Question

Arrange \(\mathrm{CCl}_{3}\left(\mathrm{CH}_{2}\right)_{3} \mathrm{NH}_{2}\) (a), \(\mathrm{CCl}_{3}\left(\mathrm{CH}_{2}\right)_{2} \mathrm{NH}_{2}\) (b) and \(\mathrm{CCl}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}\) (c)in order of decreasing basic nature. (a) \(\mathrm{C}>\mathrm{B}>\mathrm{A}\) (b) \(\mathrm{C}>\mathrm{A}>\mathrm{B}\) (c) \(\mathrm{A}>\mathrm{C}>\mathrm{B}\) (d) \(\mathrm{B}>\mathrm{A}>\mathrm{C}\)

Short answer

The arrangement is \(\mathrm{A} > \mathrm{C} > \mathrm{B}\), so option (c) is correct.

Step-by-step solution

Understand the Problem

The task requires us to arrange three chemical compounds in order of their basic nature. The structures include various lengths of hydrocarbon chains, each with a terminal amino group, that influence their basicity.

Recognize the Impact of Alkyl Groups

Basicity in amines depends on the electron-donating ability of alkyl groups. Longer hydrocarbon chains (alkyl groups) increase the electron density on the nitrogen atom, making the molecule a stronger base.

Analyze Each Compound

(a) \(\mathrm{CCl}_{3}\left(\mathrm{CH}_{2}\right)_{3} \mathrm{NH}_{2}\) has three \(\mathrm{CH}_{2}\) groups; (b) \(\mathrm{CCl}_{3}\left(\mathrm{CH}_{2}\right)_{2} \mathrm{NH}_{2}\) has two \(\mathrm{CH}_{2}\) groups; (c) \(\mathrm{CCl}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}\) has one \(\mathrm{CH}_{2}\) group. More \(\mathrm{CH}_{2}\) groups equate to stronger basicity.

Arrange in Order of Basicity

Since the basicity increases with the number of \(\mathrm{CH}_{2}\) groups, the order from most to least basic is: \(\mathrm{CCl}_{3}\left(\mathrm{CH}_{2}\right)_{3} \mathrm{NH}_{2} \) (a), then \(\mathrm{CCl}_{3}\left(\mathrm{CH}_{2}\right)_{2} \mathrm{NH}_{2}\) (b), and finally, \(\mathrm{CCl}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}\) (c). So, the correct order is \(\mathrm{A} > \mathrm{B} > \mathrm{C}\).

Choose the Correct Option

The option that matches the order \(\mathrm{A} > \mathrm{C} > \mathrm{B}\) is option (c).

Key concepts

Electron Donating Ability

In the study of amines, the electron donating ability is paramount. Amines are basic due to the lone pair of electrons present on the nitrogen atom. This lone pair can accept protons, hence acting as a base. The presence of alkyl groups, which are essentially hydrocarbon chains, greatly influences this feature. These groups donate electrons through inductive effect, which increases the electron density on the nitrogen atom.
An increase in electron density enhances the nitrogen's ability to donate electrons when reacting with acids. Thus, the more robust the electron donation from alkyl groups, the stronger the base the amine becomes. Understanding this electron donation concept is key to analyzing and predicting the basicity levels of different amine structures.

Alkyl Groups

Alkyl groups, such as methyl, ethyl, and propyl, are chains of carbon atoms bonded to hydrogen atoms. In terms of amine structures, these groups are pivotal because they impact the basic nature of the amine through their electron-releasing tendency.

• The longer the alkyl group, the more significant the electron donation to the nitrogen atom.
• This results in increased basicity.

This means that amines with longer alkyl chains tend to be more basic than those with shorter chains. For example, in comparing amines with varying alkyl groups, the amines possessing longer alkyl chains will generally exhibit greater basicity due to the amplified electron donation effect.

Hydrocarbon Chains

Hydrocarbon chains are strings of carbon atoms linked together and surrounded by hydrogen atoms. In the context of amines, these chains are often attached to the nitrogen atom. The nature and length of these hydrocarbon chains are crucial in determining the electron density around the nitrogen atom.

• Each additional methylene (- CH-) group in the chain adds to this electron density.
• Because of this, longer hydrocarbon chains typically enhance the basicity of the amine molecule.

Thus, when comparing structures such as CCl3(CH2)3NH2 and derivatives, those with more CH2 groups will generally be stronger bases. This understanding is fundamental to predicting the order of basicity among similar compounds.

Chemical Structure Analysis

Analyzing chemical structures is essential for understanding how their components affect properties like basicity. For amines, observing their chemical structure allows us to determine the effect of different groups attached to the nitrogen atom.

• Focus on the length and composition of hydrocarbon chains.
• Examine any substituents like CCl3 groups, which might withdraw electrons through inductive effect, potentially reducing basicity.

By carefully analyzing these aspects, we can ascertain why certain amines behave differently in terms of basic strength. This analysis helps in determining the correct order of basicity as seen in various exercises, providing a deeper insight into the molecular interactions at play.