Question

Which of the following compounds would exhibit detergent properties? (a) \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{10} \mathrm{CH}_{2} \mathrm{~N}^{+}\left(\mathrm{CH}_{3}\right)_{3} \mathrm{Cl}^{-}\) (b) \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{10} \mathrm{CH}_{2} \mathrm{COOCH}_{3}\) (c) \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{10} \mathrm{CH}_{2} \mathrm{SO}^{-}{ }_{3} \mathrm{Na}^{+}\)

Short answer

The compounds (a) \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{10} \mathrm{CH}_{2}\mathrm{~N}^{+}\left(\mathrm{CH}_{3}\right)_{3} \mathrm{Cl}^{-}\) and (c) \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{10} \mathrm{CH}_{2}\mathrm{SO}^{-}{ }_{3} \mathrm{Na}^{+}\) exhibit detergent properties, as they have both hydrophilic and hydrophobic parts.

Step-by-step solution

Compound (a)

The compound (a) has a long hydrocarbon chain \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{10} \mathrm{CH}_{2}\), which is hydrophobic. The end of the compound has a charged group \(\mathrm{~N}^{+}\left(\mathrm{CH}_{3}\right)_{3} \mathrm{Cl}^{-}\), which is hydrophilic.

Compound (b)

The compound (b) also has a long hydrocarbon chain \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{10} \mathrm{CH}_{2}\), which is hydrophobic. The end of the compound has an ester group \(\mathrm{COOCH}_{3}\), which is not charged and not hydrophilic.

Compound (c)

The compound (c) has a long hydrocarbon chain \(\mathrm{CH}_{3}\left(\mathrm{CH}_{2}\right)_{10} \mathrm{CH}_{2}\), which is hydrophobic. The end of the compound has a charged group \(\mathrm{SO}^{-}{ }_{3} \mathrm{Na}^{+}\), which is hydrophilic. #Step 2: Evaluate detergent properties# We are now going to evaluate the detergent properties based on the presence of both hydrophilic and hydrophobic parts in each compound.

Evaluate Compound (a)

Compound (a) has a hydrophobic part, the long hydrocarbon chain, and a hydrophilic part, the charged group \(\mathrm{~N}^{+}\left(\mathrm{CH}_{3}\right)_{3} \mathrm{Cl}^{-}\). Hence, this compound can exhibit detergent properties.

Evaluate Compound (b)

Compound (b) has a hydrophobic part, the long hydrocarbon chain, but the end group is not hydrophilic (it is an ester group \(\mathrm{COOCH}_{3}\)). This compound will not exhibit detergent properties because it lacks a hydrophilic part.

Evaluate Compound (c)

Compound (c) has a hydrophobic part, the long hydrocarbon chain, and a hydrophilic part, the charged group \(\mathrm{SO}^{-}{ }_{3} \mathrm{Na}^{+}\). This compound can also exhibit detergent properties. #Step 3: Determine the answer# Based on our evaluations, compounds (a) and (c) exhibit detergent properties. So, the answer is (a) and (c).

Key concepts

Hydrophobic

In chemistry, hydrophobic refers to molecules that do not interact well with water. This non-water-loving characteristic is typically because these molecules are nonpolar, meaning they lack a charge. They prefer to associate with other nonpolar molecules instead of with water. For instance, the long hydrocarbon chain in detergents is hydrophobic.
It resists mixing with water, making it excellent at binding with oils and fats.

• Does not dissolve in water
• Nonpolar in nature
• Attracts oils and grease

When detergents encounter water, the hydrophobic part avoids it and instead targets dirt and grease, pulling them away from surfaces.

Hydrophilic

On the opposite hand of hydrophobic is the concept of hydrophilic. Molecular components that are hydrophilic have an affinity for water. These sections are usually polar or charged, allowing them to interact and dissolve in water easily.
For instance, charged groups such as ext{N}^{+}( ext{CH}_3)_3 ext{Cl}^{-} in some detergents interact well with water.

• Dissolves in water
• Can be polar or charged
• Makes detergents effective

This property helps the detergent molecules to break and disperse grease in water, lifting it away from surfaces.

Long Hydrocarbon Chain

A typical feature of many detergents is their long hydrocarbon chain. This chain is made up of a series of carbon and hydrogen atoms connected in a row.
It is this part of the detergent molecule that makes it hydrophobic. These chains are usually lengthy because it increases the molecule's non-polarity, enhancing its ability to interact with oils and fats.
This feature is crucial in how detergents work:

• Gives the molecule its hydrophobic property
• Makes it effective at binding with grease
• Helps dissolve oily stains

Without the long hydrocarbon chain, the detergent wouldn't be able to penetrate or interact with oily residues effectively.

Charged Group

Detergents often contain a charged group at one end of the molecule, which contributes to their hydrophilic nature. A charged group can be positive, negative, or involve both charges.
In some detergents, these are like ext{SO}^{-}_3 ext{Na}^{+}, assisting them to bind with water effectively.
The significance of a charged group includes:

• Facilitates water solubility
• Ensures detergent is mixed throughout water
• Helps in the breakdown of grease into smaller droplets

By attracting water, the charged group ensures that the detergent can actively work across the water’s surface.

Ionic Surfactants

Ionic surfactants are a type of detergent that include charged particles, or ions, in their structure. These surfactants are both hydrophobic and hydrophilic, giving them the ability to interact with a wide range of substances. This dual characteristic means they can easily pull oils and greases into water.
Surfactants like ext{N}^{+}( ext{CH}_3)_3 ext{Cl}^{-} are effective at cleaning and emulsifying because:

• They have both ionic and nonionic components
• Can surround and trap oily particles
• Allow oils to be washed away with water

Ionic surfactants are foundational in many cleaning products, converting greasy residues into washable forms.