Aldehydes & Ketones contain the carbonyl group, C=O.

Aldehydes &Ketones contain the carbonyl group, C=O. O O R-C-H R-C-R’ or RCHO or R-CO-R’ Aldehyde Ketone

Both aldehydes and ketones contain the carbonyl group, C=O. The H-C=O group of an aldehyde is called the formyl group.

Aldehyde Nomenclature 1. Find longest Carbon chain that includes C of C=O. 2. Ending for name is “al” : alkane + al --> alkanal 3. Number chain to give C of C=O locant #1. 4. Aldehyde & ketone more important than alcohol group.

Example of Naming Aldehydes HO-CH2-CH2CH2CH-CH2CH2-CH O CH3 7-hydroxy-4-methylheptanal

Ketone Nomenclature 1. Find longest Carbon chain that includes C of C=O. 2. Ending for name is “one” : alkane + one --> alkanone 3. Number chain to give C of C=O the lower possible locant.

Example CH3CH2CHCH2CCH2CH3 O 5-phenyl-3-heptanone

Aldehyde & Ketone Bonding * Carbon has 120° bond angles * molecular shape around C is trigonal planar O=C

The C=O bond is polar covalent, has permanent dipole because of electronegativity difference between C and O.... C O d+ •• d– ••

Aldehyde & Ketone Reactions 1. Oxidation 2. Reduction 3. Addition

Oxidation means carbon forms more bonds to oxygen. Aldehydes are easily oxidized to carboxylic acids: R-C-H R-C-O-H O O [O] [O] means add oxygen from another source, like O2. .

Ketones are NOT easily oxidized. Reagents which oxidize aldehydes do NOT oxidize ketones.

Reduction means forming more C-H bonds or decreasing the number of C-O bonds. O OH [H] R-C-H R-CH-H [H] means add H from another source aldehyde ---> primary alcohol

Ketone Reduction O OH [H] R-C-R’ R-C-R’ H ketone ---> secondary alcohol

Practice Problem Draw the structure of the product of this reaction: O CH3CH2CCH2CH2CH3 [H] ???

Ketones are reduced to alcohols. So: what is the alcohol related to the ketone shown? CH3CH2CCH2CH2CH3 OH H

Addition Reactions of Aldehydes & Ketones d+ d– e– pair acceptor (electrophile, often H+) reacts at O C=O •• •• electron pair donor (nucleophile) reacts at C

Alcohols add to the C=O of aldehdyes and ketones •• RO-H symbol for alcohol •• Electrophile at H Nucleophile at O because electron pair donor

General Reaction for ROH addition happens in 2 steps… R-C-H + RO-H O H+ (catalyst) O-H R-C-H hemi-acetal (product of first step) OR

General Reaction for ROH addition, 2nd step is O-H OR ROH, H+ R-C-H R-C-H + H2O 2nd step OR OR hemi-acetalacetal

Example: What hemi-acetal is formed in the reaction O ??? CH3CH2C-H + CH3OH Hint: RO of alcohol bonds to C of C=O, H bonds to O of C=O

So, the answer is: O CH3CH2C-H + CH3OH OH Hemi-acetal CH3CH2C-H OCH3

Notes: • ordinarily, hemi-acetals are not stable enough to isolate from reaction. • product usually obtained is acetal.

Formation of acetals is reversible: they can be decomposed simply by reversing the steps which led to their formation. Formation uses excess ROH. Decomposition or hydrolysis uses excess H2O.

Example of Hydrolysis of Acetals: OCH3 H2O, H+ C H OCH3 O C-H+ 2 CH3OH

Ketones make hemi-acetals and acetals as well. Predict structure of the acetal from the unbalanced reaction below: O H+ CCH2CH3 + CH3OH

Here ya go! OCH3 CCH2CH3 OCH3

Aldehydes & Ketones contain the carbonyl group, C=O.