101. The compound having nitro groups at carbons \(2\), \(4\), and \(6\) of a phenol ring is named:
ⓐ. 2,4,6-trinitrophenol
ⓑ. 1,3,5-trinitrophenol
ⓒ. 2,3,4-trinitrophenol
ⓓ. 3,4,5-trinitrophenol
Correct Answer: 2,4,6-trinitrophenol
Explanation: Phenol is taken as the parent, so the carbon bonded to \(\mathrm{-OH}\) is carbon \(1\). The three nitro substituents are then located at carbons \(2\), \(4\), and \(6\). Their multiplicity is shown by the prefix tri-. The locants must be written in ascending order before the substituent name. Renumbering the ring without keeping the hydroxyl carbon as the reference would produce an inconsistent name.
102. Consider the following positional relationships.
Statement I: 2-Chlorophenol has a \(1,2\)-relationship between the substituents.
Statement II: 3-Nitrophenol has a \(1,3\)-relationship between the substituents.
Statement III: 4-Bromophenol has a \(1,4\)-relationship between the substituents.
Statement IV: \(m\)-Cresol has the same positional relationship as 3-methylphenol.
Which statements are valid?
ⓐ. Statements I, II, and IV only
ⓑ. Statements I, II, III, and IV
ⓒ. Statements I and III only
ⓓ. Statements II and III only
Correct Answer: Statements I, II, III, and IV
Explanation: Statement I is valid because locant \(2\) places chlorine adjacent to the hydroxyl-bearing carbon, giving a \(1,2\)- or ortho relationship. Statement II is valid because locant \(3\) corresponds to a \(1,3\)- or meta relationship. Statement III is valid because locant \(4\) places bromine opposite the hydroxyl group in a \(1,4\)- or para arrangement. Statement IV is also valid: \(m\)-cresol and 3-methylphenol are two names for the same positional relationship. All four statements express consistent locant and prefix notation.
103. A phenol ring contains ethyl and methyl substituents. Numbering clockwise from the hydroxyl-bearing carbon gives locants \(2\) and \(5\), while numbering anticlockwise gives \(3\) and \(6\). The preferred locant set is:
ⓐ. \(3,6\)
ⓑ. \(2,5\)
ⓒ. \(2,6\)
ⓓ. \(3,5\)
Correct Answer: \(2,5\)
Explanation: The hydroxyl-bearing carbon remains fixed as carbon \(1\). The two possible directions produce the sets \(2,5\) and \(3,6\). These sets are compared at the first point of difference, where \(2\) is lower than \(3\). Numbering must therefore proceed in the direction that gives \(2,5\). Alphabetical order determines how ethyl and methyl are written in the final name, but it does not override the lower locant set.
104. A phenol bears ethyl and methyl substituents at carbons \(3\) and \(4\), respectively. Its name is:
ⓐ. 3-ethyl-4-methylphenol
ⓑ. 4-methyl-3-ethylphenol
ⓒ. 3-methyl-4-ethylphenol
ⓓ. 4-ethyl-3-methylphenol
Correct Answer: 3-ethyl-4-methylphenol
Explanation: The parent is phenol, and the substituent locants are \(3\) for ethyl and \(4\) for methyl. Different substituent names are cited alphabetically in the complete name. Ethyl therefore appears before methyl because \(e\) precedes \(m\). Alphabetical order does not change the locants already assigned by ring numbering. Writing methyl first would not follow the usual ordering convention for different substituents.
105. A benzene ring carries hydroxyl groups at carbons \(1\), \(2\), and \(4\). Its systematic name is:
ⓐ. benzene-1,2,4-triol
ⓑ. phenol-1,2,4-triol
ⓒ. 1,2,4-hydroxybenzene
ⓓ. benzene-1,2,4-diol
Correct Answer: benzene-1,2,4-triol
Explanation: The parent ring is benzene and contains three hydroxyl groups. All three positions are stated as \(1,2,\) and \(4\). Three hydroxyl groups require the suffix \(\mathrm{-triol}\). The form \(\mathrm{-diol}\) would account for only two groups. Using hydroxy as a prefix is unnecessary when the hydroxyl groups are the principal functional groups represented by the suffix.
