(ALKANALS & ALKANONES) ALDEHYDES & KETONES (ALKANALS & ALKANONES)

alkane alcohol reduction reduction aldehyde ketone addition product nucleophilic addition oxidation carboxylic acid

Aldehydes and Ketones Some common classes of carbonyl compounds Aldehydes and ketones are characterized by the the carbonyl functional group (C=O). Some common classes of carbonyl compounds

Carbonyl Structure Carbon is sp2 hybridized. C=O bond is shorter, stronger, and more polar than C=C bond in alkenes.

Naming Aldehydes and Ketones Aldehydes are named by replacing the terminal -e of the corresponding alkane name with –al The parent chain must contain the CHO group The CHO carbon is numbered possible minimum number.

Naming Ketones Replace the terminal -e of the alkane name with –one Parent chain is the longest one that contains the ketone group Numbering begins at the end nearer the carbonyl carbon

Solubility Good solvent for alcohols. Lone pair of electrons on oxygen of carbonyl can accept a hydrogen bond from O-H or N-H. Acetone and acetaldehyde are miscible in water.

Preparation of Aldehydes & ketones 1] Oxidation of 1& 2 alcohol : C2H5OH [O] CH3CHO [O] CH3COOH CH3CHOHCH3 [O] CH3COCH3 isopropanol

Physical Properties Boiling Points More polar, so boiling point higher than corresponding alkane or ether. Absence of H-bond, so boiling point lower than corresponding alcohol.

2- Dehydrogenation A- 10 Alcohol gives aldehydes: CH3CH2OH Cu/ 350 oC CH3CHO + H2 B- Secondary Alcohol gives Ketones: OH O CH3CHCH3 Cu/350oC CH3CCH3 + H2

3] Ozonolysis of alkenes:

4- Hydration of Alkynes

5- Hydrolysis of gem-dihalides by the action of base: A) If dihalogen are terminal: CH3CHCl2 H2O/NaOH CH3CH(OH)2 H2O CH3CHO acetaldehyde B) If dihalogen aren’t terminal: CH3CCl2CH3 H2O/NaOH CH3COCH3 acetone

6-From Acid Chlorides: Rosenmund reduction R-CO-Cl H2/Pd R-CHO +HCl CH3COCl H2/Pd CH3CHO + HCl

Chemical Reactions

1] Reactions with Grignard reagent:

Nucleophilic addition to carbonyl:

Addition of Alcohol In presence of dry HCl aldehydes and ketones react with two equivalent of alcohols to form acetals and ketals

Acetal Formation Acetals are geminal diethers- structurally related to hydrates, which are geminal diols. hydrate (gem-diol) acetal (gem-diether) aldehyde hemi-acetal ketal (gem-diether) ketone hemi-ketal

4-Reduction of Aldehydes/Ketones Hydrogenation

B- Condensation reaction: 1- Hydroxylamine: -C=O + NH2OH -C=NOH + H2O (oxime) CH3COCH3 + NH2OH CH3-C=NOH CH3 2- Hydrazine: -C=O + H2N-NH2 -C=N-NH2 + H2O (hydrazone) CH3CHO +H2N-NH2 CH3CH=N.NH2+H2O

3-Aldol Condensation Aldol Condensation - Under the influence of dilute base or dilute acid two molecules of an aldehyde or a ketone may combine to form b- hydroxaldehyde or b-hydroxyketone. This reaction is called aldol condensation.

The Aldol Condensation + ol base an aldol (b-hydroxyaldehyde) H3O+ - H2O aldols easily lose water to form a double bond a,b-unsaturated aldehyde

Aldol Condensation -- Mechanism fast enolate ion slow forms new C-C bond fast

C- Substitution reaction: 1- 1-Haloform reaction: CH3COCH3 3I2 Cl3COCH3 NaOH CHI3 + CH3CO2Na 2- Cannizzaro’s reaction: 2CH2O + NaOH CH3OH + HCOONa

Cannizzaro’s reaction

Tollens Test Add ammonia solution to AgNO3 solution until precipitate dissolves. Aldehyde reaction forms a silver mirror.

Identification of aldehydes Tollen’s test Fehling’s test Schiff’s test Schiff's Test for aldehydes. Use 2 mL Schiff's reagent + 3 drops unknown. Positive test showing a magenta color after ten minutes.

