Exam Problem Set 7

Select an answer for each of the 52 multiple-choice questions below, then press Check Answers. The answer key unlocks after a genuine attempt.

Amines and Related Nitrogen Compounds

1. Which of the following is a 3°-amine?
A) 1-methylcyclohexylamine
B) triethylamine
C) tert-butylamine
D) N-methylaniline

2. Which of the following compounds is cyclopentyldiethylamine?

3 Which of the following is a proper name for CH₂=CHCH₂NHCH₃?
A) allylmethylamine
B) 4-amino-1-pentene
C) 2-amino-4-pentene
D) N-methyl-1-propenamine

4 Which of the following is tetrabutylammonium iodide?
A) C₄H₉NH₃⁺ I^–
B) C₄H₉N(CH₃)₃⁺ I^–
C) (C₄H₉)₄N⁺ I^–
D) (CH₃)₄N⁺ I^–

5 Which of the following is N,N-dimethylaniline?

6 Which of the following is a proper name for (CH₃)₂CHCH₂NHCH₂CH₂CH(CH₃)₂?
A) 2,7-dimethyl-4-azaoctane
B) butylpentylamine
C) 2,7-dimethylpropylbutylamine
D) 3-amino-2,7-dimethyloctane

7 Ethylmethylamine cannot be resolved under normal conditions. Why?
A) the favored configuration is not chiral.
B) it isomerizes rapidly with the achiral isomer trimethylamine.
C) the nitrogen atom rapidly inverts its configuration leading to a racemic mixture.
D) the C–N bond is not stable under conditions used for resolution

8 Which of the following is pyridine?

9 Which of the following is the strongest base in aqueous solution?.
A) (CH₃)₃N
B) (CH₃)₂N CH₂CH₂OH
C) CH₃CH₂CH₂NHOH
D) (CH₃)₄N OH

10 Which of the following is the strongest Brønsted base?

11 Dibutylamine, (C₄H₉)₂NH, and anisole, C₆H₅OCH₃, have similar boiling points, and are relatively insoluble in water.
  How might a mixture of these compounds be separated into the pure components?
A) i) dissolve mixture in ether;   ii) extract the anisole into 10% aqueous NaOH
B) i) dissolve mixture in ether;   ii) extract the amine into 10% aqueous HCl
C) i) dissolve mixture in ether;   ii) extract the amine into 10% aqueous NaOH
D) i) dissolve mixture in ether;   ii) extract the anisole into 10% aqueous HCl

12 Which of the following is the strongest Brønsted acid?

13 Which of the following is the strongest Brønsted base?

14 Which of the following is the weakest Brønsted base?

15 Which of the following is the weakest Brønsted base?

16 Which of the following is the strongest Brønsted base?

17 Which compound is the likely product from reaction of pyrrolidine with excess methyl iodide (equation below)?

18 For the following compounds, which is the strongest base and which the strongest acid ?

A) II = strongest base,   I = strongest acid
B) IV = strongest base,   III = strongest acid
C) III = strongest base,   IV = strongest acid
D) II = strongest base,   III = strongest acid

19 Basic reagents are used in many organic reactions. Examples are: I triethylamine, II DBU, III potassium phthalimide & IV LDA.
Which of these is the strongest base?

20 Benzylamine may be alkylated as shown in the following equation.
  C₆H₅CH₂NH₂  +  R-X  ---->  C₆H₅CH₂NHR (pyridine is used to scavange the HX produced here)
Which of the following alkyl halides is best suited for this reaction?
A) (CH₃)₃CCH₂Br
B) C₆H₅Br
C) C₆H₅CH₂Br
D) (CH₃)₃CCl

21 Three heterocyclic amines are shown below:   I = pyridine,   II = pyrimidine,   III = imidazole.
What is the order of increasing basicity? (weaker base < stronger base)
 
A) II < I < III
B) II < III< I
C) I < II < III
D) III < II < I

22 Which of the following reagents would not be a good choice for reducing an aryl nitro compound to an amine?
A) H₂ (excess) & Pt catalyst
B) LiAlH₄ in ether
C) Fe in 15% HCl
D) Zn in 10% HCl

23 What reagent is the source of nitrogen in the Gabriel synthesis of amines?
A) sodium azide, NaN₃
B) sodium nitrite, NaNO₂
C) potassium cyanide, KCN
D) potassium phthalimide, C₆H₄(CO)₂NK

24 In order to prepare a 1°-amine incorporating an additional CH₂ group from an alkyl halide, what reagent is often used as the nitrogen source?
A) sodium amide, NaNH₂
B) sodium azide, NaN₃
C) potassium cyanide, KCN
D) potassium phthalimide, C₆H₄(CO)₂NK