106. Identify the row in which the common name, systematic name, and positional description all agree.
| Row | Common name | Systematic name | Position |
|---|
| P | Catechol | Benzene-1,3-diol | Meta |
| Q | Resorcinol | Benzene-1,2-diol | Ortho |
| R | Hydroquinone | Benzene-1,4-diol | Para |
| S | \(o\)-Cresol | 4-Methylphenol | Para |
ⓐ. Row P
ⓑ. Row Q
ⓒ. Row R
ⓓ. Row S
Correct Answer: Row R
Explanation: Hydroquinone is benzene-1,4-diol, and the \(1,4\)-arrangement is para, so all entries in row R agree. Catechol is benzene-1,2-diol and has the ortho arrangement. Resorcinol is benzene-1,3-diol and has the meta arrangement. Ortho-cresol is 2-methylphenol rather than 4-methylphenol. Checking both the locants and the positional prefix is necessary because a familiar common name alone may conceal an incorrect mapping.
107. A structure contains a benzene ring with \(\mathrm{-OH}\) at carbon \(1\), bromine at carbon \(2\), and methyl at carbon \(4\). Its name is:
ⓐ. 4-bromo-2-methylphenol
ⓑ. 2-bromo-4-methylphenol
ⓒ. 2-methyl-4-bromophenol
ⓓ. 4-methyl-2-bromophenol
Correct Answer: 2-bromo-4-methylphenol
Explanation: Phenol is the parent, fixing the hydroxyl-bearing carbon as carbon \(1\). Bromine and methyl then occupy carbons \(2\) and \(4\), respectively. The substituent names are cited alphabetically, so bromo appears before methyl. Their locants remain attached to the correct substituent names during ordering. Reversing the names without their locants would describe a different substitution pattern.
108. The name “1-hydroxy-3-methylbenzene” is less preferred than 3-methylphenol because:
ⓐ. methyl groups cannot be attached to benzene
ⓑ. hydroxy is never permitted as a prefix in organic nomenclature
ⓒ. carbon \(1\) cannot carry any substituent
ⓓ. phenol is the preferred retained parent name
Correct Answer: phenol is the preferred retained parent name
Explanation: Phenol is an accepted retained parent name for hydroxybenzene. When \(\mathrm{-OH}\) is the principal functional group, using phenol as the parent expresses that priority directly. The hydroxyl-bearing carbon is automatically assigned locant \(1\), so the remaining methyl substituent receives locant \(3\). Hydroxy can be used as a prefix when another functional group has higher priority, so it is not universally forbidden. The preferred name is more concise while preserving the same ring connectivity.
109. Consider a ring numbered with the hydroxyl-bearing carbon as \(1\). Substituents occur at carbons \(2\), \(4\), and \(6\). This arrangement places:
ⓐ. all three substituents meta to the hydroxyl group
ⓑ. two ortho substituents and one para substituent
ⓒ. one substituent ortho and two meta to the hydroxyl group
ⓓ. all three substituents para to the hydroxyl group
Correct Answer: two ortho substituents and one para substituent
Explanation: Carbons \(2\) and \(6\) are the two positions directly adjacent to carbon \(1\). Substituents at these positions are ortho to the hydroxyl group. Carbon \(4\) lies opposite carbon \(1\) and is para to the hydroxyl group. The two meta positions relative to carbon \(1\) are carbons \(3\) and \(5\). Translating numerical locants into relative positions is especially useful when interpreting multiply substituted phenol structures.
110. The IUPAC name of \(\mathrm{CH_3-O-CH_2CH_3}\) is:
ⓐ. ethoxymethane
ⓑ. propan-1-ol
ⓒ. methoxyethane
ⓓ. dimethyl ether
Correct Answer: methoxyethane
Explanation: The ether contains a one-carbon methyl group and a two-carbon ethyl group. In the alkoxyalkane system, the larger carbon group is chosen as the parent chain, giving ethane. The smaller group together with oxygen becomes the methoxy substituent, \(\mathrm{CH_3O-}\). No locant is needed because methoxy can attach only to an end carbon of the two-carbon parent. The complete IUPAC name is methoxyethane, while the corresponding common name is ethyl methyl ether.
