NEET UG - Alkanes conformations halogenation mechanisms, alkenes electrophilic addition Markownikoff rule ozonolysis polymerization Online Test (MCQ Quiz)

1. Which of the following is the most stable conformation of ethane?

A) Eclipsed conformation B) Staggered conformation C) Skew conformation D) Partially eclipsed conformation

2. In the staggered conformation of ethane, the dihedral angle between adjacent C-H bonds is:

A) 0 degrees B) 60 degrees C) 120 degrees D) 180 degrees

3. The eclipsed conformation of ethane is less stable than the staggered conformation due to:

A) Steric hindrance B) Torsional strain C) Bond angle strain D) Van der Waals forces

4. Which type of strain is primarily responsible for the difference in stability between eclipsed and staggered conformations of ethane?

A) Steric strain B) Torsional strain C) Angle strain D) Resonance strain

5. Free radical halogenation of alkanes proceeds via which mechanism?

A) Nucleophilic substitution B) Electrophilic addition C) Free radical chain mechanism D) Concerted mechanism

6. The initiation step in the free radical chlorination of methane involves:

A) Reaction of chlorine with methane B) Homolytic cleavage of Cl-Cl bond by UV light C) Reaction of methyl radical with chlorine D) Reaction of chloromethyl radical with chlorine

7. Which of the following is a propagation step in the free radical bromination of ethane?

A) Br2 -> 2Br• B) CH3CH3 + Br• -> CH3CH2• + HBr C) CH3CH2• + Br2 -> CH3CH2Br + Br• D) 2Br• -> Br2

8. The termination step in free radical halogenation involves:

A) Formation of free radicals B) Combination of two free radicals C) Reaction of radical with stable molecule D) Chain branching

9. Why is free radical iodination of alkanes not synthetically useful?

A) Iodine is too reactive B) The reaction is reversible and the reverse reaction is favored C) Iodine radicals are too unstable D) Iodine is too expensive

10. Which of the following is the most stable free radical?

A) Methyl radical B) Primary radical C) Secondary radical D) Tertiary radical

11. The order of reactivity of halogens in free radical halogenation of alkanes is:

A) F2 > Cl2 > Br2 > I2 B) I2 > Br2 > Cl2 > F2 C) Cl2 > Br2 > F2 > I2 D) Br2 > Cl2 > I2 > F2

12. In the free radical chlorination of propane, which hydrogen is most likely to be substituted?

A) Primary hydrogens B) Secondary hydrogens C) Tertiary hydrogens D) All hydrogens are equally likely

13. Alkenes undergo which type of reaction primarily?

A) Addition reactions B) Substitution reactions C) Elimination reactions D) Rearrangement reactions

14. Electrophilic addition to alkenes involves the attack of an electrophile on the:

A) Sigma bond B) Pi bond C) Lone pair of electrons D) Carbonyl group

15. The first step in the electrophilic addition of HBr to an alkene is:

A) Attack of bromide ion on the carbocation B) Protonation of the alkene to form a carbocation C) Formation of a cyclic intermediate D) Rearrangement of the carbocation

16. Markownikoff's rule states that in the addition of HX to an unsymmetrical alkene, the hydrogen atom adds to the carbon atom that has:

A) Fewer hydrogen atoms B) More hydrogen atoms C) An equal number of hydrogen atoms D) A double bond

17. Which of the following carbocations is the most stable?

A) Methyl carbocation B) Primary carbocation C) Secondary carbocation D) Tertiary carbocation

18. The addition of HBr to propene in the presence of peroxides follows:

A) Markownikoff's rule B) Anti-Markownikoff's rule C) Zaitsev's rule D) Hofmann's rule

19. The addition of Br2 to ethene forms:

A) 1,1-dibromoethane B) 1,2-dibromoethane C) Bromoethane D) Ethane

20. The intermediate formed during the addition of bromine to ethene is a:

A) Carbocation B) Bromonium ion C) Free radical D) Carbanion

21. Ozonolysis of an alkene is used to determine:

A) The position of double bond B) The number of carbon atoms C) The molecular formula D) The presence of triple bonds

22. In the ozonolysis of propene followed by reductive workup (e.g., with Zn/H2O), the products are:

A) Ethanal and methanal B) Propanal and methanal C) Ethanal and propanal D) Propanone and methanal

23. Ozonolysis of cyclohexene followed by oxidative workup yields:

A) Adipic acid B) Hexanoic acid C) Cyclohexanol D) Cyclohexanone

24. Which reagent is used for reductive workup after ozonolysis of alkenes?

A) KMnO4 B) O3 C) Zn/H2O D) H2O2

25. Polymerization of alkenes involves:

A) Addition of small molecules B) Joining of many monomer units C) Elimination of small molecules D) Substitution reactions

