Splitting, methyl

Aluminium halides are not only able to split methyl groups, but to undergo other reactions, too. The chloromethyldisilane derivatives can be further reacted by rearrangement365. The products depend on the reaction conditions. Kumada et al.356 found that, under mild conditions (reaction temperature 70-80 °C), only migration of the trimethylsilyl group from silicon to carbon takes place ... 

Atisine Conformation or Configuration. An interesting controversy has developed over the origin of an apparently split methyl signal in the n.m.r. spectrum of atisine (50) in aprotic solvents. Pelletier and Oeltman suggested that this corresponds to the two conformations (51) and (52). The coalescence temperature... 

Suggestions that PIB may have structure (II) as opposed to structure (I) have been refuted by infra-red studies. These show clearly the split methyl absorption at 7-2 and 7 3 /u.m, characteristic of a gem-dimethyl group. Proton magnetic resonance spectra also indicate a CH3/CH2 proton ratio of about 3, as would be expected from structure (I). 

The physical basis for peak splitting mil dichloroethane can be explained with the aid of Figure 13 13 which examines how the chemical shift of the methyl protons IS affected by the spin of the methme proton There are two magnetic environments for... 

A very important characteristic of spin-spin splitting is that protons that have the same chemical shift do not split each other s signal Ethane for example shows only a single sharp peak m its NMR spectrum Even though there is a vicinal relationship between the protons of one methyl group and those of the other they do not split each other s signal because they are equivalent... 

FIGURE 13 14 The methyl protons of 1 1 dichloroethane split the signal of the methme proton into a quartet... 

FIGURE 13 16 The methyl ene protons of ethyl bro mide split the signal of the methyl protons into a triplet... 

The NMR spectrum of isopropyl chloride (Figure 13 17) illustrates the appearance of an isopropyl group The signal for the six equivalent methyl protons at 8 1 5 is split into a doublet by the proton of the H—C—Cl unit In turn the H—C—Cl proton signal at 8 4 2 IS split into a septet by the six methyl protons A doublet-septet pattern is char acteristic of an isopropyl group... 

IS the only phosphorus isotope present at natural abundance and has a nuclear spin of The H NMR spectrum of tnmethyl phosphite (CH30)3P exhibits a doublet for the methyl protons with a splitting of 12 Hz... 

The c/s-fused diaziridines (31a) and (31b) are also an equilibrium system, interchanging exo and endo positions of methyl and ethyl groups. The NMR spectrum shows two methyl peaks at 0 °C, coalescing to a single sharp peak at 75 °C. The ethyl group shows the sharp characteristic quartet-triplet splitting pattern at 75 °C (74JOC3187). 

Fig. 53. The temperature dependence of 7", in tiglic acid. Methyl tunnel splitting (ueV)...

The ketimine of isophorone diamine is formed by reacting it with methyl isobutylketone, splitting off water in the process. When said ketimine is added to an isocyanate-terminated prepolymer based on IPDI, a semi-stable system is established with a pot life of several hours. The ketimine is a Schiff base and thus can react even in the absence of water. The complexities and advantages of this system are reviewed by Bock and Halpaap [75] ... 

When heated with mineral acids Z-cocaine is hydrolysed into Z-ecgonine (p. 96), benzoic acid and methyl alcohol and a like change takes place with baryta water. If the alkaloid is boiled with water, methyl alcohol is split off and a new base, benzoyl-Z-ecgonine is formed, which in turn can be hydrolysed by acids or alkalis into Z-ecgoninc and benzoic acid. Cocaine is, therefore, methylbenzoyl-Z-ecgonine. 

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