101. Which common name best fits \(CH_3NHCH_2CH_3\)?
ⓐ. Ethylmethylamine
ⓑ. Ethylpropylamine
ⓒ. Dimethylamine
ⓓ. Propylamine
Correct Answer: Ethylmethylamine
Explanation: The nitrogen atom in \(CH_3NHCH_2CH_3\) is attached to one methyl group and one ethyl group. In common naming, both alkyl groups attached to nitrogen are named before “amine.” Since the groups are ethyl and methyl, the common name is ethylmethylamine. It is not diethylamine or dimethylamine because the two groups on nitrogen are different.
102. Which formula represents diethylamine?
ⓐ. \(CH_3CH_2NH_2\)
ⓑ. \(CH_3CH_2NHCH_2CH_2CH_3\)
ⓒ. \((CH_3)_3N\)
ⓓ. \(CH_3CH_2NHCH_2CH_3\)
Correct Answer: \(CH_3CH_2NHCH_2CH_3\)
Explanation: \(\textbf{Name analysis:}\)
Diethylamine contains two ethyl groups attached to nitrogen.
\(\textbf{Ethyl group:}\)
Each ethyl group is \(CH_3CH_2-\).
\(\textbf{Secondary amine structure:}\)
Two ethyl groups and one hydrogen on nitrogen give \(CH_3CH_2NHCH_2CH_3\).
\(\textbf{Final Answer:}\)
Diethylamine is \(CH_3CH_2NHCH_2CH_3\).
103. Which common-name and IUPAC-name pair is correctly matched?
ⓐ. \(CH_3NH_2\) — \(N\)-methylethanamine
ⓑ. \(CH_3CH_2NH_2\) — \(N\)-methylmethanamine
ⓒ. \((CH_3)_2NH\) — \(N\)-methylmethanamine
ⓓ. \((CH_3)_3N\) — \(N\)-methylethanamine
Correct Answer: \((CH_3)_2NH\) — \(N\)-methylmethanamine
Explanation: \((CH_3)_2NH\) has two methyl groups attached to nitrogen and one \(N-H\) bond. In systematic naming, one methyl group is treated as the parent methanamine and the other is named as an \(N\)-methyl substituent. Thus its IUPAC name is \(N\)-methylmethanamine. Its common name is dimethylamine.
104. Which name is a common name rather than the preferred systematic name for \(C_6H_5NH_2\)?
ⓐ. Benzenamine
ⓑ. Nitrobenzene
ⓒ. Phenylazide
ⓓ. Aniline
Correct Answer: Aniline
Explanation: \(C_6H_5NH_2\) is widely known by the common name aniline. Its systematic name is benzenamine because the \(-NH_2\) group is attached directly to benzene. Nitrobenzene contains \(-NO_2\), not \(-NH_2\). Phenylazide contains a different nitrogen group and is not the same compound.
105. Which formula corresponds to benzylamine?
ⓐ. \(C_6H_5CH_2CH_2NH_2\)
ⓑ. \(C_6H_5CH_2Cl\)
ⓒ. \(C_6H_5NHCH_3\)
ⓓ. \(C_6H_5CH_2NH_2\)
Correct Answer: \(C_6H_5CH_2NH_2\)
Explanation: Benzylamine contains a benzyl group, \(C_6H_5CH_2-\), attached to \(-NH_2\). Therefore, its formula is \(C_6H_5CH_2NH_2\). Aniline is \(C_6H_5NH_2\), where nitrogen is directly attached to the benzene ring. The \(CH_2\) spacer is the key feature that separates benzylamine from aniline.
106. Which common name is used for \(C_6H_5CH_2NH_2\)?
ⓐ. Benzylamine
ⓑ. Aniline
ⓒ. Phenylamine
ⓓ. Diphenylamine
Correct Answer: Benzylamine
Explanation: The group \(C_6H_5CH_2-\) is called benzyl. When this benzyl group is attached to \(-NH_2\), the common name becomes benzylamine. Aniline has nitrogen directly attached to the ring as \(C_6H_5NH_2\). Diphenylamine contains two phenyl groups attached to nitrogen.
107. Which statement correctly distinguishes phenylamine and benzylamine?
ⓐ. Both names refer to \(C_6H_5CH_2NH_2\).
ⓑ. Phenylamine has \(CH_2\) between ring and nitrogen.
ⓒ. Phenylamine is aniline; benzylamine is side-chain \(NH_2\).
ⓓ. Benzylamine has nitrogen directly bonded to the benzene ring.
Correct Answer: Phenylamine is aniline; benzylamine is side-chain \(NH_2\).
Explanation: Phenylamine is another name used for aniline, \(C_6H_5NH_2\), in which nitrogen is directly attached to the aromatic ring. Benzylamine is \(C_6H_5CH_2NH_2\), where nitrogen is attached to the side-chain \(CH_2\) group. The formulas differ by the position of the \(CH_2\) unit. This distinction is important because ring-attached and side-chain amines behave differently.
