Question 1: Examine the following structure: O ||R–C–OHWhich functional group is depicted?A) AldehydeB) Carboxylic acidC) EsterD) AmideAnswer: B) Carboxylic acidExplanation: The structure shows a carbonyl (C=O) directly bonded to a hydroxyl (–OH) group, which is the defining feature of a carboxylic acid.Question 2: Which of the following statements correctly compares an ester and a carboxylic acid?A) Esters have a free –OH group, while carboxylic acids do not.B) Carboxylic acids are generally less acidic than esters.C) Esters have a –OR group replacing the –OH of a carboxylic acid.D) Carboxylic acids do not exhibit hydrogen bonding, whereas esters do.Answer: C) Esters have a –OR group replacing the –OH of a carboxylic acid.Explanation: In an ester, the acidic –OH of a carboxylic acid is replaced by an alkoxy (–OR) group, which distinguishes it from a carboxylic acid.Question 3: An IR spectrum shows a sharp absorption near 1720 cm⁻¹ and no broad O–H stretch. Which functional group is most consistent with this data?A) Carboxylic acidB) EsterC) AlcoholD) AmideAnswer: B) EsterExplanation: A sharp absorption near 1720 cm⁻¹ corresponds to the carbonyl (C=O) stretch in esters. Carboxylic acids would show an additional broad O–H stretch due to hydrogen bonding.Question 4: Which functional group is most likely to undergo nucleophilic acyl substitution rapidly?A) AmideB) EsterC) Carboxylic acidD) Acid chlorideAnswer: D) Acid chlorideExplanation: Acid chlorides have a very electrophilic carbonyl carbon and an excellent leaving group (Cl⁻), making them the most reactive toward nucleophilic attack among carboxylic acid derivatives.Question 5: Identify the functional group in the following structure: O ||R–C–NR₂A) AmineB) AmideC) ImineD) NitrileAnswer: B) AmideExplanation: The structure shows a carbonyl group (C=O) adjacent to a nitrogen atom (–NR₂), which is characteristic of an amide.Question 6: Which feature distinguishes an aldehyde from a ketone?A) Presence of a carbonyl groupB) The carbonyl carbon in an aldehyde is bonded to at least one hydrogen.C) Ketones have a terminal carbonyl group.D) Aldehydes are more sterically hindered than ketones.Answer: B) The carbonyl carbon in an aldehyde is bonded to at least one hydrogen.Explanation: Aldehydes always have at least one hydrogen attached to the carbonyl carbon, while ketones have two carbon substituents.Question 7: Examine the two structures below:Structure A:R–OH Structure B:R–O–R'Which statement is true?A) Both A and B can donate hydrogen bonds equally.B) Structure A can form hydrogen bonds; Structure B cannot.C) Structure B is more polar than Structure A.D) Only Structure B is classified as an alcohol.Answer: B) Structure A can form hydrogen bonds; Structure B cannot.Explanation: Alcohols (R–OH) have a hydroxyl group capable of hydrogen bonding, while ethers (R–O–R') lack an O–H bond and are poorer hydrogen bond donors.Question 8: Which functional group is typically the least reactive toward nucleophilic attack?A) Acid chlorideB) EsterC) AmideD) Carboxylic acidAnswer: C) AmideExplanation: Amides are stabilized by resonance, which delocalizes the lone pair on nitrogen into the carbonyl group, reducing the electrophilicity of the carbonyl carbon.Question 9: Identify the functional group in the structure below:R–C≡NA) IsocyanideB) NitrileC) CyanateD) IsonitrileAnswer: B) NitrileExplanation: The structure shows a carbon triple-bonded to a nitrogen atom, which is the defining characteristic of a nitrile group.Question 10: Which of the following functional groups is expected to have the highest boiling point due to strong intermolecular hydrogen bonding?A) EtherB) AldehydeC) AlcoholD) KetoneAnswer: C) AlcoholExplanation: Alcohols possess an –OH group, which can form hydrogen bonds, leading to significantly higher boiling points compared to ethers, aldehydes, or ketones.Question 11: Consider the following structure:CH₃–O–CH₂CH₃What is the IUPAC name for this compound?A) MethoxyethaneB) EthoxyethaneC) Diethyl