Propyl ion

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. 

A low ion pair yield of products resulting from hydride transfer reactions is also noted when the additive molecules are unsaturated. Table I indicates, however, that hydride transfer reactions between alkyl ions and olefins do occur to some extent. The reduced yield can be accounted for by the occurrence of two additional reactions between alkyl ions and unsaturated hydrocarbon molecules—namely, proton transfer and condensation reactions, both of which will be discussed later. The total reaction rate of an ion with an olefin is much higher than reaction with a saturated molecule of comparable size. For example, the propyl ion reacts with cyclopentene and cyclohexene at rates which are, respectively, 3.05 and 3.07 times greater than the rate of hydride transfer with cyclobutane. This observation can probably be accounted for by a higher collision cross-section and /or a transmission coefficient for reaction which is close to unity. 

Proton transfer from H3 + and CH5+ to cyclopropane yields a C3H7 + ion, which at atmospheric pressures is largely stabilized by collision (9). This ion reacts as a sec-propyl ion with an added interceptor molecule (9). Hence, the protonated cyclopropane ion undergoes ring opening to acquire the sec-propyl ion structure. Similarly, it has been shown that protonated cyclobutane rearranges to the sec-C4H9 + structure. 

The reason for the low yield of hexene and high yield of nonene apparently lies in the relative reactivity of the 2-methyl-2-pentene and the original propene. In other words, the tertiary hexyl carbonium ion (XVII) adds to the olefinic double bond more rapidly than does the secondary propyl ion (XVI). 

The abnormally low energetic requirements for the release of H2 from the isomeric propyl ions contrast with the stability of all the other... 

The yields calculated using these assumptions are in satisfactory agreement with the experimental values, as illustrated in Table 18. The observation that, among all the fragmentation processes induced by the decay, only reaction (27) is prevented by collisional deactivation, supports the view that the excitation level of the propyl ions that dissociate at 10 torr into allyl ions is low indeed, and that such decomposition is possible for its low energetic requirements. The situation is completely different in the liquid phase. This is indicated, in the first place, by the substantial decrease of the yield of HT, which provides a rough indication... 

Reaction (28) was carried out by Pettersson and Lindholm (1963), bombarding CsHs with 5 eV propyl ions in the tandem mass spectrometer, and was later confirmed by Aquilanti and Volpi (1966) and by Sieck and Futrell (1966), in their study of the ionic reactions in propane. 

The radiolysis of propane has been studied extensively in experiments that have included a wide range of techniques. The gas-phase radiolysis in the absence of inhibitors yields the products hydrogen, ethane, propene, 2,3-dimethylbutane, methane, ethylene, isobutane, acetylene, isopentane and n-butane as well as small quantities of butene-1, -pentane, 2-methylpentane and -hexane ° ° . At high conversions the yield of ethylene, propene, 2,3-dimethylbutane and isobutane are all reduced. The reduction in ethylene arises from hydrogen atom addition, while the reduction in the other products may arise from the reaction of propyl ions with propene to remove both C3H6 and the source of isopropyl radicals. 

With the poly(methyl and ethyl) methacrylates, the methyl ion (m/Z 15) and the ethyl ion (m/Z 29) are respectively the most intense ion species present. In the case of the butyl isomers the ethyl ion (m/Z 29) is dominant over the propyl ion (m/Z 43) for the isobutyl isomer while with the n-butyl isomer the reverse is observed. With the lauryl isomer the (m/Z 55) is the most intense of the four ions and the other ion intensities decrease with decreasing m/Z. Silver is detected in the polymer from the silver substrate. 

After ionization, most molecules fragment by the simple loss of a portion of the molecule in the form of a free radical. For example, isobutane can readily lose a methyl radical to form the propyl ion (mje = 43). 

In the case of the propyl ion, it could be shown that there is almost complete isomerization of M-C3H7 and cyclo-CsH to sec-CaHv before ion-molecule reactions can take place 221). For protonated cyclopropane, however, an alternative explanation is possible if AH/(c-C3Ht) is higher than AH/(sec-C3H7). 

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