Question

Which of the following functional groups are found in phenylalanine?A. alkyl, double bond and aromatic ring B. amine, carboxylic acid and aromatic ring C. double bond, amide, and alcohol D. aromatic ring, halide and ketone

Short answer

B. amine, carboxylic acid, and aromatic ring

Step-by-step solution

Understand the Structure of Phenylalanine

Phenylalanine is an amino acid with the molecular formula C9H11NO2. It contains a benzene ring (aromatic ring), an amine group (-NH2), and a carboxylic acid group (-COOH).

Identify the Functional Groups in Phenylalanine

Examine the phenylalanine structure to identify the functional groups: - The benzene ring represents an aromatic ring. - The -NH2 group corresponds to an amine. - The -COOH group corresponds to a carboxylic acid.

Compare with Given Options

Check all given options to find the one matching the identified functional groups: - Option A: Doesn't include amine or carboxylic acid. - Option B: Includes an amine, carboxylic acid, and aromatic ring. - Option C: Doesn't include amine or carboxylic acid. - Option D: Doesn't include amine or carboxylic acid.

Conclude the Correct Answer

Since Option B matches all identified functional groups (amine, carboxylic acid, and aromatic ring), it is the correct answer.

Key concepts

Aromatic Ring

An aromatic ring, also known as an aromatic hydrocarbon, is a very stable ring-like structure made from alternating single and double bonds. These rings are often found in organic molecules, particularly in compounds containing benzene. Aromaticity gives these rings unique stability and chemical properties, making them crucial in many biochemical substances.

One well-known example of an aromatic ring in biochemistry is the benzene ring in phenylalanine. This amino acid contains a six-membered benzene ring, contributing to its aromaticity.
This structure makes phenylalanine easily recognizable and important in various biological processes.

• Aromatic rings are stable due to resonance stabilization, where electron density is evenly spread across all atoms.
• They often have a distinct smell, which is where the term 'aromatic' originates.
• Common aromatic rings include benzene, toluene, and phenol.

Amine Group

The amine group is a functional group characterized by a nitrogen atom attached to one or more alkyl or aryl groups. In organic chemistry, amines are classified based on the number of carbon-containing groups attached to the nitrogen: primary (one), secondary (two), or tertiary (three).

In phenylalanine, the amine group is a primary amine, denoted by -NH2. This group is essential because it allows phenylalanine to form peptide bonds with other amino acids, constructing proteins.

• Amines act as bases in chemical reactions, accepting protons (H+) due to the lone pair of electrons on the nitrogen.
• The presence of an amine group can affect the polarity and solubility of molecules.
• Examples of amine-containing molecules include amino acids, neurotransmitters like dopamine, and drugs like amphetamines.

Carboxylic Acid

The carboxylic acid group is an organic functional group characterized by a carbon atom double-bonded to an oxygen atom and single-bonded to a hydroxyl group (-COOH). This group is highly reactive and plays a pivotal role in biochemistry, particularly in the formation of biomolecules such as proteins and fats.

In phenylalanine, the carboxylic acid group is crucial for forming peptide bonds, similar to the amine group. It’s denoted by -COOH and contributes to the overall acidic nature of the molecule.

• Carboxylic acids are weak acids, partially dissociating in water to release hydrogen ions (H+).
• They have higher boiling points compared to other alcohols and ethers of similar molecular weight due to hydrogen bonding.
• Common examples include acetic acid (vinegar), citric acid (found in citrus fruits), and fatty acids in fats and oils.