etherD) MethoxypropaneAnswer: A) MethoxyethaneExplanation: The structure consists of a methyl group (methoxy) connected to an ethyl group. The IUPAC name for this simple ether is methoxyethane.Question 12: Which functional group is represented by the structure below?R–COClA) Acyl chlorideB) Acid anhydrideC) EsterD) Carboxylic acidAnswer: A) Acyl chlorideExplanation: The structure shows a carbonyl group (C=O) with a chlorine substituent (–Cl) instead of a hydroxyl group, which defines an acyl chloride.Question 13: Which of the following best describes a primary amine?A) R–NH–R'B) R–NH₂C) R–N(R')₂D) R–N≡CAnswer: B) R–NH₂Explanation: A primary amine has one alkyl or aryl group attached to an –NH₂ group, distinguishing it from secondary (two substituents) or tertiary (three substituents) amines.Question 14: Imides contain two carbonyl groups attached to the same nitrogen. Which of the following is an example of an imide?A) R–CO–NH–CO–R'B) R–CO–NH₂C) R–CO–O–R'D) R–CO–ClAnswer: A) R–CO–NH–CO–R'Explanation: The structure R–CO–NH–CO–R' shows a nitrogen atom flanked by two carbonyl groups, which is characteristic of an imide functional group.Question 15: Which of the following properties is most commonly associated with carboxylic acids?A) Low boiling points due to weak intermolecular forcesB) High boiling points due to strong hydrogen bondingC) Inability to form dimers in the gas phaseD) Lack of acidic characterAnswer: B) High boiling points due to strong hydrogen bondingExplanation: Carboxylic acids form strong hydrogen bonds (often as dimers), which results in higher boiling points compared to compounds that cannot hydrogen bond effectively.Question 16: Examine the structure below: O ||R–C–OHWhich functional group is depicted?A) AldehydeB) Carboxylic acidC) EsterD) AmideAnswer: B) Carboxylic acidExplanation: The structure shows a carbonyl (C=O) directly bonded to a hydroxyl (–OH) group, which is the hallmark of a carboxylic acid. Question 17: Identify the functional group represented by the following structure: O ||R–C–ClA) Acid chlorideB) Carboxylic acidC) AnhydrideD) EsterAnswer: A) Acid chlorideExplanation: Here, the –OH group of a carboxylic acid is replaced by a chlorine atom, giving the structure of an acid chloride. Question 18: Examine the structure below: O ||R–C–O–R'Which functional group does this represent?A) Carboxylic acidB) EsterC) AmideD) Acid anhydrideAnswer: B) EsterExplanation: An ester is formed when the –OH group of a carboxylic acid is replaced by an alkoxy (–OR') group.Question 19: Consider the following structure: O ||R–C–NH₂Which functional group is shown?A) ImineB) AmideC) NitrileD) Carboxylic acidAnswer: B) AmideExplanation: The structure features a carbonyl (C=O) directly attached to an –NH₂ group, which defines a primary amide.Question 20: Examine the structure:R–C≡NWhat is the functional group?A) IsonitrileB) NitrileC) CyanateD) IsocyanateAnswer: B) NitrileExplanation: A nitrile consists of a carbon triple-bonded to a nitrogen atom. The connectivity shown (R–C≡N) is characteristic of a nitrile. Question 21: Functional Group Comparison – Aldehyde vs. KetoneWhich statement best distinguishes an aldehyde from a ketone?A) Aldehydes have a terminal carbonyl group (bonded to at least one hydrogen), whereas ketones have the carbonyl carbon bonded to two carbon groups.B) Ketones are typically more reactive than aldehydes.C) Aldehydes lack a carbonyl group.D) Ketones always have a higher boiling point than aldehydes.Answer: A) Aldehydes have a terminal carbonyl group (bonded to at least one hydrogen), whereas ketones have the carbonyl carbon bonded to two carbon groups.Explanation: The defining difference is that in aldehydes one of the substituents on the carbonyl carbon is hydrogen, while ketones have two carbon substituents.Question 22: Given the two structures below:Structure A:R–OHStructure B:R–O–R'Which statement is true?A) Both can form hydrogen bonds equally.B) Only Structure A (the alcohol) can donate hydrogen