Carbonyl compounds, factors influencing acidity

For acyclic compounds the regioselectivity depends upon statistical factors and the relative acidities of the different 3-hydrogens, the elimination preferring to take place towards the most acidic hydrogen. This can also influence the regioselectivity of elimination from alicyclic compounds, e.g. the a,3-unsatu-rated carbonyl compound (14) was obtained from the 3-aminocarbonyl compound (13), and the allylic alcohol (16) was the major product obtained on oxidation and pyrolysis of the hydroxyamine (15). ... 

At this point we consider some general relationships concerning the reactivity of carbonyl compounds toward addition of nucleophiles. Several factors influence the overall rate of a reaction under various conditions. Among the cmcial factors are (1) structural features of the carbonyl compound (2) the role of protons or other Lewis acids in activating the carbonyl group toward nucleophilic attack (3) the reactivity of the nucleophilic species and its influence on subsequent steps and (4) the stability of the tetrahedral intermediate and the extent to which it proceeds to product rather than reverting to starting material. 

An important factor influencing the reactivity of amino acids and carbonyl compounds is pH. Reactivity of amino acids also depends greatly on basicity, or more precisely on the nucleophihcity, of the amino group, but also on other factors that are described in detail in Section 4.7.5. 

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