Chemistry 125: Lecture 64 April 2, 2010 Carbonyl Compounds Overview This For copyright notice see final page of this file

Carbonyl Compounds This Chapters (268 pages!)

Mechanism for Acid-Catalyzed Hydrolysis of Acetal RO CH 2 + H HOH : : RO CH 2 + HROH RO-CH 2 + HO RO CH 2 + H First remove RO, and replace it by HO. HO RO CH 2 Now remove second RO, then H (from HO) + H : HO RO CH 2 + H RO=CH 2 + cation unusually stable; thus easily formed ROH H-O-CH 2 + O=CH 2 ROH RO CH 2 O H H  : Overall Transformation: H 2 O + Acetal Carbonyl + 2 ROH H+H+ (pp ) (hemiacetal) Good News: Much of this is review! e.g. secs

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) Chapter 16 O Nu O Rare for C=C 2) Nucleophilic Substitution of “Acid Derivatives” (A/D, like Aromatic) Chapter 18 L L ** H+H+ especially interesting for alcohol synthesis Nu = “R - ” (e.g. CH 3 Li) Nu = “H - ” (e.g. LiAlH 4 ) Secs ,16.16

HO Hydrate (gem-diol) RO Hemiacetal (  Acetal) RNH Carbinolamine (  Imine) HOSO 2 Bisulfide addition product NC Cyanohydrin etc. Secs 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 Chapter 19 H then Nucleophile

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!

RCOOH Reactions (Chapter 17) OH RC O H substitution at  -C substitution at C R substitution at O R addition A Nu

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