JEE Advanced Mock Test - Chemistry Organic Paragraph Test

📋 Test Information

• Exam: JEE Advanced Part Syllabus Test
• Subject: Chemistry
• Topic: Organic Chemistry (Advanced)
• Test Duration: 60 minutes
• Total Questions: 18
• Total Marks: 72
• Question Types:
  • Paragraph Type Questions (3 paragraphs × 4 questions each)
  • Multiple Choice Questions (Single Correct)
  • Multiple Choice Questions (Multiple Correct)
  • Matching Type Questions
• Marking Scheme:
  • MCQs: +4 for correct, -1 for incorrect
  • Matching Type: +4 for correct, -1 for incorrect

🎯 Syllabus Coverage

Topics Covered:

• Reaction Mechanisms
• Organic Synthesis
• Stereochemistry
• Biomolecules
• Polymers
• Named Reactions

📝 Section A: Paragraph Type Questions (3 Paragraphs × 4 Questions = 12 Questions × 4 Marks = 48 Marks)

Paragraph I (Questions 1-4):

Grignard reagents are organomagnesium compounds with general formula RMgX, where R is an alkyl or aryl group and X is a halogen. These reagents are highly nucleophilic and react with various electrophiles to form carbon-carbon bonds. They are prepared by reacting alkyl or aryl halides with magnesium metal in dry ether solvent. The reaction mechanism involves the formation of a carbon-magnesium bond through single electron transfer (SET) process. Grignard reagents react with carbonyl compounds (aldehydes, ketones, esters, etc.) to give corresponding alcohols after aqueous workup.

Question 1: Which of the following conditions is essential for the preparation of Grignard reagents?

(a) Presence of moisture (b) Dry ether solvent (c) High temperature (d) Acidic medium

Question 2: The reaction of ethylmagnesium bromide with acetone followed by aqueous workup gives:

(a) 2-propanol (b) 2-methyl-2-propanol (c) 1-butanol (d) 2-butanol

Question 3: Grignard reagents do not react with which of the following functional groups?

(a) Aldehydes (b) Ketones (c) Carboxylic acids (d) Alkenes

Question 4: The mechanism of Grignard reagent formation involves:

(a) SN2 pathway (b) SN1 pathway (c) Single electron transfer (SET) (d) Free radical mechanism

Paragraph II (Questions 5-8):

The Diels-Alder reaction is a [4+2] cycloaddition reaction between a conjugated diene and a dienophile to form a six-membered ring. This reaction is thermally allowed and follows the Woodward-Hoffmann rules. The reaction is stereospecific and regioselective. Electron-donating groups on the diene and electron-withdrawing groups on the dienophile accelerate the reaction. The transition state is cyclic and suprafacial, meaning that the new bonds form on the same face of the reacting molecules. The reaction is reversible at high temperatures and can be catalyzed by Lewis acids to increase reaction rate and regioselectivity.

Question 5: In a Diels-Alder reaction between 1,3-butadiene and maleic anhydride, the major product is:

(a) cis adduct (b) trans adduct (c) mixture of cis and trans (d) no reaction occurs

Question 6: Which of the following statements about the Diels-Alder reaction is correct?

(a) It follows anti-addition stereochemistry (b) It is a photochemical reaction (c) It involves a concerted mechanism (d) It requires high pressure

Question 7: The Diels-Alder reaction between cyclopentadiene and maleic anhydride gives:

(a) Norbornene derivative (b) Cyclohexene derivative (c) Cyclopentene derivative (d) Bicyclic compound with bridgehead

Question 8: The presence of electron-withdrawing groups on the dienophile:

(a) Decreases reaction rate (b) Increases reaction rate (c) Does not affect reaction rate (d) Changes the mechanism

Paragraph III (Questions 9-12):

Proteins are biopolymers composed of amino acids linked by peptide bonds. The primary structure is the linear sequence of amino acids, while the secondary structure includes regular arrangements like α-helices and β-sheets. The tertiary structure is the three-dimensional folding of the protein, and the quaternary structure involves the assembly of multiple protein subunits. Denaturation disrupts the secondary, tertiary, and quaternary structures but leaves the primary structure intact. Enzymes are biological catalysts that follow the lock-and-key or induced-fit models. The active site of an enzyme binds specifically to its substrate through various non-covalent interactions including hydrogen bonds, ionic interactions, and hydrophobic effects.

Question 9: Which type of interaction is primarily responsible for the stability of α-helix structure?

(a) Hydrogen bonds (b) Disulfide bonds (c) Hydrophobic interactions (d) Ionic interactions

Question 10: The enzyme-substrate complex formation is primarily driven by:

(a) Covalent bonding (b) Non-covalent interactions (c) Electrostatic repulsion (d) Hydrolysis

Question 11: Denaturation of proteins typically affects:

(a) Primary structure (b) Secondary structure (c) Tertiary structure (d) Both (b) and (c)

Question 12: The induced-fit model of enzyme action suggests that:

(a) The active site is rigid (b) The substrate changes shape to fit the enzyme (c) The enzyme changes shape to accommodate the substrate (d) Both enzyme and substrate remain unchanged

📝 Section B: Multiple Choice Questions (4 Questions × 4 Marks = 16 Marks)

Question 13: The major product of the following reaction is: CH₃-CH=CH₂ + HBr (in presence of peroxides) → ?

