215 HH W08-Ch 16 - Chem 215 HH W08 Notes Dr. Masato Koreeda...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Chem 215 HH W08 Notes – Dr. Masato Koreeda - Page 1 of 4. Date: March 17, 2008 Chapter 16-1, 3-5: Acidity and Basicity; Enolization/Enolate Formation I. Inductive and Resonance Effects in Acidity and Basicity (1) Carboxylic acids • Inductive effect in aromatic carboxylic acids O C O H O C O H O C O H F O C O H F F pKa 4.2 4.1 3.9 3.3 stronger acid; F closer to the C(=O)O H note: Inductive effect through the ! -bond framework • Combination of inductive and resonance effects O C O H O C O H N O C O H N N O O O O O O pKa 3.4 pKa 3.5 pKa 2.2 mostly inductive effect weak inductive effect strong inductive effect & extremely strong resonance effect O C O N O O O C O N O O O C O N O O O C O N O O attractive charge-charge interaction Resonance structures of the conjugate base of 4-nitrobenzoic acid : (2) Aromatic amines (or anilines) Instead of using the basicity scale (pKb), the dissociation acidity (pKa) of the conjugate acids is typically used. So, a stronger base has a higher pKa of its conjugate acid. H N H H BH B + H pKa H 3 C N H H H pKa 10.6 pKa 4.6 H N H H N H Because of the delocalizable N lone pair in aniline (as a result of resonance with the benzene ! -system), the aniline N atom is considerably less basic compared with that of R-NH 2 .
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 02/13/2012 for the course CHEM 215 taught by Professor Koreeda during the Winter '07 term at University of Michigan.

Page1 / 4

215 HH W08-Ch 16 - Chem 215 HH W08 Notes Dr. Masato Koreeda...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online