Which of the following is not a correct statement for primary aliphatic amines?
(a) The intermolecul

Q: Why is methylamine an exception when reacting with nitrous acid?

Methylamine ($CH_3NH_2$) reacts with nitrous acid to form a mixture of products, primarily dimethyl ether and methyl nitrite, rather than methanol. This is because the intermediate methyl carbocation is highly unstable and undergoes different pathways compared to higher primary amines.

Q: Why are secondary amines more basic than primary amines in aqueous solution?

Basicity in aqueous solution depends on both the +I effect of alkyl groups (which increases basicity) and solvation by water (which stabilizes the conjugate acid). Secondary amines strike the optimal balance between these two factors, making them generally more basic than primary amines.

Q: Can Gabriel phthalimide synthesis be used for secondary amines?

No, Gabriel phthalimide synthesis is specifically designed to produce pure primary amines. The reaction involves the alkylation of phthalimide, which can only accept one alkyl group, thus preventing over-alkylation to secondary or tertiary amines.

Q: Does tertiary amine show hydrogen bonding?

Tertiary amines ($R_3N$) have no hydrogen atoms attached to the nitrogen. Therefore, they cannot form intermolecular hydrogen bonds with each other, resulting in the lowest boiling points among isomeric amines.

Q: How does hydrogen bonding affect the boiling point?

Extensive hydrogen bonding leads to stronger intermolecular forces, which require more energy (higher temperature) to break. Thus, primary amines have higher boiling points than secondary amines of comparable molecular mass.

Question

Which of the following is not a correct statement for primary aliphatic amines?

Options:

(A) The intermolecular association in primary amines is less than the intermolecular association in secondary amines.

(B) Primary amines on treating with nitrous acid solution form corresponding alcohols except methyl amine.

(C) Primary amines are less basic than the secondary amines.

(D) Primary amines can be prepared by the gabriel phthalimide synthesis.

Sigma Percentile · Accepted Answer

### Analyzing the Setup
The question asks us to identify the **incorrect** statement regarding primary aliphatic amines among the given options. To do this, we need to evaluate each statement based on the fundamental properties of amines, such as their physical state, basicity, and methods of preparation.

### The Master Concept: Intermolecular Association
Let's dive into the first statement, which compares the intermolecular association of primary ($1^\circ$) and secondary ($2^\circ$) amines.

Intermolecular association in amines is primarily governed by **hydrogen bonding**. For hydrogen bonding to occur, we need a highly electronegative atom (like Nitrogen) bonded directly to a Hydrogen atom.

If we look at the structure of a primary amine ($R-NH_2$), the nitrogen atom is bonded to one alkyl group and **two hydrogen atoms**. This allows a single primary amine molecule to participate in multiple hydrogen bonds with neighboring molecules.

On the other hand, a secondary amine ($R_2NH$) has two alkyl groups and only **one hydrogen atom** attached to the nitrogen. With fewer hydrogen atoms available, the extent of hydrogen bonding is significantly reduced.

### Final Conclusion
Because primary amines have more hydrogen atoms available for hydrogen bonding, their intermolecular association is **greater** than that of secondary amines. This directly contradicts statement (a), which claims the association is less. Therefore, statement (a) is the incorrect statement we are looking for!

As a quick verification:
- **Statement (b)** is true: Primary aliphatic amines react with nitrous acid ($HNO_2$) to form alcohols, with methylamine being a notable exception (it forms dimethyl ether and methyl nitrite).
- **Statement (c)** is true: In aqueous solutions, secondary amines are generally more basic than primary amines due to a combination of inductive (+I) effects and solvation effects.
- **Statement (d)** is true: Gabriel phthalimide synthesis is a classic and specific method for preparing pure primary aliphatic amines.

Animated Solution for Chemistry - Organic Compounds: Which of the following is not a correct statement for primary aliphatic amines?

Select Answer:

Visualized Solution

Evaluating Statement (a)

Role of Hydrogen Bonding

Primary Amine Structure

Secondary Amine Structure

Conclusion for Statement (a)

Verifying Other Statements

The Sigma Insight: Amines

Analyzing the Setup The question asks us to identify the incorrect statement regarding primary aliphatic amines among the given options

The Master Concept

Final Conclusion Because primary amines have more hydrogen atoms available for hydrogen bonding, their intermolecular association is greater than that of secondary amines

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