(a) 1-bromopropane (b) 2-bromopropane (c) 1,2-dibromopropane (d) 2-bromo-1-propene

Question 14: Which of the following compounds will show optical activity?

(a) 2,3-dimethylbutane (b) 2-chlorobutane (c) 1,2-dichloroethane (d) trans-1,2-dichloroethene

Question 15: The polymerization of ethene gives:

(a) Polypropene (b) Polyethene (c) Polyvinyl chloride (d) Polystyrene

Question 16: The IUPAC name of CH₃-CH(OH)-CH₂-CH₃ is:

(a) 1-butanol (b) 2-butanol (c) 1-propanol (d) 2-propanol

📝 Section C: Multiple Correct Questions (1 Question × 4 Marks = 4 Marks)

Question 17: Which of the following reagents can convert primary alcohol to aldehyde?

(a) PCC (Pyridinium chlorochromate) (b) Collins reagent (c) NaBH₄ (d) MnO₂

📝 Section D: Matching Type Questions (1 Question × 4 Marks = 4 Marks)

Question 18: Match the reactions in Column I with the products in Column II:

Column I: (a) Hoffmann rearrangement (b) Beckmann rearrangement (c) Claisen rearrangement (d) Fries rearrangement

Column II: (p) Phenyl acetate → o-hydroxyacetophenone (q) Primary amide → Primary amine with one carbon less (r) Oxime → Amide (s) Allyl phenyl ether → o-allyl phenol

🔑 Answer Key

Paragraph I (Questions 1-4):

1. (b) Dry ether solvent
2. (b) 2-methyl-2-propanol
3. (d) Alkenes
4. (c) Single electron transfer (SET)

Paragraph II (Questions 5-8):

5. (a) cis adduct
6. (c) It involves a concerted mechanism
7. (d) Bicyclic compound with bridgehead
8. (b) Increases reaction rate

Paragraph III (Questions 9-12):

9. (a) Hydrogen bonds
10. (b) Non-covalent interactions
11. (d) Both (b) and (c)
12. (c) The enzyme changes shape to accommodate the substrate

Section B (Questions 13-16):

13. (a) 1-bromopropane
14. (b) 2-chlorobutane
15. (b) Polyethene
16. (b) 2-butanol

Section C (Question 17):

17. (a), (b), (d) - PCC, Collins reagent, MnO₂

Section D (Question 18):

18. (a)-(q), (b)-(r), (c)-(s), (d)-(p)

📊 Detailed Solutions

Paragraph I Solutions:

Q1: Grignard reagents are highly reactive to moisture, so dry ether solvent is essential to prevent their decomposition.

Q2: Ethylmagnesium bromide (CH₃MgBr) reacts with acetone (CH₃COCH₃) to give CH₃C(OH)(CH₃)CH₃ after workup, which is 2-methyl-2-propanol.

Q3: Grignard reagents are strong nucleophiles that react with electrophilic carbonyl groups but do not add to non-polar double bonds like alkenes.

Q4: The formation of Grignard reagents involves single electron transfer from magnesium to the organic halide.

Paragraph II Solutions:

Q5: The Diels-Alder reaction between 1,3-butadiene and maleic anhydride gives a cis adduct due to the suprafacial nature of the reaction.

Q6: The Diels-Alder reaction proceeds through a concerted cyclic transition state where all bond formations occur simultaneously.

Q7: The reaction gives a bicyclic compound (norbornene derivative) with a bridgehead structure.

Q8: Electron-withdrawing groups on the dienophile lower the LUMO energy, making the reaction faster.

Paragraph III Solutions:

Q9: The α-helix is stabilized by hydrogen bonds between the carbonyl oxygen of one amino acid and the amide hydrogen of the fourth amino acid away.

Q10: Enzyme-substrate binding is primarily through non-covalent interactions like hydrogen bonds, ionic interactions, and hydrophobic effects.

Q11: Denaturation disrupts the higher-order structures (secondary, tertiary, quaternary) but leaves the primary structure (peptide bonds) intact.

Q12: The induced-fit model proposes that the enzyme changes its conformation to better accommodate the substrate.

🎯 Performance Analysis

Section-wise Performance:

• Paragraph Questions: Test reading comprehension and application of multiple concepts
• MCQs: Test individual concept understanding
• Multiple Correct: Require comprehensive knowledge
• Matching Type: Test pattern recognition and correlation skills

Score Interpretation:

• 65-72 marks: Excellent performance
• 45-64 marks: Good performance
• 25-44 marks: Average performance
• Below 25 marks: Need improvement

Time Management:

• Paragraph Questions: 35 minutes (3 minutes per question)
• Other Questions: 25 minutes (5 minutes per question)

💡 Preparation Tips

For Paragraph Questions:

1. Read the passage carefully - understand all details
2. Identify key concepts mentioned
3. Apply concepts to specific questions
4. Eliminate wrong options systematically

For Organic Chemistry:

1. Master reaction mechanisms
2. Understand stereochemistry
3. Learn named reactions with conditions
4. Practice synthesis problems

All the best for your JEE Advanced preparation! ⚗️