Chemistry 125: Lecture 64 April 7, 2010 Carbonyl Compounds Preliminary This For copyright notice see final page of this file

Chapter 16: Aldehydes & Ketones C=O Stable, but Reactive! Average Bond Energies (kcal/mole) C-C 83 C=C 146 C-O 86 C=O 176 (aldehyde) 179 (ketone) “second bond” (more substituted sp 2 C )

PMR Spectrum R-C O H  9.5 Spectrometer Frequency? 1 ppm = 180 Hz  180 MHz

CMR Spectrum TMS CDCl 3

Carbonyl Reactivity O Nu 1) Nucleophilic Addition (B ü rgi-Dunitz Angle) O Nu O Rare for C=C 2) Nucleophilic Substitution of “Acid Derivatives” (A/D, like Aromatic) Chapter 18 L L ** H+H+ Chapter 19

Carbonyl Reactivity O H A B 3) Electrophilic Addition n (acid catalysis) O H (Easier than for C=C) O H 4) Allylic Rearrangement Ketone to Enol O H A A O H A O 5)  Substitution (electrophilic)  -proton Nu

Enols, Enolates and Enolization O >10 13 OH -3 O H O O 93 O O pK a 19 K enol formation 5  O H (ketone ~11 kcal below enol) (ketone  enol help from conjugation, H-bonding) (ketone >17 kcal above enol help from aromaticity) pK a = 10 (anion only ~ 13 kcal/mol above phenol) H B (base catalysis) Chapter 19 pK a ~11!

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RCOOH Reactions (sec. 20.7, pp ) OH RC O H substitution at  -C substitution at C R substitution at O R addition A Nu

OH RC O Fischer Esterification (sec. 20.8, p. 965) H + H + + RO H + Tetrahedral Intermediate (A/D, not pentavalent transition state) substitution at C OR starts with addition