Editing Pyrrole (section)

===Reaction of deprotonated pyrrole===
The NH proton in pyrroles is moderately acidic with a [[Acid dissociation constant|p''K''<sub>a</sub>]] of 17.5.<ref>{{cite book|first1=C.&nbsp;W.|last1=Bird|first2=G.&nbsp;W.&nbsp;H.|last2=Cheeseman|title=Comprehensive Heterocyclic Chemistry|url=http://www.sciencedirect.com/science/article/pii/B9780080965192000527|publisher=Pergamon|year=1984|pages=39–88|isbn=978-0-08-096519-2|postscript=None}}, although note that {{cite journal|doi=10.1016/S0040-4020(01)89212-7|journal=Tetrahedron|volume=45|issue=23|pages=7501–7504|year=1989|publisher=Pergamon|location=Great Britain|title=The acid-base properties of pyrrole and its benzologs indole and carbazole: a re-examination from the excess acidity method|first1=M.|last1=Balón|first2=M.&nbsp;C.|last2=Carmona|first3=M.&nbsp;A.|last3=Muñoz|first4=J.|last4=Hidalgo|postscript=None}} suggests that figure's revision to 17.3.</ref> Pyrrole can be deprotonated with strong bases such as [[butyllithium]] and [[sodium hydride]].<ref>{{cite book|first1=Heinz-Gerhard|last1=Franck|first2=Jürgen&nbsp;Walter|last2=Stadelhofer|title=Industrielle Aromatenchemie: Rohstoffe, Verfahren, Produkte|trans-title=Industrial Chemistry of the Aromatics: Raw materials, processes, products|lang=de|publisher=Springer|location=Berlin|year=1987|isbn=978-3-662-07876-1|pages=403–404}}</ref> The resulting alkali pyrrolide is [[nucleophilic]]. Treating this conjugate base with an electrophile such as [[iodomethane]] gives ''N''-methylpyrrole. 

''N''-Metalated pyrrole can react with electrophiles at the N or C positions, depending on the coordinating metal. More ionic nitrogen–metal bonds (such as with lithium, sodium, and potassium) and more solvating solvents lead to ''N''-alkylation. Nitrophilic metals, such as MgX, lead to alkylation at C (mainly C2), due to a higher degree of coordination to the nitrogen atom.  In the cases of ''N''-substituted pyrroles, metalation of the carbons is more facile. Alkyl groups can be introduced as electrophiles, or by cross-coupling reactions.{{citation needed|date=July 2016}} 
[[File:Pyrrole C Metallation.jpg|center|class=skin-invert-image|Pyrrole ''C''-metalation]]

Substitution at C3 can be achieved through the use of ''N''-substituted 3-bromopyrrole, which can be synthesized by bromination of ''N''-silylpyrrole with [[N-Bromosuccinimide|NBS]].{{citation needed|date=July 2016}}