Ketones, Aldehydes, Amines Unit 14

Aldehydes and Ketones The simplest carbonyl compounds are aldehydes and ketones A ketone has two alkyl (or aryl) groups bonded to the carbonyl carbon. An aldehyde has one alkyl (or aryl) group and one hydrogen bonded to the carbonyl carbon.

Ketones IUPAC nomenclature requires ketones to be named replacing the –e ending of the alkyl name with –one. Alkane  Alkanone

Ketone Nomenclature 1 O B r 3-bromocyclohexanone 3 For cyclic ketones, the carbonyl carbon is assigned the number 1.

Aldehydes Systematic names for aldehydes are obtained by replacing –e with –al. An aldehyde has to be at the end of a chain, thus it is carbon number 1. If the aldehyde is attached to a large unit, the suffix carbaldehyde is used. Cyclohexane carbaldehyde

Aldehydes and Ketones Aldehyde and ketone groups can also be named as a substituent on a molecule with another functional group as its root. The ketone carbonyl is given the prefix oxo- and the aldehyde carbonyl is named with the prefix formyl- 3-oxopentanal 2-formylbenzoic acid

group as a prefix: methanoyl or formyl group group as a prefix: ethanoyl or acetyl group (Ac) groups as a prefix: alkanoyl or acyl groups

Aldehydes and Ketones Common Names The widespread use of carbonyl compounds means many common names are entrenched in their everyday use. Acetophenone

Tollen’s Test (Silver Mirror) AgNO3+NaOH→AgOH+HNO3 2AgOH→Ag2O+H2O Ag2O + 4NH3 + H2O → 2Ag(NH3)2+ + 2OH- This type of oxidation reaction is the basis of the most common chemical test for aldehydes. The Tollen’s reagent is added to an unknown compound and if an aldehyde is present, it is oxidized. This process reduces Ag+ to Ag which precipitates and sticks to the flask wall forming a mirror.

Boiling Points Ketones and aldehydes are more polar, so they have a higher boiling point than comparable alkanes or ethers. They cannot hydrogen-bond to each other, so their boiling point is lower than comparable alcohol.

Industrial Importance Acetone and methyl ethyl ketone are important solvents. Formaldehyde is used in polymers like Bakelite. Flavorings and additives like vanilla, cinnamon, and artificial butter.

Amines Amines are derivatives of ammonia with one or more alkyl groups bonded to the nitrogen. Amines can be classified as primary, secondary or tertiary, meaning one, two or three alkyl groups bonded to the nitrogen respectively. Quaternary ammonium salts have four alkyl groups bonded to the nitrogen and the nitrogen bears a full positive charge.

Amines C H N ( ) N H C B r N,N-dimethyl-3-hexanamine Amines are a very common functional group in organic chemistry, and especially so for naturally occurring compounds. The IUPAC nomenclature for amines is analogous to that for alcohols, except the –e ending is replaced with –amine Other substituents on the carbon chain are given numbers and the prefix N- is used for each substituent on Nitrogen C H 3 2 N ( ) N H 2 C 3 B r N,N-dimethyl-3-hexanamine 3-bromo-1-pentanamine

Amines Aromatic amines are called by their historical/trivial names, with phenylamine being called aniline. Synthesis of amines is really reactions of amines – increasing the number of alkyl substituents on the Nitrogen.

Biologically Active Amines The alkaloids are an important group of biologically active amines, mostly synthesized by plants to protect them from being eaten by insects and other animals. Many drugs of addiction are classified as alkaloids.

Biological Activity of Amines Dopamine is a neurotransmitter. Epinephrine is a bioregulator. Niacin, Vitamin B6, is an amine. Alkaloids: nicotine, morphine, cocaine Amino acids

Common Names

Amine as Substituent On a molecule with a higher priority functional group, the amine is named as a substituent.

Aromatic Amines In aromatic amines, the amino group is bonded to a benzene ring. Parent compound is called aniline.

When naming a cyclic amine the nitrogen is assigned position number 1. Heterocyclic Amines When naming a cyclic amine the nitrogen is assigned position number 1.

Solubility and Odor Small amines (< 6 Cs) are soluble in water. All amines accept hydrogen bonds from water and alcohol. Branching increases solubility. Most amines smell like rotting fish. N H 2 C 1,5-pentanediamine or cadaverine

Basicity of Amines Lone pair of electrons on nitrogen can accept a proton from an acid. Aqueous solutions are basic to litmus. Ammonia pKb = 4.74 Alkyl amines are usually stronger bases than ammonia. Increasing the number of alkyl groups decreases solvation of ion, so 2 and 3 amines are similar to 1 amines in basicity.