bonds.C) Structure B (the ether) is more polar than Structure A.D) Both are classified as alcohols.Answer: B) Only Structure A (the alcohol) can donate hydrogen bonds.Explanation: Alcohols (R–OH) have a free hydroxyl group that can donate hydrogen bonds, whereas ethers (R–O–R') lack an O–H bond and cannot donate hydrogen bonds effectively.Question 23: Which functional group is expected to be more acidic?A) Alcohol (R–OH)B) Carboxylic acid (R–COOH)C) Ether (R–O–R')D) Amine (R–NH₂)Answer: B) Carboxylic acid (R–COOH)Explanation: Carboxylic acids are more acidic than alcohols due to the resonance stabilization of the carboxylate anion formed upon deprotonation. Question 24: What is the IUPAC name for the compound with the structure:CH₃CH₂CH₂OHA) MethanolB) EthanolC) Propan-1-olD) Butan-1-olAnswer: C) Propan-1-olExplanation: The structure has three carbon atoms with an –OH group at the end; hence, its IUPAC name is propan-1-ol.Question 25: What is the IUPAC name for CH₃CHO?A) AcetaldehydeB) PropionaldehydeC) ButyraldehydeD) MethanalAnswer: A) AcetaldehydeExplanation: CH₃CHO consists of a two-carbon aldehyde; its common name is acetaldehyde, and its IUPAC name is ethanal. (Acetaldehyde is the widely accepted common name.)Question 26: Examine the structure:R₂C=NR'Which functional group is represented?A) IminesB) AmidesC) NitrilesD) OximesAnswer: A) IminesExplanation: Imines contain a C=N double bond, where the nitrogen is attached to one or two alkyl or aryl groups. The structure given is typical for an imine. Question 27: Dehydration of a carboxylic acid (R–COOH) with an alcohol (R'–OH) under acid catalysis leads to the formation of which functional group?A) AmideB) EsterC) AnhydrideD) EtherAnswer: B) EsterExplanation: The reaction between a carboxylic acid and an alcohol under acid catalysis produces an ester (R–COO–R') along with water.Question 28: Functional Group Reactivity TrendArrange the following functional groups in order of increasing boiling point (considering their ability to form hydrogen bonds):I. Ether (R–O–R')II. Alcohol (R–OH)III. Carboxylic acid (R–COOH)A) I < II < IIIB) II < I < IIIC) III < II < ID) I < III < IIAnswer: A) I < II < IIIExplanation: Ethers have no hydrogen-bond donating ability, alcohols can hydrogen-bond, and carboxylic acids often form dimers via strong hydrogen bonds, leading to the highest boiling points.Question 29: Which of the following structures represents an acid anhydride?A) R–CO–O–CO–R'B) R–CO–OHC) R–CO–ClD) R–CO–NH–R'Answer: A) R–CO–O–CO–R'Explanation: Acid anhydrides consist of two acyl groups joined by an oxygen atom. The structure R–CO–O–CO–R' is characteristic of an acid anhydride.Question 30: Which statement best distinguishes a simple amide from an imide?A) In an amide, the carbonyl is bonded to one nitrogen; in an imide, one nitrogen is flanked by two carbonyl groups.B) Amides are more reactive than imides.C) Imides lack a carbonyl group.D) Amides are typically less polar than imides.Answer: A) In an amide, the carbonyl is bonded to one nitrogen; in an imide, one nitrogen is flanked by two carbonyl groups.Explanation: The key structural difference is that imides have two carbonyl groups attached to the same nitrogen, whereas simple amides have only one carbonyl group bonded to nitrogen.Question 31: Examine the structure below: R–N=C=OWhich functional group is depicted?A) NitrileB) IsocyanateC) CyanateD) Urea derivativeAnswer: B) IsocyanateExplanation: The structure shows a nitrogen atom double-bonded to carbon (which is further double-bonded to oxygen) in the sequence N=C=O—a hallmark of an isocyanate group.Question 32: Examine the structure below: O ||R–C–S–R'Which functional group is represented?A) EsterB) ThioesterC) AmideD) Acid chlorideAnswer: B) ThioesterExplanation: In a thioester, the oxygen in a typical ester (R–C(=O)–O–R') is replaced by sulfur, giving R–C(=O)–S–R', which is characteristic of thioesters.Question 33: What is the correct IUPAC name for the compound with the