Inorganic Arrow Pushing Thinking Like a Lone Pair

23 INORGANIC ARROW PUSHING THINKING LIKE A LONE PAIR 

Generally speaking, the mechanisms of p-block element reactions are not particularly consistent with the rules outlined above. The reason for this boils down to the so-called first-row anomaly, where both first- and second-period elements (H-Ne) are all somewhat unreasonably lumped together as first row. The expression means that the chemical properties of first-row elements are anomalous relative to those of their heavier congeners. Let us go through the above four rules one by one and see how well they hold up in a main-group inorganic context. 

As mentioned in Section 1.9, nucleophilic attack on a heavier main-group center with a noble gas configuration does not necessarily lead to immediate bond breakage. Instead, the first step may be an A reaction leading to a hypervalent intermediate with an expanded octet. The leaving group would them depart in a subsequent D process. As mentioned, this two-step process is known as SN2-Si. In this book, we have 

Compared with organic chemistry, charged centers are much more common in main-group element chemistry. Thus, monatomic anions such as 0 , 8 , and 

Look at the product structure(s) carefully and determine what bonds have been broken in the course of the reaction and what new bonds have been formed. 

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