Topic 3 Synthesis, Addition, and Addition- Elimination Reactions of - PowerPoint PPT Presentation

Chem 2312 Solomons and Fryhle: Chapters 12.1, .2 .3, Lecture 15, September 26, 2003 16.1, .2, .3, .4 Topic 3 Synthesis, Addition, and Addition- Elimination Reactions of Aldehydes and Ketones New Molecule of the Week Part - 1 H 3 C H O ( R )-2-methylbutanal Pungent, peculiar to burnt cocoa and coffee like Fragrance reminiscent of citronellal O 1

N.R. 2

O O N.R. H O R R' Carbonyl Group O 3

N.R. O O O Cl Butan-2-one Cyclohexyl-cyclopentyl-methanone Methyl,ethyl ketone 3-Chloro-4-ethyl-benzaldehyde O O O Butan-2-one 3-Methyl-pentanal 4-Methyl-hex-1-en-3-one Methyl,ethyl ketone 4

Nomenclature of Aldehydes Aldehydes are named by adding the suffix -al to the name of the corresponding hydrocarbon and the carbonyl carbon is given the # 1. H methanal Methanal; common name>> formaldehyde O H H 3 C O Ethanal; common name>> acetaldehyde H O O heptanal 5-ethyl-7-methylnonanal 5

Nomenclature of Aldehydes When -CHO is attached to a ring, the suffix carbaldehyde is used. H O Benzenecarbaldehyde; common name> benzaldehyde O O O cyclohexanecarbaldehyde cyclopropanecarbaldehyde 3-methylcyclopentanecarbaldehyde 6

Nomenclature of Ketones Ketones are named using the name of the corresponding hydrocarbon followed by the suffix>> one . The position of the carbonyl carbon must be indicated. H 3 C Propanone; Common Name>>> Acetone O H 3 C Or you can also name the compound by the two R and R’ groups followed by the word ketone. >>> or dimethyl ketone. 7

Nomenclature of Ketones-- Examples O O heptan-3-one 5-ethyl-7-methylnonan-4-one O O O pentan-2-one 1-cyclohexyl-2,2-dimethylpropan-1-one pentan-3-one 8

Nomenclature of Ketones-- Examples O Diphenylmethanone, common name>> benzophenone O Phenylethanone, common name >>> acetophenone CH 3 9

A Closer Look at the Bonding of Carbonyl Groups Third sp 2 for σ -bond Sigma Bonding Oxygen is sp 2 O O O R R' Carbon is sp 2 R R' Two sp 2 orbitals each having two electrons – Lone pairs O R' R 120 o p p orbital π Bonding R' R 10

N.R. H O H R R R R δ - δ - δ - δ + δ + δ + H δ - δ + H O R H O O O O O H O R' R' R' R' 11 Water soluble with small R groups R'

N.R. 1 o alcohol Aldehyde Carboxylic Acid C =-3 C=-1 C=+1 C= +3 12

O O R H R OH N.R. O NR R R N.R. 13

Potassium Permanganate (+7) RCO 2 H (+6) O N.R. R R O O OH 14

R H O NH + CrO 3 Cl - NB: Oxidation stops at aldehyde!!! N.R. PCC CrO 3 ` H Acetone H O HO H O OH Milder than acidic chromate Also >> remember KMnO 4 Attacks double bonds 15

(LAH) R-CH 2 -OH 1 o alcohol N.R. 16

Lithium tri-tert-butoxy- Aluminum hydride O H O Diisobutylaluminum Hydride H N.R. DIBAL N H H 2 O O H The severe steric hinderance of these agents reduces their reactivity 17

What’s Going On????? O Al O Li H O Li O O CH 3 CH 3 O O H O O Al O Li O O O O Al N.R. CH 3 O O H CH 3 O H O O Al O O O O Al O O H H H 2 O 18