Alkynes acidic character addition reactions and polymerization - Question Bank

1. The polymerization of ethyne to polyacetylene is a type of:
A) Addition polymerization
B) Condensation polymerization
C) Chain growth polymerization
D) Step growth polymerization
2. Acid-catalyzed hydration of internal alkynes like 2-butyne yields:
A) An aldehyde
B) A ketone
C) A mixture of aldehyde and ketone
D) A carboxylic acid
3. The conversion of an alkyne to a trans-alkene can be achieved by using:
A) Lindlar's catalyst
B) Pd/C
C) Na in liquid NH3
D) H2/Ni
4. The addition of one mole of HBr to 1-butyne follows Markovnikov's rule and produces:
A) 1-Bromo-1-butene
B) 1-Bromo-2-butene
C) 2-Bromo-1-butene
D) 2-Bromo-2-butene
5. Which of the following terminal alkynes is the most acidic?
A) Phenylacetylene
B) 1-Butyne
C) Propyne
D) Ethyne
6. The reaction of ethyne with dilute nitric acid and mercuric nitrate yields:
A) Mercury acetylide
B) Nitroacetylene
C) Benzene
D) Acetaldehyde
7. Which of the following is a property of the sp hybridized carbon atom in alkynes?
A) It is less electronegative than sp2 hybridized carbon.
B) It has a bond angle of 120 degrees.
C) It has 50% s-character.
D) It forms longer bonds than sp2 hybridized carbon.
8. The polymerization of alkynes can be catalyzed by:
A) Lewis acids
B) Transition metal complexes
C) Protic acids
D) All of the above
9. Ozonolysis of 2-butyne followed by workup yields:
A) Acetaldehyde
B) Pyruvic acid
C) Two molecules of acetaldehyde
D) Two molecules of pyruvic acid
10. The reaction where an alkyne is converted to a cis-alkene using a poisoned palladium catalyst is known as:
A) Dissolving metal reduction
B) Catalytic hydrogenation
C) Lindlar reduction
D) Ozonolysis
11. The addition of H2O to 1-butyne in the presence of HgSO4 and dil. H2SO4 will yield:
A) 1-Butanol
B) 2-Butanol
C) 1-Butanone
D) 2-Butanone
12. The formation of a precipitate with ammoniacal silver nitrate solution is a test for:
A) Internal alkynes
B) Terminal alkynes
C) Alkenes
D) Alkanes
13. When ethyne reacts with one equivalent of Br2, the product is:
A) 1,1-Dibromoethane
B) 1,2-Dibromoethane
C) Bromoethene
D) Vinyl bromide
14. Which statement is FALSE regarding the acidic character of alkynes?
A) Ethyne is more acidic than ethene.
B) Terminal alkynes are more acidic than internal alkynes.
C) The conjugate base of ethyne is more stable than the conjugate base of ethene.
D) Acidity decreases with increasing s-character of the hybrid orbital.
15. Reaction of acetylene with hot concentrated nitric acid results in the formation of:
A) Nitroacetylene
B) Benzene
C) Oxalic acid
D) Carbon dioxide
16. Which of the following is a consequence of the sp hybridization of carbon atoms in alkynes?
A) Increased bond length between carbon atoms
B) Decreased bond angle
C) Increased acidity
D) Decreased reactivity towards electrophiles
17. The polymerization of ethyne can produce conjugated polymers with interesting electronic properties.
A) True, such polymers are called polyalkynes.
B) True, such polymers are called polyenes.
C) False, ethyne does not polymerize.
D) False, only alkenes polymerize.
18. The ozonolysis of propyne followed by reductive workup yields:
A) Acetaldehyde and formaldehyde
B) Pyruvic acid and formaldehyde
C) Acetic acid and formaldehyde
D) Glyoxal and formaldehyde
19. Which catalyst is used for the complete reduction of alkynes to alkanes?
A) Lindlar's catalyst
B) Pd/BaSO4
C) Raney Nickel or Pt/Pd
D) Na/NH3
20. The reduction of an alkyne with Na/NH3 (liquid) yields a mixture of cis and trans alkenes.
A) True, primarily trans alkene is formed.
B) True, primarily cis alkene is formed.
C) False, only cis alkene is formed.
D) False, only trans alkene is formed.
