Q.Consider the compounds I to VII:
I. CH3—CH2—CH2—CH2—OH
II. CH3—CH2—CH(OH)—CH3
III. (CH3)3C—OH
IV. CH3—CH(CH3)—CH2—OH
V. CH3—CH2—O—CH2—CH3
VI. CH3—O—CH2—CH2—CH3
VII. CH3—O—CH(CH3)2
Which of the above compounds form pairs of metamers?

Showing the 12 most recent of 31 on this concept.

1. TG EAPCET 2026Set eng-2026-05-09-FN1 markMCQ
   Q.Identify the compound which has $1^\circ$, $2^\circ$, $3^\circ$ and $4^\circ$ carbons (A) 2, 2, 3, 3-Tetramethylpentane (B) 2, 2-Dimethylpentane (C) 2, 2, 3-Trimethylpentane (D) 2-Methylpentane

   ›Reveal solutionSolution

   The key is to classify each carbon in the molecule by the number of other carbons it is bonded to. Only 2,2,3-trimethylpentane contains at least one primary, one secondary, one tertiary, and one quaternary carbon. The correct option is (C).

   ---

   The question asks for a compound that has all four types of carbon atoms:

   • Primary (1°) – bonded to exactly 1 other carbon
   • Secondary (2°) – bonded to exactly 2 other carbons
   • Tertiary (3°) – bonded to exactly 3 other carbons
   • Quaternary (4°) – bonded to exactly 4 other carbons

   We need to check each option’s structure and count the carbon types.

   ---

   1. Draw the carbon skeleton for each option and label each carbon’s degree.

      Option (A): 2,2,3,3-Tetramethylpentane

      • Main chain: 5 carbons (pentane).
      • At C2: two methyl groups (so C2 is quaternary, bonded to 4 carbons).
      • At C3: two methyl groups (so C3 is also quaternary).
      • The remaining carbons: C1, C4, C5 are primary (each bonded to only one other carbon).
      • No tertiary or secondary carbons exist. → Missing 2° and 3°.

      Option (B): 2,2-Dimethylpentane

      • Main chain: 5 carbons.
      • At C2: two methyl groups → C2 is quaternary.
      • C1, the two methyls on C2, and C5 are primary.
      • C3 and C4 are secondary (each bonded to two other carbons).
      • No tertiary carbon. → Missing 3°.

      Option (C): 2,2,3-Trimethylpentane

      • Main chain: 5 carbons.
      • At C2: two methyl groups → C2 is quaternary.
      • At C3: one methyl group → C3 is tertiary (bonded to C2, C4, and the methyl).
      • C1 and the methyl on C3 are primary.
      • C4 is secondary (bonded to C3 and C5).
      • C5 is primary.
      • So we have: 1° (C1, C5, methyl on C3), 2° (C4), 3° (C3), 4° (C2). → All four types present.

      Option (D): 2-Methylpentane …

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2. TG EAPCET 2026Set eng-2026-05-09-FN1 markMCQ
   Q.Which of the following represents the correct structure of $\gamma$-Ethyl cyclohexane carbaldehyde? (A) Cyclohexane ring bearing $-\mathrm{CH_2-CH_3}$ and $-\mathrm{CH_2CHO}$ on two adjacent ring carbons (B) Cyclohexane ring bearing $-\mathrm{CHO}$ directly on a ring carbon and $-\mathrm{CH_2-CH_3}$ on the $\gamma$ (third) ring carbon from it (C) Aromatic (benzene) ring bearing $-\mathrm{CHO}$ and $-\mathrm{CH_2-CH_3}$ (D) Cyclohexene ring bearing $-\mathrm{CHO}$ and $-\mathrm{CH_2-CH_3}$ (the ethyl group on a doubly-bonded ring carbon)

   ›Reveal solutionSolution

   "Cyclohexane carbaldehyde" = $-\mathrm{CHO}$ bonded straight onto a saturated six-membered ring; the $\gamma$-carbon is the third ring carbon from the $\mathrm{CHO}$-bearing one. Only option (B) shows exactly that.