108. Which common name matches \(C_6H_5NHCH_3\)?
ⓐ. Benzylmethylamine
ⓑ. \(N\)-methylaniline
ⓒ. Methylbenzylamine
ⓓ. Dimethylbenzeneamine
Correct Answer: \(N\)-methylaniline
Explanation: \(C_6H_5NHCH_3\) is derived from aniline by replacing one hydrogen on nitrogen with a methyl group. Since the methyl group is attached directly to nitrogen, the name uses the \(N\)- locant. The compound is therefore called \(N\)-methylaniline. It is not benzylmethylamine because no \(CH_2\) group separates the ring from nitrogen.
109. Which compound is commonly called aniline?
ⓐ. \(C_6H_5NO_2\)
ⓑ. \(C_6H_5CH_2NH_2\)
ⓒ. \((C_6H_5)_2NH\)
ⓓ. \(C_6H_5NH_2\)
Correct Answer: \(C_6H_5NH_2\)
Explanation: Aniline is the common name for \(C_6H_5NH_2\). The compound has an \(-NH_2\) group attached directly to a benzene ring. \(C_6H_5CH_2NH_2\) is benzylamine because the amino group is on the side chain. \((C_6H_5)_2NH\) is diphenylamine, and \(C_6H_5NO_2\) is nitrobenzene.
110. Which common-name pair correctly represents a secondary and a tertiary simple amine respectively?
ⓐ. Methylamine and ethylamine
ⓑ. Ethylamine and dimethylamine
ⓒ. Trimethylamine and dimethylamine
ⓓ. Dimethylamine and trimethylamine
Correct Answer: Dimethylamine and trimethylamine
Explanation: Dimethylamine, \((CH_3)_2NH\), is secondary because nitrogen is attached to two methyl groups and one hydrogen atom. Trimethylamine, \((CH_3)_3N\), is tertiary because nitrogen is attached to three methyl groups and no hydrogen atom. Methylamine and ethylamine are both primary amines. The prefixes mono-, di-, and tri- help identify how many alkyl groups are attached to nitrogen.
111. Which name best represents \(CH_3CH_2N(CH_3)_2\) in common naming?
ⓐ. Ethylmethylamine
ⓑ. Ethyldimethylamine
ⓒ. Diethylmethylamine
ⓓ. Triethylamine
Correct Answer: Ethyldimethylamine
Explanation: In \(CH_3CH_2N(CH_3)_2\), nitrogen is bonded to one ethyl group and two methyl groups. Common naming lists the alkyl groups attached to nitrogen before “amine.” Since the groups are one ethyl and two methyl groups, the name is ethyldimethylamine. The molecule is tertiary because nitrogen is attached to three carbon groups.
112. Which formula is best represented by the common name ethyldimethylamine?
ⓐ. \(CH_3NHCH_2CH_3\)
ⓑ. \(CH_3CH_2NHCH_2CH_3\)
ⓒ. \(CH_3CH_2N(CH_3)_2\)
ⓓ. \((CH_3CH_2)_3N\)
Correct Answer: \(CH_3CH_2N(CH_3)_2\)
Explanation: \(\textbf{Read the common name:}\)
Ethyldimethylamine contains one ethyl group and two methyl groups attached to nitrogen.
\(\textbf{Write the groups:}\)
The ethyl group is \(CH_3CH_2-\), and the two methyl groups are shown as \((CH_3)_2\).
\(\textbf{Attach all groups to nitrogen:}\)
Putting one ethyl and two methyl groups on nitrogen gives \(CH_3CH_2N(CH_3)_2\).
\(\textbf{Final Answer:}\)
Ethyldimethylamine is \(CH_3CH_2N(CH_3)_2\).
113. Which IUPAC name is suitable for \(C_6H_5NH_2\)?
ⓐ. Benzylamine
ⓑ. Nitrobenzene
ⓒ. Benzenamine
ⓓ. Benzamide
Correct Answer: Benzenamine
Explanation: \(C_6H_5NH_2\) has an \(-NH_2\) group directly attached to a benzene ring. In systematic naming, benzene bearing an amino group is named benzenamine. The common name aniline is also widely used for the same compound. Benzylamine would require a \(CH_2\) group between the ring and nitrogen, as in \(C_6H_5CH_2NH_2\).
114. Which pair represents two acceptable names for \(C_6H_5NH_2\)?
ⓐ. Aniline and benzenamine
ⓑ. Benzylamine and phenylmethanamine
ⓒ. Nitrobenzene and benzenamine
ⓓ. Benzamide and phenylamine oxide
Correct Answer: Aniline and benzenamine
Explanation: \(C_6H_5NH_2\) is commonly known as aniline and systematically named benzenamine. Both names refer to an amino group directly bonded to the benzene ring. Benzylamine is different because it has the formula \(C_6H_5CH_2NH_2\). Nitrobenzene and benzamide contain different functional groups, so they do not name the same compound.