Carboxylic Acids O A carboxylic acid Contains a carboxyl group, which is a carbonyl group (C=O) attached to a hydroxyl group (—OH). Has the carboxyl group on carbon 1. carbonyl group O  CH3 — C—OH hydroxyl group or CH3COOH carboxyl group

IUPAC Names The IUPAC names of carboxylic acids Replace the -e in the alkane name with -oic acid. CH4 methane HCOOH methanoic acid CH3—CH3 ethane CH3—COOH ethanoic acid Number substituents from the carboxyl carbon 1. CH3 O | ║ CH3—CH—CH2—C—OH 4 3 2 1 3-methylbutanoic acid

Carboxylic acid Nomenclature : R-COOH Ar-COOH Aliphatic (carboxylic cid) aromatic (benzoic acid) Nomenclature : 1) replace ane by -ic acid Common IUPAC Formula No. C Formic acid Acetic acid Prpionic acid Butyric acid valeric acid Methanoic acid Ethanoic acid Prpanoic acid Butanoic acid Pentanoc acid HCOOH CH3COOH CH3CH2COOH CH3(CH2)2COOH CH3(CH2)3COOH 1 2 3 4 5

2) Longest continuous chain CH3CH2CHCH2CH2COOH 4-Methyl hexanoic acid CH3      C-C-C-C-C-COOH CH3CH2CHCH2CH2COOH γ-Methyl hexenoic acid CH3 commmone: -- Dimethyl butyric acid IUPAC: 2,3-Dimethyl butanoic a CH3-CHBr-CHCl-CO2H 3-Bromo-2-chlorobutnoic acid

Common Carboxylic Acids Methanoic acid (formic acid) O ║ H─C─OH ethanoic acid (acetic acid) CH3─C─OH

Physical properties: 1] They form hydrogen 2] comp. 1-7 soli in H2O . 3] mor than 7 carbon less soli. (bec. R increased) 4] Aromatic acids insoluble. In H2O 5] BP. Acid > Alcohol

Polarity of Carboxylic Acids Are strongly polar. Have two polar groups: hydroxyl (−OH) and carbonyl (C=O). δ- O ║δ+ δ- δ+ CH3CO H

Boiling Points of Carboxylic Acids The boiling points of carboxylic acids Are higher than alcohols, ketones, and aldehydes of similar mass. Are high because they form dimers in which hydrogen bonds form between the polar groups in the two carboxyl groups. O H—O || | CH3—C C—CH3 | || O—H O A dimer of acetic acid

Solubility in Water Carboxylic acids Form hydrogen bonds with many water molecules. With 1-4 carbon atoms are very soluble in water. Water molecules 37

Preparation of carboxylic acid 1] Oxidation a) 1 alcohols & Aldehydes

Preparation of Carboxylic Acids Carboxylic acids can be prepared by oxidizing primary alcohols or aldehydes. The oxidation of ethanol produces ethanoic acid (acetic acid). OH O O | [O] || [O] || CH3—CH2 CH3—C—H CH3—C—OH ethanol ethanal ethanoic acid (ethyl alcohol) (acetaldehyde) (acetic acid)

2] Carbonation of Grignard reagent:

Chemical Reaction

Reactions of acids 1)Salt formation: it react with strong base & we can use Ca or K It reacts with weak base Sodium bicarb. Can be used to distinguish between carboxylic acid and phenols

nucleophilic substitution 2) Formation of Ester: nucleophilic substitution H+ + + H2O carboxylic acid alcohol ester condensation reaction reverse = hydrolysis H+ ester + H2O carboxylic acid + alcohol

2) Formation of Ester: 3) Formation of acid chloride: 4) Formation of acid anhydride: 2RCOOH + P2O5 (RCO)2O + H2O 2CH3COOH + P2O5 (CH3CO)2O + H2O

5- Reduction: RCO2H + LiAlH4; then H+  RCH2OH 1o alcohol 6- Decarboxylation:( Soda lime) CH3COOH + NaOH/CaO CH4 + Na2CO3 Alkane

ketone aldehyde RCOOH ROH ROR alkene Alcohols are central to organic syntheses RX RH alkyne