   The concept first

   Two naming conventions are being tested at once.

   1. "-carbaldehyde". When $-\mathrm{CHO}$ is attached to a ring, the ring cannot include the carbonyl carbon in its own numbering, so we use the suffix carbaldehyde: cyclohexanecarbaldehyde is a cyclohexane ring with $-\mathrm{CHO}$ hanging off one of its carbons. The word cyclohexane also tells you the ring is fully saturated — no double bonds, and certainly not benzene.

   2. Greek locants. In carbonyl chemistry, the carbon next to the carbonyl carbon is $\alpha$, the next $\beta$, then $\gamma$, and so on:

   $\overset{\gamma}{\mathrm{C}}-\overset{\beta}{\mathrm{C}}-\overset{\alpha}{\mathrm{C}}-\underset{\text{carbonyl}}{\mathrm{CHO}}$

   For our ring, the carbon that carries the $\mathrm{CHO}$ is $\alpha$; walking around the ring, the next is $\beta$ and the next is $\gamma$. So $\gamma$ is the third ring carbon (equivalently, ring position 3 if the $\mathrm{CHO}$ carbon is position 1).

   Step-by-step through the options

   (A) Ring with $-\mathrm{CH_2CH_3}$ and $-\mathrm{CH_2CHO}$ on adjacent carbons. Two faults: the $\mathrm{CHO}$ is separated from the ring by a $\mathrm{CH_2}$ (so this is a cyclohexyl-acetaldehyde, not a carbaldehyde), and the ethyl group sits on the neighbouring carbon, not the $\gamma$ one. ✗ …

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3. TG EAPCET 2026Set eng-2026-05-11-AN1 markMCQ
   Q.IUPAC names of the following compounds X and Y are respectively

   [!FORMULA] $\begin{array}{|c|c|} \hline \text{CH}_3\text{CH(Br)CH} = \text{C(CH}_3)_2 & \includegraphics[height=0.8cm]{Y_structure} \\ \hline X & Y \\ \hline \end{array}$

   (A) 2-Bromo-4-methylpent-3-ene ; 3-Ethoxy phenyl ethane (B) 2-Bromo-4-methylpent-3-ene ; 1-Ethyl-3-ethoxy benzene (C) 4-Bromo-2-methylpent-2-ene ; 1-Ethoxy-3-ethyl benzene (D) 4-Bromo-2-methylpent-2-ene ; 3-Ethoxy phenyl ethane

   ›Reveal solutionSolution

   The key is to apply IUPAC rules: for X, the longest chain includes the double bond, so numbering gives the alkene priority and the bromo substituent the lowest locant; for Y, the ethoxy group is the principal substituent on an ethylbenzene core. The correct pair is 4-Bromo-2-methylpent-2-ene and 1-Ethoxy-3-ethylbenzene, which corresponds to option (C).

   Concept and intuition

   IUPAC naming for alkenes requires the longest carbon chain that contains the double bond, and numbering must give the double bond the lowest possible locant. For substituted benzenes, the parent is the benzene ring; substituents are named alphabetically, and the principal functional group (here, alkoxy) determines the suffix. The pitfall is misidentifying the chain in X or confusing the parent in Y.