21. The anti-Markovnikov addition of water to alkynes is achieved by:
A) HgSO4/dil. H2SO4
B) BH3 followed by H2O2/OH-
C) Br2/H2O
D) HCl
22. What is the intermediate formed during the hydration of ethyne before tautomerization?
A) Vinyl alcohol
B) Ethanal
C) Ethene
D) Acetaldehyde hydrate
23. The reaction of ethyne with dilute H2SO4 and HgSO4 is an example of:
A) Electrophilic addition
B) Nucleophilic addition
C) Free radical addition
D) Cycloaddition
24. Which of the following can be synthesized using the alkylation of terminal alkynes?
A) Alkanes
B) Primary alcohols
C) Internal alkynes
D) Ethers
25. The structure of the acetylide ion formed from ethyne is:
A) CH3-C≡C-
B) HC≡C-
C) CH2=C=CH-
D) CH3-C=C-
26. The rate of deprotonation of alkynes with a base increases in the order:
A) Ethyne < Propyne < 1-Butyne
B) Ethyne > Propyne > 1-Butyne
C) Propyne > Ethyne > 1-Butyne
D) 1-Butyne > Propyne > Ethyne
27. Which type of bond is broken during the addition of HBr to ethyne?
A) Sigma bond
B) Pi bond
C) Both sigma and pi bonds
D) Only one of the pi bonds
28. The product of the reaction of propyne with NaNH2 followed by CH3I is:
A) 2-Butyne
B) 1-Butyne
C) 1-Butene
D) 2-Butene
29. Which of the following is a characteristic reaction of terminal alkynes that distinguishes them from internal alkynes?
A) Electrophilic addition of H2
B) Addition of halogens
C) Formation of metal acetylides with Ag+ or Cu+
D) Hydration
30. The reaction of ethyne with hot concentrated sulfuric acid leads to:
A) Benzene
B) Ethene
C) Ethanal
D) Ethanoic acid
31. The acidic hydrogen in ethyne can be replaced by:
A) A methyl group
B) A hydroxyl group
C) A halogen atom
D) All of the above
32. Which of the following conditions favors polymerization of alkynes?
A) Low temperature and high pressure
B) High temperature and presence of catalysts
C) Low temperature and absence of catalysts
D) High pressure and absence of catalysts
33. Polymerization of ethyne leads to the formation of:
A) Polyethylene
B) Polyvinyl chloride
C) Polyacetylene
D) Polystyrene
34. Ozonolysis of ethyne followed by reductive workup yields:
A) Glyoxal
B) Oxalic acid
C) Ethylene glycol
D) Acetic acid
35. Dissolving metal reduction (e.g., Na in liquid NH3) of an alkyne yields:
A) cis-Alkene
B) trans-Alkene
C) Alkane
D) Alkyne
36. Which catalyst is used for the partial reduction of alkynes to cis-alkenes?
A) Raney Nickel
B) Platinum dioxide
C) Lindlar's catalyst
D) Palladium on charcoal
37. The reaction of ethyne with hydrogen gas in the presence of a catalyst like Pd/BaSO4 (Lindlar's catalyst) produces:
A) Ethane
B) Ethene
C) Acetylene
D) Ethanal
38. Hydroboration-oxidation of a terminal alkyne results in the formation of:
A) An aldehyde
B) A ketone
C) A carboxylic acid
D) An ester
39. The hydration of an unsymmetrical alkyne like propyne follows Markovnikov's rule, leading to the formation of a(n):
A) Aldehyde
B) Ketone
C) Carboxylic acid
D) Alcohol
40. Addition of H2O to ethyne in the presence of HgSO4 and dil. H2SO4 yields:
A) Ethanol
B) Acetaldehyde
C) Acetic acid
D) Ethane
41. The addition of halogens (e.g., Br2) to alkynes follows:
A) Markovnikov's rule
B) Anti-Markovnikov's rule
C) Anti-addition mechanism
D) Syn-addition mechanism
42. When ethyne reacts with excess HBr, the product formed is:
A) Vinyl bromide
B) 1,1-Dibromoethane
C) 1,2-Dibromoethane
D) Ethane
43. Which of the following is NOT a product of the addition of HBr to ethyne?
A) Vinyl bromide
B) 1,1-Dibromoethane
C) 1,2-Dibromoethane
D) Bromoethane
44. The reaction of a terminal alkyne with a strong base like NaNH2 followed by an alkyl halide (R-X) is an example of:
A) Electrophilic substitution
B) Nucleophilic addition
C) Nucleophilic substitution (alkylation)
D) Oxidation
45. Terminal alkynes can react with heavy metal ions like silver (Ag+) and copper(I) (Cu+) to form:
A) Alkenes
B) Alkanes
C) Explosive metal acetylides
D) Ethers
46. Which of the following reactions demonstrates the acidic character of alkynes?
A) Electrophilic addition of HBr
B) Reaction with sodium amide in liquid ammonia
C) Hydroboration-oxidation
D) Ozonolysis
47. The conjugate base of ethyne is called:
A) Acetylide ion
B) Vinyl anion
C) Ethynyl anion
D) Carbanion
48. Which reagent is commonly used to deprotonate terminal alkynes?
A) Sodium hydroxide (NaOH)
B) Sodium amide (NaNH2)
C) Water (H2O)
D) Ammonia (NH3)
49. The acidic nature of terminal alkynes is due to:
A) The presence of a pi bond
B) The high s-character of the sp hybridized carbon atom
C) The electronegativity of the hydrogen atom
D) The resonance stabilization of the conjugate base
50. Which of the following is the most acidic alkyne?
A) Ethyne
B) Propyne
C) 1-Butyne
D) 2-Butyne