25 What set of conditions would be useful for preparing a 2°-amine?
A) 2°-RBr + NaNH₂
B) (i) 2°-RBr + NaN₃   (ii) H₂ & Pt
C) (i) 1°-RNH₂ + 1°-RCHO   (ii) H₂ & Pt
D) (i) 2 1°-RBr + potassium phthalimide   (ii) H₃O⁺ & heat

26 What reagent is used in the Hinsberg test of amines?
A) (CH₃CO)₂O & pyridine
B) C₆H₅SO₂Cl in aq. NaOH
C) NaNO₂ in aq. H₂SO₄
D) CH₃I (excess) followed by AgOH

27 Which of the following will be the favored product from the reaction shown below?

28 Which of the following procedures would be best for preparing isobutylisopropylamine, (CH₃)₂CHNHCH₂CH(CH₃)₂?
A) (CH₃)₂CHBr + (CH₃)₂CHCH₂NH₂
B) (i) (CH₃)₂CHBr + (CH₃)₂CHCONHNa   (ii) LiAlH₄ in ether
C) (i) (CH₃)₂CHNH₂ + (CH₃)₂CHCH=O   (ii) H₂ & Pt
D) (CH₃)₂CHCN + (CH₃)₂CHNH₂

29 What is the chief product from the Hofmann elimination of 4-methyl-2-aminopentane?
A) 4-methyl-1-pentene
B) 4-methyl-2-pentene
C) 2-methyl-1-pentene
D) 2-methyl-2-pentene

30 Which of the following procedures would be best for preparing dimethylcyclohexylamine, C₆H₁₁N(CH₃)₂?
A) (i) dimethylamine + cyclohexanone   (ii) NaBH₃CN in methanol
B) dimethylamine + cyclohexylbromide in ether
C) cyclohexylamine + 2 CH₃I in ether
D) (i) cyclohexylbromide + NaCN in methanol   (ii) 2 CH₃Li in THF

31 What reagent would be best for converting the amide of (R)-2-phenylpropanoic acid, C₆H₅CH(CH₃)CONH₂, into (R)-1-amino-2-phenylpropane?
A) excess H₂ & Pt.
B) NaOBr in aqueous base.
C) NaBlH₄ in methanol
D) LiAlH₄ in ether.

32 What reagent would be best for converting the amide of (R)-2-phenylpropanoic acid, C₆H₅CH(CH₃)CONH₂, into (R)-1-phenylethylamine?
A) excess H₂ & Pt.
B) NaOBr in aqueous base.
C) NaBlH₄ in methanol
D) LiAlH₄ in ether.

33 The structural formulas of four physiologically active amines are displayed below.
  choline is a nerve transmission agent, benzedrine is an amphetamine, benadryl is an antihistamine, and coniine is a toxic alkaloid found in hemlock.
  Which of these would be classified as a tertiary amine?
 
A) choline
B) benzedrine
C) benadryl
D) coniine

34 Many kinds of amino alcohols are known, but α-amino alcohols such as 1-dimethylaminocyclopentanol are not stable under most conditions.
  Which of the following statements best accounts for their instability?
A) carbon does not like to form bonds to two more electronegative atoms such as O and N.
B) the α-isomer rapidly rearranges to the more stable β amino alcohol.
C) rapid loss of water (a stable small molecule) leads to an imine product.
D) rapid loss of amine leads to a stable carbonyl compound (aldehyde or ketone).

35 Which of the following amines reacts most rapidly with para-nitrophenylacetate, p-NO₂C₆H₄OCOCH₃?
A) para-methoxyaniline,.p-CH₃OC₆H₄NH₂
B) para-nitroaniline, p-NO₂C₆H₄NH₂.
C) aniline, C₆H₅NH₂.
D) cyclopentylamine, C₅H₉NH₂.

36 What product mixture is expected from reaction of (S)-2-aminobutane with 2-butanone in the presence of NaBH₃CN?
A) a pair of enantiomers.
B) a pair of diastereomers, both meso.
C) a pair of diastereomers, one meso one chiral.
D) a pair of diastereomers, both chiral (not enantiomers).

37 Which of the following compounds is the strongest base?
A) (CH₃)₂NCH₂CO₂CH₃.
B) (CH₃)₂NCOCH₃.
C) (CH₃)₂NC≡N.
D) (CH₃)₂N-N=O.

38 What is the chief product from the following reaction?

39 The nitrogen atom in each of the following tertiary amines may be removed as trimethyl amine by repeated Hofmann eliminations (exhaustive methylation followed by heating with AgOH).
  Which of the amines requires the greater number of Hofmann sequences to accomplish this?

