THEME: Aldehydes and ketones of the aliphatic row. Aldehydes and ketones of the aromatic row. LECTURE № 7 associate. prof. Ye. B. Dmukhalska, assistant.

THEME: THEME: Aldehydes and Aldehydes and ketones of ketones of the the aliphatic rowaliphatic row. .

Aldehydes and ketones of Aldehydes and ketones of the the aaromaticromatic row row..

LECTURE № 7

associate. prof. Ye. B. Dmukhalska, assistant. I.I. Medvid

PlanePlane

1.1. Structure of aldehydes and ketones.Structure of aldehydes and ketones.

2.2. Nomenclature of aldehydesNomenclature of aldehydes

3.3. Nomenclature for ketones.Nomenclature for ketones.

4.4. Physical properties of aldehydes and ketonesPhysical properties of aldehydes and ketones

5.5. MMethodethodss of aldehydes and ketones obtaining of aldehydes and ketones obtaining..

6.6. Chemical properties of aldehydes and ketonesChemical properties of aldehydes and ketones

7. Unsaturated aldehydes and ketones.

8. Chemical properties of unsaturated aldehydes and ketones.

9.9. Dialdehydes and diketones.Dialdehydes and diketones.

10.10. Nomenclature of aromatic aldehydes and ketones.Nomenclature of aromatic aldehydes and ketones.

11.11. Methods of obtaining of aromatic aldehydes and ketones.Methods of obtaining of aromatic aldehydes and ketones.

12.12. Chemical properties of aromatic aldehydes and ketones.Chemical properties of aromatic aldehydes and ketones.

13.13. Some representatives of aromatic aldehydes and ketones.Some representatives of aromatic aldehydes and ketones.

AldehydeAldehyde - а carbonyl compound containing two - а carbonyl compound containing two hydrogen atoms or hydrogen and alkyl group. hydrogen atoms or hydrogen and alkyl group.

Example:Example:

Acetaldehyde Propionaldehyde Butyraldehyde

Benzaldehyde Phenylethanal

Structure of aldehydes and ketones.Structure of aldehydes and ketones.

When two alkyl groups are attached to the carbonyl, the When two alkyl groups are attached to the carbonyl, the compound is а compound is а ketoneketone. .

When two hydrogen atoms, or one hydrogen and one When two hydrogen atoms, or one hydrogen and one alkyl group are attached to the carbonyl, the compound is an alkyl group are attached to the carbonyl, the compound is an aldehydealdehyde..

Lewis structure Kekule structure Condensed structureLewis structure Kekule structure Condensed structure

R, R’ = Н or alkyl R, R’ = Н or alkyl

KetoneKetone - а carbonyl compound containing а pair of - а carbonyl compound containing а pair of cumulative double bonds, one of which is the cumulative double bonds, one of which is the carbonyl group, or ketone is а carbonyl compound carbonyl group, or ketone is а carbonyl compound containing two alkyl groups. containing two alkyl groups.

Example:

5–methylhexan-3-one 1-phenylethanone diphenylmethanone

The structure of formaldehyde, the simplest The structure of formaldehyde, the simplest member member of the class, is depicted below, along with of the class, is depicted below, along with its its experimental bond lengths and bond experimental bond lengths and bond angles.angles.

Bond lengths Bond angles Bond lengths Bond angles С = С = OO 1.203 Н — С — 1.203 Н — С — OO 121.8 121.8

С — Н 1.101 Н — С — Н 116.6С — Н 1.101 Н — С — Н 116.6

The actual structure is а composite of the normal octet The actual structure is а composite of the normal octet structure, СНstructure, СН22 =О and the polarized structure +СН =О and the polarized structure +СН22 - O - O¯̄, , which corresponds to а carbonium oxide. The composite which corresponds to а carbonium oxide. The composite structure may be represented with dotted line symbоlism structure may be represented with dotted line symbоlism which shows the partial charges in carbon and oxygen and which shows the partial charges in carbon and oxygen and the partial single bond character of the C –O bond.the partial single bond character of the C –O bond.

One physical consequence of this bond polarity is One physical consequence of this bond polarity is that carbonyl compounds generally have rather high that carbonyl compounds generally have rather high dipole moments. The experimental dipole moments dipole moments. The experimental dipole moments of formaldehyde and acetone are 2.27 D and 2.85 of formaldehyde and acetone are 2.27 D and 2.85 D, respectively.D, respectively.

