Problem 167 - A Complete Resource Book in Chemistry for JEE Main

Question

The two functional groups present in a typical carbohydrate are: (a) \(-\mathrm{CHO}\) and \(-\mathrm{COOH}\) (b) \(>\mathrm{C}=\mathrm{O}\) and \(-\mathrm{OH}\) (c) \(-\mathrm{OH}\) and \(-\mathrm{CHO}\) (d) \(-\mathrm{OH}\) and \(-\mathrm{COOH}\)

Step-by-Step Solution

Answer

The correct answer is (c) \(-\mathrm{OH}\) and \(-\mathrm{CHO}\).

Step 1: Understanding Functional Groups in Carbohydrates

Carbohydrates are organic compounds that are primarily composed of carbon, hydrogen, and oxygen. The key to identifying the functional groups in a carbohydrate is understanding that they typically contain hydroxyl groups \(-\mathrm{OH}\) and an aldehyde group \(-\mathrm{CHO}\) or a ketone group \(>\mathrm{C}=\mathrm{O}\).

Step 2: Evaluating the Options

We need to identify the option that contains the correct functional groups present in most carbohydrates. 1. Option (a) \(-\mathrm{CHO}\) and \(-\mathrm{COOH}\): This combination does not correctly represent typical carbohydrates because \(-\mathrm{COOH}\) (carboxylic acid) is not generally present in carbohydrates.2. Option (b) \(>\mathrm{C}=\mathrm{O}\) and \(-\mathrm{OH}\): This could be a possibility for ketose carbohydrates, which contain a ketone group and hydroxyl groups.3. Option (c) \(-\mathrm{OH}\) and \(-\mathrm{CHO}\): This is the correct combination for aldose carbohydrates, as they contain aldehyde and hydroxyl groups.4. Option (d) \(-\mathrm{OH}\) and \(-\mathrm{COOH}\): Again, this is incorrect as \(-\mathrm{COOH}\) isn't typical in carbohydrates.

Step 3: Selecting the Correct Answer

Based on the evaluation, option (c) \(-\mathrm{OH}\) and \(-\mathrm{CHO}\) accurately describes the functional groups present in a typical carbohydrate. Aldose carbohydrates specifically fit this description, which is common in nature.

Key Concepts

Aldose Carbohydrates

Aldose carbohydrates are a vital category of carbohydrates. They contain an aldehyde group early in their structure. An aldehyde group is found at the end of a carbon chain. This specific structure classifies them as aldoses. Aldose carbohydrates occur naturally. You'll find them in many foods like honey and fruits. These sugars play significant roles in energy production and storage in the body, making them crucial to understand in organic chemistry studies related to living organisms. While aldoses have their own distinct features, they also share characteristics with other carbohydrates, especially their structural presence of hydroxyl groups.

Organic Chemistry

Organic chemistry is a branch of science dealing with carbon-based compounds. These compounds include carbohydrates like aldoses. Organic chemistry explores how molecules are structured, their properties, and reactions they undergo. Learning about functional groups is crucial here. Functional groups are specific groupings of atoms within molecules that determine how the molecule behaves in chemical reactions. In carbohydrates, the aldehyde group and hydroxyl group significantly influence these properties, determining whether the carbohydrate is an aldose or ketose. The foundational knowledge in organic chemistry helps in understanding complex interactions in biology, chemistry, and related fields.

Hydroxyl Group (-OH)

The hydroxyl group is an essential functional group present in carbohydrates. Characterized by the elemental notations of oxygen and hydrogen, this group is represented as a single bond: \(-\mathrm{OH}\). Its presence drastically influences the chemical properties of carbohydrates generating polarity, enhancing solubility in water. Hydroxyl groups are also highly reactive in chemical reactions especially when paired with an aldehyde group in aldoses. Additionally, hydroxyl groups endow carbohydrates with certain sweetness and are responsible for hydrogen bonding, which is a major contributing factor for the physical properties of sugars such as viscosity in solutions.

Aldehyde Group (-CHO)

The aldehyde group is a defining feature in aldose carbohydrates. This functional group contains a carbon (double-bonded to an oxygen atom) and also bonded to a hydrogen atom, forming the structure: \(-\mathrm{CHO}\). It is typically found at the end of a carbon atom chain. The aldehyde group plays a crucial role in the reactivity of carbohydrates, famously participating in addition reactions. It leads to the formation of various hemiacetals or acetals when reacting with hydroxyl groups. In aldoses, the combination of the aldehyde and various hydroxyl groups defines the carbohydrate’s distinct features, including its behavior under acidic or basic conditions. This knowledge is fundamental in the realm of organic chemistry for understanding the nature and reactions of sugars and similar organic compounds.