   Step-by-step reasoning

   1. Compound X: $\ce{CH3CH(Br)CH=C(CH3)2}$
      • Draw the structure: $\ce{CH3-CH(Br)-CH=C(CH3)2}$ means a 5-carbon chain with a double bond between C3 and C4 (if numbered from left).
      • The longest chain containing the double bond has 5 carbons → parent name = pentene.
      • Number from the end nearest the double bond:
        • If numbered from left: C1=CH3, C2=CH(Br), C3=CH, C4=C(CH3)2 → double bond at C3–C4 → “pent-3-ene”.
        • If numbered from right: C1=C(CH3)2, C2=CH, C3=CH(Br), C4=CH3 → double bond at C1–C2 → “pent-1-ene”.
        • Rule: double bond gets lowest locant → “pent-2-ene” is not possible here; actually, compare: left numbering gives double bond at 3, right gives at 1 → choose right numbering (lower locant for double bond).
      • With right numbering: C1=C(CH3)2, C2=CH, C3=CH(Br), C4=CH3.
        • Substituents: at C2? No, C2 is part of double bond. At C3: Br (bromo). At C1: two methyl groups → methyl at C2? Wait, careful: C1 has two methyls, so the methyl groups are on C1? Actually, C1 is the carbon of the double bond with two methyls → that carbon is C1, so the methyls are at C1. But numbering from right gives:
          • C1: =C(CH3)2 → two methyls on C1.
          • C2: =CH–
          • C3: –CH(Br)–
          • C4: –CH3
        • The double bond is between C1 and C2 → “pent-1-ene”.
        • Substituents: bromo at C3, and two methyl groups at C1 → but methyl at C1 is not a substituent; it’s part of the chain? Actually, the chain is pentene, so the methyl groups are substituents on the parent chain. The parent chain is the longest chain containing the double bond; here the longest chain is 5 carbons, but the two methyls are on C1? Wait, C1 is part of the chain, so the two methyls are attached to C1 → they are substituents: two methyl groups at C1.
        • However, IUPAC: if the double bond is at C1, the methyl groups are at C1 → “2-methyl” is not correct. Let’s re-evaluate the structure: $\ce{CH3CH(Br)CH=C(CH3)2}$ — the rightmost carbon is part of $\ce{C(CH3)2}$, so that carbon is a quaternary carbon with two methyls. The chain is: C1 – C2 – C3 = C4 – (C5 and C6 are the two methyls on C4). Actually, the longest chain: $\ce{CH3-CH(Br)-CH=C(CH3)2}$ has 5 carbons in a row:
          • C1: CH3–
          • C2: –CH(Br)–
          • C3: –CH=
          • C4: =C< (with two methyls)
          • The two methyls are attached to C4, so they are substituents.
          • Numbering: to give the double bond the lowest locant, we number from the end nearer the double bond.
            • From left: double bond at C3–C4 → “pent-3-ene”.
            • From right: double bond at C1–C2 → “pent-1-ene”.
            • “1” is lower than “3”, so choose right numbering.
          • With right numbering:
            • C1: =C(CH3)2 → but C1 is the carbon of the double bond with two methyls. However, the parent chain must be continuous; the two methyls are substituents on C1? Actually, C1 is part of the chain, so the methyls are attached to C1 → they are methyl substituents at C1.
            • C2: =CH–
            • C3: –CH(Br)–
            • C4: –CH3
          • So the name would be: 3-bromo-1,1-dimethylpent-1-ene? But that’s not among options.
      • Correction: The double bond is between C3 and C4 in the left numbering, but the chain is actually 5 carbons. The correct IUPAC name:
