Question

Write the structural formula of each of the following amines: (a) methylpropylamine; (b) dimethylamine; (c) m-methylphenylamine. Reactivity Patterns and Functional Groups

Short answer

The structural formula for (a) methylpropylamine is an NH2 group attached to the end of a three-carbon chain with a methyl group on the nitrogen atom; for (b) dimethylamine, it's an NH group with two methyl groups attached to the nitrogen atom; and for (c) m-methylphenylamine, it is a benzene ring with an NH2 group attached to one carbon and a CH3 group attached to the carbon two positions away (meta position).

Step-by-step solution

Interpreting the Name for Methylpropylamine

The name 'methylpropylamine' indicates that the molecule has a propyl group (a three-carbon chain) and a methyl group (a one-carbon group) attached to an amine group (NH2). The 'methyl' is a substituent on the nitrogen of the 'propylamine,' meaning the nitrogen is attached to two carbons: one from the propyl group and one from the methyl group.

Drawing Methylpropylamine

To draw methylpropylamine, start with the propyl chain as the main skeleton, then add the amine (NH2) group on one end. Finally, attach a methyl group to the nitrogen atom. The structure will have the nitrogen with two hydrogens and one methyl group attached to it while it is also bonded to the propyl group.

Interpreting the Name for Dimethylamine

Dimethylamine has the prefix 'di-' which indicates that there are two methyl groups attached to the amine. The base 'amine' implies the NH2 group.

Drawing Dimethylamine

To draw dimethylamine, start with the amine (NH2) and attach two methyl groups (CH3) to the nitrogen atom, resulting in a central nitrogen bonded to two methyl groups and one hydrogen.

Interpreting the Name for m-Methylphenylamine

The name 'm-Methylphenylamine' indicates a phenyl group (a benzene ring) with an amine (NH2) and a methyl group (CH3) attached. The 'm-' prefix tells us that the methyl group is on the meta position relative to the amine group on the benzene ring.

Drawing m-Methylphenylamine

Draw the benzene ring, then attach the amine group (NH2) to one of the carbons in the ring. Counting either clockwise or counter-clockwise, locate the meta position which is two carbons away from amine's attached carbon, and attach the methyl group on the third carbon. This completes the structural formula for m-methylphenylamine.

Key concepts

Organic Chemistry

Organic chemistry is the branch of chemistry that involves the scientific study of the structure, properties, composition, reactions, and synthesis of organic compounds and organic materials. These compounds primarily consist of carbon and hydrogen, and may also contain other elements like nitrogen, oxygen, phosphorus, and sulfur. One of the principles that make organic chemistry particularly interesting is the ability to predict the physical and chemical properties of molecules based on their structure.

For example, when we look at amines, which are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair, understanding their structure helps us anticipate their reactivity and interaction with other molecules. This knowledge is foundational for designing and synthesizing new molecules in chemical industries, pharmaceuticals, and biomedical research.

Amine Group

The amine group is one of the most common and important functional groups in organic chemistry. It is characterized by a nitrogen atom attached to hydrocarbon groups or hydrogen atoms. Depending on the number of hydrocarbon groups attached to the nitrogen, amines are classified as primary (one hydrocarbon group), secondary (two hydrocarbon groups), or tertiary (three hydrocarbon groups).

In the given exercise, you have come across several examples of amines: methylpropylamine, a primary amine with a methyl and a propyl group; dimethylamine, a secondary amine with two methyl groups; and m-methylphenylamine, which involves a more complex aromatic ring. Understanding how to identify and visualize the amine group in different molecular contexts is essential in organic chemistry, as it affects the compound's solubility, boiling point, and overall reactivity.

Functional Groups

Functional groups are specific groups of atoms within molecules that have characteristic properties and determine the reactivity and behavior of the molecules they are part of. They are like the 'functional' centers that dictate how a molecule will interact with other substances.

Amines are just one type of functional group. Others include alcohols, aldehydes, ketones, carboxylic acids, and esters, to name a few. Each group has its own unique set of reactions that it undergoes. In the context of the exercise, recognizing the presence of the amine group allows us to predict its basicity and nucleophilicity, factors which are important when considering how a molecule might react during synthesis or with biological systems. By familiarizing oneself with various functional groups and their properties, students of organic chemistry can approach problem-solving with a toolkit of predictable outcomes.