111. In the IUPAC name of a simple unsymmetrical dialkyl ether, the smaller alkyl group is generally represented as:
ⓐ. an alkoxy substituent
ⓑ. the principal alcohol group
ⓒ. an alkene suffix
ⓓ. an acyl substituent
Correct Answer: an alkoxy substituent
Explanation: An ether is named systematically as an alkoxy-substituted hydrocarbon. The smaller alkyl group and the oxygen atom together form an alkoxy group such as methoxy or ethoxy. The larger carbon group normally provides the parent alkane in simple dialkyl ethers. The ether oxygen is not expressed by an alcohol suffix because no \(\mathrm{O-H}\) bond is present. This method converts the \(\mathrm{R-O-R'}\) linkage into a substituent-parent description.
112. The structure \(\mathrm{CH_3OCH_2CH_2CH_3}\) is named:
ⓐ. 2-methoxypropane
ⓑ. 1-methoxypropane
ⓒ. ethoxyethane
ⓓ. butan-1-ol
Correct Answer: 1-methoxypropane
Explanation: The larger carbon group contains three carbon atoms, so propane is selected as the parent. The smaller group attached through oxygen is methyl, producing the methoxy substituent. Oxygen is bonded to the terminal carbon of the propane chain, so the substituent receives locant \(1\). The name is therefore 1-methoxypropane. The isomer 2-methoxypropane would have oxygen attached to the middle carbon of the propane chain.
113. A molecular model represents \(\mathrm{CH_3OCH(CH_3)_2}\). Its preferred IUPAC name is:
ⓐ. 1-methoxypropane
ⓑ. ethoxyethane
ⓒ. methyl propyl ether
ⓓ. 2-methoxypropane
Correct Answer: 2-methoxypropane
Explanation: The three-carbon part is chosen as the propane parent. The \(\mathrm{CH_3O-}\) group is a methoxy substituent. It is attached to the middle carbon of propane, so its locant is \(2\). The systematic name is therefore 2-methoxypropane. A name based on 1-methoxypropane would describe the unbranched ether \(\mathrm{CH_3OCH_2CH_2CH_3}\), not the structure shown.
114. Consider the following statements about alkoxy groups.
Statement I: \(\mathrm{CH_3O-}\) is called methoxy.
Statement II: \(\mathrm{C_2H_5O-}\) is called ethoxy.
Statement III: \(\mathrm{C_3H_7O-}\) must always be called isopropoxy.
ⓐ. Statements I and II only
ⓑ. Statements II and III only
ⓒ. Statements I and III only
ⓓ. Statements I, II, and III
Correct Answer: Statements I and II only
Explanation: The group \(\mathrm{CH_3O-}\) is methoxy, and \(\mathrm{C_2H_5O-}\) is ethoxy, so Statements I and II are true. A three-carbon alkoxy group may be propoxy or isopropoxy depending on its carbon skeleton and point of attachment. The formula \(\mathrm{C_3H_7O-}\) alone does not force one arrangement. Statement III is therefore too restrictive. Alkoxy names must reflect the actual structure of the carbon group bonded to oxygen.
115. Assertion: \(\mathrm{CH_3OCH_2CH_2CH_3}\) and \(\mathrm{CH_3CH(OCH_3)CH_3}\) have different IUPAC names.
Reason: The methoxy group is attached to different positions of the propane parent chain.
ⓐ. Both Assertion and Reason are true, but Reason does not explain Assertion
ⓑ. Assertion is true, but Reason is false
ⓒ. Assertion is false, but Reason is true
ⓓ. Both Assertion and Reason are true, and Reason explains Assertion
Correct Answer: Both Assertion and Reason are true, and Reason explains Assertion
Explanation: The first structure has the methoxy group attached to carbon \(1\) of propane and is named 1-methoxypropane. The second has methoxy attached to carbon \(2\) and is named 2-methoxypropane. Both compounds contain the same ether functional group and have the same molecular formula. Their difference is the position at which oxygen connects to the propane skeleton. The Reason directly accounts for the different locants and names.
