3Aldehydes 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
4Carbonyl StructureCarbon is sp2 hybridized. C=O bond is shorter, stronger, and more polar than C=C bond in alkenes.
5Naming Aldehydes and Ketones Aldehydes are named by replacing the terminal -e of the corresponding alkane name with –alThe parent chain must contain the CHO groupThe CHO carbon is numbered possible minimum number.
6Naming Ketones Replace the terminal -e of the alkane name with –one Parent chain is the longest one that contains the ketone groupNumbering begins at the end nearer the carbonyl carbon
7Solubility 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.
8Preparation of Aldehydes & ketones 1] Oxidation of 1& 2 alcohol :C2H5OH [O] CH3CHO [O] CH3COOHCH3CHOHCH [O] CH3COCH3isopropanol
9Physical 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.
135- Hydrolysis of gem-dihalides by the action of base: A) If dihalogen are terminal:CH3CHCl2 H2O/NaOH CH3CH(OH)2 H2O CH3CHO acetaldehydeB) If dihalogen aren’t terminal:CH3CCl2CH3 H2O/NaOH CH3COCH3 acetone
223-Aldol CondensationAldol 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.
23The Aldol Condensation +olbasean aldol(b-hydroxyaldehyde)H3O+- H2Oaldols easily losewater to form adouble bonda,b-unsaturated aldehyde
27Tollens TestAdd ammonia solution to AgNO3 solution until precipitate dissolves.Aldehyde reaction forms a silver mirror.
28Identification of aldehydes Tollen’s testFehling’s testSchiff’s testSchiff's Test for aldehydes. Use 2 mL Schiff's reagent + 3 drops unknown. Positive test showing a magenta color after ten minutes.
29Carboxylic 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 groupOCH3 — C—OH hydroxyl group or CH3COOHcarboxyl group
30IUPAC Names The IUPAC names of carboxylic acids Replace the -e in the alkane name with -oic acid.CH4 methane HCOOH methanoic acidCH3—CH3 ethane CH3—COOH ethanoic acidNumber substituents from the carboxyl carbon 1.CH O| ║CH3—CH—CH2—C—OH3-methylbutanoic acid
34Physical properties:1] They form hydrogen2] comp. 1-7 soli in H2O .3] mor than 7 carbon less soli. (bec. R increased)4] Aromatic acids insoluble. In H2O5] BP. Acid > Alcohol
35Polarity of Carboxylic Acids Are strongly polar.Have two polar groups:hydroxyl (−OH) and carbonyl (C=O).δ-O║δ+ δ δ+CH3CO H
36Boiling Points of Carboxylic Acids The boiling points of carboxylic acidsAre 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 OA dimer of acetic acid
37Solubility in Water Carboxylic acids Form hydrogen bonds with many water molecules.With 1-4 carbon atoms are very soluble in water.Water molecules37
38Preparation of carboxylic acid 1] Oxidationa) 1 alcohols & Aldehydes
39Preparation 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—CH CH3—C—H CH3—C—OHethanol ethanal ethanoic acid(ethyl alcohol) (acetaldehyde) (acetic acid)