structure:CH₃–CO–CH₂–CH₃A) Butan-1-oneB) Butan-2-oneC) Pentan-2-oneD) Propan-2-oneAnswer: B) Butan-2-oneExplanation: The molecule has a four carbon chain with a carbonyl group on the second carbon; thus, its name is butan-2-one.Question 34: Which structure represents a nitroso group?A) R–NO₂B) R–NOC) R–N=O⁺D) R–N≡CAnswer: B) R–NOExplanation: A nitroso group consists of a nitrogen atom doubly bonded to an oxygen atom (R–NO), in contrast to the nitro group.Question 35: Examine the structure: R–SO₃HWhich functional group is present?A) Sulfonyl chlorideB) Sulfonic acidC) SulfoxideD) SulfoneAnswer: B) Sulfonic acidExplanation: The structure R–SO₃H contains a sulfur atom bonded to three oxygens (one as –OH), which is characteristic of a sulfonic acid.Question 36: Examine the structure: R–SO₂ClWhich functional group does this structure represent?A) Sulfonic acidB) Sulfonyl chlorideC) SulfoneD) SulfideAnswer: B) Sulfonyl chlorideExplanation: The –Cl replacing the –OH in a sulfonic acid forms a sulfonyl chloride, R–SO₂Cl.Question 37: Identify the functional group in the structure: R–SO₂–NH₂A) SulfonamideB) SulfoxideC) SulfoneD) Sulfonic acidAnswer: A) SulfonamideExplanation: A sulfonamide features a sulfonyl group (SO₂) bonded to an amino group (–NH₂).Question 38: Examine the structure: R–S–R'Which functional group is depicted?A) EtherB) ThioetherC) ThiolD) SulfideAnswer: B) ThioetherExplanation: A thioether (also known as a sulfide) consists of a sulfur atom bonded to two carbon groups (R–S–R').Question 39: Which structure represents a thiol?A) R–SHB) R–S–R'C) R–SOHD) R–S–OHAnswer: A) R–SHExplanation: A thiol is defined by the presence of an –SH (sulfhydryl) group.Question 40: Examine the structure: R₂S=OWhich functional group is shown?A) SulfoxideB) SulfoneC) ThioetherD) DisulfideAnswer: A) SulfoxideExplanation: A sulfoxide contains a sulfur atom double-bonded to oxygen, with two organic substituents attached (R₂S=O).Question 41: Identify the functional group in the structure: R₂SO₂A) SulfoxideB) SulfoneC) ThioetherD) SulfideAnswer: B) SulfoneExplanation: A sulfone features a sulfur atom bonded to two oxygen atoms (double bonds) along with two carbon groups.Question 42: Examine the structure: R–O–C(=O)–O–R'Which functional group does this represent?A) EsterB) CarbonateC) CarboxylateD) UrethaneAnswer: B) CarbonateExplanation: This structure is characteristic of a carbonate, where a central carbonyl is bonded to two alkoxy groups.Question 43: Examine the structure: R–C(OH)(OR')Which functional group is represented?A) HemiacetalB) AcetalC) KetalD) LactolAnswer: A) HemiacetalExplanation: A hemiacetal features one –OH and one –OR group attached to the same carbon.Question 44: Which of the following best describes a lactone?A) A cyclic etherB) A cyclic esterC) A cyclic amideD) A cyclic carboxylic acidAnswer: B) A cyclic esterExplanation: Lactones are formed when a hydroxy acid undergoes intramolecular esterification, resulting in a cyclic ester.Question 45: Which structure represents a lactam?A) A cyclic esterB) A cyclic amideC) A cyclic etherD) A cyclic imineAnswer: B) A cyclic amideExplanation: Lactams are cyclic amides, often formed by the cyclization of amino acids.Question 46: Which structure represents an isonitrile?A) R–C≡NB) R–N≡CC) R–N=CD) R–C≡OAnswer: B) R–N≡CExplanation: In an isonitrile (or isocyanide), the nitrogen is directly bonded to the R group and triple-bonded to carbon, in contrast to a nitrile (R–C≡N).Question 47: Examine the structure: R–B(OH)₂Which functional group is depicted?A) BoraneB) Boronic acidC) OrganoboraneD) Boronate esterAnswer: B) Boronic acidExplanation: The presence of a boron atom bonded to two hydroxyl groups (–B(OH)₂) is characteristic of a boronic acid.Question 48: Examine the structure: R₃P=OWhich functional group does this represent?A) PhosphineB) Phosphine oxideC) PhosphateD) PhosphonateAnswer: B) Phosphine oxideExplanation: A phosphine oxide features a phosphorus atom double-bonded to oxygen and bonded to three organic groups (R₃P=O).