CHAPTER 18 KETONES AND ALDEHYDES

PROBLEMS 1,3,4,6,7-11,12C15,17,19,20,24,27A,C,31,33,34A,B,D,35A,C,39A-E,45A,B,51A-D,61,65,66

CARBONYL COMPOUNDS

O

CONTAIN A C=O GROUP

IMPORTANT MEMBERS

R H

O

ALDEHYDE

R R

O

R OH

O

KETONE CARBOXYLIC ACID

R OR

O

R NH2

O

R Cl

O

ESTER AMIDE ACID CHLORIDE

CHAPTER 18 CHAPTER 20 CHAPTER 21

STRUCTURE OF THE CARBONYL GROUPDIPOLE MOMENT

C O

H

E+

:NUC

BASE:

CHAPTER 22NOTE: NUC ATTACKOCCURS AT PI ORBITALNOT BACKSIDE OF C=O

NOMENCLATURE

KETONES: ALKANONE, MUST NUMBER TO GIVE CARBONYL LOWEST NUMBER

IUPAC SYSTEM

O

12

34

56

5,5-DIMETHYL-3-HEXANONE

(5,5-DIMETHYLHEXAN-3-ONE)

O

OH

4-HYDROXY-2-BUTANONE

BUT

O

OH

O

3-OXOBUTANOIC ACID

ALDEHYDES - IUPACALDEHYDE CARBON IS NUMBERED “ONE”

O

H12

34

5

6

3-ISOPROPYLHEXANAL

O

H

FORMYLCYCLPENTANE

O

H

O

1

2345

6

3-ISOPROPYL-5-OXOHEXANAL

ALDEHYDES COMMON NAMESSTEM PLUS ALDEHYDE

R-CHO R-CO2H

HCHO

FORMALDEHYDE

HCO2H

FORMIC ACIDFORMICA - ANTS

CH3CHOACETUM - SOUR

CH3COOHACETALDEHYDE ACETIC ACID

CH3CH2CHO CH3CH2CO2H

PROPIONALDEHYDE PROTOS PION - FIRST FAT PROPIONIC ACID

CH3CH2CH2CHO CH3CH2CH2CO2H

BUTRYM - BUTTERBUTYRALDEHYDEBUTYRIC ACID

CH3CH2CH2CH2CH2CHO

CAPROALDEHYDE CAPER - GOAT

CH3CH2CH2CH2CH2CO2H

CAPROIC ACID

Ketones common namesRADICAL SYSTEM

NAME RADICALS IN ALPHA ORDER + KETONE

Me

O

Methyl phenyl ketone

STEM CONVENTION - ALKYL METHYL KETONES

NAME STEM OF ALKYL GROUP ACCORDING tTO THE PREVIOUS SLIDE FOLLOWED BY PHENONE

ACETOPHENONE

Write the structure for butyrophenoneCH3CH2CH2

O

Ph

SPECTROSCOPY OF ALDEHYDES AND KETONES

1. IR READ PAGE 780 2. NMR Read pp 780-782

MASS SPECTRA

H3CH2C

CH3

O

ALPHA CLEAVAGE

H3C

O CH3CH2+

H2C

CH3

O

CH3 +

H3C

O

H2C

CH3

O

TWO ACYLIUM IONS ARE ABOUT THE SAME

ETHYL RADICAL IS MORE STABLE THAN METHYL

THEREFORE

RADICAL STABILITY CONTROLS FRAGMENTATION

McLAFFERTY REARRANGEMENT

CHARACTERISTICS

CLEAVAGE OF ALPHA-BETA CARBON (WITH RESPECT TO C=OOCCURS

A GAMMA HYDROGEN IN THE PARENT CATION-RADICAL IS TRANSFERRED TO CARBONYL OXYGEN ATOM INTRAMOLECULARLY

A STABLE ALKENE IS LOST AND A NEW RESONANCE STABILIZED CATION RADICAL(ENOL) IS FORMED

NOTE- THE PARENT CATION, STABLE ALKENE LOST, AND THE NEW STABILIZED CATION RADICAL HAVE EVEN MOLECULAR MASSES

EXAMPLE

H3C CH2

H2C

CH2

O H

H3C CH2

OH

even mw

+ CH2=CH2

Even mw

Even mw

MECHANISM OF McLAFFERTY

REARRANGEMENT

C

O

H3C CH2

CH2

CH2

H

C

OH

H3C CH2

H2CCH2+

THERE IS A NICE SUMMARY ON BOTTOM OF PAGE 784. LOOK IT OVER.

REVIEW OF SYNTHESIS OF KETONES AND ALDEHYDES

OXIDATION OF ALCOHOLS - LAST SEMESTER

OZONOLYSIS OF ALKENES - LAST SEMESTER

FRIEDEL ACEYLATION AND GATTERMAN KOCHWILL BE COVERED ON NEXT TEST

HYDRATION OF ALKYNES - LAST SEMESTER

HYDROBORATION AND OXIDATION - LAST SEMESTER

1,3-DITHIANE METHODPREPARATION OF 1,3-DITHIANES

H H

O

Dream up a mechanism for this reaction.

HS-CH2CH2CH2SH

H+S SH H

WHY HIGH ACIDITY OF 1,3-DITHIANES?

Old explanation

S C S=CVacant d-orbitals

Modern explanation

RECALL

A-B has bonding mo and non-bonding mo

A B

C S CThus

neg charge

S SH H

S SH

-n-BuLi

Synthetic Methodology1. Deprotonation of 1,3-dithiane with n-BuLi

2. Alkylation or dithane anion (SN2)

3. Hydrolysis of alkylated dithiane.

R must be methyl or primaryR can not be Ar, CH2=CH

S S

H H

n-BuLiS S

H Li

S S

H Li+ R-X

S S

H R

SN2

S S

H R

H+ / HgCl2

H R

O

Preparation of Ketones via 1,3-dithianes

INSTEAD OF STOPPING AT MONO-ALKYLATION STEP, ONE CAN REPEAT PROCESS USING THE REMAINING ACIDIC HYDROGEN ATOM

H+

HgCl2R' R

OS S

H R

R'XS S

R' R

UMPOLUNG OF C=O

H R

O

electrophilic carbonyl

S S

H

-

nucleophilic "masked" carbonyl

"acyl anion equivalent"

Retrosynthetic analysisPrepare 1-phenyl-2-pentanone

PhO

From

H H

O

S SPhH2C CH2CH2CH3 hydrolysis

S SPhH2C H

CH3CH2CH2Br

n-BuLi

S SH H

n-BuLi

PhCH2B

HSCH2CH2CH2SH