Question

Identify the class of organic substance for each of the following molecules. (a) \(\mathrm{H}_{3} \mathrm{C}-\mathrm{NH}_{2}\) (d) \(\mathrm{H}_{3} \mathrm{C}-\stackrel{\|}{\mathrm{C}}-\mathrm{H}\) (b) \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}_{2}\) (e) \(\mathrm{C}_{6} \mathrm{H}_{6}\) (c) CC=O

Short answer

The class of each molecule is - (a) Amine, (d) Alkene, (b) Alkene, (e) Aromatic Compound, (c) Aldehyde.

Step-by-step solution

Identify Molecule (a)

\(\mathrm{H}_{3} \mathrm{C}-\mathrm{NH}_{2}\) is an amine. This is because it has a nitrogen atom directly bonded to a carbon atom, which is the defining characteristic of an amine.

Identify Molecule (d)

\(\mathrm{H}_{3} \mathrm{C}-\stackrel{\|}{\mathrm{C}}-\mathrm{H}\) is an alkene. It contains a carbon-carbon double bond, which is the defining characteristic of an alkene.

Identify Molecule (b)

\(\mathrm{H}_{2} \mathrm{C}=\mathrm{CH}_{2}\) is an alkene. It contains a carbon-carbon double bond, which is the defining characteristic of an alkene.

Identify Molecule (e)

\(\mathrm{C}_{6} \mathrm{H}_{6}\) is an example of an aromatic compound. The molecule is composed of hydrogen and carbon atoms arranged in a ring structure with alternating single and double bonds which is the defining characteristic of an aromatic compound.

Identify Molecule (c)

CC=O represents an aldehyde. This is because it has a carbonyl group (C=O) at the end of a carbon chain, which is the defining characteristic of an aldehyde.

Key concepts

Amines

Amines are organic compounds that feature a nitrogen atom bonded to one or more alkyl or aryl groups. This bonding forms a characteristic functional group, known as the amino group. The simplest form of an amine is when the nitrogen is connected to just one carbon atom, as shown in the molecule \( \mathrm{H}_{3} \mathrm{C}-\mathrm{NH}_{2} \).

• Amines are classified based on the number of carbon groups attached to the nitrogen: primary, secondary, and tertiary.
• Primary amines have one carbon group connected to the nitrogen, secondary have two, and tertiary have three.

Amines are commonly found in nature, often as part of amino acids, which are the building blocks of proteins.
They have significant biochemical relevance and are also used in pharmaceuticals. It's important to recognize the unique presence of nitrogen to identify amines in molecular structures.

Alkenes

Alkenes are hydrocarbons characterized by having at least one carbon-carbon double bond. This double bond is what sets them apart, leading to unsaturation in the molecule. The formula \( \mathrm{H}_{2} \mathrm{C}=\mathrm{CH}_{2} \) illustrates a simple alkene, ethylene.

• The double bond gives alkenes specific reactivity such as addition reactions.
• Alkenes are frequently used in the production of polymers, like polyethene.

A key feature of alkenes is their ability to rotate around the double bond, which affects their geometric configuration.
This can lead to different isomers, with varying properties. Identifying a double bond is crucial in recognizing alkenes in organic chemistry.

Aromatic Compounds

Aromatic compounds are a special class of organic molecules characterized by their stability and unique ring structures. Benzene \( \mathrm{C}_{6} \mathrm{H}_{6} \) is the classic example,
featuring a hexagonal ring with alternating double bonds, a concept known as resonance.

• The stability of aromatic rings is due to delocalized electrons shared across the structure.
• These compounds can participate in substitution reactions rather than addition reactions.

Aromaticity adds specific chemical properties to a compound, making it distinct from alkenes or alkanes. These features are important for understanding the behavior of aromatic compounds in chemical reactions and are utilized in designing drugs and synthetic materials.

Aldehydes

Aldehydes are organic compounds containing a carbonyl group (C=O) bonded to at least one hydrogen atom. The structure CC=O represents the simplest type of aldehyde, known as acetaldehyde.

• Aldehydes are usually found at the end of a carbon chain.
• They can be synthesized through the oxidation of primary alcohols.

A distinctive trait of aldehydes is their often pungent or fruity smell, which makes them useful in fragrances and flavorings.
The carbonyl group in aldehydes is reactive, enabling them to undergo a variety of chemical transformations. Recognizing the terminal carbonyl is essential for identifying them in molecular structures.

Molecular Identification

Molecular identification is the process of deducing the identity of a molecule by studying its structure and components.
This is crucial in organic chemistry when dealing with various classes of compounds, like amines, alkenes, aromatic compounds, and aldehydes.

• The functional groups present in a molecule help determine its chemical properties and reactivity.
• Understanding molecular geometry aids in predicting behavior and types of reactions a molecule can undergo.

By analyzing the presence of characteristic bonds or functional groups, chemists can identify and classify molecules efficiently.
This skill is not only vital in academic settings but also in industries like pharmaceuticals, material science, and environmental chemistry, where understanding molecule structures can lead to innovation and development of new products.