116. Match each structure in Column I with its IUPAC name in Column II.
| Column I | Column II |
|---|
| P. \(\mathrm{CH_3OCH_3}\) | 1. 1-Methoxypropane |
| Q. \(\mathrm{CH_3OCH_2CH_3}\) | 2. Methoxymethane |
| R. \(\mathrm{CH_3OCH_2CH_2CH_3}\) | 3. Ethoxyethane |
| S. \(\mathrm{C_2H_5OC_2H_5}\) | 4. Methoxyethane |
ⓐ. P-4, Q-2, R-1, S-3
ⓑ. P-2, Q-1, R-4, S-3
ⓒ. P-2, Q-4, R-3, S-1
ⓓ. P-2, Q-4, R-1, S-3
Correct Answer: P-2, Q-4, R-1, S-3
Explanation: Dimethyl ether is named methoxymethane, so P matches 2. Methyl ethyl ether is methoxyethane, making Q match 4. The three-carbon parent in R carries methoxy at carbon \(1\), so R matches 1-methoxypropane. Diethyl ether is ethoxyethane and therefore S matches 3. The mapping follows the rule of expressing one side as alkoxy and the other as the parent hydrocarbon.
117. Anisole is the retained common name of:
ⓐ. hydroxybenzene
ⓑ. phenylmethanol
ⓒ. methoxybenzene
ⓓ. ethoxybenzene
Correct Answer: methoxybenzene
Explanation: Anisole has the structure \(\mathrm{C_6H_5OCH_3}\). The benzene ring is treated as the parent, and the \(\mathrm{CH_3O-}\) group is named methoxy. Its systematic name is therefore methoxybenzene. Hydroxybenzene is phenol, while phenylmethanol is benzyl alcohol. Ethoxybenzene is a different aromatic ether commonly called phenetole.
118. Phenetole has the structure \(\mathrm{C_6H_5OC_2H_5}\) and the IUPAC name:
ⓐ. ethoxybenzene
ⓑ. methoxybenzene
ⓒ. phenoxyethane
ⓓ. ethyl phenol
Correct Answer: ethoxybenzene
Explanation: The oxygen atom connects an ethyl group to a phenyl group. Using benzene as the parent, the \(\mathrm{C_2H_5O-}\) unit becomes the ethoxy substituent. The resulting name is ethoxybenzene. Methoxybenzene contains a methyl group and is anisole. The structure has no \(\mathrm{O-H}\) bond, so it cannot be named as an ethyl-substituted phenol.
119. The name phenoxybenzene corresponds to:
ⓐ. \(\mathrm{C_6H_5-O-H}\)
ⓑ. \(\mathrm{C_6H_5-O-CH_3}\)
ⓒ. \(\mathrm{C_6H_5-CH_2-O-H}\)
ⓓ. \(\mathrm{C_6H_5-O-C_6H_5}\)
Correct Answer: \(\mathrm{C_6H_5-O-C_6H_5}\)
Explanation: A phenoxy group has the structure \(\mathrm{C_6H_5O-}\). Attachment of this group to a benzene ring gives \(\mathrm{C_6H_5OC_6H_5}\). The compound is also commonly called diphenyl ether. Phenol contains an \(\mathrm{O-H}\) bond, while anisole contains one phenyl and one methyl group. Benzyl alcohol has oxygen attached to a side-chain carbon rather than between two aryl groups.
120. Identify the row in which the common name and IUPAC name refer to the same compound.
| Row | Common name | IUPAC name |
|---|
| P | Anisole | Ethoxybenzene |
| Q | Phenetole | Methoxybenzene |
| R | Diphenyl ether | Phenoxybenzene |
| S | Diethyl ether | Methoxyethane |
ⓐ. Row P
ⓑ. Row Q
ⓒ. Row R
ⓓ. Row S
Correct Answer: Row R
Explanation: Diphenyl ether contains two phenyl groups joined through oxygen and can be named phenoxybenzene. Anisole is methoxybenzene rather than ethoxybenzene. Phenetole is ethoxybenzene rather than methoxybenzene. Diethyl ether has the IUPAC name ethoxyethane, while methoxyethane contains methyl and ethyl groups. Comparing the carbon groups on both sides of oxygen resolves each name pair.