        • The longest chain containing the double bond is 5 carbons: $\ce{C-C-C=C-C}$ (the two methyls are on the fourth carbon).
        • Number from the end nearer the double bond: from left, double bond at C3; from right, double bond at C2? Let’s count: Structure: $\ce{CH3-CH(Br)-CH=C(CH3)2}$ Write as: $\ce{CH3}$ (C1) – $\ce{CH(Br)}$ (C2) – $\ce{CH}$ (C3) = $\ce{C}$ (C4) – $\ce{CH3}$ (C5) and $\ce{CH3}$ (C6) on C4. Actually, the two methyls are on C4, so C4 has two methyls and a double bond. The longest chain is C1–C2–C3–C4–C5? But C5 is one of the methyls? No, the chain is: C1: CH3– C2: –CH(Br)– C3: –CH= C4: =C< (with two methyls attached) So the chain has 4 carbons in a row? Wait, C4 is connected to C3 and to two methyls. So the longest continuous chain is C1–C2–C3–C4, and then one of the methyls on C4 is a branch. That gives a 4-carbon chain? But the formula has 5 carbons total: CH3 (1), CH(Br) (2), CH (3), C (4) with two CH3 (5 and 6). So the longest chain is actually 4 carbons? No, because C4 is connected to two methyls, so the chain can be extended through one of those methyls: C1–C2–C3–C4–C5 (where C5 is one of the methyls). That gives a 5-carbon chain. So the parent is pentene.
        • Numbering:
          • From left: C1=CH3, C2=CH(Br), C3=CH, C4=C(CH3)2 → double bond at C3–C4 → pent-3-ene.
          • From right: C1=C(CH3)2, C2=CH, C3=CH(Br), C4=CH3 → double bond at C1–C2 → pent-1-ene.
          • Lower locant for double bond: 1 < 3, so choose right numbering.
          • Then substituents: at C1, two methyl groups → “1,1-dimethyl”. At C3, bromo → “3-bromo”.
          • Name: 3-bromo-1,1-dimethylpent-1-ene.
        • But this is not among the options. The options have “4-Bromo-2-methylpent-2-ene” or “2-Bromo-4-methylpent-3-ene”. So perhaps the chain is numbered differently.
      • Re-evaluate: The structure $\ce{CH3CH(Br)CH=C(CH3)2}$ can also be seen as: $\ce{CH3-CH(Br)-CH=C(CH3)-CH3}$? No, it’s $\ce{C(CH3)2}$, so two methyls on the same carbon.
        • If we number from the left, double bond at C3–C4 → pent-3-ene. Substituents: bromo at C2, and two methyls at C4 → “2-bromo-4,4-dimethylpent-3-ene”? That’s not in options.
        • Options have “4-Bromo-2-methylpent-2-ene” — that would imply the double bond is at C2–C3, and bromo at C4, methyl at C2. Let’s see if that fits: $\ce{CH3-CH(Br)-CH=C(CH3)2}$ — if we number from the right: C1: C(CH3)2, C2: CH, C3: CH(Br), C4: CH3 → double bond at C1–C2 → pent-1-ene. Not pent-2-ene. If we number from left: C1: CH3, C2: CH(Br), C3: CH, C4: C(CH3)2 → double bond at C3–C4 → pent-3-ene. Not pent-2-ene.
        • So how do we get “pent-2-ene”? That would require the double bond to be between C2 and C3. That would mean the structure is $\ce{CH3-C(Br)=C(CH3)-CH2-CH3}$ or similar. But our structure has the double bond at the end.
      • Insight: The given structure $\ce{CH3CH(Br)CH=C(CH3)2}$ is actually 4-bromo-2-methylpent-2-ene if we renumber? Let’s draw: Write as: $\ce{CH3-CH(Br)-CH=C(CH3)-CH3}$? No, it’s $\ce{C(CH3)2}$, so the rightmost carbon has two methyls, not one.
        • Actually, $\ce{C(CH3)2}$ means that carbon is attached to two methyl groups. So the structure is: $\ce{CH3-CH(Br)-CH=C(CH3)-CH3}$? That would be $\ce{C(CH3)CH3}$, which is $\ce{CH(CH3)2}$? No, $\ce{C(CH3)2}$ means the carbon has two methyls and a double bond, so it is $\ce{=C(CH3)2}$. So the rightmost part is $\ce{=C(CH3)2}$, which is a terminal double bond with two methyls on the terminal carbon. That is exactly $\ce{(CH3)2C=CH-}$ something. So the structure is $\ce{(CH3)2C=CH-CH(Br)-CH3}$. That is the same as $\ce{CH3-CH(Br)-CH=C(CH3)2}$ but written backwards.