The chemical consequences of this bond polarity will be are The chemical consequences of this bond polarity will be are become apparent during our discussions of the reactions of become apparent during our discussions of the reactions of carbonyl groups. We shall find that the positive carbon can carbonyl groups. We shall find that the positive carbon can react with bases and that much of the chemistry оf the react with bases and that much of the chemistry оf the carbonyl function corresponds to that of а relatively stable carbonyl function corresponds to that of а relatively stable carbonium ion.carbonium ion.

The ione pair electrons in the carbonyl oxygen have weakly The ione pair electrons in the carbonyl oxygen have weakly basic properties. In acidic solution, acetone acts as а Lewis basic properties. In acidic solution, acetone acts as а Lewis base and is protonated to а small but significant extent.base and is protonated to а small but significant extent.

In fact, acetone is а much weaker Lewis base than is In fact, acetone is а much weaker Lewis base than is water. The material is one half protonated only in water. The material is one half protonated only in 82% sulfuric acid. This corresponds to an 82% sulfuric acid. This corresponds to an approximate pKa for the conjugate acid of acetone of approximate pKa for the conjugate acid of acetone of - 7.2 (the approximate рKa of НО+ is - 1.7). - 7.2 (the approximate рKa of НО+ is - 1.7).

Nomenclature of aldehydesNomenclature of aldehydes The longest continuous chain that contains the group

provides the base name for aldehydes. The -e ending of the corresponding alkane name is replaced by -al, and substituents are specified in the usual way. It is not necessary to specify the location of the group in the name, since the chain must be numbered by starting with this group as C-1. The suffix -dial is added to the appropriate alkane name when the compound contains two aldehyde functions.

4,4-Dimethylpentanal5-Hexenal

2-Phenylpropanedial

When a formyl group (-CH=O) is attached to a ring, the ring name is followed by the suffix -carbaldehyde.

Cyclopentanecarbaldehyde 2-Naphthalenecarbaldehyde

Certain common names of familiar aldehydes are acceptable as IUPAC names. A few examples include

Formaldehyde(methanal)

Acetaldehyde(ethanal)

Benzaldehyde(benzenecarbaldehyde)

The IUPAC rules for naming aldehydes are as follows:The IUPAC rules for naming aldehydes are as follows:

1. Select as the parent carbon chain the longest chain 1. Select as the parent carbon chain the longest chain that includes the carbon atom of the carbonyl group.that includes the carbon atom of the carbonyl group.

2. Name the parent chain by changing the -е ending of 2. Name the parent chain by changing the -е ending of the corresponding alkane name to -al.the corresponding alkane name to -al.

3. Number the parent chain by assigning the number 1 3. Number the parent chain by assigning the number 1 to the carbonyl carbon atom of the aldehyde group.to the carbonyl carbon atom of the aldehyde group.

4. Determine the identity and location of any 4. Determine the identity and location of any substituents, and append this information to the front substituents, and append this information to the front of the parent chain name.of the parent chain name.

propanal 5-methylhexanalpropanal 5-methylhexanal

Nomenclature of ketones.

With ketones, the -e ending of an alkane is replaced by -one in the longest continuous chain containing the carbonyl group. The chain is numbered in the direction that provides the lower number for this group.

Although substitutive names of the type just described are preferred, the IUPAC rules also permit ketones to be named by functional class nomenclature. The groups attached to the carbonyl group are named as separate words followed by the word “ketone.” The groups are listed alphabetically.

3-Hexanone 4-Methyl-2-pentanone 4-Methylcyclohexanone

Ethyl propylketone

Benzyl ethyl ketone Divinyl ketone

A few of the common names acceptable for ketones in the IUPAC system are

(The suffix -phenone indicates that the acyl group is attached to a benzene ring.)

MMethodethodss of obtaining of obtaining of of aldehydes and ketonesaldehydes and ketones..1. Ozonolysis of alkenes. This cleavage reaction is more often

seen in structural analysis than in synthesis. The substitution pattern around a double bond is revealed by identifying the carbonyl-containing compounds that make up the product. Hydrolysis of the ozonide intermediate in the presence of zinc (reductive workup) permits aldehyde products to be isolated without further oxidation.

2. 2. Hydration of alkynes (Kucherov reaction). Reaction occurs by way of an enol intermediate formed by Markovnikov addition of water to the triple bond.

3. Friedel-Crafts acylation of aromatic compounds. Acyl chlorides and carboxylic acid anhydrides acylate aromatic rings in the presence of aluminum chloride. The reaction is electrophilic aromatic substitution in which acylium ions are generated and attack the ring.

4. Oxidation of primary alcohols to aldehydes. Pyridinium dichromate (PDC) or pyridinium chlorochromate (PCC) in anhydrous media such as dichloromethane oxidizes primary alcohols to aldehydes while avoiding overoxidation to carboxylic acids.

