51. Which of the following statements is correct about the structure of formaldehyde?
a) It contains a double bond between carbon and oxygen
b) It contains a triple bond between carbon and oxygen
c) It contains a hydroxyl group (-OH)
d) It contains an ester group (-COOR)
Answer: a) It contains a double bond between carbon and oxygen
Explanation: Formaldehyde (HCHO) contains a carbonyl group (C=O), which consists of a double bond between carbon and oxygen.
52. Which of the following compounds will undergo nucleophilic substitution?
a) Acetaldehyde
b) Acetone
c) Acetyl chloride
d) Benzaldehyde
Answer: c) Acetyl chloride
Explanation: Acetyl chloride contains a good leaving group (Cl⁻), making it susceptible to nucleophilic substitution reactions.
53. Which of the following statements is correct about the Cannizzaro reaction?
a) It occurs in aldehydes without alpha-hydrogens
b) It occurs in ketones without alpha-hydrogens
c) It involves nucleophilic addition to aldehydes
d) It involves oxidation of alcohols
Answer: a) It occurs in aldehydes without alpha-hydrogens
Explanation: The Cannizzaro reaction occurs in aldehydes that lack alpha-hydrogens, leading to the simultaneous oxidation and reduction of two aldehyde molecules.
54. Which of the following reactions will convert an alkene into an aldehyde?
a) Hydroboration-oxidation
b) Ozonolysis
c) Friedel-Crafts acylation
d) Grignard reaction
Answer: b) Ozonolysis
Explanation: Ozonolysis of alkenes cleaves the carbon-carbon double bond, forming aldehydes or ketones depending on the structure of the alkene.
55. The reaction of a ketone with hydrazine (NH₂NH₂) followed by heating in basic conditions produces:
a) Alcohol
b) Alkane
c) Amine
d) Aldehyde
Answer: b) Alkane
Explanation: The Wolff-Kishner reduction involves the conversion of a ketone into an alkane by treatment with hydrazine followed by heating under basic conditions.
56. Which of the following compounds will give a positive iodoform test?
a) Propanone
b) Acetaldehyde
c) Benzaldehyde
d) Propanal
Answer: a) Propanone
Explanation: Propanone (CH₃COCH₃) gives a positive iodoform test because it contains the methyl ketone group (-COCH₃).
57. Which of the following statements is correct regarding ketones?
a) Ketones cannot be oxidized under normal conditions
b) Ketones can be easily oxidized to carboxylic acids
c) Ketones can be reduced to primary alcohols
d) Ketones undergo oxidation with Tollen’s reagent
Answer: a) Ketones cannot be oxidized under normal conditions
Explanation: Ketones are relatively resistant to oxidation under normal conditions. Strong oxidizing agents may break the carbon-carbon bond to form carboxylic acids, but this is not common under mild conditions.
58. Which of the following will give a positive Tollen’s test?
a) Acetone
b) Acetaldehyde
c) Benzene
d) Propanone
Answer: b) Acetaldehyde
Explanation: Tollen’s reagent reacts with aldehydes like acetaldehyde, oxidizing them to carboxylic acids and producing a silver mirror.
59. The reaction between benzaldehyde and acetone in the presence of dilute NaOH is an example of:
a) Cannizzaro reaction
b) Aldol condensation
c) Perkin reaction
d) Benzoin condensation
Answer: b) Aldol condensation
Explanation: In the presence of dilute NaOH, acetone and benzaldehyde undergo aldol condensation to form a β-hydroxy ketone, which can further dehydrate to form an α,β-unsaturated ketone.
60. Which of the following is formed when acetone reacts with methylmagnesium bromide followed by hydrolysis?
a) Primary alcohol
b) Secondary alcohol
c) Tertiary alcohol
d) Ketone
Answer: c) Tertiary alcohol
Explanation: The reaction of a ketone like acetone with a Grignard reagent (methylmagnesium bromide) followed by hydrolysis produces a tertiary alcohol.
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