ALDEHYDES AND KETONES

ALDEHYDES AND KETONES “carbonyl” functional group: Aldehydes Ketones

Nomenclature: Aldehydes, common names: Aldehyde name comes from Alcohol DEHYDrogenation butyraldehyde isobutyraldehyde (α-methylpropionaldehyde)

Aldehydes, IUPAC nomenclature: Parent chain = longest continuous carbon chain containing the carbonyl group; alkane, drop –e, add –al. -CH=O is carbon #1.) CH3 CH3CH2CH2CH=O CH3CHCH=O butanal 2-methylpropanal H2C=O CH3CH=O methanal ethanal

Ketones, common names: Special name: acetone “alkyl alkyl ketone” or “dialkyl ketone”

Ketones: IUPAC nomenclature: Parent = longest continuous carbon chain containing the carbonyl group. Alkane, drop –e, add –one. Prefix a locant for the position of the carbonyl using the principle of lower number.

Physical Properties The polar carbonyl group makes ketones and aldehydes polar. Their melting and boiling points increase as the molecular weights increase. Their boiling points are comparable with alcohols or carboxylic acids. The lower aldehydes and ketones are appreciably soluble in water and borderline solubility is reached at about five carbons. They are soluble in the normal organic solvents. Formaldehyde is a gas at room temperature (BP -21 oC) and is used either as an aqueous solution (formalin - formaldehyde dissolved in methanol)

Preparation of Aldehydes and Ketones Oxidation of alcohols

Oxidation of methylbenzenes

Reduction of acid chlorides LiAlH(O-t-Bu)3 tritertier butoxylithium aluminum hydride

Preparation of Ketones Oxidation of Secondary alcohols

Friedel-Crafts acylation Acid chloride Ketone

Reactions of Aldehydes Ketones Addition of Grignard regents

Addition of Alcohols. Acetal formation

Addition of cyanide. This reaction extends chain by one carbon

Keto-enol tautomerism of aldehydes and ketones.

In keto-enol tautomerism, the aldehyde or the ketone is called the keto form and the enol is called the enol form.   In most keto-enol tautomerisms, the equilibrium lies by far toward the keto form, indicating that the keto form is usually much more stable than the enol form, which can be attributed to the feet that a carbon-oxygen double bond is significantly stronger than a carbon-carbon double bond.