cation ion pairs and ion aggregates. Carbon-13 chemical shift data provide an indication of electron density at the nucleophilic caibon in enolates. These shifts have been found to be both cation-dependent and solvent-dependent. Apparent electron density increases in the order > Na > Li and THF/HMPA > DME > THF >ether. There is a good correlation with observed reactivity under the corresponding conditions. [Pg.438]

H and 13C NMR Data. The examples in Scheme 3.23 provide characteristic proton and carbon chemical shift and coupling constant data for fluorinated alcohols, ethers, thioethers, sulfoxides, and sul-fones. An ether substituent serves to deshield the carbon of a CH2F by about 20 ppm. This can be compared to the 40-ppm deshielding generally observed in a nonfluorinated ether system. Thus, the fluorine substituent seems to have a damping effect on the usual effects of other substituents. [Pg.66]

Again, one would not expect hydroxy or ether substituents more distant (i.e., y or 5) to the CF2 group to have significant effect upon fluorine chemical shifts. [Pg.124]

H and 13C NMR Data. The H chemical shifts of CF2H protons of difluoromethyl ethers lie between 6.00 and 6.3 ppm, with a significantly enhanced F—H two-bond coupling constant of around... [Pg.124]

An oxygen bound to a trifluoromethyl group has much less effect upon its chemical shift than a chlorine substituent. Thus, the fluorines of trifluoromethyl ethers (—58 ppm) are not as deshielded as those of CF3C1 (—28ppm). Those of CF3 sulfides and selenides are deshielded... [Pg.154]

H and13C NMR Data. Some typical proton and carbon NMR data for trifluoromethyl ethers, sulfides, and esters are given in Scheme 5.11. Continuing the trend observed going from CH2F to CF2H to CF3 carbons, the 13C chemical shift of a trifluoromethyl ether is actually more shielded (by about 5 ppm) than that of a trifluoromethyl hydrocarbon. Scheme 5.12 summarizes the relative impact of an ether substituent upon the chemical shifts of various fluorinated carbons. [Pg.156]

Regarding proton spectra, as was the case with 2,2,2-trifluoroethyl chloride (Scheme 5.7), the chemical shifts of the CH2 protons of 2,2,2-tri-fluoroethanol and of 2,2,2-trifluoroethyl ethers are more affected by the OH or ether substituents than they are by the CF3 group. [Pg.157]

Enol ether protons are interesting in that their chemical shifts are unusually high field in comparison with other alkenes on account of lone pair donation into the double bond from oxygen (Structure 5.5). No special precautions are necessary when dealing with them as this is reflected in the values obtained using Table 5.6. [Pg.63]

The analysis of 1H NMR spectra of aliphatic and aromatic polyanhydrides has been reported by Ron et al. (1991), and McCann et al. (1999) and Shen et al. (2002), and 13C NMR has been reported by Heatley et al. (1998). In 1H NMR, the aliphatic protons have chemical shifts between 1 and 2 ppm, unless they are adjacent to electron withdrawing groups. Aliphatic protons appear at about 2.45 ppm when a to an anhydride bond and can be shifted even further when adjacent to ether oxygens. Aromatic protons typically appear with chemical shifts between 6.5 and 8.5 ppm and are also shifted up by association with anhydride bonds. The sequence distribution of copolymers can be assessed, for example in P(CPH-SA), by discerning the difference between protons adjacent to CPH-CPH bonds, CPH SA bonds, and SA-SA bonds (Shen et al., 2002). FTIR and 111 NMR spectra for many of the polymers mentioned in Section II can be found in their respective references. [Pg.190]

These highly fluorinated homopolymers (7,8) derived from hydroxy fluor-ovinyl ethers (5,6), in contrast to typtical highly fluorinated compounds and polymers, exhibit unusually good solubility in common organic solvents. The NMR chemical shifts of residual protons in these polymers are highly sensitive to the polarity of the solvent as shown in Table 4.3. [Pg.55]

Compounds 1 and 2 were identified by FTIR and 13C-NMR. The 13C proton decoupled spectra for 1 and 2 are dominated by signals ranging from 62 to 195 ppm. The 13C chemical shift assignments were made based on comparisons with 4,4 -(hexafluoroisopropylidene)diphenol and from calculations based on substituted benzenes and naphthalenes.15 The 13C-NMR spectrum clearly showed that the Friedel-Crafts acylation of 1 by 4-fluorobenzoyl chloride yielded the 1,4-addition product exclusively. The 13C chemical shifts for 2 are listed in Table 8.1. The key structural features in the FTIR spectrum of2 include the following absorptions aromatic C-H, 3074 cnr1, ketone C=0, 1658 cm-1, aromatic ether Ar—0—Ar, 1245 cm-1, and C—F, 1175 cm-1. [Pg.116]


See other pages where Ethers chemical shifts is mentioned: [Pg.145]    [Pg.217]    [Pg.232]    [Pg.73]    [Pg.96]    [Pg.97]    [Pg.36]    [Pg.824]    [Pg.136]    [Pg.1308]    [Pg.88]    [Pg.460]    [Pg.236]    [Pg.460]    [Pg.603]    [Pg.271]    [Pg.116]    [Pg.125]    [Pg.155]    [Pg.292]    [Pg.134]    [Pg.6]    [Pg.491]    [Pg.188]   
See also in sourсe #XX -- [ Pg.710 , Pg.715 ]




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Ethers shifts 214

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