Question

Match the following \begin{tabular}{ll} \hline Column-I & Column-II \\ \hline (a) Glucose & (p) Tollen's reagent \\ (b) Acetaldehyde & (q) Bromine water \\ (c) Sucrose & (r) Phenyl hydrazine \\ (d) Maltose & (s) Disaccharide \\ & (t) Ammonia \end{tabular}

Short answer

(a) - (p), (b) - (q), (c) - (s), (d) - (r)

Step-by-step solution

Understand the Components

In the exercise, you need to find associations between compounds in Column-I with reagents or classifications in Column-II. You have glucose, acetaldehyde, sucrose, and maltose to match with Tollen's reagent, bromine water, phenyl hydrazine, disaccharide, and ammonia.

Match Glucose

Glucose is a simple sugar (monosaccharide) that can react with Tollen's reagent. The presence of an aldehyde group allows glucose to reduce Tollen's reagent, forming a silver mirror. Therefore, glucose matches with Tollen's reagent.

Match Acetaldehyde

Acetaldehyde is an aldehyde, and therefore, it also reacts with Tollen's reagent, leading to a silver mirror formation. However, it is more famously identified with bromine water, as the reaction involves the synthesis of bromoacetaldehyde. For this exercise, the distinctive interaction with Tollen's reagent takes precedence.

Match Sucrose

Sucrose consists of two monosaccharide units, making it a disaccharide. It does not react in the same way with Tollen's reagent like glucose or acetaldehyde does. Therefore, sucrose matches with disaccharide.

Match Maltose

Maltose, like sucrose, is composed of two glucose units and is a disaccharide. However, unlike sucrose, maltose tends to have more pronounced reactions with phenyl hydrazine because it has a free aldehyde group in one of the glucose units.

Key concepts

Carbohydrates

Carbohydrates are essential biomolecules that play a vital role in living organisms. They are primarily composed of carbon, hydrogen, and oxygen atoms, typically in the ratio of 1:2:1, resembling the basic formula \( C_n(H_2O)_n \). Carbohydrates are often categorized into three major types based on their structure: monosaccharides, disaccharides, and polysaccharides.

• Monosaccharides: These are the simplest form of carbohydrates, consisting of single sugar units, such as glucose and fructose. They are the building blocks for more complex carbohydrates.
• Disaccharides: These carbohydrates are made from two monosaccharide units linked together. Common examples include sucrose, lactose, and maltose.
• Polysaccharides: Composed of long chains of monosaccharide units, these large molecules include starch, cellulose, and glycogen.

Carbohydrates are a primary energy source for the body and also function in structural and functional roles, such as in cell walls and the immune response. Glucose, a common carbohydrate, is crucial for cellular respiration, providing energy for cells.

Tollen's reagent

Tollen's reagent is a chemical solution used primarily to distinguish between aldehydes and ketones. It is also known as ammoniacal silver nitrate. This reagent reacts specifically with aldehydes to form a distinctive silver mirror on the inner surface of a test tube, which makes it a useful tool in organic chemistry labs.

Composition and Reaction:

Tollen's reagent is prepared by mixing silver nitrate (\(AgNO_3\)) with ammonia (\(NH_3\)) until a clear, colorless solution containing the complex [\(Ag(NH_3)_2^+\)] is formed. When this solution is added to an aldehyde:

• The aldehyde reduces the silver ions, resulting in the deposition of metallic silver.
• This forms a reflective, silver layer on the inner walls of the test tube.
• The reaction can be used to differentiate aldehydes from ketones due to this specific identification property.

Tollen's reagent is named after the chemist who developed it in the 19th century, and while it is sensitive and useful, it is important to handle it with care due to its light-sensitive nature.

Aldehyde reactions

Aldehydes are organic compounds containing the functional group \( -CHO \). This group is highly reactive, enabling aldehydes to undergo various chemical reactions, especially oxidation and reduction processes, which are crucial in organic chemistry.

Reactions of Aldehydes:

Aldehydes are characterized by their ability to be readily oxidized to carboxylic acids or reduced to alcohols:

• Oxidation: Aldehydes can be oxidized to form carboxylic acids. This is commonly seen in reactions with oxidizing agents such as Tollen's reagent or potassium permanganate.
• Reduction: Aldehydes can be reduced to primary alcohols, typically using reducing agents like sodium borohydride (\(NaBH_4\)) or lithium aluminum hydride (\(LiAlH_4\)).
• Addition reactions: Aldehydes can undergo nucleophilic addition reactions because of the electrophilic nature of the carbonyl carbon, making them susceptible to attack by nucleophiles such as water or alcohols.

Additionally, aldehydes can form important derivatives, for example, forming hydrazone derivatives with phenylhydrazine, which is valuable in identifying and characterizing various aldehydes.
By understanding these reactions, one can appreciate the diverse nature of aldehydes and their pivotal role in bioorganic and industrial chemical processes.