Methylene chloride chemical shift

Scheme 7.11 shows the product structures resulting from the dithionite reduction of a simplified version of WV-15. The symmetric sulfite diester was extracted from the reaction mixture with methylene chloride. The isolation and characterization of the sulfite diester confirmed that this species can form in dithionite reductive activation reactions and provided the chemical shift for the 10a-13C center of a mitosene sulfite ester (49.37 ppm). The aqueous fraction of the reaction contained the mitosene sulfonate and trace amounts of Bunte salt, based on their 13C chemical shifts. 

Infrared spectra were obtained with a Perkin-Elmer 1800 and a Nicolet Magna-IR 750 FTIR spectrophotometer, and the absorption frequencies are reported in wave numbers (cm4). NMR spectra were obtained with BZH-300 and CA-F-300 Bruker FTNMR 300 MHz spectrometers. Chloroform-d was used as solvent, and all chemical shifts are reported in parts per million downfield (positive) of the standard. H-NMR and 13C-NMR chemical shifts are reported relative to internal tetramethylsilane, while 19F-NMR chemical shifts are reported relative to internal fluorotrichloromethane, Rf values were obtained from silica gel thin-layer chromatography developed with a mixture of 1.5 mL methylene chloride and three drops of acetone. The number of hydrate water molecules was calculated from the integration of H-NMR spectra. 

In 1982 Hall and Sukumar118 demonstrated the ability to select species processing distinct chemical shifts in images, where the chemical shifts do not overlap, using capillaries of water, acetone, benzene and methylene chloride. Since then, volume-localized spectroscopy and chemical-shift imaging have been applied to a number of medical and non-medical problems. Most of these studies, however, are focused on the H and 31P nucleides, especially those investigations which are clinically oriented119,120. 

FIG. 8.6 Chemical shifts of protons in benzene, pyridium rings, and methylene groups versus the ratio of moles of solubilized benzene to moles of hexadecyl pyridinium chloride. (Redrawn, with permission, from J. C. Eriksson, Acta Chem. Scand., 17, 1478 (1963).)... 

Methyl chloride Methylene chloride Chloroform Chemical shift (8) 3.1 5.3 7.3... 

At very low levels of vinylidene chloride, the VCI2 monomer will be flanked by VCl monomer. The isolated structure is shown in Figure 2a. The carbon bearing both chlorine atoms has a chemical shift or 87.50 ppm and is identified in Figure lb. The chemical shift at 52.33 ppm in Figure lb is assigned to the methylene carbon adjacent to a vinylidene (or dichloro carbon) structure. 

Figure 5 shows the chemical shift of the methylene protons of Al-i-Bu3 as a function of the ratios of concentrations of [Al-i-Bu3]/[MeCl] in cyclopentane solution at ambient temperature. The sharp break in the plot at 1.7 [Al-i-Bu3]/[MeCl] suggests complex formation between these compounds. Similarly, the plot of the corrected chemical shift of methyl chloride—i.e., the chemical shift of MeCl in Al-i-Bu3-cyclopen-tane solutions minus the chemical shift of MeCl in the same concentration in cyclopentane solutions vs. [Al-i-Bu3]/[MeCl] (Figure 6), indicate complex formation. Obtaining more chemical shift measurements on... 

The authors also reported chemical shift assignments for one additional compound. Refluxing the t-butyl substituted precursor of 77 in methylene chloride with triphenylphosphine, iodine and triethylamine led to the formation of the substituted p-carboline, 79. 

Figure 8. Proton chemical shifts of iso-HMTT LiBr in mixed benzene-methylene chloride solution. The upfield methylene shift ACH is defined as zero in pure methylene chloride (see Table II). Resuhs are shown for two concentrations of chelated salt.

No account was taken of the reaction field of the solvents and therefore the conclusions drawn can be regarded as correct only if the chemical shift change is in excess of that which would be expected from the reaction field of the solvent in going from a solvent of low dielectric constant (n-pentane) to one of high dielectric constant (dimethyl sulphoxide). A determination of the reaction field-induced shift for the protons of methylene chloride (as a model compound for dichloro-acetaldehyde) supports the conclusions regarding the anisotropy of the carbonyl group. 

Proton NMR was used routinely to confirm a number of the structures, especially those of the disiloxanes. In general, these measurements utilized a Varian EM-390 at room temperature with a methylene chloride or benzene chemical shift reference. 

As might be expected on the basis of the C NMR chemical shift data, 3-methoxycarbonyl-2-pyrone 33 is less reactive toward vinyl ethers than 3-chlorocarbonyl-2-pyrone. In fact, at room temperature in methylene chloride, no cycloadduct formation was observed with a number of different vinyl ethers. Marko and co-workers, however, coaxed these pyrone dienes into reacting with representative vinyl ethers at elevated temperatures (70°-80 C) in polar aprotic solvents, leading to bicyclic lactones 34-37. In all cases, each of these bicycloadducts is obtained as a single stereoisomer. 

---