Reaction fragment

In examples 2.22 a and b the metals increase their valence by two, and this is not just a formalism as indeed the titanium(II) and the nickel(O) are very electron rich metal centres. During the reaction a flow of electrons takes place from the metal to the organic fragments, which end up as anions. In these two reactions the metal provides two electrons for the process as in oxidative addition reactions. The difference between cycloaddition and oxidative addition is that during oxidative addition a bond in the adding molecule is being broken, whereas in cycloaddition reactions fragments are combined. 

M.J.A. Shiddiky, D.-S. Park and Y.-B. Shim, Detection of polymerise chain reaction fragments using a conducting polymer-modified screen-printed electrode in a microfluidic device, Electrophoresis, 26 (2005) 4656-4663. 

Neutral gaseous molecules entering the ionization area are bombarded with electrons to smash the compound of interest to yield positively charged ions. Ionization is often followed by a series of spontaneous competitive decomposition reactions (fragmentation) which produce additional ions. The instrument operates under a high vacuum to prevent absorption of the charged particles by air molecules. 

We shall discuss this type of reaction-fragmentation—in Chapter 38. 

Some t-CaHg s are also formed by related reactions (fragmentation of heavier isoalkyl cations, as shown in Table III). 

Perhaps the most surprising trapping reaction is that observed when nitromethane is added. The adduct formed in this reaction fragments to give 1,2-dibenzoylethene. 

Fragmentation of appropriate bicyclic sulfonyloxy alcohols or ketones is a general route towards cy-cloalkene ketones or carboxylic acids. Thus, the hydroazulene alcohol (59 Scheme 22), precursor for the synthesis of daucene (60), jaeschkeana diol and others, has been synthesized by a one-pot reaction (fragmentation and isopropylation) of the hydroxy tosylate (57) with Pr Li. The fragmentation of (57) to give the ketone (58) as the primary product can be achieved by treatment with pyridine. 

In an elimination reaction, fragments of a molecule are removed and form a new molecule. Elimination involving a free radical mechanism operates in many pyrolytic reactions. First, an initiation occurs by pyrolytic cleavage, followed by... 

In addition to thc above polymerization and recombination reactions, fragmentation of large carbon clusters (m > 30) due to collisions with H atoms and recombination of C2 H clusters with H atoms, reactions 7.6 and 7.7, may also be responsible for the production of C2 H2 (n = 4-8) polyynes. 

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