Inductive cleavage

Common notations were used in the previous reactions, such as - e for the subtraction of an electron during the ionization process, / for the inductive cleavage, /-Ha for H rearrangement with the formation of an odd electron ion, rHe for cleavage with the H rearrangement and the formation of an even electron ion.)... 

As shown by the above reactions, the products of the fragmentation are an EE+ ion and a neutral radical. The preference for the i-cleavage is reverse of the a-cleavage, that is, halogens exhibit a greater tendency for inductive cleavage than O, S, or N atoms. 

C. Charge-Site-Initiated Cleavage Inductive Cleavage... 

FIGURE 4.2 Representative inductive-cleavage fragmentations (Y = heteroatom). 

The appearance of an M - 1 peak due to the loss of one hydrogen atom is very characteristic of aldehydes. This peak is observed at miz = 85 in the mass spectrum of valeraldehyde (Fig. 4.41). The peak due to the formation of HCO" can be observed at mIz = 29 this is also a very characteristic peak in the mass spectra of aldehydes. The second important mode of fragmentation for aldehydes is known as P-cleavage (inductive cleavage). In the case of valeraldehyde, P-cleavage creates a propyl cation (m/z = 43). 

A heterolytic cleavage of an ion. For an odd electron ion, inductive cleavage results from the pair of electrons that forms a bond to the atom at the apparent charge site moving to that atom while the charge site moves to the adjacent atom. The movement of the electron pair is represented by a double-barbed arrow. 

Designations oe and "/" are alpha and inductive cleavages, respectively. as explained in the text. Two / reactions lead to the same charge behavior (retention or migration) as two a reactions. Brackets indicate products of reactions discussed in Chapter 8. 

This reaction will not cleave a multiple bond to a heteroatom. For the carbonyl group (Equation 4.25), electron-pair attraction to the charge site yields the canonical resonance structure inductive cleavage of this then gives the alkyl ion and acyl radical. However, these products are the complements of the alkyl radical and acylium ion formed by a-cleavage (Equation 4.14), in contrast to the a- and i-reactions (Equations 4.13 and 4.22) at a saturated heteroatom. 

Another common one-bond cleavage is charge-site-initiated or inductive cleavage, often indicated in a fragmentation mechanism by the symbol i. Inductive cleavage involves the attraction of an electron pair by an electronegative heteroatom that ends up as a radical or as a closed-shell neutral... 

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