Of ethyl group

Conditions CDCI3, 25 °C, 500 MHz (H), 125 MHz ( C). (a) //NMR spectrum and HH COSY plot of ethyl groups (b) HC HSQC plot with inserted zoomed section of ethyl groups ... 

In their study of the conformations of oligosilanes with methyl and ethyl substituents,9 Michl and co-workers pinpointed the specific substituent-substituent interactions in tetrasilanes responsible for inducing C, Z), and A conformations, allowing a prediction of backbone dihedral angle and direction of twist, given a specific arrangement of ethyl groups. 

The starting diol was transformed into the dibromide by elemental bromine with triphenyl phosphine adduct which undergoes the Arbuzov-Michaelis reaction under somewhat drastic conditions at 150 °C (step a). Catalytic removal of the benzyl group was performed by a Pd/C catalyst (step b) and the alcohol formed was allowed to react with dichloropurine in the presence of triphenylphosphine and diethylazodicarboxylate (Mit-sunobu reaction) (step c). Finally the desired product was obtained by reaction with methylamine (step d) and the removal of ethyl groups at the phosphorus centre was performed by transilylation using trimethyliodosilane (step e). 

To study the possibility of electronic effects on the photodissociation localized to the porphyrin ring, we examined -CO, a compound similar to 1 -CO except for the substitution of ethyl groups in place of vinyl groups on the outside of the porphyrin ring. Earlier bmolecular kinetic studies (11,15) had shown that this change in the electron distribution of the porphyrin had no effect on the reaction of CO with the heme. Our results also indicate that this perturbation has no apparent effect on the picosecond photodissociation. 

According to n.m.r. analysis the use of boron trifluoride diethyl etherate does not cause any detectable introduction of ethyl groups into the product. 

The results obtained are plotted in Table III. In the same table, for purposes of comparison, are recorded the amounts of ethyl groups derived from the Al(C2H6)a, as found in certain fractions of the polymer by the radiochemical methods. The amount of aluminum bound in the polymer is higher in the test performed with higher triethylaluminum concentrations. A comparison with the tests performed with the same alkylaluminum concentrations, but with different amount of a-TiCU, shows, on the contrary, that the amount of aluminum bound to the polymer decreases remarkably... 

The kinetics of the above reported chain transfer reactions seem to be also catalytically affected by the titanium compound present in the reaction system. In fact we have observed (Table III) that both the numbers of ethyl groups and aluminum atoms bound to the polymeric chains decrease with decreasing amount of titanium compound in the catalytic system. 

The reciprocal of the intrinsic viscosities of the polymer would be a unique and linear function of the amount of ethyl groups (deriving from ethylaluminum found in the polymer. 

The following method was applied in an attempt to evaluate the amount of ethyl groups fixed on the a-titanium trichloride surface by treating it with ethylaluminum solutions ... 

The amount of ethyl groups bound to the a-titanium trichloride surface, treated with diethylaluminum monochloride, is somewhat smaller than the one observed by the treatment with triethylaluminum (49). 

Within the range —18 to 50° the amount of ethyl groups found in the polymer is smaller than the total amount, initially bound to the a-titanium trichloride surface. In other tests, carried out with other samples of a-titanium trichloride, the same behavior was also observed when operating at 70° (see Table X, last line). 

If the temperature of washing of the a-TiCU, after being treated with radioactive ethylaluminum, is kept below about 50°, the number of ethyl groups found in the polymer remains practically independent of the temperature at which the adsorption of the triethylaluminum was made and of the amount and kind of polymer (polypropylene or polyethylene) obtained in each experiment. 

If the washing-temperature is higher (e.g., 70°), the number of ethyl groups found in the pol)Tner is lower. 

The number of ethyl groups, and, therefore, the number of the corresponding active centers found in the catalytic system diethylaluminum monochloride-a-titanium trichloride, is smaller than the one found in the system triethylaluminum-a-titanium trichloride. It is interesting to notice that for the two samples of a-TiCh (A and B), the activity ratio in the propylene polymerization is almost equal to the ratio (determined from ethyl groups) between the number of active centers (Table XI) (38). 

The processes leading to the entry of ethyl groups into the polymer are ... 

We shall indicate by (ra -f- rt) the sum of the entry rates of ethyl groups into the polymeric chains, during the polymerization, and by C the amount of conventional active centers (in mols), involved in the polymerization within the interval of time 0, t. 

Since at the end of the reaction the catalyst is decomposed and then the polymeric chains, which were growing at the moment when the polymerization was interrupted, were separated from the catalyst, the whole amount of ethyl groups that may be found in the polymer is as a result (we suppose that at the beginning of the reaction, one —CjHs groups corresponds to each active center) ... 

DDT p,p -dichloro-diphenyl-trichloroethane. deacetylation removal of acetyl group, dealkylation removal of alkyl group, deaminate removal of amine group, dechlorination removal of chlorine group, de-ethylation removal of ethyl group, dehalogenation removal of halogen atom(s). 

Assignments of the Vibrational Spectra of Ethyl Groups Adsorbed on Metal Surfaces... 

The LiF spectrum of the species obtained after hydrogenation of associa-tively chemisorbed ethylene shows bands at 3.38 and 3.42 ft of equal intensity. In attempting to determine the relative number of CHa and CH2 groups from these band intensities, one encounters the inherent difficulty of obtaining accurate comparisons with compounds of known structure. If the intensities of the bands of the chemisorbed alkyl radicals are compared with those of ethyl groups in lead tetraethyl, it appears that the CH2/CH3 ratio in the adsorbed species is 0.9. Comparison with ethyl groups in paraffinic hydrocarbons indicates that when the 3.38- and 3.42-// bands are of equal intensity, the CH2/CH3 ratio is 1.6. 

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