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Answer true or false. (a) In the IUPAC system, primary aliphatic amines are named as alkanamines. (b) The IUPAC name of \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\) is 1-pentylamine. (c) 2 -Butanamine is chiral and shows enantiomerism. (d) \(N, N\) -Dimethylaniline is a \(3^{\circ}\) aromatic amine.

Short Answer

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(a) True; (b) False; (c) True; (d) True.

Step by step solution

01

Understanding IUPAC Naming for Primary Amines

In the IUPAC naming system, primary aliphatic amines are named by identifying the longest carbon chain attached to the amine group (NH2) and then using the suffix -amine. Therefore, primary aliphatic amines are indeed named as alkanamines, where 'alkan' represents the alkane portion. So, statement (a) is true.
02

Naming the Given Compound

The compound given is \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{NH}_{2}\). The longest carbon chain has 5 carbon atoms, thus it's a 'pentane'. When the NH2 (amine group) is attached as a substituent, it is called 'pentanamine'. According to IUPAC nomenclature, the amine attached to the first carbon position makes it 1-pentanamine, not 1-pentylamine. Hence, statement (b) is false.
03

Checking Chiral Center in 2-Butanamine

A molecule is chiral if it has at least one carbon atom with four different substituents (asymmetric carbon atom). In 2-butanamine, the second carbon is attached to an amine group, a methyl group, and two other different carbon chains, making it a chiral center. Thus, it can show enantiomerism. Therefore, statement (c) is true.
04

Identifying Type of Amine for N,N-Dimethylaniline

N,N-Dimethylaniline is derived from aniline where two hydrogens on the nitrogen are replaced with two methyl groups. This makes it a tertiary amine (\(3^\circ\)), as it has three carbon groups attached to nitrogen. It is also aromatic due to the presence of the benzene ring. Therefore, statement (d) is true.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Primary Aliphatic Amines
Primary aliphatic amines are a fascinating class of compounds in organic chemistry. These amines feature the simple yet versatile NHâ‚‚ group directly attached to a chain of carbon atoms, which is termed the aliphatic chain. In the International Union of Pure and Applied Chemistry (IUPAC) naming system, the task is to identify the longest continuous chain of carbon atoms bonded to the NHâ‚‚ group. The name of the compound is derived by naming this chain as an alkane and then appending the suffix -amine.
  • The name might look like 'alkanamine', where 'alkan' represents the alkane name of the carbon chain.
  • For example, if the longest chain has five carbons, the amine is called 'pentanamine'.

This IUPAC naming aids chemists and students in clearly and uniformly identifying specific amine compounds, eliminating any ambiguity in chemical communication. Understanding these naming rules is crucial for correctly interpreting and writing chemical names.
Chiral Molecules
Chirality in molecules is a key concept in stereochemistry, which refers to the geometric property of a molecule having a non-superimposable mirror image. This quality often manifests in molecules that possess a carbon atom bonded to four distinct groups, referred to as a chiral center.
  • Chiral molecules can exhibit enantiomerism, meaning they exist in two forms (called enantiomers) that are mirror images but cannot be superimposed onto one another.

In the case of 2-butanamine, the second carbon atom is bonded to different groups: one part of an amine group (NH₂), a methyl group (CH₃), a hydrogen, and another carbon chain. This configuration allows the molecule to have a chiral center, rendering it capable of existing as two enantiomers. The property of chirality is essential in many biochemical processes and pharmaceuticals, where the specific 3D orientation of molecules can greatly influence their activity and function.
Tertiary Aromatic Amines
Tertiary aromatic amines combine the chemistry of both aromatic compounds and amines. These molecules feature a nitrogen atom bound to three carbon groups, which may include aromatic rings. Aromatic amines, like aniline derivatives, are known for their stable benzene ring systems.
  • In tertiary amines, such as N,N-Dimethylaniline, the nitrogen atom has three substituents, making it a tertiary ( 3^ o}) amine.
  • This nitrogen atom is bonded to an aromatic ring, thus classifying it as aromatic.

  • The tertiary nature of these amines impacts their chemical properties, such as their electron density and reactivity, due to the delocalization of electrons in the aromatic ring. Recognizing and understanding these characteristics help in predicting how these compounds will behave in different chemical reactions and applications.

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    Most popular questions from this chapter

    Account for the fact that most low-molecular-weight amines are very soluble in water, whereas lowmolecular-weight hydrocarbons are not.

    Name these amine salts. (a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{3}+\mathrm{Cl}^{-}\) (b) \(\left(\mathrm{CH}_{3} \mathrm{CH}_{2}\right)_{2} \mathrm{NH}_{2}+\mathrm{Cl}^{-}\)

    Suppose you have two test tubes, one containing 2-methylcyclohexanol and the other containing 2-methylcyclohexanamine (both of which are insoluble in water) and that you do not know which test tube contains which compound. Describe a simple chemical test by which you could tell which compound is the alcohol and which is the amine.

    Answer true or false. (a) Hydrogen bonding between \(2^{\circ}\) amines is stronger than that between \(2^{\circ}\) alcohols. (b) Primary and secondary amines generally have higher boiling points than hydrocarbons with comparable carbon skeletons. (c) The boiling points of amines increase as the molecular weight of the amine increases.

    Answer true or false. (a) Aqueous solutions of amines are basic. (b) Aromatic amines such as aniline in general are weaker bases than aliphatic amines such as cyclohexanamine. (c) Aliphatic amines are stronger bases than inorganic bases such as \(\mathrm{NaOH}\) and \(\mathrm{KOH}\) (d) Water-insoluble amines react with strong aqueous acids such as HCl to form water-soluble salts. (e) If the pH of an aqueous solution of a \(1^{\circ}\) aliphatic amine, \(\mathrm{RNH}_{2}\), is adjusted to pH 2.0 by the addition of concentrated \(\mathrm{HCl}\), the amine will be present in solution almost entirely as its conjugate acid, \(\mathrm{RNH}_{3}^{+}\) (f) If the pH of an aqueous solution of a \(1^{\circ}\) aliphatic amine, \(\mathrm{RNH}_{2}\), is adjusted to pH 10.0 by the addition of \(\mathrm{NaOH}\), the amine will be present in solution almost entirely as the free base, \(\mathrm{RNH}_{2}\) (g) For a \(1^{\circ}\) aliphatic amine, the concentrations of \(\mathrm{RNH}_{3}^{+}\) and \(\mathrm{RNH}_{2}\) will be equal when the \(\mathrm{pH}\) of the solution is equal to the \(\mathrm{p} K_{\mathrm{b}}\) of the amine.

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