Question

A substance forms zwitter ion. It can have functional groups \([2002]\) (a) \(-\mathrm{NH}_{2},-\mathrm{COOH}\) (b) \(-\mathrm{NH}_{2},-\mathrm{SO}_{3} \mathrm{H}\) (c) both (d) none of these

Short answer

The correct answer is (c) both.

Step-by-step solution

Understanding Zwitterions

A zwitterion is a molecule that contains equal numbers of positively and negatively charged groups, but the molecule as a whole is neutral. Typically, this occurs in amino acids where one group tends to donate a proton and another group accepts it.

Identifying Functional Groups

Analyze the given functional groups: - \(-\mathrm{NH}_{2}\) is a basic amine group, which can accept a proton to become \(-\mathrm{NH}_{3}^{+}\). - \(-\mathrm{COOH}\) is a carboxylic acid group which can donate a proton to form \(-\mathrm{COO}^{-}\). - \(-\mathrm{SO}_{3}\mathrm{H}\) is a sulfonic acid group which can also donate a proton to become \(-\mathrm{SO}_{3}^{-}\).

Assessing Each Option

- Option (a): Contains \(-\mathrm{NH}_{2}\) and \(-\mathrm{COOH}\). Here, \(-\mathrm{NH}_{2}\) can accept a proton, becoming positively charged, and \(-\mathrm{COOH}\) can donate a proton, becoming negatively charged, forming a zwitterion.- Option (b): Contains \(-\mathrm{NH}_{2}\) and \(-\mathrm{SO}_{3}\mathrm{H}\). Similarly, \(-\mathrm{NH}_{2}\) can accept a proton and \(-\mathrm{SO}_{3}\mathrm{H}\) can donate a proton to form a zwitterion.- Option (c): Indicating both, which is consistent as both options (a) and (b) form zwitterions.- Option (d): Indicating none, which is inconsistent as both (a) and (b) can form zwitterions.

Selecting the Correct Answer

Since both (a) and (b) contain functional groups that can form zwitterions by proton donation and acceptance, option (c) which says "both" is correct.

Key concepts

Amino Acids

Amino acids are the building blocks of proteins and play a crucial role in various biological functions. These organic compounds have two main characteristic functional groups: an amino group

• The amino group ( \(-\mathrm{NH}_{2} \)) generally acts as a base. It has the ability to accept protons, thereby turning into a positively charged ammonium ion ( \(\mathrm{NH}_{3}^{+} \)).
• A carboxyl group ( \(-\mathrm{COOH} \)), which tends to release protons. Upon donating a proton, this group transforms into a negatively charged carboxylate ion ( \(-\mathrm{COO}^{-} \)).

Amino acids are characterized by these functional groups, which allow them to participate in the formation of zwitterions, substances that contain both positively and negatively charged regions. In the right conditions, such as neutral pH, amino acids can exist as zwitterions, enabling them to interact with other molecules and play essential roles in metabolism and protein synthesis.

Functional Groups

Functional groups are specific groupings of atoms within molecules that have their own characteristic properties and reactivity. They play a significant role in the chemical behavior of molecules. For amino acids, two primary functional groups are of interest, both contributing to the formation of zwitterions:

• The ( \(-\mathrm{NH}_{2} \)) group, known for its ability to accept a proton due to its basic nature.
• The \(-\mathrm{COOH} \) group, which typically donates a proton because it acts as a weak acid.
• Both these groups allow for the creation of zwitterions, where the amino group becomes \(-\mathrm{NH}_{3}^{+} \) and the carboxyl group turns into \(-\mathrm{COO}^{-} \).

Such interactions are central to understanding how zwitterions form and dissolve in water, aiding in cellular and biochemical processes.

Proton Donation and Acceptance

The concept of proton donation and acceptance is integral to the behavior of zwitterions and amino acids. In essence, some groups within a molecule can donate a proton (or extra hydrogen ion, (\[\text{H}^+\])), while others can accept a proton.

A closer look

The \(\text{carboxyl group } (-\mathrm{COOH})\) in amino acids is a classic proton donor. It loses a hydrogen ion to become \(-\mathrm{COO}^{-}\), allowing the molecule to carry a negative charge in a specific condition.
The amino group \(-\mathrm{NH}_2\), on the other hand, acts as a proton acceptor. It gains a proton to form \(-\mathrm{NH}_3^{+}\), a positive ion.
Together, these transformations allow molecules to align as zwitterions, incorporating both negative and positive charges. This interplay is vital, helping amino acids maintain structural integrity and participate effectively in metabolic pathways.