5. Oxidation of secondary alcohols to ketones. Many oxidizing agents are available for converting secondary alcohols to ketones. PDC or PCC may be used, as well as other Cr(VI)-based agents such as chromic acid or potassium dichromate and sulfuric acid.

6. 6. HydrolysisHydrolysis of of heminal heminals s dyhalohendyhalohenderivaties. Dderivaties. During uring hydrolysis hydrolysis of hem-of hem-ddiihalohenalkanhalohenalkaneses with atoms with atoms of of halogenhalogen at at primary atomprimary atom of of carbon formed aldehydes, while the carbon formed aldehydes, while the secondary – secondary – kketonesetones::

7. 7. Pyrolysis salts Pyrolysis salts of of carboxylic acidcarboxylic acidss : salt mixture : salt mixture of of formic acid formic acid and other acid – aldehydeand other acid – aldehyde. . Salts of other acids – Salts of other acids – kketonesetones..

CH3 - C

H - C

O

O

OCa

O

CH3 - C + CaCO3

O

H

300 C

CH3 - CH2 - C

CH3 - C

O

O

=_

O

_Ca

=_

_

O

CH3 - CH2 - C - CH3 + CaCO3t

O

=

8. Oxosynthesis. Interaction of alkenes 8. Oxosynthesis. Interaction of alkenes with carbone (II) oxide, at the higher with carbone (II) oxide, at the higher temperature, pressure and presence of temperature, pressure and presence of catalyst. catalyst.

6. Chemical properties of aldehydes and ketones 6. Chemical properties of aldehydes and ketones

The reactions of aldehydes and ketones can be The reactions of aldehydes and ketones can be divided into the following types:divided into the following types:

Keto – enol equilibrium.Keto – enol equilibrium. Aldehydes and ketones exist in Aldehydes and ketones exist in solution as an equilibrium mixture of two isomeric forms, the solution as an equilibrium mixture of two isomeric forms, the keto form and the enol (from -ene + -ol, unsaturated alcohol) keto form and the enol (from -ene + -ol, unsaturated alcohol) form. For simple aliphatic ketones, there is very little of the form. For simple aliphatic ketones, there is very little of the enol form present at equilibrium, as shown by the following enol form present at equilibrium, as shown by the following examples.examples.

1. Reactions of reduction and oxidation

1). Reduction to hydrocarbons. Two methods for converting carbonyl groups to methylene units are the Clemmensen reduction (zinc amalgam and concentrated hydrochloric acid) and the Wolff–Kishner reduction (heat with hydrazine and potassium hydroxide in a highboiling alcohol).

2). Reduction to alcohols . Aldehydes are reduced to primary alcohols, and ketones are reduced to secondary alcohols by a variety of reducing agents. Catalytic hydrogenation over a metal catalyst and reduction with sodium borohydride or lithium aluminum hydride are general methods.

3). Reactions of aldehyde oxidation3). Reactions of aldehyde oxidation

With Tollens’ reagent – “silver mirror” With Tollens’ reagent – “silver mirror” reaction.reaction.

With Fehling reagent: after heating red precipitate of copper (I) oxide formed.

Reaction of “silver mirror” and reaction with Fehling reagent used for identification of aldehyde group.

Aldehydes are readily oxidized to carboxylic acids by a number of reagents, including those based on Cr(VI) in aqueous media.

4). Oxidation of ketones4). Oxidation of ketones Only in the presence of strong oxidant Only in the presence of strong oxidant

(potassium permanganate or bichromate). As a (potassium permanganate or bichromate). As a result mixture of acids formed.result mixture of acids formed.

2. Reactions of nucleophilic addition (A2. Reactions of nucleophilic addition (ANN))1). 1). Addition of Grinjar’s reagents and organolithium

compounds . Products of additions be carbonyl group formed which hydrolyzed at the presence of diluted mineral acids to alcohols.

2). Cyanohydrine (α-hydroxinitrile) formation. Reaction is catalyzed by cyanide-ion. Cyanohydrins are useful synthetic intermediates;cyano-group can be hydrolyzed to -CO2H or reduced to -CH2NH2.

Reaction goes at the presence of base

4). 4). Hydratation. Aldehydes form hydrates at the dissolution in water. Hydrates are not stable in water

5). 5). Acetal formation. Reaction is acid-catalyzed. Equilibrium constant normally favorable for aldehydes, unfavorable for ketones. Cyclic acetals from vicinal diols form readily.