26. Which type of polymerization is typically followed by ethene to form polyethene?

A) Condensation polymerization B) Addition polymerization C) Chain growth polymerization D) Step growth polymerization

27. The monomer unit in polypropylene is:

A) Ethene B) Propene C) Styrene D) Vinyl chloride

28. Free radical polymerization of alkenes is initiated by:

A) Acids B) Bases C) Free radical initiators D) Lewis acids

29. The process of formation of a polymer from monomers is called:

A) Isomerization B) Polymerization C) Cracking D) Reforming

30. Which of the following is a common application of polyethene?

A) Teflon B) PVC pipes C) Plastic bags D) Nylon

31. The structure of the repeating unit in polypropene is:

A) (-CH2-CH2-) B) (-CH2-CHCl-) C) (-CH2-CH(CH3)-) D) (-CH=CH-)

32. Which of the following is an example of a polymer derived from an alkene?

A) Polyester B) Polyamide C) Polyvinyl chloride D) Bakelite

33. The anti-Markownikoff addition of HBr to 1-butene will primarily yield:

A) 1-bromobutane B) 2-bromobutane C) 1,1-dibromobutane D) 2,2-dibromobutane

34. Which conformation of cyclohexane is the most stable?

A) Boat conformation B) Twist-boat conformation C) Half-chair conformation D) Chair conformation

35. In the chair conformation of cyclohexane, axial and equatorial positions are:

A) Equivalent B) Non-equivalent C) Interconverting rapidly D) Dependent on temperature

36. The interconversion of chair conformations of cyclohexane is called:

A) Epimerization B) Ring flipping C) Tautomerization D) Resonance

37. Free radical chlorination of cyclohexane primarily produces:

A) Chlorocyclohexane B) 1,1-dichlorocyclohexane C) 1,2-dichlorocyclohexane D) Cyclohexene

38. The electrophilic addition of water to ethene in the presence of an acid catalyst yields:

A) Ethanol B) Ethanal C) Ethanoic acid D) Ethane

39. Ozonolysis of 2-methylbut-2-ene followed by reductive workup yields:

A) Propanone and methanal B) Ethanal and propanone C) Ethanal and ethanal D) Propanal and ethanal

40. Which of the following is a Ziegler-Natta catalyst used in alkene polymerization?

A) Peroxides B) Benzoyl peroxide C) Titanium tetrachloride and triethylaluminium D) Azobisisobutyronitrile (AIBN)

41. The reaction of an alkene with KMnO4 under cold, dilute, alkaline conditions leads to:

A) Oxidative cleavage B) Diol formation C) Epoxide formation D) Halogenation

42. The product of oxidative cleavage of 2,3-dimethylbut-2-ene using hot KMnO4 is:

A) Propanone B) Ethanal C) Carbon dioxide D) Two molecules of propanone

43. Which type of strain is present in the boat conformation of cyclohexane that is absent in the chair conformation?

A) Torsional strain B) Steric strain (flagpole interaction) C) Angle strain D) Van der Waals strain

44. The addition of halogens to alkenes is an example of:

A) Electrophilic addition B) Nucleophilic addition C) Free radical addition D) Syn addition

45. In the electrophilic addition of HBr to 2-methylbut-2-ene, the major product is:

A) 2-bromo-2-methylbutane B) 2-bromo-3-methylbutane C) 1-bromo-2-methylbutane D) 3-bromo-2-methylbutane

46. The process of breaking down larger hydrocarbon molecules into smaller, more useful ones is called:

A) Polymerization B) Cracking C) Reforming D) Hydrogenation

47. Which of the following is an example of condensation polymerization?

A) Polyethylene B) Polypropylene C) Nylon-6,6 D) Polyvinyl chloride

48. The mechanism of addition of H2O to alkenes in the presence of acid catalyst involves:

A) Formation of a bromonium ion B) Attack by water molecule on carbocation C) Free radical chain reaction D) Nucleophilic attack on pi bond

49. The anti-Markownikoff addition of HBr to an alkene in the presence of peroxides proceeds via:

A) Carbocation intermediate B) Free radical intermediate C) Bromonium ion intermediate D) Carbanion intermediate

50. The IUPAC name of the product of ozonolysis of 2,4,4-trimethylpent-1-ene followed by reductive workup is:

A) 3,3-dimethylbutanal and methanal B) 2,2-dimethylpropanal and methanal C) 3,3-dimethylbutanal and ethanal D) 2,2-dimethylpropanal and ethanal

Alkanes conformations halogenation mechanisms, alkenes electrophilic addition Markownikoff rule ozonolysis polymerization - Online Test

Test Results