Question

The true statement regarding glycerol is/are (A) two \(1^{\circ}\) alcohol (B) Trihydric alcohol (C) one \(2^{\circ}\) alcohol (D) All of these

Short answer

The true statement regarding glycerol is (B) Trihydric alcohol, as glycerol has three hydroxyl groups (-OH) and all alcohol groups are primary alcohols (1°).

Step-by-step solution

Identifying the Hydroxyl Group in Glycerol

The molecular formula for glycerol is C3H8O3. It has three carbon atoms and each carbon atom is attached to one hydroxyl functional group (-OH). Therefore, it is a polyhydric (specifically trihydric) alcohol.

Classifying the Alcohols

Since each of the carbon atoms in glycerol connected to the -OH groups are only attached to one other carbon atom, all alcohol groups in glycerol are primary alcohols (1°). There are no secondary (2°) or tertiary (3°) alcohols in glycerol.

Verifying the Statements

Based on the information derived in previous steps: (A) 'Two 1° alcohols' - this statement is incorrect, as there are three primary alcohols, not two. (B) 'Trihydric alcohol' - this statement is correct, as glycerol has three hydroxyl groups and hence categorized as a trihydric alcohol. (C) 'One 2° alcohol' - this statement is incorrect, as none of the alcohol groups in glycerol are secondary alcohols. (D) 'All of these' - this statement is incorrect as not all previous points are correct. The correct statement regarding glycerol is only (B) - it is a trihydric alcohol.

Key concepts

Alcohol Classification

In organic chemistry, alcohols are classified based on the number of carbon atoms linked to the carbon bearing the hydroxyl (-OH) group. This classification determines whether an alcohol is primary, secondary, or tertiary. It's a simple system:

• Primary (1°) alcohols: The carbon with the -OH group is linked to only one other carbon.
• Secondary (2°) alcohols: The carbon with the -OH group is linked to two other carbons.
• Tertiary (3°) alcohols: The carbon with the -OH group is linked to three other carbons.

Understanding this classification helps predict the reactivity and properties of different alcohols. In the case of glycerol, all the -OH groups are attached to primary carbons, classifying all as primary alcohols. This classification affects glycerol's solubility, boiling point, and other physical properties.

Functional Groups

Functional groups are specific groups of atoms within molecules that dictate how those molecules behave in chemical reactions. They are often the site of chemical reactions. The hydroxyl group (-OH) is one such functional group found in alcohols. The presence of these groups drastically changes the properties of the molecule.

• The hydroxyl group makes alcohols polar, allowing them to form hydrogen bonds.
• This increases their solubility in water and affects their boiling points.

In glycerol, each carbon is bonded to a hydroxyl group. This makes it highly polar and very soluble in water. It’s why glycerol is used in various cosmetic and pharmaceutical products, taking advantage of its moisturizing properties due to the hydrogen bonding capability of its functional groups.

Glycerol Structure

Glycerol, also known as glycerine, is a simple polyhydric alcohol with the molecular formula C3H8O3. It's a colorless, odorless liquid that is sweet-tasting and non-toxic, often used in the food and cosmetic industries. The structure of glycerol consists of three carbon atoms, each bearing a hydroxyl group (-OH).

• Carbon 1, 2, and 3: Each of these carbon atoms is connected to one hydroxyl group, making it a trihydric alcohol.
• The presence of three -OH groups contributes to its high viscosity and hygroscopic nature.

Glycerol's structure enables extensive hydrogen bonding, leading to its unique physical properties like being a good humectant. Understanding its structure is crucial in fields like biochemistry and materials science, where glycerol's role as a backbone in triglycerides is essential.