Identifying Tertiary Amino Groups in Organic Molecules

The question asks us to identify which of the given compounds contains a tertiary amino group. To answer this, we need to understand what a tertiary amino group is and examine the chemical structure of each option.

An amino group is a functional group that contains a nitrogen atom ($\text{N}$). Amines are classified based on the number of carbon atoms directly bonded to the nitrogen atom:

• Primary amine: The nitrogen atom is bonded to one carbon atom and two hydrogen atoms ($\text{-NH}_2$).
• Secondary amine: The nitrogen atom is bonded to two carbon atoms and one hydrogen atom ($\text{-NHR}$, where R is an alkyl or aryl group).
• Tertiary amine: The nitrogen atom is bonded to three carbon atoms ($\text{-NRR'R''}$, where R, R', and R'' are alkyl or aryl groups). The nitrogen has no hydrogen atoms directly attached.

Let's look at the structures of the given options:

Analyzing the Structures for Tertiary Amines

Let's break down the structure of each compound concerning its amino group:

1. Novocain (Procaine):

Its structure includes a nitrogen atom bonded to two ethyl ($\text{-CH}_2\text{CH}_3$) groups. Since the nitrogen is bonded to three carbon atoms (two from the ethyl groups and one from the $-\text{CH}_2-$ linked to the ester), and no hydrogen atoms, this is a tertiary amino group ($\text{-N}(\text{CH}_2\text{CH}_3)_2$).

2. Ephedrine:

Ephedrine contains a nitrogen atom bonded to one carbon atom (from the methyl group, $\text{-CH}_3$) and one hydrogen atom, and another carbon from the carbon chain. This means the nitrogen is bonded to two carbon atoms and one hydrogen atom, classifying it as a secondary amino group ($\text{-NHCH}_3$).

3. Benadryl (Diphenhydramine):

Benadryl's structure includes a nitrogen atom bonded to two methyl ($\text{-CH}_3$) groups and one carbon atom from the ethyl chain connected via the ether linkage. Since the nitrogen is bonded to three carbon atoms (two from methyls, one from $-\text{CH}_2-$), and no hydrogen atoms, this is a tertiary amino group ($\text{-N}(\text{CH}_3)_2$).

4. Adrenaline (Epinephrine):

Adrenaline has a nitrogen atom bonded to one methyl ($\text{-CH}_3$) group and one hydrogen atom, and another carbon from the chain. Similar to Ephedrine, this is a secondary amino group ($\text{-NHCH}_3$).

Conclusion on Tertiary Amino Groups

Based on the structural analysis, both Novocain and Benadryl contain a tertiary amino group. Ephedrine and Adrenaline contain secondary amino groups.

The question asks which compound contains a tertiary amino group. Both Novocain and Benadryl fit this description. However, considering the provided option, Benadryl is the intended answer among the choices given.

Revision Table: Amino Group Classification

Additional Information: Types of Amines and their Properties

The classification of amines (primary, secondary, tertiary) is important because it affects their chemical properties, such as basicity, reactivity, and physical properties like boiling point. For example:

• Primary and secondary amines can form hydrogen bonds between amine molecules, which generally gives them higher boiling points than tertiary amines of similar molecular weight.
• The nitrogen atom in amines is basic due to the lone pair of electrons, and they can accept a proton ($\text{H}^+$) to form ammonium ions ($\text{RNH}_3^+$, $\text{R}_2\text{NH}_2^+$, $\text{R}_3\text{NH}^+$).
• The reactivity towards certain reagents, like acyl chlorides or sulfonyl chlorides, differs between primary, secondary, and tertiary amines. Tertiary amines, lacking a hydrogen on the nitrogen, react differently or not at all in reactions requiring N-H bonds.

Understanding these classifications helps predict how different amine-containing compounds will behave in various chemical reactions and biological systems.