Primary ionizations

As noted previously, ionized primary and secondary alkylamines isomerize to DIs provided they have sufficiently long alkyl chains and are allowed enough time. These... 

Generally, the evaporated mobile phase acts as the ionizing gas and reactant ions are produced from the effect of a corona discharge on the nebulized solvent. Typically, the corona discharge forms by electron ionization primary ions such as N2 + or 02 +. Then, these ions collide with vaporized solvent molecules to form secondary reactant gas ions. 

Ionized primary enamines of low energy may also be reaction intermediates in the loss of ammonia. Scheme 34 shows a mechanism proposed for the extensive loss of ammonia from low-energy ionized 3-amino steroids. Enamine 63 may lose ammonia after two successive 1,4 H-transfers. The participation of the H at C(5) has been established by D-labelling42. Only higher energy ions lead to m/z 82 fragment ions through the ionized dienamine 64,... 

This cycloreversion reaction has been utilized to generate 34 and study its reactions with olefins in a FTICR spectrometer43. 34 has been found to react with various olefins essentially along two competing channels H atom abstraction leading to the immonium ion m/z 44 (Scheme 36) and regioselective cycloaddition-cycloreversion. The latter reaction opens up a new possible access to ionized primary enamines in the gas phase. 

The discussion up to this point has been limited to the effects of the ionization produced directly by the incident particle. This is called primary ionization. There are types of gas counters in which the electric field is so strong that the electrons of the primary ionization acquire enough kinetic energy between collisions to produce new electron-ion pairs. These new charges constitute the secondary ionization. Primary and secondary ionization are generated within such a short period of time that they contribute to one and the same pulse. 

This chapter will show that the potent ionizing ability of water is a key to predicting bimolecular versus unimolecular reactions. Aprotic solvents favor bimo-lecular reactions. It is assumed that water is required for ionization. Primary alkyl halides rmdergo Sn2 reactions under most conditions, whereas tertiary alkyl halides never undergo Sn2. If a nucleophile is classified as the conjugate base of a strong acid, it is a weak base and will probably not induce an E2 reaction. 

Chiral crown ether selectors are derivatized forms of polyoxyethylene crown-6 [27]. This crown ether has a cavity that exactly match the size of an ionized primary amine group, -NHs". The host-guest ammonium-crown ether interaction, one point of attachment, is the driving force of the enantiomer with this class of chiral selector. The two other necessary interactions are a steric and a hydrophobic one. They will occur between the crown ether substituents and the host substituent. Chiral crown ether can only discriminate chiral molecules with a primary amine group at low pH (where the amine is protonated). 

The record m the number of absorbed photons (about 500 photons of a CO2 laser) was reached with the CgQ molecule [77]. This case proved an exception in that the primary reaction was ionization. The IR multiphoton excitation is the starting pomt for a new gas-phase photochemistry, IR laser chemistry, which encompasses numerous chemical processes. 

Rearrangement is especially prevalent with primary alkyl halides of the type RCH2CH2X and R2CHCH2X Aluminum chloride induces ionization with rearrangement to give a more stable carbocation Benzylic halides and acyl halides do not rearrange... 

The fragmentation patterns of relatively volatile derivatives of penicillins (e.g. benzyl-penicillin methyl ester) under electron impact (B-72MI51101) and chemical ionization (75MI51100) conditions have been described. For both techniques the primary fragmentation is that shown in Scheme 1. 

Static Secondary Ion Mass Spectrometry (SIMS) involves the bombardment of a sample with an energetic (typically 1-10 keV) beam of particles, which may be either ions or neutrals. As a result of the interaction of these primary particles with the sample, species are ejected that have become ionized. These ejected species, known as secondary ions, are the analytical signal in SIMS. 

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