CUET Chemistry Set-6: Organic Chemistry - Functional Groups II
Question 1
Which of the following will give a positive iodoform test?
(1) $CH_3CH_2OH$ (2) $CH_3COCH_3$ (3) $CH_3CH_2CHO$ (4) $CH_3CH_2CH_2OH$
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Answer: (2)
Solution: Acetone ($CH_3COCH_3$) has the $CH_3CO-$ group attached to carbon, hence gives iodoform.
Question 2
The reagent used to distinguish between $1^\circ$, $2^\circ$ and $3^\circ$ alcohols is
(1) Lucas reagent (2) Fehling’s solution (3) Tollen’s reagent (4) Benedict’s solution
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Answer: (1)
Solution: Lucas reagent ($conc.;HCl+ZnCl_2$) gives immediate turbidity with $3^\circ$, delayed with $2^\circ$ and no reaction with $1^\circ$ at room temp.
Question 3
When phenol is treated with $Br_2/H_2O$, the product is
(1) o-bromophenol (2) p-bromophenol (3) 2,4,6-tribromophenol (4) bromobenzene
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Answer: (3)
Solution: Phenol is highly activated; $Br_2/H_2O$ gives white ppt of 2,4,6-tribromophenol.
Question 4
Which of the following is the strongest acid?
(1) $CH_3COOH$ (2) $ClCH_2COOH$ (3) $Cl_2CHCOOH$ (4) $Cl_3CCOOH$
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Answer: (4)
Solution: –I effect of Cl increases with number; $Cl_3CCOOH$ stabilises conjugate base most.
Question 5
The product of reduction of $CH_3CH_2COCl$ with $H_2/Pd-BaSO_4$ is
(1) $CH_3CH_2CHO$ (2) $CH_3CH_2CH_2OH$ (3) $CH_3CH_2COOH$ (4) $CH_3CH_2CH_3$
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Answer: (1)
Solution: Rosenmund reduction converts acid chloride to aldehyde.
Question 6
Which reagent converts benzamide to aniline?
(1) $Br_2/NaOH$ (2) $LiAlH_4$ (3) $NaBH_4$ (4) $H_3O^+$
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Answer: (1)
Solution: Hofmann bromamide degradation gives $RNH_2$ with one C less.
Question 7
The IUPAC name of $CH_3CH(NH_2)CH_2CH_3$ is
(1) 1-aminobutane (2) 2-aminobutane (3) sec-butylamine (4) isobutylamine
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Answer: (2)
Solution: Longest chain is butane; amino at C-2.
Question 8
Which of the following does not give a primary amine on reduction?
(1) $CH_3CN$ (2) $CH_3NC$ (3) $CH_3NO_2$ (4) $CH_3CONH_2$
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Answer: (2)
Solution: $CH_3NC$ (isocyanide) gives secondary amine $CH_3NHCH_3$.
Question 9
The coupling product of benzenediazonium chloride with phenol in NaOH is
(1) azobenzene (2) p-hydroxyazobenzene (3) aniline (4) benzene
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Answer: (2)
Solution: Diazonium salt couples with activated ring of phenol at para.
Question 10
Which of the following is a $3^\circ$ amine?
(1) $(CH_3)_3N$ (2) $(CH_3)_2NH$ (3) $CH_3NH_2$ (4) $C_2H_5NH_2$
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Answer: (1)
Solution: $(CH_3)_3N$ has three alkyl groups on N.
Question 11
The product of hydrolysis of $CH_3CH_2CN$ is
(1) $CH_3CH_2COOH$ (2) $CH_3CH_2CHO$ (3) $CH_3CH_2CH_2NH_2$ (4) $CH_3CH_2OH$
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Answer: (1)
Solution: Nitriles hydrolyse to carboxylic acids.
Question 12
Which of the following will not give Fehling’s test?
(1) $CH_3CHO$ (2) $HCHO$ (3) $C_6H_5CHO$ (4) $CH_3CH_2CHO$
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Answer: (3)
Solution: Aromatic aldehydes do not have α-H and do not reduce Fehling’s.
