ECAT — Engineering College Admission Test (UET)
Take the ECAT Chemistry — Organic Chemistry: Hydrocarbons to Carbonyls (Set 5): 30 multiple-choice questions (40 minutes) with instant scoring and a full…
What this test covers
The first 5 questions of this test, with the correct answer and explanation.
Q1. How many structurally different alcohols (ignoring stereoisomers) have the molecular formula C₅H₁₂O?
Answer: A. 8
Explanation: Pentanols: 1-, 2- and 3-pentanol (3). Methylbutanols: 2-methylbutan-1-ol, 3-methylbutan-1-ol, 2-methylbutan-2-ol, 3-methylbutan-2-ol (4). 2,2-Dimethylpropan-1-ol (1). Total 8.
Q2. Hexa-2,4-diene, CH₃–CH=CH–CH=CH–CH₃, can exist as how many geometrical (cis–trans) isomers?
Answer: D. 3
Explanation: Each double bond can be E or Z, but the molecule is symmetric, so the EZ and ZE forms are identical. The distinct isomers are EE, ZZ and EZ: 3.
Q3. Which systematic name correctly describes the alkene CH₃–CH=C(CH₃)–CH₂–CH₃ ?
Answer: A. 3-Methylpent-2-ene
Explanation: The longest chain containing the double bond has 5 carbons (pentene). Numbering from the left gives the double bond locant 2 (not 3), so the methyl group is on C-3: 3-methylpent-2-ene.
Q4. In the free-radical chlorination of isobutane, (CH₃)₃CH, a tertiary hydrogen is 5 times as reactive as a primary hydrogen. What percentage of the monochloro product is the tertiary chloride, (CH₃)₃CCl?
Answer: D. 36 %
Explanation: There are 9 primary H (reactivity 1) and 1 tertiary H (reactivity 5). Tertiary share = 5/(9 + 5) = 0.357 ≈ 36 %.
Q5. Sodium 2-methylpropanoate, (CH₃)₂CHCOONa, is heated with soda lime. Which hydrocarbon is formed?
Answer: D. Propane
Explanation: Soda lime decarboxylation replaces –COONa by –H: (CH₃)₂CH–COONa + NaOH → (CH₃)₂CH₂ = CH₃CH₂CH₃ (propane) + Na₂CO₃. One carbon is lost.
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Q6. 2-Bromo-2-methylbutane is heated with alcoholic KOH. According to Saytzeff's rule the major alkene is
Q7. Reductive ozonolysis (O₃, then Zn/H₂O) of (CH₃)₂C=CH–CH₃ gives
Q8. 3,3-Dimethylbut-1-ene reacts with HCl. The major product is
Q9. How many acyclic terminal alkynes (R–C≡CH) have the molecular formula C₅H₈?
Q10. But-2-yne is reduced by sodium in liquid ammonia. The main product is
Q11. 7.8 g of benzene (M = 78) is nitrated with an 80 % yield: C₆H₆ + HNO₃ → C₆H₅NO₂ + H₂O. What mass of nitrobenzene (M = 123) is obtained?
Q12. Arrange the following in decreasing order of reactivity towards electrophilic nitration: benzene, toluene, nitrobenzene, chlorobenzene.
Q13. Benzene is treated with 1-chloropropane and anhydrous AlCl₃. The major product is
Q14. According to Hückel's rule (a planar, cyclic, fully conjugated ring with (4n + 2) π electrons), which species is aromatic?
Q15. (R)-2-Bromobutane reacts with aqueous NaOH by a pure SN2 mechanism. What is the stereochemical outcome?
Q16. Which order correctly shows decreasing speed of reaction with Lucas reagent (ZnCl₂/conc. HCl) at room temperature?
Q17. Ethylmagnesium bromide is added to propanone and the product is hydrolysed with dilute acid. The product is
Q18. 9.2 g of ethanol (M = 46) is converted completely to diethyl ether (M = 74) by heating with concentrated H₂SO₄ at 140 °C: 2C₂H₅OH → C₂H₅OC₂H₅ + H₂O. What mass of ether is formed?
Q19. Propan-1-ol is oxidised completely to propanoic acid by acidified potassium dichromate (Cr₂O₇²⁻ → 2Cr³⁺). How many moles of K₂Cr₂O₇ are needed for 0.30 mol of the alcohol?
Q20. Which reagent distinguishes benzoic acid from phenol by a visible change at room temperature?
Q21. In the Reimer–Tiemann reaction (phenol + CHCl₃ + NaOH, then H⁺) the electrophile that attacks the phenoxide ring is
Q22. Which pair of reagents gives tert-butyl methyl ether in the best yield by the Williamson synthesis?
Q23. Which pair of compounds can be distinguished using Fehling's solution (red-brown precipitate with one only)?
Q24. Ethanal, CH₃CHO, reacts with excess I₂ and NaOH to give yellow iodoform, CHI₃ (M = 393.7). What mass of CHI₃ forms from 4.4 g of ethanal (M = 44) at 100 % yield? (I = 127)
Q25. Which of the following undergoes the Cannizzaro reaction with concentrated NaOH?
Q26. Which of these carbonyl compounds is the most reactive towards nucleophilic addition of HCN?
Q27. 10 cm³ of ethyne, C₂H₂, is exploded with 40 cm³ of oxygen and the mixture is cooled to the initial temperature so that water is liquid. What is the total volume of the gaseous residue?
Q28. How many different tribromobenzenes, C₆H₃Br₃, exist?
Q29. What is the degree of unsaturation (rings plus π bonds) of naphthalene, C₁₀H₈?
Q30. Excess bromine water is added to a solution containing 0.94 g of phenol (M = 94). Assuming complete conversion to 2,4,6-tribromophenol (M = 331), what mass of precipitate forms?