Question

In addition to aldehyde group glucose contains (a) one secondary OH and four primary OH groups (b) one primary OH and four secondary OH groups (c) two primary \(\mathrm{OH}\) and three secondary OH groups (d) three primary OH and two secondary OH groups

Short answer

(b) one primary OH and four secondary OH groups.

Step-by-step solution

Understanding the Structure of Glucose

Glucose is a monosaccharide with the chemical formula \(\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6\). It has an aldehyde group at the first carbon, and the rest of the carbons have hydroxyl (OH) groups attached.

Identifying Types of OH Groups

Primary OH groups are attached to a carbon that is connected to only one other carbon, whereas secondary OH groups are attached to a carbon connected to two other carbons.

Analyzing Carbon Chain of Glucose

Glucose consists of a chain of six carbon atoms. The aldehyde group is on carbon 1. The OH groups on the subsequent carbons are positioned as follows: the OH at carbon 1 is part of the aldehyde group, the OH on carbon 6 is primary because it's at the end of the chain, and the OH groups on carbons 2, 3, 4, and 5 are secondary because each of these carbons is connected to two other carbon atoms.

Counting Primary and Secondary OH Groups

From the analysis of the carbon chain, glucose has one primary OH group (on carbon 6) and four secondary OH groups (on carbons 2, 3, 4, and 5).

Choosing the Correct Answer

Based on the analysis, glucose has one primary OH group and four secondary OH groups. Therefore, the correct option is (b) one primary OH and four secondary OH.

Key concepts

Monosaccharide

Glucose is part of a fascinating class of sugars known as monosaccharides. These are the simplest forms of carbohydrates. The term 'monosaccharide' itself suggests a "single" sugar unit. Simple sugars like glucose are vital because they serve as the building blocks for more complex carbohydrates.
Monosaccharides have a general formula of \(\mathrm{(CH_2O)}_n\), where \(n\) can be any number from three to seven. In the case of glucose, \(n = 6\), which contributes to its formula \(\mathrm{C_6H_{12}O_6}\). Glucose is particularly crucial because:

• It is a primary source of energy for cells.
• It participates in vital biochemical processes, like glycolysis and photosynthesis.
• It can bond with other monosaccharides to form disaccharides and polysaccharides.

Understanding monosaccharides is essential for unraveling the chemistry of life itself because they are involved in numerous biological processes.

Primary OH Groups

In glucose, knowing the difference between primary and secondary hydroxyl (OH) groups helps in grasping its structure and reactivity. A primary OH group is attached to a carbon atom that is bonded to just one other carbon. This configuration usually appears at the end of a carbon chain.
For glucose, the primary OH group is located at carbon 6. This position makes it distinct from the others and impacts the molecule's properties and reactivity.
Here's why primary OH groups are significant:

• They often engage in distinct chemical reactions due to being terminal OH groups.
• They affect the solubility and physical properties of glucose in solution.
• Some specific reactions target primary OH groups due to their relative accessibility in the molecule.

By identifying the primary OH groups in glucose, students can better understand its chemical behavior and how it interacts with other molecules.

Secondary OH Groups

Secondary OH groups in glucose are attached to a carbon atom bonded to two other carbons. This makes them integral to the internal structure of the glucose molecule, especially concerning its stability and function.
In the glucose molecule, the secondary OH groups are found at carbons 2, 3, 4, and 5. These OH groups influence both the molecule's physical characteristics and its biological work.
Key points about secondary OH groups include:

• They possess a slightly different reactivity profile compared to primary OH groups.
• They play a crucial role in glucose's ability to form hydrogen bonds, impacting solubility and binding capacity.
• These groups allow glucose to partake in various chemical modifications needed for energy metabolism.

Grasping the distribution of secondary OH groups aids in understanding the diverse roles glucose plays in biological systems, especially its solubility and reactivity in aqueous environments.