6) Reaction with sodium hydrosulfite.6) Reaction with sodium hydrosulfite.Aldehydes give this reaction and ketones with CH3-CO-Aldehydes give this reaction and ketones with CH3-CO-

group.group.

3. Accession- elimination reactions1). Reaction with primary amines. Isolated products are imines (Schiff’s

base). A carbinolamine intermediate is formed, which undergoes dehydrates to imine.

2). Reaction with secondary amines. Isolated product is an enamine. Carbinolamine intermediate cannot dehydrates to a stable imine.

3). 3). The Wittig reaction. Reaction of a phosphorus ylide with aldehydes and ketones leads to the formation of an alkene. A versatile method for the preparation of alkenes.

4) Interaction with ammonium.4) Interaction with ammonium.Aldehydes with ammonium give aldiminesAldehydes with ammonium give aldimines

5) Interaction with hydroxylamine5) Interaction with hydroxylamine – – aldehydes give aldoxymes, ketones – ketoxymes.

6) Interaction with hydrazine and its 6) Interaction with hydrazine and its derivativesderivatives

4. Reactions of condensation4. Reactions of condensation1). 1). Aldol condensationAldol condensation

As noted earlier, an aldehyde is partially converted to its enolate anion by bases such as hydroxide ion and alkoxide ions. This type of condensations is character for aldehydes which have hydrogen atoms at the α-carbon atom.

In a solution that contains both an aldehyde and its enolate ion, the enolate undergoes nucleophilic addition to the carbonyl group.

Product of aldol addition at the heating eliminates water and form α, β-unsaturated aldehydes (crotone condensation) :

The alkoxide formed in the nucleophilic addition step then abstracts a proton from the solvent (usually water or ethanol) to yield the product of aldol addition. This product is known as an aldol because it contains both an aldehyde function and a hydroxyl group (ald+ol=aldol). An important feature of aldol addition is that carbon–carbon bond formation occurs between the -carbon atom of one aldehyde and the carbonyl group of another. This is because carbanion (enolate) generation can involve proton abstraction only from the α-carbon atom.

Ketones also give aldol condensation but at Ketones also give aldol condensation but at the more hard conditions the more hard conditions

In a strong acidic medium ketones give crotone condensation with formation of unsaturated ketones.

2). Condensation by Tishchenko2). Condensation by Tishchenko

The Tishchenko The Tishchenko rreaction is a disproportionation reaction that eaction is a disproportionation reaction that allows the preparation of esters from two equivalents of an allows the preparation of esters from two equivalents of an aldehyde. aldehyde.

Mechanism of the Tishchenko Mechanism of the Tishchenko condensation:condensation:

5. Reactions by the 5. Reactions by the αα-carbone atom-carbone atom

Halogenation. Iodoformic test.Halogenation. Iodoformic test.

CH3 - CO

CH3

+ J2 + NaOHNaOH

CH3 - CO

CJ3

CH3 - CO

ONa+ CHJ2

6. Reactions of polymerization.6. Reactions of polymerization.In the presence of sulfate acid.In the presence of sulfate acid.

7. Unsaturated aldehydes and ketones.The carbonyl group withdraws electron density from the double bond, and both the carbonyl carbon and the carbon are positively polarized. Their greater degree of charge separation makes the dipole moments of ,-unsaturated carbonyl compounds significantly larger than those of comparable aldehydes and ketones.

α,β-Unsaturated carbonyl compounds contain two electrophilic sites: the carbonyl carbon and the carbon atom that is β to it. Nucleophiles such as organolithium and Grignard reagents and lithium aluminum hydride tend to react by nucleophilic addition to the carbonyl group, as shown in the following example:

8. Chemical properties of unsaturated aldehydes andketones.

1). Conjugate accession to α,β-unsaturated carbonyl compounds . The β-carbon atom of an α,β-unsaturated carbonyl compound is electrophilic; nucleophiles, especially weakly basic ones, yield the products of conjugate addition to α,β- unsaturated aldehydes and ketones.

2). With cyanic acid – cyanehydrines 2). With cyanic acid – cyanehydrines formform

3). Crotone condensation

4). Robinson annulation. A combination of conjugate addition of an enolate anion to an α,β- unsaturated ketone with subsequent intramolecular aldol condensation.

5). Conjugate addition of organocopper compounds. The principal synthetic application of lithium dialkylcuprate reagents is their reaction with α,β- unsaturated carbonyl compounds. Alkylation of the β-carbon occurs.

