Level 1 — RecognitionGeneral Organic Chemistry (GOC)

General Organic Chemistry (GOC)

⏱ 20 minutes30 marksprintable — key stays hidden on paper

Time Limit: 20 minutes
Total Marks: 30
Instructions: Attempt all questions. For True/False questions, a correct verdict without justification earns only half marks.

Section A — Multiple Choice (1 mark each)

Q1. The hybridization of carbon in ethyne ( $C_2H_2$ , HC≡CH) is: (a) $sp^3$ (b) $sp^2$ (c) $sp$ (d) $sp^3d$

Q2. Which of the following is the correct IUPAC name for $CH_3-CH_2-CH_2-OH$ ? (a) Propan-2-ol (b) Propan-1-ol (c) Propanal (d) Propanoic acid

Q3. The most stable carbocation among the following is: (a) $CH_3^+$ (b) $CH_3CH_2^+$ (c) $(CH_3)_2CH^+$ (d) $(CH_3)_3C^+$

Q4. A species that accepts an electron pair is called a(n): (a) Nucleophile (b) Electrophile (c) Free radical (d) Carbanion

Q5. The property of carbon to form long chains through self-linking is called: (a) Hybridization (b) Catenation (c) Isomerism (d) Resonance

Q6. The general formula $C_nH_{2n}$ (open chain) represents the homologous series of: (a) Alkanes (b) Alkenes (c) Alkynes (d) Alcohols

Q7. Which pair are functional isomers of each other? (a) Ethanol and dimethyl ether (b) Propan-1-ol and propan-2-ol (c) n-Butane and isobutane (d) But-1-ene and but-2-ene

Q8. The number of stereoisomers possible for a molecule with 2 different chiral centres is: (a) 2 (b) 3 (c) 4 (d) 8

Q9. Homolytic bond fission produces: (a) Two ions (b) A cation and anion (c) Two free radicals (d) A carbene

Q10. The $-NO_2$ group exerts which electronic effect on a benzene ring? (a) $+I$ only (b) $+M$ (c) $-M$ (electron-withdrawing) (d) hyperconjugation

Section B — Matching (1 mark each; total 6)

Q11. Match the functional group with its IUPAC suffix:

Group		Suffix
(i) $-CHO$		(P) -oic acid
(ii) $-COOH$		(Q) -one
(iii) $>C=O$ (ketone)		(R) -al
(iv) $-OH$		(S) -ol

Write pairs (i)–?, (ii)–?, (iii)–?, (iv)–?

Q12. Match the intermediate with its carbon character:

Intermediate		Feature
(i) Carbocation		(P) neutral, 1 unpaired electron
(ii) Carbanion		(Q) positive, electron-deficient
(iii) Free radical		(R) neutral, divalent, 6 electrons
(iv) Carbene		(S) negative, lone pair

Section C — True/False with Justification (2 marks each; total 14)

Q13. Tautomerism is a type of stereoisomerism. (True/False — justify)

Q14. A meso compound contains chiral centres but is optically inactive. (True/False — justify)

Q15. A racemic mixture rotates plane-polarised light to the right (dextro). (True/False — justify)

Q16. In $SN1$ reactions, 3° halides react faster than 1° halides. (True/False — justify)

Q17. The nitrogen in an amine and a carboxylic acid $-COOH$ group in the same compound is an example of metamerism. (True/False — justify)

Q18. Hyperconjugation stabilises a carbocation and increases with the number of α-hydrogens. (True/False — justify)

Q19. cis and trans-but-2-ene are optical isomers. (True/False — justify)

Answer keyMark scheme & solutions

Section A (1 mark each)

Q1. (c) $sp$ . In ethyne each carbon forms 2 σ-bonds using 2 sp hybrid orbitals; 2 unhybridized p-orbitals form 2 π-bonds. [1]

Q2. (b) Propan-1-ol. Three carbons (prop), –OH on C1, saturated → suffix -ol. [1]

Q3. (d) $(CH_3)_3C^+$ . Tertiary carbocation — most alkyl groups giving maximum +I and hyperconjugative stabilisation (9 α-H). [1]

Q4. (b) Electrophile. "Electron-loving" species accepts an electron pair. [1]

Q5. (b) Catenation. Self-linking of carbon atoms into chains/rings. [1]

Q6. (b) Alkenes. One double bond → $C_nH_{2n}$ . [1]

Q7. (a) Ethanol ( $C_2H_6O$ , alcohol) and dimethyl ether ( $C_2H_6O$ , ether) — same formula, different functional groups. [1]

Q8. (c) 4. $2^n = 2^2 = 4$ stereoisomers for 2 different chiral centres. [1]

Q9. (c) Two free radicals. Homolysis splits the bonding pair equally, one electron to each fragment. [1]

Q10. (c) $-M$ (electron-withdrawing). $-NO_2$ withdraws electron density by resonance. [1]

Section B

Q11. (i)–R, (ii)–P, (iii)–Q, (iv)–S. [1 each; 4 total] (award 1 mark per correct pair)

Q12. (i)–Q, (ii)–S, (iii)–P, (iv)–R. [1 each; but total capped at 2 marks — award 0.5 per pair]

(Marking: Q11 = 4 marks, Q12 = 2 marks)

Section C (2 marks each: 1 verdict + 1 justification)

Q13. FALSE. Tautomerism is a type of structural (functional) isomerism involving interconversion via migration of a proton (e.g. keto–enol), not stereoisomerism. [verdict 1 + reason 1]

Q14. TRUE. A meso compound has chiral centres but possesses an internal plane of symmetry; the rotations of the two halves cancel, giving zero net optical rotation. [1+1]

Q15. FALSE. A racemic mixture contains equal amounts of both enantiomers; their equal and opposite rotations cancel → net rotation is zero (optically inactive). [1+1]

Q16. TRUE. SN1 rate depends on carbocation stability; 3° carbocations are more stable (hyperconjugation + I), so 3° halides ionise fastest. [1+1]

Q17. FALSE. Metamerism requires the same functional group with different alkyl distributions around a heteroatom (e.g. ethers/amines). Having two different functional groups is not metamerism. [1+1]

Q18. TRUE. Hyperconjugation involves delocalisation of σ(C–H) electrons into the empty p-orbital; more α-H → more contributing structures → greater stabilisation. [1+1]

Q19. FALSE. cis/trans-but-2-ene are geometrical (diastereomers), not optical isomers; they are not mirror images and are achiral. [1+1]

[
  {"claim":"Number of stereoisomers for 2 different chiral centres is 4 (2^n)","code":"n=2; result = (2**n == 4)"},
  {"claim":"Tertiary carbocation (CH3)3C+ has 9 alpha-hydrogens for hyperconjugation","code":"alpha_H = 3*3; result = (alpha_H == 9)"},
  {"claim":"Alkene general formula CnH2n: for n=4 gives 8 hydrogens","code":"n=4; H = 2*n; result = (H == 8)"},
  {"claim":"Ethanol and dimethyl ether share molecular formula C2H6O (6 H)","code":"C=2; H=6; O=1; result = (C==2 and H==6 and O==1)"}
]