Chapter 16: Amines -N- - - Amines are classified as 1°, 2°, or 3° depending on the number of carbon groups bonded to nitrogen. Low molecular weight amines are toxic and some are easily absorbed through the skin. Many higher molecular weight amines are highly active biologically. Amphetamine Nicotine Serotonin Adenine

Chapter 16: Amines Example: Example: Mark each of the following amines as primary, secondary, or tertiary: a) b) c) d)

Chapter 16: Amines -N- - - Amines are classified as 1°, 2°, or 3° depending on the number of carbon groups bonded to nitrogen. Aliphatic amine: Aliphatic amine: All carbons bonded to nitrogen are derived from alkyl groups. See the three above. Aromatic amine: Aromatic amine: One or more of the groups bonded to nitrogen are aryl groups.

Chapter 16: Amines Heterocyclic amine: Heterocyclic amine: An amine in which the nitrogen atom is part of a ring. Heterocyclic aliphatic amine: Heterocyclic aliphatic amine: A heterocyclic amine in which the ring is saturated (has no C=C bonds). Heterocyclic aromatic amine: Heterocyclic aromatic amine: The amine nitrogen is part of an aromatic ring.

Nomenclature -e-amine. Drop the final -e of the parent alkane and replace it by -amine. Use a number to locate the amino group on the parent chain. Name unsymmetrical secondary and tertiary amines as N- substituted primary amines. Take the largest group bonded to nitrogen as the parent amine. Name the smaller group(s) bonded to nitrogen, and show their location on nitrogen by using the prefix N- (indicating that they are bonded to nitrogen).

Nomenclature Common names amine For most aliphatic amines, list the groups bonded to nitrogen in alphabetical order in one word ending in the suffix -amine. We already spoke about how to name aniline and its derivatives:

Nomenclature Amine salts When four atoms or groups of atoms are bonded to a nitrogen atom, as for example CH 3 NH 3 +, nitrogen bears a positive charge and is associated with an anion as a salt. Name the compound as a salt of the corresponding amine. -amine- ammonium Replace the ending -amine (or aniline or pyridine or the like) by - ammonium (or anilinium or pyridinium or the like) and add the name of the anion.

Physical Properties Low-molecular-weight amines have very sharp, penetrating odors. Amines are Polar compounds. 1° and 2° amines have N-H bonds, and can form hydrogen bonds with one another. 3° Amines have no N-H bond and cannot form hydrogen bonds with one another.

Physical Properties An N-H---N hydrogen bond is weaker than an O-H---O hydrogen bond, because the difference in electronegativity between N and H ( = 0.9) is less than that between O and H ( = 1.4). Most low-molecular-weight amines are completely soluble in water. Higher-molecular-weight amines are only moderately soluble in water or are insoluble.

Like ammonia, amines are weak bases, and aqueous solutions of amines are basic. The acid-base reaction between an amine and water involves transfer of a proton from water to the amine. Chemical Properties

Amines, whether soluble or insoluble in water, react quantitatively with strong acids to form water-soluble salts. It is possible to predict which form of the amine is prevalent given the pKb of the amine and the pH of the environment: (see example in the next slide)

Chapter 16: Amines Assume that the amine, RNH 2, has a pK b of 3.50 and that it is dissolved in blood, pH 7.40 (pOH 6.60). We first write the base dissociation constant for the amine and then solve for the ratio of RNH 3 + to RNH 2. Substituting values for K b and OH - gives: That means that if an aliphatic amine is dissolved in blood, it is present predominantly as its protonated (conjugated acid) form.

Chapter 16: Amines Example: Example: Complete each acid-base reaction and name the salt formed.

Chapter 16: Amines Example: Example: Complete each acid-base reaction and name the salt formed.Solution: