Organic Chemistry MCQs set 2 for HEC USAT-E (Pre-Engineering) Chemistry — 20 solved questions.
Q1. Which of the following compounds is most acidic?
Answer: HCOOH
Explanation: The acidity is determined by the stability of the conjugate base; HCOOH has the most stable conjugate base due to resonance.
Q2. The hybridization of carbon in CH₂=CH₂ is
Answer: sp²
Explanation: The carbon atoms in alkenes are sp² hybridized, resulting in a trigonal planar geometry.
Q3. The reaction of an alkene with HBr is an example of
Answer: Electrophilic addition
Explanation: The reaction involves the addition of an electrophile (H⁺) to the alkene, followed by the addition of Br⁻.
Q4. The compound C₆H₅CH₂Cl is an example of
Answer: Benzyl halide
Explanation: The compound has a halogen atom attached to a benzylic carbon, making it a benzyl halide.
Q5. The reaction of phenol with NaOH is an example of
Answer: Acid-base reaction
Explanation: Phenol reacts with NaOH to form sodium phenoxide, an acid-base reaction.
Q6. The reaction of an aldehyde with Tollens' reagent results in the formation of
Answer: Silver mirror
Explanation: Tollens' reagent oxidizes aldehydes to carboxylates, resulting in the formation of a silver mirror.
Q7. The compound that is most likely to undergo SN1 reaction is
Answer: (CH₃)₃CBr
Explanation: Tertiary halides are more likely to undergo SN1 reactions due to the stability of the tertiary carbocation.
Q8. The most stable carbocation is
Answer: Tertiary
Explanation: Tertiary carbocations are more stable due to hyperconjugation and inductive effects.
Q9. The reaction of benzene with CH₃Cl in the presence of AlCl₃ is an example of
Answer: Electrophilic substitution
Explanation: The reaction involves the substitution of a hydrogen atom on the benzene ring with a methyl group, an electrophilic substitution.
Q10. The compound that is most likely to be aromatic is
Answer: Benzene
Explanation: Benzene is aromatic due to its planar, cyclic structure with 6π electrons.
Q11. The reaction of an alkyl halide with NaCN is an example of
Answer: Nucleophilic substitution
Explanation: The reaction involves the substitution of the halide with the cyanide ion, a nucleophilic substitution.
Q12. The hybridization of the nitrogen atom in an amine is
Answer: sp³
Explanation: The nitrogen atom in an amine is sp³ hybridized, resulting in a tetrahedral geometry.
Q13. The reaction of an aldehyde with a Grignard reagent results in the formation of
Answer: Alcohol
Explanation: The Grignard reagent adds to the carbonyl group, resulting in the formation of an alcohol after hydrolysis.
Q14. The reaction of an alkene with H₂ in the presence of Pd/C is an example of
Answer: Hydrogenation
Explanation: The reaction involves the addition of hydrogen to the alkene, a hydrogenation reaction.
Q15. Which compound is most acidic?
Answer: CH3COOH
Explanation: Carboxylic acids are more acidic than alcohols and phenols due to resonance stabilization of the conjugate base.
Q16. What is the product of the reaction between CH3MgBr and CO2?
Answer: CH3COOH
Explanation: Grignard reagent (CH3MgBr) reacts with CO2 to form a carboxylate salt, which upon acidification gives CH3COOH.
Q17. The compound C6H5CH2Cl is an example of?
Answer: Benzyl halide
Explanation: C6H5CH2Cl is a benzyl halide because the halogen is attached to the benzylic carbon.
Q18. What is the order of stability of carbocations?
Answer: Tertiary > Secondary > Primary
Explanation: Tertiary carbocations are most stable due to maximum hyperconjugation.
Q19. What is the major product of the nitration of benzene?
Answer: Nitrobenzene
Explanation: Nitration of benzene gives nitrobenzene as the major product due to the directing effect of the benzene ring.
Q20. The reaction of 2-bromobutane with KOH (alc) is an example of?
Answer: E2 reaction
Explanation: The reaction is an E2 reaction, a concerted elimination mechanism favored by strong base (KOH) in alcohol.