Positively charged species

Later discussion will show that fluorine directly attached to a carbocation centre, as in 1.16A and 1.17 A, overall is clearly a stabilising influence, but the effect of fluorine more remote from the centre, as in 1.16B, is strongly destabilising. 

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Electron distribution governs the electrostatic potential of molecules. The electrostatic potential describes the interaction of energy of the molecular system with a positive point charge. Electrostatic potential is useful for finding sites of reaction in a molecule positively charged species tend to attack where the electrostatic potential is strongly negative (electrophilic attack). 

Thus two electrons exit the reaction zone, leaving a positively charged species (M ) called an ion (in this case, a molecular ion). Strictly, M" is a radical-cation. This electron/molecule interaction (or collision) was once called electron impact (also El), although no impact actually occurs. 

Because of the greater resistance to elimination of chlorine as a positively charged species, p-chloroanisole does not undergo dechlorination under similar conditions. 

Only the positively charged species are accelerated out of the ionization region neutral radicals—e.g., CULE in Equation 2, and molecules— e.g.y ME in Equation 3, produced by fragmentation and rearrangement, and un-ionized sample are pumped away. 

For many years, electron ionization, then more usually known as electron impact, was the only ionization method used in analytical mass spectrometry and the spectra encountered showed exclusively the positively charged species produced during this process. Electron ionization also produces negatively charged ions although these are not usually of interest as they have almost no structural significance. Other ionization techniques, such as Cl, FAB, thermospray, electrospray and APCI, however, can be made to yield negative ions which are of analytical utility. 

Apart from metal cations, the negative framework can also be compensated by other positively charged cations such as NH4+ and H+. The protonated forms of zeolites have a high acidity because the proton can be easily removed from the zeolite and replaced by other positively charged species. This feature makes them very efficient solid-state acids, which can be used for acid-catalyzed reactions. 

So now the word carbocation is used to cover all such electron deficient and positively charged species, although some authors still prefer to use the word carbonium ions. 

As before, we define c as the total concentration of positively charged species, which is the same as what Stannett s group designate as [C+], the total concentration of cations which have escaped geminate recombination, so that... 

Upon addition of acid the charge determining positively charged species will increase at the expense of the negatively charged charge determining species... 

The production of ions from neutral compounds and the examination of how these ions subsequently fragment is fundamental to mass spectrometry. Neutral sample molecules can be ionized by a variety of processes. The most important of these for the production of positively charged species is the removal of an electron or the addition of one or more protons to give either molecular ions (M+ ) or protonated molecular species (M+nH)"+. This initial stage of ionization is often followed by fragmentation to produce ionized fragments, fragment ions . 

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