        • Now, if we name $\ce{(CH3)2C=CH-CH(Br)-CH3}$:
          • Longest chain containing double bond: 5 carbons.
          • Number from the end nearer the double bond: from left, double bond at C1–C2 → pent-1-ene. From right, double bond at C4–C5 → pent-4-ene. Choose left: pent-1-ene.
          • Substituents: at C1, two methyls → 1,1-dimethyl; at C3, bromo → 3-bromo. Name: 3-bromo-1,1-dimethylpent-1-ene.
        • Still not matching options.
      • Key: The options all have “pent-2-ene” or “pent-3-ene”. So perhaps the chain is numbered differently to give the double bond the lowest locant and the substituents the next lowest. IUPAC rule: double bond gets priority for lowest locant, then substituents.
        • For $\ce{CH3CH(Br)CH=C(CH3)2}$, if we number from left: C1: CH3, C2: CH(Br), C3: CH, C4: C(CH3)2 → double bond at C3–C4 → pent-3-ene. Substituents: bromo at C2, methyl at C4 (two methyls, but one is considered part of the chain? Actually, C4 has two methyls, but one of them could be considered as part of the chain if we extend? No, the chain is C1–C2–C3–C4, and the two methyls are branches. So we have two methyl groups at C4 → “4,4-dimethyl”. Name: 2-bromo-4,4-dimethylpent-3-ene.
        • That is not in options. Options have “2-Bromo-4-methylpent-3-ene” (only one methyl) or “4-Bromo-2-methylpent-2-ene”.
      • Realization: The structure might be misread. The given $\ce{CH3CH(Br)CH = C(CH3)2}$ actually has a double bond and a bromine. The correct IUPAC name, following the rule that the double bond gets the lowest number, is 4-bromo-2-methylpent-2-ene. How?
        • Write the structure as: $\ce{CH3-C(Br)=C(CH3)-CH2-CH3}$? No.
        • Let’s systematically assign: The longest carbon chain that includes the double bond is 5 carbons. Number from the end that gives the double bond the lowest locant.
          • If we number from the left: C1: CH3– C2: –CH(Br)– C3: –CH= C4: =C< (with two CH3) Double bond at C3–C4 → pent-3-ene.
          • If we number from the right: C1: =C(CH3)2 C2: –CH= C3: –CH(Br)– C4: –CH3 Double bond at C1–C2 → pent-1-ene.
          • Since 1 < 3, we choose right numbering → pent-1-ene.
          • But then the name is 3-bromo-1,1-dimethylpent-1-ene.
        • However, the options suggest that the double bond is not terminal. So perhaps the structure is actually $\ce{CH3CH(Br)CH=C(CH3)2}$ but the double bond is internal? Wait, $\ce{CH=C(CH3)2}$ is a terminal double bond (the =C has two methyls, so it’s a disubstituted terminal alkene). So it is terminal.
      • Pitfall: Many students mistakenly number the chain to give the substituent (bromo) the lowest number, but the double bond takes priority. The correct name is indeed 3-bromo-1,1-dimethylpent-1-ene, but that is not an option. So perhaps the intended structure is different?
      • Check the options: (A) 2-Bromo-4-methylpent-3-ene (B) 2-Bromo-4-methylpent-3-ene (same as A) (C) 4-Bromo-2-methylpent-2-ene (D) 4-Bromo-2-methylpent-2-ene (same as C) So only two distinct names for X: either 2-bromo-4-methylpent-3-ene or 4-bromo-2-methylpent-2-ene.
      • Which one fits? …

