101. Which name is suitable for \(CH_3CH_2COCH_2CH_3\)?
ⓐ. Pentan-\(2\)-one
ⓑ. Pentan-\(3\)-one
ⓒ. Butan-\(2\)-one
ⓓ. Propanone
Correct Answer: Pentan-\(3\)-one
Explanation: The compound contains a five-carbon chain with an internal carbonyl group. The carbonyl carbon is the third carbon when counted from either end. Since it is a ketone, the suffix is \(-one\). The name is pentan-\(3\)-one.
102. Which ketone has the common name methyl ethyl ketone?
ⓐ. \(CH_3COCH_3\)
ⓑ. \(CH_3COCH_2CH_3\)
ⓒ. \(C_6H_5COCH_3\)
ⓓ. \(CH_3CH_2COCH_2CH_3\)
Correct Answer: \(CH_3COCH_2CH_3\)
Explanation: In common ketone naming, the two groups attached to the carbonyl carbon are named as alkyl or aryl groups, followed by the word ketone. \(CH_3COCH_2CH_3\) has a methyl group and an ethyl group attached to \(C=O\). Therefore its common name is methyl ethyl ketone. Its IUPAC name is butan-\(2\)-one.
103. Which common name is used for \(CH_3COCH_3\)?
ⓐ. Methyl ethyl ketone
ⓑ. Formaldehyde
ⓒ. Benzaldehyde
ⓓ. Dimethyl ketone
Correct Answer: Dimethyl ketone
Explanation: In common naming of ketones, the two groups attached to the carbonyl carbon are named first, followed by the word ketone. In \(CH_3COCH_3\), both groups attached to \(C=O\) are methyl groups. Hence the common name is dimethyl ketone. Its IUPAC name is propanone, and its widely used common name is acetone.
104. Which IUPAC name corresponds to acetophenone?
ⓐ. \(1\)-phenylethan-\(1\)-one
ⓑ. \(2\)-phenylpropanal
ⓒ. Phenyl methanoate
ⓓ. Benzene carbaldehyde
Correct Answer: \(1\)-phenylethan-\(1\)-one
Explanation: Acetophenone has the structure \(C_6H_5COCH_3\). The carbonyl group is part of a ketone, and the parent ketone chain is ethanone with a phenyl group attached to carbon \(1\). A more precise IUPAC-style name is \(1\)-phenylethan-\(1\)-one. Benzene carbaldehyde refers to benzaldehyde, which contains \(CHO\), not a ketone group.
105. Which name best fits \(C_6H_5COC_6H_5\)?
ⓐ. Acetophenone
ⓑ. Benzaldehyde
ⓒ. Benzoic acid
ⓓ. Benzophenone
Correct Answer: Benzophenone
Explanation: The formula \(C_6H_5COC_6H_5\) contains a carbonyl group attached to two phenyl groups. This makes it a diaryl ketone. Its common name is benzophenone. Acetophenone has one phenyl group and one methyl group, while benzaldehyde and benzoic acid contain \(CHO\) and \(COOH\) respectively.
106. Which rule is applied while numbering the parent chain of an unsymmetrical ketone?
ⓐ. Start from the end nearer the longest branch only.
ⓑ. Give the carbonyl carbon the lowest locant.
ⓒ. Always number the carbonyl carbon as carbon \(1\).
ⓓ. Number from the end nearer the terminal hydrogen.
Correct Answer: Give the carbonyl carbon the lowest locant.
Explanation: In ketones, the carbonyl carbon is part of the main chain and must receive the lowest possible locant. Unlike aldehydes, ketones do not automatically place the carbonyl carbon at carbon \(1\), because the carbonyl group is internal. For example, \(CH_3COCH_2CH_3\) is butan-\(2\)-one, not butan-\(3\)-one. The numbering begins from the end closer to \(C=O\).
107. What is the IUPAC name of \(CH_3CH_2CH_2COCH_3\)?
ⓐ. Pentan-\(3\)-one
ⓑ. Butan-\(2\)-one
ⓒ. \(2\)-methylbutanal
ⓓ. Pentan-\(2\)-one
Correct Answer: Pentan-\(2\)-one
Explanation: The longest chain containing the carbonyl carbon has five carbon atoms. Numbering must give the carbonyl carbon the lowest possible locant. Starting from the \(CH_3CO-\) end places the carbonyl carbon at carbon \(2\). Hence the name is pentan-\(2\)-one.
