Question

Which one of the following compounds exists as a dipolar ion? (a) carbohydrate (b) amino acid (c) long chain fatty acids (d) \(\alpha\)-halo carbonyl compound

Short answer

(b) amino acid

Step-by-step solution

Understanding the Concept of Dipolar Ion

A dipolar ion, also known as a zwitterion, is a molecule that contains both positive and negative charges, but is overall neutral. In biological and chemical contexts, amino acids are the typical examples known to exist as zwitterions, especially in solution.

Reviewing Each Option

We examine each compound type to determine which can exist as a dipolar ion: (a) Carbohydrates do not have distinct positive and negative charges. (b) Amino acids can adopt a zwitterionic form with a positive amino group (NH3+) and a negative carboxylate group (COO-). (c) Long chain fatty acids usually do not form zwitterions; they primarily have hydrophobic hydrocarbon chains and a single carboxyl group. (d) \(\alpha\)-halo carbonyl compounds are typically not zwitterionic.

Evaluating Amino Acids

Amino acids in water at neutral pH exist in a form where the amino group is protonated and the carboxyl group is deprotonated, forming positive and negative charges, respectively. This balances out to a molecule that is neutral but has internal charges, classifying it as a zwitterion.

Key concepts

Zwitterion

A zwitterion is an intriguing type of molecule. It remarkably features both positive and negative charges within the same molecule, yet it doesn't bear any overall net charge. This neutrality despite internal charges makes zwitterions unique among molecules.

In the realm of chemistry, a zwitterion is also known as a dipolar ion. "Zwitter" is a German term meaning hybrid or hermaphrodite, capturing the essence of these `hybrid` charges co-existing. Typically, you would find such structures in amino acids, which naturally switch to a zwitterionic form in aqueous environments.

• Due to their dual charge setup, zwitterions play a crucial role in biological systems.
• They stabilize molecular structures by mitigating reactions with other charged particles.
• Their unique charge distribution is key to the solubility and stability of proteins and enzymes in water.

Amino Acids

Amino acids are the building blocks of proteins. These small yet essential molecules carry both an amino group \(\text{NH}_2\) and a carboxyl group \(\text{COOH}\). In the general structure of an amino acid, you will find a central carbon atom bonded to the following:

• Amino group \(\text{NH}_2\)
• Carboxyl group \(\text{COOH}\)
• An R-group or side chain (which varies among different amino acids)
• A hydrogen atom

Interestingly, when amino acids are placed in water at a neutral pH of around 7, a fascinating transformation occurs. The amino group gains a proton, becoming positively charged \(\text{NH}_3^+\), while the carboxyl group loses a proton, becoming negatively charged \(\text{COO}^-\). This unique setup results in a zwitterion.

Thus, the amino acid remains neutral overall, but with distinct charges internally. This dual charge is critical, allowing amino acids to connect and form complex proteins that are crucial for life's processes.

Chemical Compounds

In chemistry, a chemical compound is a substance composed of two or more different elements that are chemically bonded in fixed proportions. Understanding chemical compounds is fundamental in grasping how molecules like zwitterions behave and interact.

• Compounds can be organic, containing carbon (like amino acids), or inorganic, lacking carbon-based molecules.
• They may exist as solids, liquids, or gases depending on the temperature and pressure.
• In their stability, chemical compounds determine the multiple reactions facilitated in biological systems.

For biochemical compounds like amino acids, their ability to form zwitterions means they can easily dissolve and interact in aqueous environments. This is crucial in biological systems where watery environments assist in chemical processes needed for life.

Each chemical compound's unique properties influence biochemical pathways and affect the way organisms grow and develop.

Neutral Molecules with Charges

Neutral molecules with charges sound paradoxical, but they're an essential part of chemistry. These molecules, like zwitterions, have internal positive and negative charges that balance out to zero. This unique feature helps maintain the stability and function of many biochemical processes.

• Though the overall molecular charge remains neutral, internal charge distributions affect how molecules orient and react with each other.
• In biological systems, this neutrality with opposite charges allows proteins to fold correctly and interact appropriately with cellular components.
• Having both charges within the same molecule minimizes conflicts in binding with other charged molecules.

These charges, while neutral as a whole, enable reactions through energetic interactions. This quality of having internal but neutralizing charges is a key reason why molecules like amino acids are so foundational to life. Thus, even when not appearing reactive at first glance due to neutrality, such internal charges play an unspoken yet critical role in chemistry.