Ethyl ion

As a result of the conclusions reached in these studies, a simple competition method was devised 12, 32) to determine relative rates of hydride transfer reactions rather accurately. For example, to obtain relative reaction rates of ethyl ions with various additives, a suitable source of fully deuterated ethyl ions such as C3D8 or iso-C4Di0 was irradiated in the presence of a perprotonated additive (RH), leading to the formation of C2D6 and C2D5H by Reactions 2 and 3. 

From the observed drop in yield, one can calculate the rate of Reaction 10 relative to hydride transfer with cyclobutane (on the rate scale used in Table I) as 1.55 for the ethyl ion and 0.83 for the propyl ion. 

Recent observations (14, 15) indicate that ethyl ions react with ethane via... 

The authors also frequently confuse termination with the various forms of transfer. The confusion arises partly through their use of the unfortunate term molecular termination due to Endres and Overberger [85]. Moreover they formulate their mechanistic schemes in terms of reactions, some of which are known not to occur, such as the formation of ethyl ions from ethyl chloride and aluminium chloride. 

Pfeiffer and Jewett (1970), however, have made ab initio calculations on the ethyl cation and report the charge distributions in Figure 4b for the most stable ethyl ion. Their calculations agree with Hoffmann s in predicting that the classical ethyl structure is more stable than a bridged structure, but their calculated charge distribution is entirely different. 

The labeled ethyl ions from reaction (9) do not react with CH4, but undergo a fast hydride-ion transfer from CgHg ... 

Reactions (8) to (10) not only explain qualitatively the formation of the three major products, but allow a rough evaluation of the abundance of labeled methyl ions former", from the decay. Assuming, in the absence of more detailed information, a statistical distribution of tritium between the products of reaction (9), the activity of HT from reaction (9) is equivalent to 2/5 of the activity contained in the ethyl ions, eventually isolated as tritiated ethane. Therefore, the yield of HT from reaction (9) can be calculated to be 7-0 x 2/5 = 2-8%, and the fraction of the methyl ion undergoing reaction (9), 9-8%. Comparing this figure with the fraction (78%) of labeled methyl ions that react with CgHg to yield... 

The ethyl ions do not react appreciably with CH4, and readily abstract a hydride-ion from CsHg. 

Processes similar to reactions (8) and (9) have in fact repeatedly been found in the ion source of the mass spectrometer (Lampe and Field, 1959 Derwish et al., 1964a, b Field eiaZ., 1964 Munson and Field, 1964 Haynes and Kebarle, 1966). In particular, it is generally agreed that the reaction of methyl ions with CH4 leads to the exclusive formation of ethyl ions, and the C2H ions observed in early experiments are currently ascribed to the presence of impurities in the methane (Field and Munson, 1965). 

The hydride-ion transfer from CgHg to ethyl ions was also repeatedly demonstrated in the study of the gas-phase radiolysis of CgHg (Ausloos and Lias, 1962 Borkowski and Ausloos, 1964) and of CgDg (Sandoval and Ausloos, 1963). 

The insensitivity of the total yield to the addition of propane suggests that the ethyl ion is not the precursor of the products identified. 

The methyl ions from the dissociation process (43a) react with methane forming tritiated ethyl ions which are completely unreactive towards methane, as discussed in Section TV. 

In the presence of propane, even at the relatively low concentration of 2 mole %, the ethyl ions yield tritiated ethane, through the exothermic hydride-ion transfer ... 

The formation of tritiated ethylene observed in neat CH4 was ascribed, on the other hand, to an exothermic proton transfer from the unreactive ethyl ions to an acceptor, for instance water, contained in the system as an impurity at an extremely low concentration. 

Recently, however, Field 4 h s cast doubt on some of Stevenson s results, and given new evidence which leads to Z)(C2H3 -H) = 122 kcal. Field measured the appearance potential of the ethyl ion in 1-butene to be 13 30 0 2 eV, or 1 3 eV greater than Stevenson s value. Similarly, for the appearance potential of the vinyl ion in 1-butene, Field obtained 14 96 0 1 compared with Stevenson s value of 13 6 0 3 eV, an increase of 1 4 eV. If Field s value for (C2H5+) in 1-butene is correct, then Z)(C2H3 H) ==122 kcal follows. The same value, within 2 kcal, is obtained from the appearance potential of the methyl ion in propylene and the tertiary butyl ion from 3 3-dimethyl-1-butene. 

Radioactive decay of tritium in H-labelled ethane leads to the formation of ethyl ions ( 80%) and fragments of ethane (s 20%). Because the recoil energy is too low to break C-C bonds, fragmentation of the ethane molecule must be due to excitation effects. 

In this case ethylate ions are formed instead of hydroxyl ions. Evidently we limit ourselves to water as a solvent when we define a base as a substance which yields hydroxyl ions in solution. Furthermore we should need a separate definition for each solvent. This difficulty is eliminated by the terminology of BrOnsted, for his method of expression is more general. Thus the dissociation of ammonia in water is the analogue of the process in alcohol, as is shown by... 

In considering the other reactions with isotopically labelled ions, ethyl ion is produced by three different reactants (Reactions 7, 8a, and 9b), but since the neutral products can only be inferred, the mechanisms of these processes are not entirely clear. While all three reactions might be considered to involve Cl" transfer from the neutral reactant (as implied by the reactions as written), the same ionic product could also be formed by dissociative charge transfer (Reaction 12). 

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