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Haloalkanes and Haloarenes WBCHSE Class 12 MCQ & Practice Questions

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Haloalkanes and Haloarenes Revision Guide for WBCHSE Class 12 Chemistry

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Top 20 Haloalkanes and Haloarenes MCQs with Answers

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WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

1. SN1 বিক্রিয়ার জন্য কোন haloalkane সবচেয়ে অনুকূল?

  • A. CH3Cl
  • B. C2H5Cl
  • C. (CH3)2CHCl
  • D. (CH3)3CCl
Answer: D
Explanation: SN1 বিক্রিয়ায় carbocation তৈরি হয়; tertiary carbocation সবচেয়ে স্থিতিশীল, তাই tert-butyl chloride দ্রুততম।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

2. SN2 বিক্রিয়ার জন্য কোনটি সবচেয়ে দ্রুত?

  • A. CH3Br
  • B. C2H5Br
  • C. (CH3)2CHBr
  • D. (CH3)3CBr
Answer: A
Explanation: SN2-তে steric hindrance কম হলে গতি বেশি; methyl bromide সবচেয়ে কম hindered।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

3. Aqueous KOH-এর সঙ্গে bromoethane-এর প্রধান উৎপাদ কী?

  • A. Ethene
  • B. Ethanol
  • C. Ethanal
  • D. Ethane
Answer: B
Explanation: Aqueous KOH nucleophilic substitution ঘটিয়ে bromoethane থেকে ethanol দেয়।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

4. Alcoholic KOH-এর সঙ্গে 2-bromopropane-এর প্রধান উৎপাদ কী?

  • A. Propan-2-ol
  • B. Propene
  • C. Propane
  • D. Propanal
Answer: B
Explanation: Alcoholic KOH β-elimination ঘটায়; 2-bromopropane থেকে propene তৈরি হয়।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

5. Chlorobenzene nucleophilic substitution-এ chloroethane-এর তুলনায় কম সক্রিয় কেন?

  • A. C–Cl বন্ধন দীর্ঘতর
  • B. resonance-এ C–Cl বন্ধনে partial double-bond character
  • C. Cl কম electronegative
  • D. benzene nonpolar
Answer: B
Explanation: Chlorobenzene-এ lone-pair conjugation-এর ফলে C–Cl বন্ধনে partial double-bond character ও বেশি শক্তি আসে।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

6. Wurtz reaction-এ 2 mol CH3Br থেকে প্রধান hydrocarbon কোনটি?

  • A. Methane
  • B. Ethane
  • C. Propane
  • D. Butane
Answer: B
Explanation: 2CH3Br + 2Na → C2H6 + 2NaBr; তাই ethane।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

7. Finkelstein reaction-এ সাধারণত কোন reagent ব্যবহৃত হয়?

  • A. NaI in acetone
  • B. AgF
  • C. KOH(aq)
  • D. Zn/HCl
Answer: A
Explanation: Finkelstein reaction-এ alkyl chloride/bromide-কে NaI in acetone দিয়ে alkyl iodide-এ রূপান্তর করা হয়।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

8. Swarts reaction-এর উদ্দেশ্য কী?

  • A. Alkyl fluoride প্রস্তুতি
  • B. Alkyl iodide প্রস্তুতি
  • C. Alcohol প্রস্তুতি
  • D. Alkene প্রস্তুতি
Answer: A
Explanation: Swarts reaction-এ metal fluoride ব্যবহার করে alkyl chloride/bromide থেকে alkyl fluoride তৈরি করা হয়।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

9. Chloroform আলোর উপস্থিতিতে বায়ু দ্বারা জারিত হয়ে কোন বিষাক্ত পদার্থ দেয়?

  • A. COCl2
  • B. CO2
  • C. HCOOH
  • D. CCl4
Answer: A
Explanation: CHCl3 বায়ু ও আলোতে oxidation হয়ে phosgene, COCl2, তৈরি করতে পারে।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

