Organic Chemistry ReviewsChapter 16

Cindy Boulton

April 5, 2009

Ketones and Aldehydes Carbonyl Group:

C=O Ketone

Two carbons attached Aldehyde

One carbon attached One hydrogen attached

Aldehydes Nomenclature

Drop –e from (-ane) ending Add –al

Formaldehyde Two hydrogens attached Methanal Formyl Group: carbonyl group with one hydrogen

Acetaldehyde One methane group attached and one hydrogen

attached Ethanal Acetyl Group: carbonyl group with the methane group

attached Benzaldehyde

Benzene with a formyl group attached Oil of bitter almond

Ketone Nomenclature

Drop –e from (-ane) ending Add –one Identify the carbon that is the carbonyl group

Acetone 2-propane Dimethyl ketone Two methly groups attached to a carbonyl group

2-butanone Methyl ethyl ketone (MEK) Methyl and ethyl groups attached to a carbonyl

group

Spectroscopy IR Spectroscopy

C=O: 1700 Big absorption depends on symmetry of the two carbon

groups attached to the carbonyl group

C-13 NMR C=O: 180

H-1 NMR (C=O)-H: 9-11

Hydrogen near the carbonyl group will shift downfield

Physical Properties Carbonyl bond is polar

Partial positive carbon Partial negative oxygen Nucleophile will attack the partial positive carbon

Boiling and Melting Points Higher due to hydrogen bonding

Solubility in Water With 4 carbons or less, it is soluble in water due to

hydrogen bonding

Synthesis of Aldehydes Ozonolysis of Alkenes

Reactants: 1) O3 2) Zn, CH3CO2H The alkene double bond is broken and two separate

carbonyl groups are formed Either ketones or aldehydes depending on the groups

attached to the alkene Oxidation of Primary Alcohols

PCC or Organic Chromic Acid without water If in the presence of water, the primary alcohol will be

oxidized to carboxylic acid Reduction of Acyl Chloride, Esters, and Nitriles

Al(OtBu3)H and DIBAL-H are used Friedel Craft Formylation

Forms aromatic aldehyde by adding a formyl group to a benzene ring

Synthesis of Ketones Ozonolysis of Alkenes

Reactants: 1) O3 2) Zn, CH3CO2H The alkene double bond is broken and two

separate carbonyl groups are formed Either ketones or aldehydes depending on the groups

attached to the alkene Oxidation of Secondary Alcohols

PCC or Organic Chromic Acid without water Aqueous Chromic Acid

The alcohol will not be oxidized into carboxylic acid Friedle Crafts Acylation

Forms aromatic ketone by adding a acyl group to a benzene ring

Synthesis of Ketones From Nitriles

A nitrile (C≡N) reacts with an organic metallic and hydromium

Ketone and Ammonium is formed Mechanism:

The carbanion from the organic metallic will react with the polar carbon in the nitrile

Addition of Water to Alkynes Alkyne reacts with water and HgSO4 to form an alkene

with a hydroxyl group attached, an enol Keto-enol tautomerization Keto is formed because the carbonyl group is more stable

Acyl Chlorides and Lithium Dialkyl Cuprates Forms a ketone by the carbanion reacts with the partial

positive carbon in the carbonyl group

Nucleophilic Addition NOT substitution Reactions to ketones or aldehydes Ketones are less reactive than aldehydes

Due to sterics and electronics Ketones are stablized by two alkyl groups

donating electron density Aldehydes are less stable with only one alkyl

group and are more susceptible Carbonyl group is polar

Partial positive carbon Partial negative oxygen

Nucleophilic Addition General Reaction

Nucleophile reacts with the partial positive in the carbonyl group

The carbonyl double bond is broken Hydrogen is added to the oxygen forming an alcohol Addition reaction, NOT substitution, because there is no

leaving group Two Mechanisms: 1) Strong Nucleophile

First, nucleophile attacks partial positive carbon in carbonyl group

Then, oxygen gains a hydrogen from a hydride source 2) Acid Catalyzed

First, hydrogen reacts with the partial negative oxygen Then, nucleophile attacks the carbon

Hydrates Addition of water to Aldehyde

Forms an aldehyde hydrate with two hydroxyl groups attached

Aldehyde is oxidated More reactive

Addition of water to Ketone Forms a ketone hydrate with two hydroxyl groups

attached Ketone is oxidated Less reactive, ketone is greatly favored

Hydrate Mechanisms Nucleophile: H2O

Nucleophile attacks first the partial positive carbon Hydrogen is removed from the water and reacts with the

negative oxygen from the carbonyl group Nucleophile: -OH

Basic Hydroxyl as the nucleophile attacks the partial positive

carbon A hydrogen is removed from a water in solution and reacts

with the negative oxygen from the carbonyl group Acid Catalyzed

Acidic H3O+ donates a hydrogen to the partial negative oxygen Water attacks the carbon from the carbonyl group, the

hydrogen is removed by another water Hydrate is more stable only if it has electron

withdrawing groups attached

Hemiacetal Carbonyl group reacts with an alcohol Forms a carbon with a hydroxyl group attached and an

ester bond attached Acetal

Carbonyl group reacts with 2 alcohols and a proton source Forms a carbon with 2 ester groups attached

Cyclic acetals Carbonyl reacts with a dihydroxyl group Carbon becomes bonded with 2 ester bonds connected Acts as a protecting group on the carbonyl carbon

Chelate Affect The two alcohols bound to the carbon will remain strongly

attached If one of the alcohols becomes disconnected, it will not be

a free alcohol and can easily reattached

Thioacetals/Raney Nickle Reduction Ketone reacts with 2 R-SH Forms a carbon with two alkyl groups attached

and two sulfur-alkyl groups attached Reacts with Raney Nickle, a hydride source, which

replaces the sulfur-alkyl groups with hydrogen to form an alkane

Ammonia Derivatives Carbonyl reacts with a primary amine, which

contains 2 hydrogens The 2 hydrogens react with the oxygen from

the carbonyl group to from water The remaining nitrogen reacts with the carbon Forms an Imine (C=N-R) Ammonia Derivatives:

2,4-DNP: 2,4-Dinitrophenyl Hydrazine Wolff-Kishner reduction:

Wolff derivative is reduced to an alkane and nitrogen gas

Oximes and Semicarbazane reactions

Hydrogen Cyanide (H-C≡N) Acid Catalyzed Reaction:

Carbonyl group reacts with Hydrogen Cyanide Partial negative oxygen reacts with hydrogen Negative carbon from C≡N reacts with positive

carbon in carbonyl group Forms Cyanohydrine

Wittig Reaction Carbonyl group reacts with Ylide to form an

alkene and phosphoryl Ylide Formation:

Phosphine (Phosphorous with 3 phenyl groups attached) acts as a nucleophile on an alkyl halide

Phosphorous forms a double bond with the carbon which has two alkyl groups attached (carbene)

Reaction: The =O from the carbonyl group and the carbene

from the Ylide are swapped forming an alkene and phosphoryl

Baeyer Villiger Ketone reacts with a peroxy acid to form an

ester and a carboxylic acid Migratory Aptitude Series

More basic group More electron density become more free to

migrate