Organic Chemistry Reviews Chapter 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) O 3 2) Zn, CH 3 CO 2 H  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(OtBu 3 )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) O 3 2) Zn, CH 3 CO 2 H  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 HgSO 4 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: H 2 O  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  H 3 O + 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