Protons on heteroatoms

Chart E.l. Protons Subject to Hydrogen-Bonding Effects (Protons on Heteroatoms)  

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PROTONS SUBJECT TO HYDROGEN-BONDING EFFECTS APPENDIX E (PROTONS ON HETEROATOMS)"... 

Protons on heteroatoms are more variable than protons on carbon... 

Table 3.14 Protons subject to Hydrogen. Bonding Effects (protons on Heteroatoms) ...

This simple neutralization reaction always favors the weaker base. Thus the most acidic H is deprotonated, even if the acid has an adjacent CH. Because of the higher electronegativity of heteroatoms, protons on heteroatoms are usually lost before protons on carbon. The base n-butyllithium deprotonates the nitrogen of diisopropyl amine. The adjacent CH is about 14 orders of magnitude less acidic. Always check the eq to be sure your proton transfer is energetically reasonable. The Xgq for the reaction below is highly favorable, 10(50 - 36) = 10+14. 

Anionic eliminations of the following type will also be considered as belonging to the ElcB class of eliminations. Since protons on heteroatoms are usually rather acidic because of the electronegativity of the heteroatom, the first step, deprotonation, can occur with a rather weak base. The second step is beta elimination from an anion, Ep, the reverse of nucleophile addition to a polarized multiple bond. 

PROTONS ON HETEROATOMS HAVE MORE VARIABLE SHIFTS THAN PROTONS ON CARBON... 

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