Ald&KetoneII (Origin)

Reactions of aldehydes and ketones:oxidationreductionnucleophilic addition

Aldehydes are easily oxidized, ketones are not.Aldehydes are more reactive in nucleophilic additions than ketones.

alkanealcoholaldehydeketonecarboxylic acidoxidationreductionreductionadditionproductnucleophilicaddition

nucleophilic addition to carbonyl:

Mechanism: nucleophilic addition to carbonyl1)2)

Mechanism: nucleophilic addition to carbonyl, acid catalyzed 1)

2)

3)

Aldehydes & ketones, reactions:OxidationReductionAddition of cyanideAddition of derivatives of ammoniaAddition of alcoholsCannizzaro reaction Addition of Grignard reagents8) (Alpha-halogenation of ketones)9) (Addition of carbanions)

1) OxidationAldehydes (very easily oxidized!)

CH3CH2CH2CH=O + KMnO4, etc. CH3CH2CH2COOH carboxylic acid

CH3CH2CH2CH=O + Ag+ CH3CH2CH2COO- + Ag Tollens test for easily oxidized compounds like aldehydes. (AgNO3, NH4OH(aq)) Silver mirror

Ketones only oxidize under vigorous conditions via the enol.

b) Methyl ketones:

test for methyl ketonesYellow ppt

2) Reduction:To alcohols

Then + H+ alcohol

Reductionb) To hydrocarbons

3) Addition of cyanide

1)

2)

Cyanohydrins have two functional groups plus one additional carbon. Nitriles can be hydrolyzed to carboxylic acids in acid or base:

4) Addition of derivatives of ammonia

1)

2)

3)

melting points of derivativesketonesbpsemi-2,4-dinitro- oxime carbazonephenylhydrazone

2-nonanone195119 56

acetophenone202199 24060

menthone209189 14659

2-methylacetophenone214205 15961

1-phenyl-2-propanone216200 15670

propiophenone220174 19154

3-methylacetophenone220198 20755

isobutyrophenone222181 16394

5) Addition of alcohols

Cannizzaro reaction. (self oxidation/reduction) a reaction of aldehydes without -hydrogens

Formaldehyde is the most easily oxidized aldehyde. When mixed with another aldehyde that doesnt have any alpha-hydrogens and conc. NaOH, all of the formaldehyde is oxidized and all of the other aldehyde is reduced.Crossed Cannizzaro:

7) Addition of Grignard reagents.

1)

2)

#3 synthesis of alcohols. Used to build larger molecules from smaller organic compounds.

Aldehydes & ketones, reactions:OxidationReductionAddition of cyanideAddition of derivatives of ammoniaAddition of alcoholsCannizzaro reaction Addition of Grignard reagents8) (Alpha-halogenation of ketones)9) (Addition of carbanions)

Planning a Grignard synthesis of an alcohol:The alcohol carbon comes from the carbonyl compound.The new carbon-carbon bond is to the alcohol carbon.New carbon-carbon bond

The Grignard Song (sung to the tune of America the Beautiful)Harry Wasserman

The carbonyl is polarized,the carbon end is plus.A nucleophile will thus attackthe carbon nucleus.

The Grignard yields an alcoholof types there are but three.It makes a bond that correspondsfrom C to shining C.

or

ROHRX-C=ORMgXROHHXMgox.H2Olarger alcohol

Stockroom:alcohols of four-carbons or less:(methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, 2-methyl-1-propanol.)benzenecyclohexanolany needed inorganic reagents or solvents.

Grignard synthesis of 4-methyl-2-pentanol from alcohols of four-carbons or less:Step one: determine the carbonyl compound and Grignard reagent that you would use: CH3CH3CHCH2CHCH3 OHH2O CH3CH3CHCH2MgBr + CH3CH=OStep two: show the syntheses of the Grignard reagent and the carbonyl compound from alcohols

CH3 HBr CH3 Mg CH3CH3CHCH2OH CH3CHCH2Br CH3CHCH2MgBr

H+

K2Cr2O7 CH3CH3CH2OH CH3CH=O CH3CHCH2CHCH3 special cond. OH4-methyl-2-pentanol

2-phenyl-2-propanol

1-methylcyclohexanol

cyclohexylmethanol

aldehydeRCOOHketoneRORalkynealkeneRHRXROHAlcohols are central to organic syntheses

ROHRX-C=ORMgXROHHXMgox.H2Olarger alcohol

Using the Grignard synthesis of alcohols we can make any alcohol that we need from a few simple alcohols. From those alcohols we can synthesize alkanes, alkenes, alkynes, alkyl halides, ethers, aldehydes, ketones, carboxylic acids

eg. Outline all steps in a possible laboratory synthesis of 3-methyl-1-butene from alcohols of four carbons or less.

CH3CH3CHCH=CH2

Retrosynthesis:alkenes, syntheses:1. Dehydrohalogenation of an alkyl halide2. Dehydration of an alcohol3. Dehalogenation of a vicinal dihalide4. Reduction of an alkyne

Methods 3 & 4 start with compounds that are in turn made from alkenes.

Dehydration of an alcohol?

CH3 H+CH3CHCHCH3 yields a mixture of alkenes OH

CH3 H+CH3CHCH2CH2-OH yields a mixture of alkenes

E1 mechanism via carbocation!

Dehydrohalogenation of an alkyl halide?

CH3 KOH(alc)CH3CHCHCH3 yields a mixture of alkenes Br

CH3 KOH(alc) CH3CH3CHCH2CH2-BrCH3CHCH=CH2

only product E2 mechanism, no carbocation, no rearrangement

CH3 HBr CH3CH3CHCH2CH2-OH CH3CHCH2CH2-Br

1o alcohol, SN2 mechanism, no rearrangement!

CH3 KOH(alc) CH3CH3CHCH2CH2-BrCH3CHCH=CH2

Use the Grignard synthesis to synthesize the intermediate alcohol from the starting materials.

CH3 PBr3 CH3 Mg CH3 CH3CHCH2-OH CH3CHCH2Br CH3CHCH2MgBr

K2Cr2O7CH3OH H2C=O special cond. H2O

CH3 CH3CHCH2CH2-OH

HBr

CH3 KOH(alco) CH3CH3CHCH=CH2CH3CHCH2CH2-Br

Notes on Exam I:Given the structures, be able to name aldehydes/ketones using either common or IUPAC names.Be able to outline all steps in the mechanisms: nucleophilic addition & acid catalyzed nucleophilic addition.Be able to draw structures for the organic products of the reactions of aldehydes/ketones.Be able to outline possible laboratory syntheses of aldehydes/ketones and Grignard syntheses of alcohols, etc.Be able to match structures with their IR spectra.Be able to predict the 1H-nmr spectrum, given the structure.Given the 1H-nmr spectrum and formula, be able to draw the structure of the compound.