Methyl chloride chemical shifts

Wells and coworkers53 have prepared a series of deuterated tetramethyltin compounds, which they used to study the long-range deuterium isotope effects on the proton chemical shifts of tetramethyltin. The various deuterated tetramethyltin compounds, with one to four trideuteromethyl groups on the tin atom, were prepared by a series of methyl group exchanges beginning with tri-trideuteromethyltin chloride and undeuterated tetramethyltin (Scheme 12). 

Rhinebarger et al. [35] and Eyring et al. [36,37] have used lithium-7 nuclear magnetic resonance (NMR) chemical shift data to determine the stability constants for crown-ether complexes of Li+ in two IL systems consisting of 55/45 mole% N-butylpyridinium chloride-aluminum chloride and l-ethyl-3-methyl-imidazolium chloride-aluminum chloride. The stability constants for... 

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

In suitably selected cases metal complexing can change the conformational rather than the chemical equilibrium. Methyl /3-D-ribopy-ranoside in aqueous solution consists of an equilibrium between the C1(d) (ll) andlC(D) (12) forms, the former predominating (17). Only the 1C (d) form has an ax-eq-ax sequence of hydroxyl groups. On addition of calcium chloride to the solution, the equilibrium shifts in favor of the IC(d) form, as seen from the value of Jit2 which decreases from 5.4 Hz in D20 to 2.5 Hz in 2.1 M CaCl2. This corresponds to a change of the proportion of the C1(d) form from 57 to 12%. 

The 4H NMR spectra of some methyl-,79-83 halo-,81 mercapto-,84 nitro-,84 and methoxybenzo[6]thiophenes,85 and of some sulfonic acids, sulfonyl chlorides, and sulfonate esters86 have been recorded. Two groups of workers87,88 have independently studied the 4H NMR spectra of a range of benzo[6]thiophene derivatives in an attempt to correlate the chemical shifts of the protons with the substituents. Such a correlation helps to assign structures to new benzo[6]thiophene derivatives, and it also throws light on the influence of substituents on the NMR parameters of heteroaromatic systems in general. 

Hz). Several pieces of spectroscopic evidence lead to the conclusion the Me5C5 ring of V is not bonded in the monohapto manner. First, the 1h and 13c spectra of V indicate that the ring and Me carbons of the Me5C5 moiety are equivalent moreover, the equivalence of the methyl groups persists to -100°C and -80°C in lH and 13c NMR experiments, respectively. Second, the 31p chemical shift of V (111.0 ppm) is 33.8 ppm upfield (i.e. shielded) compared to that of the phosphorus(III) chloride precursor, 2Z 1° aH cases reported to date, phosphenium ion for-... 

The observation that the chemical shift of added methyl chloride in Al2Me6-cyclopentane solutions is very close to the chemical shift of the same concentration of methyl chloride in cyclopentane solutions (Figure 3, Tables I and II) indicates that there is little if any Al2Me6 MeCl complex formed in solutions in cyclopentane. Therefore, the chemical shift of MeCl in Al2Me6-cyclopentane solutions is a convenient measure of MeCl concentration, and the plot of the W /2 of AlMe3 vs. the chemical shift of MeCl in cyclopentane solutions should be linear. This is observed and is illustrated in Figure 4. 

Figure 3. Concentration dependence of the chemical shift of methyl chloride in cyclopentane solutions...

Table II. Chemical Shifts of Cyclopentane Solutions of Methyl Chloride...

CHEMICAL SHIFT OF METHYL CHLORIDE, HZ FROM CYCLOPENTANE AT 100 MHZ... 

Figure 4. Reciprocal of the line width of tri-methylaluminum as a function of the chemical shift of methyl chloride. Measured at —25°C. chemical shifts measured at room temperature...

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... 

In addition to the study of the bis-benzo[c]phenanthridines just discussed above, Marek and coworkers have also extensively studied other benzojcjphenanthridine alkaloids [111,121]. The structures of the alkaloids for which data have been reported and their respective chemical shifts are collected in Figure 14.12. These alkaloids include the methyl chloride salts, sanguinarine chloride (110), chelrythine chloride (111), sanguilutine chloride (112) and chelirubine chloride (113). 6-Substituted and... 

Complex formation results in a downfield change in the chemical shift of the methyl protons and a decrease in the double-bond infrared stretching frequency from 1680 to 1532 cm h In the presence of a small excess of PdCl2, the complex is rapidly converted to hexamethylbenzene and palladium chloride. 

Photoheterolysis of benzylic chlorides [204] yielded results signifying that simple benzyl cations, such as cumyl and 1-phenylethyl cations, can exist in the solution as free ions radicals arising from a competing photohomolysis are also observed frequently. Haloalkyl-carbocations are studied by heterolysis of the corresponding dihalides in super acid media [205]. NMR chemical shifts are interpreted as evidence for an interaction between the vacant orbital of cationic center of the haloalkyl carbocations with a lone electron pair of the halogen atom. 3-chloro-l-methylcyclopentyl cation 73, thermally eliminates hydrogen chloride and yields l-methyl-2-cyclopentyl cation 74, a similar behavior reported for y-chloroalkyl carbocations [206] (Scheme 5). 

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