115. Which formula corresponds to \(p\)-methylaniline?
ⓐ. \(C_6H_5CH_2NH_2\)
ⓑ. \(m\)-\(CH_3C_6H_4NH_2\)
ⓒ. \(o\)-\(CH_3C_6H_4NH_2\)
ⓓ. \(p\)-\(CH_3C_6H_4NH_2\)
Correct Answer: \(p\)-\(CH_3C_6H_4NH_2\)
Explanation: \(\textbf{Read the base name:}\)
Aniline means \(C_6H_5NH_2\), where \(-NH_2\) is directly attached to benzene.
\(\textbf{Read the substituent:}\)
Methylaniline means a \(CH_3\) group is also attached to the benzene ring.
\(\textbf{Interpret }p\textbf{-:}\)
The prefix \(p\)- means para, so the \(CH_3\) group is at the \(1,4\)-relationship with respect to \(-NH_2\).
\(\textbf{Formula match:}\)
The para isomer is represented as \(p\)-\(CH_3C_6H_4NH_2\).
\(\textbf{Final Answer:}\)
\(p\)-methylaniline corresponds to \(p\)-\(CH_3C_6H_4NH_2\).
116. In substituted anilines, what does the prefix \(m\)- indicate?
ⓐ. Substituents occupy the 1,2-positions.
ⓑ. Substituents occupy the \(1,3\)-positions.
ⓒ. Substituents occupy the \(1,4\)-positions.
ⓓ. Substituents are attached to nitrogen only.
Correct Answer: Substituents occupy the \(1,3\)-positions.
Explanation: The prefix \(m\)- stands for meta substitution on a benzene ring. In a disubstituted benzene, meta means that the two substituents occupy the \(1,3\)-positions. For an aniline derivative, the \(-NH_2\) group is usually treated as being at position \(1\), and the meta substituent is at position \(3\). Ortho corresponds to \(1,2\), while para corresponds to \(1,4\).
117. Which name correctly describes \(o\)-\(NO_2C_6H_4NH_2\)?
ⓐ. \(p\)-nitroaniline
ⓑ. \(m\)-nitroaniline
ⓒ. \(o\)-nitroaniline
ⓓ. \(N\)-nitroaniline
Correct Answer: \(o\)-nitroaniline
Explanation: In \(o\)-\(NO_2C_6H_4NH_2\), the nitro group and the amino group are adjacent on the benzene ring. Adjacent disubstitution corresponds to the ortho or \(o\)-position. The name is therefore \(o\)-nitroaniline. \(N\)-nitroaniline would mean that the nitro group is attached to nitrogen, not to the benzene ring carbon.
118. Which formula best represents \(N\)-methylaniline?
ⓐ. \(C_6H_5CH_2NH_2\)
ⓑ. \(CH_3C_6H_4NH_2\)
ⓒ. \(C_6H_5N(CH_3)_2\)
ⓓ. \(C_6H_5NHCH_3\)
Correct Answer: \(C_6H_5NHCH_3\)
Explanation: \(\textbf{Base structure:}\)
Aniline is \(C_6H_5NH_2\).
\(\textbf{Meaning of }N\textbf{-methyl:}\)
The \(N\)- locant shows that the methyl group is attached directly to nitrogen.
\(\textbf{Modify aniline:}\)
Replacing one \(N-H\) hydrogen of aniline by \(CH_3\) gives \(C_6H_5NHCH_3\).
\(\textbf{Avoid ring substitution confusion:}\)
\(CH_3C_6H_4NH_2\) represents methylaniline with the methyl group on the ring, not on nitrogen.
\(\textbf{Final Answer:}\)
\(N\)-methylaniline is \(C_6H_5NHCH_3\).
119. Which name is suitable for \(C_6H_5N(CH_3)_2\)?
ⓐ. \(N,N\)-dimethylaniline
ⓑ. \(o\)-dimethylaniline
ⓒ. \(m\)-dimethylbenzenamine
ⓓ. \(p\)-methyl-\(N\)-methylaniline
Correct Answer: \(N,N\)-dimethylaniline
Explanation: In \(C_6H_5N(CH_3)_2\), the benzene ring is directly attached to nitrogen, so the parent structure is aniline. The two \(CH_3\) groups are attached to nitrogen, not to ring carbons. The repeated \(N,N\)- locant shows that both methyl groups are bonded directly to nitrogen. This gives \(N,N\)-dimethylaniline.
120. Which distinction between \(N\)-methylaniline and \(o\)-methylaniline is accurate?
ⓐ. In both compounds, the methyl group is attached to nitrogen.
ⓑ. In \(N\)-methylaniline, methyl is on nitrogen; in \(o\)-methylaniline, methyl is on the ring.
ⓒ. In \(N\)-methylaniline, methyl is on the ring; in \(o\)-methylaniline, methyl is on nitrogen.
ⓓ. Both names describe the same compound written in different systems.
Correct Answer: In \(N\)-methylaniline, methyl is on nitrogen; in \(o\)-methylaniline, methyl is on the ring.
Explanation: The locant \(N\)- means that the substituent is directly bonded to nitrogen. Thus \(N\)-methylaniline has the structure \(C_6H_5NHCH_3\). In \(o\)-methylaniline, the methyl group is attached to the benzene ring adjacent to the \(-NH_2\) group. The two compounds have different connectivities, so they are not the same substance.
