3 Naming Aldehydes An aldehyde Has an IUPAC name in which the -e in the alkane name is changed to -al. Has a common name for the first four aldehydes that use the prefixes form (1C), acet (2C), propion (3C), and butyr (4C), followed by aldehyde. O O O ║ ║ ║ H − C − H CH 3 − C − HCH 3 − CH 2 − C − H methanal ethanal propanal (formaldehyde) (acetaldehyde) (propionaldehyde)
6 Naming Ketones Ketones are named In the IUPAC system by replacing the -e in the alkane name with one. The carbonyl carbon is indicated by a number. With a common name by indicating the alkyl groups attached to the carbonyl group in alphabetical order followed by ketone. O O ║ ║ CH 3 − C − CH 3 CH 3 − C − CH 2 − CH 3 propanone 2-butanone (dimethyl ketone) (ethyl methyl ketone)
13 Polar Carbonyl Group The polar carbonyl group Provides dipole-dipole interactions. + - + - C=O Does not have H on the oxygen atom. Cannot form hydrogen bonds.
14 Boiling Points Aldehydes and ketones have Polar carbonyl groups (C=O). + - C=O Attractions between polar groups. + - + - C=O Higher boiling points than alkanes and ethers of similar mass. Lower boiling points than alcohols of similar mass.
25 Addition Reactions When a polar molecule adds to the carbonyl group of an aldehyde or ketone The negative part of the added molecule bonds to the positive carbonyl carbon. The positive part of the added molecule bonds to the negative carbonyl oxygen. | + - + - | —C=O + X—Y — C—O—X | Y
35 Learning Check Identify each as a chiral or achiral compound.
36 Fischer Projections A Fischer projection Is a 2-dimensional representation of a 3-dimensional molecule. Places the most oxidized group at the top. Uses vertical lines in place of dashes for bonds that go back. Uses horizontal lines in place of wedges for bonds that come forward.