40 Only one of the following amines will lose its nitrogen atom as trimethyl amine by repeated Hofmann elimination reactions (exhaustive methylation followed by heating with AgOH).
  Identify that amine.

41 A nitrogen containing compound dissolves in 10% aq. sulfuric acid..
  The Hinsberg test (C₆H₅SO₂Cl in base) gives a solid product that is not soluble in 10% aq. NaOH..
  Which of the following would best fit these facts?
A) N,N-dimethylaniline, C₆H₅N(CH₃)₂.
B) N-methylbenzamide, C₆H₅CONHCH₃.
C) N-methylaniline, C₆H₅NHCH₃.
D) benzylamine, C₆H₅CH₂NH₂.

42 Which of the following reagents would be best for converting phenylacetamide (C₆H₅CH₂CONH₂) to benzylamine (C₆H₅CH₂NH₂)?
A) LiAlH₄ in ether.
B) i) P₂O₅ & heat; ii) LiAlH₄ in ether.
C) H₂ & Pt catalyst.
D) aqueous NaOBr.

43 The Hinsberg test of a C₅H₁₄N₂ compound produces a solid that is insoluble in 10% aq. NaOH.
  This solid derivative dissolves in 10% aq. sufuric acid. Which of the following would best fit these facts?
A) NH₂CH₂CH₂CH₂N(CH₃)₂.
B) (CH₃)₂NCH₂CH₂NHCH₃.
C) NH₂CH₂C(CH₃)₂CH₂NH₂.
D) (CH₃)₂NCH₂N(CH₃)₂.

44 Which of the following reagents and conditions would be best for the preparation of cyclohexylamine?
A) cyclohexanone + NH₃ + NaBH₃CN.
B) cyclohexylbromide + 2 NH₃.
C) cyclohexylbromide + NaNH₂.
D) cyclohexene + NH₃.

45 Which of the following reagents would be best for converting phenylacetamide (C₆H₅CH₂CONH₂) to phenethylamine (C₆H₅CH₂CH₂NH₂)?
A) H₂ & Pt catalyst.
B) NaBH₃CN.
C) LiAlH₄ in ether.
D) aqueous NaOBr.

46 Repeated Hofmann elimination reactions (exhaustive methylation followed by heating with AgOH) will often remove a nitrogen atom from an amine molecule.
  Which of the following compounds is the likely product in this case?

47 What sequence of reactions would best accomplish the following reaction?
 
A) i) LiAlH₄ in ether; ii) 3 CH₃I followed by heating with AgOH
B) i) LiAlH₄ in ether; ; ii) P₂O₅ & heat
C) i) 20% H₂SO₄ & heat; ii) P₂O₅ & heat
D) H₂ & Lindlar catalyst

48 What is the likely product from the following reaction?

49 Which of the following statements concerning amine oxides is not true?
A) chiral amine oxides may be resolved.
B) the nitrogen has a positive formal charge.
C) the nitrogen hybridization is sp³.
D) all types of amines can form amine oxide derivatives.

50 Amines are well known to be stronger bases and nucleophiles than alkenes.
  Why do enamines, such as 1-dimethylaminocyclopentene, preferentially react with electrophiles at a double bond carbon rather than at nitrogen?
A) the nitrogen is sterically hindered by alkyl substituents.
B) nitrogen is more electronegative than carbon.
C) the carbocation formed by electrophilic attack at C-2 is stabilized by pi-bonding with the lone pair of electrons on nitrogen.
D) ammonium cations are less stable than carbocations.

51 A C₅H₁₃N compound gives a base soluble derivative in the Hinsberg test (C₆H₅SO₂Cl in base).
  The ¹³Cnmr spectrum of this compound has four resonance signals at δ 8.7, 29.9, 37.5 & 49.5 ppm.
  Which of the following fits these facts best?
A) 1,1-dimethylpropylamine.
B) isopropyldimethylamine.
C) 2,2-dimethylpropylamine.
D) N-methyl-2-methylpropylamine.

52 Reaction of para-chloroaniline with acetic anhydride in pyridine gave a mixture of 94% of para-chloroacetanilide, contaminated with 6% unreacted amine.
  Which of the following treatments would be best used to purify the amide?
A) react the unreacted amine with methyl iodide.
B) wash an ether solution of the crude product with concentrated brine (aq. NaCl).
C) wash an ether solution of the crude product with 5% aqueous sulfuric acid.
D) wash an ether solution of the crude product with 5% aqueous sodium carbonate.