Dialdehydes and diketonesDialdehydes and diketonesDialdehDialdehyyddeses to include compounds that contain two to include compounds that contain two aldehaldehyyddicic group groupss, to diketones - two keto groups. The , to diketones - two keto groups. The simplest representative dialdehsimplest representative dialdehyyddeses is is glyoxglyoxal or etal or ethhandial andial and diketones - diaand diketones - diaccetyl or butandionetyl or butandion..

GlyoxalGlyoxal is an organic compound with the is an organic compound with the formula formula OCHCHO. This yellow colored liquid is OCHCHO. This yellow colored liquid is the the smallest dialdehyde (two aldehyde smallest dialdehyde (two aldehyde groups). Commercial glyoxal is prepared either by the gas phase groups). Commercial glyoxal is prepared either by the gas phase oxidation of ethylene glycol in the presence of a silver or copper catalyst oxidation of ethylene glycol in the presence of a silver or copper catalyst or by the liquid phase oxidation of acetaldehyde with nitric acid. or by the liquid phase oxidation of acetaldehyde with nitric acid.

DiacetylDiacetyl (IUPAC systematic name: (IUPAC systematic name: butanedionebutanedione or or 2,3-butanedione2,3-butanedione) is a ) is a natural byproduct of fermentation. It is a natural byproduct of fermentation. It is a

vicinal diketone (two C=O groups, side-by-side) with the vicinal diketone (two C=O groups, side-by-side) with the molecular formula Cmolecular formula C44HH66OO22. Diacetyl occurs naturally in . Diacetyl occurs naturally in alcoholic beverages and is added to some foods to impart a alcoholic beverages and is added to some foods to impart a buttery flavor.buttery flavor.

CCO

O

HH

O O

CH3 C C CH3

1) Kaniccarro reaction – intermolecular 1) Kaniccarro reaction – intermolecular oxidation reduction.oxidation reduction.

2) Interaction with hydroxylamine2) Interaction with hydroxylamine

Nomenclature of aromatic aldehydes Nomenclature of aromatic aldehydes and ketonesand ketones

Aromatic aldehydes and ketones divided on two groups: Aromatic aldehydes and ketones divided on two groups: 1). Aldehydes which have aldehyde group in benzene 1). Aldehydes which have aldehyde group in benzene

ring; ring; ββ 2). Aldehydes which have aldehyde group in side chaine.2). Aldehydes which have aldehyde group in side chaine.

Aromatic ketones divided on two groups:Aromatic ketones divided on two groups: 1) truly aromatic (carbonyl group connected 1) truly aromatic (carbonyl group connected

with two aromatic radicals);with two aromatic radicals); 2) fatty aromatic (carbonyl group connected 2) fatty aromatic (carbonyl group connected

with one aromatic and one alifatic radical.with one aromatic and one alifatic radical.

Methods of obtainingMethods of obtaining 1). Oxidation of aromatic hydrocarbons.1). Oxidation of aromatic hydrocarbons.

2) Hattermane-Koch (formylation reaction).2) Hattermane-Koch (formylation reaction).

3). Fridel-Krafts reaction (acylation).3). Fridel-Krafts reaction (acylation).

Chemical propertiesChemical properties1). Interaction with ammonium (in the ratio of 1). Interaction with ammonium (in the ratio of

3:2).3:2).

2). Kaniccarro reaction. In the presence of strong base 2). Kaniccarro reaction. In the presence of strong base or concentrated alkali solution ( reaction of or concentrated alkali solution ( reaction of disproportionation).disproportionation).

Mechanism of reaction:Mechanism of reaction:

3). Reactions of condensation.3). Reactions of condensation. In the presence of bases aromatic aldehydes In the presence of bases aromatic aldehydes

gives condensations with aldehydes, ketones, gives condensations with aldehydes, ketones, anhydrides of carboxylic acids. anhydrides of carboxylic acids.

Perkin's condensation:Perkin's condensation:

Mechanism:

Benzoic condensationBenzoic condensation Condensation of two molecules of aldehydes in the Condensation of two molecules of aldehydes in the

presence of cyanic acids salts with formation of presence of cyanic acids salts with formation of aromatic aromatic αα-oxiketones (benzoines).-oxiketones (benzoines).

Mechanism of benzoic condensation:

4). Halogenation.4). Halogenation.

5). Electrophilic substitution5). Electrophilic substitution

Some representatives of Some representatives of aromatic aldehydes and aromatic aldehydes and

ketonesketones1). Benzophenone – C6H5-CO-C6H5. 1). Benzophenone – C6H5-CO-C6H5.

Obtaining:Obtaining:

2). Quinones2). Quinones

Obtaining:

Thank you for attention!