108. Which formula matches pentan-\(3\)-one?
ⓐ. \(CH_3CH_2COCH_2CH_3\)
ⓑ. \(CH_3COCH_2CH_2CH_3\)
ⓒ. \(CH_3CH_2CH_2CH_2CHO\)
ⓓ. \(CH_3CH_2CH_2COOH\)
Correct Answer: \(CH_3CH_2COCH_2CH_3\)
Explanation: Pentan-\(3\)-one is a five-carbon ketone with the carbonyl group at carbon \(3\). The structure \(CH_3CH_2COCH_2CH_3\) places \(C=O\) in the middle of a five-carbon chain. \(CH_3COCH_2CH_2CH_3\) is pentan-\(2\)-one. The formulas ending in \(CHO\) and \(COOH\) represent an aldehyde and a carboxylic acid respectively.
109. Which common ketone name is based on the two groups attached to \(C=O\)?
ⓐ. Ethanal oxime
ⓑ. Propanoic anhydride
ⓒ. Methyl ethyl ketone
ⓓ. Acetaldehyde hydrazone
Correct Answer: Methyl ethyl ketone
Explanation: Common names of simple ketones are formed by naming the two alkyl or aryl groups attached to the carbonyl carbon, followed by ketone. Methyl ethyl ketone contains a methyl group and an ethyl group attached to \(C=O\). Its IUPAC name is butan-\(2\)-one. Ethanal and methanal are aldehydes, while propanoic acid is a carboxylic acid.
110. Which name-formula pair is correctly matched?
ⓐ. \(CH_3COCH_3\) — butan-\(2\)-one
ⓑ. \(CH_3COCH_2CH_3\) — butan-\(2\)-one
ⓒ. \(CH_3CH_2CH_2CHO\) — butan-\(2\)-one
ⓓ. \(C_6H_5CHO\) — acetophenone
Correct Answer: \(CH_3COCH_2CH_3\) — butan-\(2\)-one
Explanation: \(CH_3COCH_2CH_3\) has four carbon atoms and an internal carbonyl group at carbon \(2\), so it is butan-\(2\)-one. \(CH_3COCH_3\) is propanone, not butan-\(2\)-one. \(CH_3CH_2CH_2CHO\) is butanal because it contains the aldehyde group \(CHO\). \(C_6H_5CHO\) is benzaldehyde, not acetophenone.
111. Which suffix is used in IUPAC naming of carboxylic acids?
ⓐ. \(-oic\ acid\)
ⓑ. \(-carbaldehyde\)
ⓒ. \(-al\)
ⓓ. \(-hydroxy\)
Correct Answer: \(-oic\ acid\)
Explanation: Carboxylic acids are named using the suffix \(-oic\ acid\). For example, \(CH_3COOH\) is named ethanoic acid. Ketones use \(-one\), aldehydes use \(-al\), and alcohols use \(-ol\). The suffix directly indicates the principal functional group.
112. What is the IUPAC name of \(HCOOH\)?
ⓐ. Ethanoic acid
ⓑ. Propanoic acid
ⓒ. Methanal
ⓓ. Methanoic acid
Correct Answer: Methanoic acid
Explanation: \(HCOOH\) contains one carbon atom and the carboxyl group \(COOH\). The one-carbon parent name is based on methane. Replacing the hydrocarbon ending with \(-oic\ acid\) gives methanoic acid. Its common name is formic acid.
113. The common name formic acid corresponds to which IUPAC name?
ⓐ. Ethanoic acid
ⓑ. Methanoic acid
ⓒ. Propanoic acid
ⓓ. Benzoic acid
Correct Answer: Methanoic acid
Explanation: Formic acid is the common name of \(HCOOH\). Since it has one carbon atom, its IUPAC name is methanoic acid. Ethanoic acid is acetic acid, \(CH_3COOH\). Benzoic acid is aromatic and contains a benzene ring.
