Haloalkanes and Haloarenes Mock Test – Class 12 Chemistry

1. Which two-step sequence converts propene into propan--ol through a haloalkane intermediate?

2. -Bromobutane is treated with a very bulky strong base under heated conditions. The less substituted alkene is formed in unusually high proportion because the bulky base:

3. Four cyanide-substitution records are shown.
P. gives .
Q. gives .
R. gives .
S. gives .

Choose the appropriate evaluation.

4. The carbon atom of cyanide ion is isotopically labelled in . When this reagent reacts with bromoethane, which product correctly shows the position of the label?

5. Among the following chlorides, the one most clearly capable of forming a resonance-stabilised carbocation during substitution is:

6. Evaluate the following compound–hazard connections.

The appropriate evaluation is:

7. Use the graph description below. A reaction-coordinate diagram has reactants and products separated by a single energy maximum, with no minimum between them. This profile is most consistent with:

8. Which option correctly describes iodoform?

9. The combined electrophilic and nucleophilic substitution description that fits haloarenes is:

10. A learner predicts that chlorobenzene will rapidly give iodobenzene with in dry acetone. The prediction is unsuitable mainly because:

11. Arrange the following events in the correct order for peroxide-assisted addition of to propene.
P. The carbon radical abstracts hydrogen from .
Q. The peroxide bond undergoes homolytic cleavage.
R. A bromine radical adds to the carbon–carbon double bond.
S. An alkoxy radical generates from .

12. Assertion: Zinc can convert a vicinal dihalide into an alkene.
Reason: Removal of halogen atoms from adjacent carbons permits formation of a carbon–carbon pi bond.

13. A laboratory notebook records the use of dichloromethane to extract an organic compound. The stopper is left open, the operation is performed in a small closed room, and the solvent odour becomes strong. The best response is:

14. Which comparison of ordinary nucleophilic-substitution behaviour is most accurate?

15. A set of observations is recorded for four halo-compound samples.

The appropriate evaluation is:

16. Steric hindrance at four alkyl bromides is assessed for an ideal reaction.
P. — minimal hindrance
Q. — low hindrance
R. — moderate hindrance
S. — severe hindrance

Select the appropriate evaluation.

17. Under identical nitration conditions, the expected initial-rate comparison is:

18. A reaction-coordinate graph for benzene chlorination shows two pathways with the same reactant and product energy levels. The curve for the -catalysed pathway has a lower maximum than the uncatalysed curve. The graph indicates that :

19. Assertion: Chlorobenzene requires much harsher hydrolysis conditions than chloroethane.
Reason: The carbon–chlorine bond in chlorobenzene is shortened and strengthened by resonance and bonding to an -hybridised carbon.

20. Assess the following stages of chlorofluorocarbon-related ozone depletion.

The appropriate evaluation is:

21. Two reactions are proposed.
Case P: with in dimethyl sulfoxide
Case Q: in aqueous ethanol

The most appropriate mechanism assignment is:

22. A student records the following observations after treating suitable haloalkanes with ethanolic .

The appropriate evaluation is:

23. The carbon–chlorine bond in chlorobenzene has partial double-bond character mainly because:

24. Ethanol is often added in small quantity to stored chloroform because ethanol:

25. Chlorination of an unsymmetrical alkane often produces a mixture of monochloro products because:

26. Chlorobenzene is treated with acetyl chloride and anhydrous under ordinary Friedel–Crafts acylation conditions. The most reasonable expectation is:

27. A student names as ethyl cyanide and concludes that it contains only two carbon atoms. The correct interpretation is:

28. Benzyl chloride is the common name of:

29. The common and IUPAC names of are, respectively:

30. A reaction-coordinate graph for a substitution contains two energy maxima separated by a minimum. The minimum corresponds to a carbocation. This graph is most consistent with:

31. Arrange the following stages in the correct order for a rearranged substitution.
P. The leaving group departs and forms an initial carbocation.
Q. A -hydride or alkyl shift produces a more stable carbocation.
R. The nucleophile attacks the rearranged carbocation.
S. Proton transfer gives a neutral product when the nucleophile is neutral.

32. During a reaction, one species donates an electron pair to an electron-deficient carbon centre. The roles of the two participants are:

33. Approximate bond lengths for a series of similar alkyl halides are shown below.

The bond represented by S is most reasonably:

34. In the balanced reaction below, the missing coefficient before is ______.

35. A facility uses a volatile chlorinated solvent and also handles a persistent organohalogen pesticide. Which management plan best addresses both immediate and long-term risks?

36. Ortho- and para-nitrochlorobenzene react with hydroxide much more readily than the meta isomer in the standard addition–elimination pathway. The most direct explanation is:

37. Relative initial rates are measured for four bromides under identical conditions.

P: , relative rate
Q: , relative rate
R: , relative rate
S: , relative rate

The data are best explained by:

38. A laboratory preparation produces of butane by Wurtz coupling of bromoethane. If sodium is used in the exact stoichiometric amount and its molar mass is , the required mass of sodium is:

39. The condensed structure corresponding to -bromo--methylpropane is:

40. Which distinction between bioaccumulation and biomagnification is correct?

41. Match each treatment of chlorobenzene with its principal product class.

Which evaluation is appropriate?

42. A nucleophile normally attacks the carbon atom of a haloalkane because that carbon:

43. Assertion: Carbocation rearrangements can help distinguish from an ideal pathway.
Reason: A free carbocation intermediate can undergo hydride or alkyl migration before nucleophile attack.

44. Complete homolytic cleavage of of produces how many moles of chlorine radicals?

45. Two reaction-coordinate curves describe hydroxide substitution of chlorobenzene and -nitrochlorobenzene by an addition–elimination pathway. The -nitro compound has a lower first energy maximum and a lower intermediate minimum. The best interpretation is:

46. Assertion: Allylic halides often show enhanced substitution reactivity compared with ordinary primary haloalkanes.
Reason: Allylic intermediates or transition states can receive stabilisation through interaction with the neighbouring pi system.

47. Assertion: Radical termination becomes possible when two radical species collide.
Reason: Combination of the two unpaired electrons can produce a stable covalent bond without generating another radical.

-Bromobutane is treated with under two otherwise comparable conditions.
Case P: polar protic solvent
Case Q: polar aprotic solvent

The more reasonable prediction for an reaction is:

49. Match each structure in Column I with its common name in Column II.

50. A reaction notebook contains the following entries.

Which sequence represents the Balz-Schiemann route?