Basic Factors that Influence Ion Abundance

The following general guidelines for predicting unimolecular ion decompositions follow basic chemical principles. 

Stability of the product ion. The most important general factor affecting the abundance of a product ion is its stability. Key types of ion stabilization include electron sharing involving a nonbonding orbital of a heteroatom, such as in the acetyl ion CH3—C—O CH3—C=0 (the latter is isoelectronic 

Loss of the largest alkyl. A notable exception, in which abundance decreases with increasing ion stability, is the widespread preference for the loss of the largest alkyl radical at a reactive site (Equation 4.2). 

Unknown 4.1. Predict the most abundant product ion in the mass spectrum 

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