114. What is the IUPAC name of \(CH_3COOH\)?
ⓐ. Methanoic acid
ⓑ. Propanoic acid
ⓒ. Ethanoic acid
ⓓ. Ethanoyl alcohol
Correct Answer: Ethanoic acid
Explanation: \(CH_3COOH\) has two carbon atoms, including the carbon of the carboxyl group. A two-carbon carboxylic acid is named ethanoic acid. Its common name is acetic acid. The formula should not be confused with \(CH_3CHO\), which is ethanal.
115. Which common name corresponds to ethanoic acid?
ⓐ. Acetic acid
ⓑ. Formic acid
ⓒ. Oxalic acid
ⓓ. Acrylic acid
Correct Answer: Acetic acid
Explanation: Ethanoic acid, \(CH_3COOH\), is commonly called acetic acid. It is the main acid associated with vinegar. Formic acid is methanoic acid, while oxalic acid is a dicarboxylic acid. Acrylic acid is an unsaturated carboxylic acid.
116. In naming an open-chain carboxylic acid, which carbon is counted as carbon \(1\)?
ⓐ. The terminal methyl carbon
ⓑ. The first branched carbon
ⓒ. The carbon farthest from \(COOH\)
ⓓ. The carboxyl carbon
Correct Answer: The carboxyl carbon
Explanation: The carbon atom of the \(COOH\) group is included in the parent chain. It is assigned number \(1\) in carboxylic acid nomenclature. Substituent positions are then counted from this carboxyl carbon. This rule is similar to aldehyde numbering, but the suffix used is \(-oic\ acid\).
117. What is the IUPAC name of \(CH_3CH_2COOH\)?
ⓐ. Ethanoic acid
ⓑ. Butanoic acid
ⓒ. Propanoic acid
ⓓ. Methanoic acid
Correct Answer: Propanoic acid
Explanation: The structure \(CH_3CH_2COOH\) has three carbon atoms, including the carboxyl carbon. A three-carbon carboxylic acid is named propanoic acid. Propanal has the group \(CHO\), not \(COOH\). Ethanoic acid and butanoic acid contain two and four carbons respectively.
118. Which formula represents butanoic acid?
ⓐ. \(CH_3CH_2CH_2CHO\)
ⓑ. \(CH_3CH_2CH_2COOH\)
ⓒ. \(CH_3COCH_2CH_2CH_3\)
ⓓ. \(CH_3CH_2COOH\)
Correct Answer: \(CH_3CH_2CH_2COOH\)
Explanation: Butanoic acid is a four-carbon carboxylic acid, and its formula is \(CH_3CH_2CH_2COOH\). \(CH_3CH_2CH_2CHO\) is butanal because it contains the aldehyde group \(CHO\). \(CH_3COCH_2CH_2CH_3\) is a ketone. \(CH_3CH_2COOH\) is propanoic acid because it has three carbon atoms.
119. Which name-formula pair is incorrect?
ⓐ. \(HCOOH\) — methanoic acid
ⓑ. \(CH_3COOH\) — ethanoic acid
ⓒ. \(CH_3CH_2COOH\) — propanoic acid
ⓓ. \(CH_3CHO\) — ethanoic acid
Correct Answer: \(CH_3CHO\) — ethanoic acid
Explanation: \(CH_3CHO\) is ethanal because it contains the aldehyde group \(CHO\). Ethanoic acid must contain the carboxyl group \(COOH\), so its formula is \(CH_3COOH\). The pairs \(HCOOH\) — methanoic acid and \(CH_3CH_2COOH\) — propanoic acid are properly matched. The error arises from confusing \(CHO\) with \(COOH\).
120. Which compound is named benzoic acid?
ⓐ. \(C_6H_5CH_2OH\)
ⓑ. \(C_6H_5CHO\)
ⓒ. \(C_6H_5COCH_3\)
ⓓ. \(C_6H_5COOH\)
Correct Answer: \(C_6H_5COOH\)
Explanation: Benzoic acid contains a carboxyl group attached to a benzene ring. Its formula is \(C_6H_5COOH\). \(C_6H_5CHO\) is benzaldehyde, and \(C_6H_5COCH_3\) is acetophenone. \(C_6H_5CH_2OH\) is benzyl alcohol, not a carboxylic acid.