10. Iodoform test কোন compound দেয়?

  • A. Methanol
  • B. Ethanol
  • C. tert-Butanol
  • D. Benzene
Answer: B
Explanation: Ethanol oxidation-এ acetaldehyde গঠন করে এবং iodoform test দেয়।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

11. DDT-এর প্রধান পরিবেশগত সমস্যা কী?

  • A. দ্রুত biodegradation
  • B. bioaccumulation ও biomagnification
  • C. জলে সম্পূর্ণ hydrolysis
  • D. ozone তৈরি
Answer: B
Explanation: DDT persistent organochlorine; এটি খাদ্যশৃঙ্খলে bioaccumulation ও biomagnification ঘটায়।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

12. Freons-এর পরিবেশগত ক্ষতি প্রধানত কী?

  • A. Acid rain
  • B. Ozone layer depletion
  • C. Eutrophication
  • D. Soil salinity
Answer: B
Explanation: CFC/Freon stratosphere-এ chlorine radicals উৎপন্ন করে ozone ধ্বংস করে।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

13. C2H5Cl + KCN-এর প্রধান উৎপাদ কী?

  • A. C2H5NC
  • B. C2H5CN
  • C. C2H5OH
  • D. CH3CN
Answer: B
Explanation: KCN ionic ও carbon-end nucleophile হওয়ায় alkyl cyanide, C2H5CN, প্রধানত তৈরি হয়।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

14. C2H5Cl + AgCN-এর প্রধান উৎপাদ কী?

  • A. C2H5CN
  • B. C2H5NC
  • C. C2H5OH
  • D. C2H6
Answer: B
Explanation: AgCN অধিক covalent; N-end attack থেকে ethyl isocyanide তৈরি হয়।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

15. Vicinal dihalide-কে Zn দিয়ে treatment করলে কী হয়?

  • A. Alkane
  • B. Alkene
  • C. Alcohol
  • D. Ether
Answer: B
Explanation: Zn dehalogenation করে vic-dihalide থেকে alkene উৎপন্ন করে।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

16. R/S nomenclature নির্ধারণে কোন নিয়ম ব্যবহৃত হয়?

  • A. Markovnikov rule
  • B. Cahn–Ingold–Prelog priority
  • C. Hückel rule
  • D. Zaitsev rule
Answer: B
Explanation: Chiral centre-এর configuration নির্ধারণে CIP priority rule ব্যবহৃত হয়।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

17. 2-bromobutane-এ chiral carbon কোনটি?

  • A. C-1
  • B. C-2
  • C. C-3
  • D. কোনোটিই নয়
Answer: B
Explanation: C-2 চারটি ভিন্ন group-এর সঙ্গে যুক্ত, তাই এটি stereogenic centre।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

18. Chlorobenzene + NaOH (উচ্চ T,P) থেকে শেষে কী পাওয়া যায়?

  • A. Phenol
  • B. Benzyl alcohol
  • C. Cyclohexanol
  • D. Aniline
Answer: A
Explanation: Dow process-এ chlorobenzene থেকে sodium phenoxide এবং acidification-এর পরে phenol পাওয়া যায়।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

19. Benzyl chloride SN1-এ দ্রুত কেন?

  • A. benzyl carbocation resonance-stabilized
  • B. Cl খুব শক্তিশালী base
  • C. C–Cl bond ionic
  • D. benzene ring electron-poor
Answer: A
Explanation: Benzyl carbocation resonance দ্বারা স্থিতিশীল, তাই ionization সহজ।

WBCHSE Class 12 Chemistry · Haloalkanes and Haloarenes · Very Hard

20. Allyl chloride SN1/SN2 উভয় ক্ষেত্রেই তুলনামূলক reactive কেন?

  • A. allylic intermediate/transition state resonance-stabilized
  • B. C–Cl bond triple
  • C. Cl positive
  • D. steric hindrance সর্বাধিক
Answer: A
Explanation: Allylic system resonance stabilization দেয়, ফলে substitution সহজ হয়।

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