Question 13
The reagent to convert $C_6H_5COOH$ to $C_6H_5CH_2OH$ is
(1) $LiAlH_4$ (2) $NaBH_4$ (3) $H_2/Pd$ (4) $Zn/HCl$
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Answer: (1)
Solution: $LiAlH_4$ reduces –COOH to –$CH_2OH$.
Question 14
Which of the following is least basic?
(1) $NH_3$ (2) $CH_3NH_2$ (3) $(CH_3)_2NH$ (4) $C_6H_5NH_2$
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Answer: (4)
Solution: Lone pair on N in aniline is delocalised into ring, lowering basicity.
Question 15
The product of reaction of $CH_3COCl$ with $NH_3$ is
(1) $CH_3CONH_2$ (2) $CH_3COONH_4$ (3) $CH_3NH_2$ (4) $CH_3CN$
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Answer: (1)
Solution: Acid chloride + $NH_3$ gives amide.
Question 16
Which of the following gives a positive carbylamine test?
(1) $N$-methylaniline (2) $N,N$-dimethylaniline (3) Aniline (4) $CH_3NH_2$
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Answer: (1)
Solution: Only $1^\circ$ amines (or $1^\circ$ aryl-amines) give offensive isocyanide; $N$-methylaniline has N–H.
Question 17
The intermediate in Hoffmann bromamide degradation is
(1) isocyanate (2) nitrene (3) carbocation (4) free radical
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Answer: (1)
Solution: R–N=C=O (isocyanate) is formed before hydrolysis to amine.
Question 18
Which of the following has the highest boiling point?
(1) $CH_3CH_2OH$ (2) $CH_3COOH$ (3) $CH_3CHO$ (4) $CH_3OCH_3$
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Answer: (2)
Solution: Carboxylic acids form strong dimers via H-bonding.
Question 19
The product of oxidation of $CH_3CH_2CH_2OH$ with PCC is
(1) $CH_3CH_2COOH$ (2) $CH_3CH_2CHO$ (3) $CH_3CH_2CH_2OH$ (4) $CH_3CH_2COCH_3$
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Answer: (2)
Solution: PCC stops at aldehyde stage.
Question 20
Which of the following will give a white precipitate with Tollen’s reagent?
(1) $CH_3CHO$ (2) $CH_3COCH_3$ (3) $CH_3CH_2OH$ (4) $CH_3COOH$
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Answer: (1)
Solution: Aldehydes reduce Tollen’s reagent to metallic Ag mirror/ppt.
Question 21
The number of isomeric amines with formula $C_3H_9N$ is
(1) 2 (2) 3 (3) 4 (4) 5
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Answer: (3)
Solution: $1^\circ$: n-propylamine, iso-propylamine; $2^\circ$: $N$-methylethylamine; $3^\circ$: trimethylamine → total 4.
Question 22
Which of the following is the most acidic?
(1) Phenol (2) p-Cresol (3) p-Nitrophenol (4) p-Methoxyphenol
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Answer: (3)
Solution: –NO₂ is strong –I/–R, stabilises phenoxide ion most.
Question 23
The product of reaction of $CH_3MgBr$ with $CH_3CN$ followed by hydrolysis is
(1) $CH_3COCH_3$ (2) $CH_3CHO$ (3) $(CH_3)_2CHOH$ (4) $CH_3CH_2OH$
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Answer: (1)
Solution: Grignard adds to CN, hydrolysis gives ketone.
Question 24
Which of the following will not undergo aldol condensation?
(1) $CH_3CHO$ (2) $CH_3COCH_3$ (3) $HCHO$ (4) $CH_3CH_2CHO$
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Answer: (3)
Solution: HCHO has no α-H.
Question 25
The reagent that converts $C_6H_5COCH_3$ to $C_6H_5CH_2CH_3$ is
(1) $H_2/Ni$ (2) $LiAlH_4$ (3) $NaBH_4$ (4) $H_2/Pd-BaSO_4$
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Answer: (1)
Solution: Clemmensen ($Zn-Hg/HCl$) or catalytic $H_2/Ni$ reduces C=O to $CH_2$.
BETA
