Koreeda_Chap16-1 - Chem 215 F10 Notes - Dr. Masato Koreeda...

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Unformatted text preview: Chem 215 F10 Notes - Dr. Masato Koreeda - Page 1 of 5. Date: October 27 ,2010 Chapter l6-L,3-5: Acidity and Basicity; Enolization/Enolate Formation I. lnductive and Resonance Effects in Acidity and Basicity (1) Carboxylic acids Examples of the lnductive Effect pKa o ['9'6'o@ H o "l\'o'oo H o cr\.c.o@ ct7il o :,tf"" HH I 4.52 clr"-c-6-d.o@ H'H HH Cl H O 4.05 H-c-b'-c-d-o@ n' u' H r-r HH a *.",c_"-d.o@ H' H cr'h pKa 4.8 2.8 1.3 more Cl atoms Cl closer to the C(=o)oH 2.86 o.64 stronger acid o !:e'd'o@ F 0.23 . Inductive effect in aromatic carboxylic acids stronger acid o a'^ortt-o.@ ilt \Z\F J,J stronger acid; F closer to the C(=Q)QH oo ryo-"t ,g"-o@ .-\-6-o@ pKa 3.+ o--Rl(/ oo weak inductive ffict & strong resonance fficl ? a'\/c'o v o-!'{,9o" o pKa 3.5 ,,i\,,-6-o @ pKa2.2 \r\fr.o" 6 mostly inductive ffict strong inductive effect & extremely strong resonance ffict Resonance structures of the conjugate base of 4-nitrobenzoic acid: ?? ri\ft-o" a oA.ctoo g.ffiA/ "o'ft)'-2 $o $o 99 ^g)i,,^;'*fi-# " charge interaction o *'d-o@ o il-+ *'C.OO * H@ electrons are withdrawn more charge more stabilized to the O atom of the O-H by the presence of the bond by the halogen atom(s) halogen atom(s) o qo'"t pKa 4.2 4.1 F z.g note: Inductive effect through the o-bond framework . Combination of inductive and resonance effects Chem 215 F10 Notes - Dr. Masato Koreeda - Page 2 of 5. Date: October Z7 ,2010 (2) Aromatic amines (or anilines) Instead of using the basicity scale (pKb), the dissociation...
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Koreeda_Chap16-1 - Chem 215 F10 Notes - Dr. Masato Koreeda...

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