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4. TG EAPCET 2025Set eng-2025-05-03-AN1 markMCQ
   Q.Match the following

   [!FORMULA] $\begin{array}{|c|c|c|c|} \hline \text{List - 1 (Type of colloid)} & & \text{List - 2 (Example)} & \\ \hline \text{A Sol} & & \text{I Cloud} & \\ \text{B Foam} & & \text{II Whipped cream} & \\ \text{C Gel} & & \text{III Paint} & \\ \text{D Aerosol} & & \text{IV Butter} & \\ \hline \end{array}$

   The correct answer is (A) A – IV, B – II, C – III, D – I (B) A – III, B – I, C – IV, D – II (C) A – III, B – II, C – IV, D – I (D) A – IV, B – I, C – III, D – II

   ›Reveal solutionSolution

   The key is to classify each colloid by its dispersed phase and dispersion medium: a sol is solid-in-liquid, foam is gas-in-liquid, gel is liquid-in-solid, and aerosol is solid or liquid-in-gas. Matching these gives A–III (paint), B–II (whipped cream), C–IV (butter), D–I (cloud), so the correct option is (C).

   Concept and intuition:

   Colloids are mixtures where one substance (the dispersed phase) is finely distributed throughout another (the dispersion medium). The type depends on the physical states of these two components. For example, if a solid is dispersed in a liquid, it’s a sol; if a gas is trapped in a liquid, it’s a foam; if a liquid is held in a solid network, it’s a gel; and if a liquid or solid is suspended in a gas, it’s an aerosol. By identifying the states in each example, we can match them correctly.

   Step-by-step reasoning:

   1. Identify the colloid type for each List-1 entry.

      • A: Sol – A solid dispersed in a liquid. Common examples: paint (pigment particles in a liquid medium), ink, blood.
      • B: Foam – A gas dispersed in a liquid or solid. Whipped cream is air bubbles trapped in liquid cream (gas-in-liquid foam).
      • C: Gel – A liquid dispersed in a solid (a semi-solid network). Butter is a water-in-oil emulsion that sets into a gel-like structure (liquid fat traps water droplets).
      • D: Aerosol – A solid or liquid dispersed in a gas. Clouds are tiny water droplets (liquid) suspended in air.

   2. Analyze each List-2 example.

      • I: Cloud – Liquid water droplets in air → aerosol.
      • II: Whipped cream – Air bubbles in cream → foam.
      • III: Paint – Solid pigment particles in a liquid binder → sol.
      • IV: Butter – Water droplets trapped in solid fat → gel.

   3. Match systematically.

      • A (sol) matches III (paint).
      • B (foam) matches II (whipped cream). …

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5. TG EAPCET 2025Set eng-2025-05-04-AN1 markMCQ
   Q.The condensed, bond line and complete formulae of n-butane are respectively (A) II, I, III (B) I, II, III (C) I, III, II (D) II, III, I

   ›Reveal solutionSolution

   condensed = I, bond-line = II, complete = III.

   A structural formula can be written three ways. The condensed formula groups each carbon with its hydrogens on one line — CH3CH2CH2CH3 (structure I). The bond-line (skeletal) formula shows only the carbon skeleton as a zig-zag, with carbons at the vertices and hydrogens implied (structure II). The complete (expanded) formula draws every atom and every bond explicitly, H-C-C-C-C-H with all H atoms shown (str …

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6. TG EAPCET 2025Set eng-2025-05-04-AN1 markMCQ
   Q.An alcohol X ($\mathrm{C_5H_{12}O}$) produces turbidity instantly with conc. $\mathrm{HCl/ZnCl_2}$. Isomer (Y) of X undergoes dehydration with conc. $\mathrm{H_2SO_4}$ at 443 K. X and Y respectively are (A) $\mathrm{(CH_3)_3C-CH_2OH}$ (2,2-dimethylpropan-1-ol) , $\mathrm{CH_3CH_2CH(CH_3)CH_2OH}$ (2-methylbutan-1-ol) (B) $\mathrm{CH_3CH_2C(CH_3)_2OH}$ (2-methylbutan-2-ol) , $\mathrm{(CH_3)_2CHCH_2CH_2OH}$ (3-methylbutan-1-ol) (C) $\mathrm{(CH_3)_3C-CH_2OH}$ (2,2-dimethylpropan-1-ol) , $\mathrm{CH_3CH_2C(CH_3)_2OH}$ (2-methylbutan-2-ol) (D) $\mathrm{(CH_3)_2CHCH_2CH_2OH}$ (3-methylbutan-1-ol) , $\mathrm{CH_3CH_2C(CH_3)_2OH}$ (2-methylbutan-2-ol)

   ›Reveal solutionSolution

   The key is that instant turbidity with Lucas reagent identifies a tertiary alcohol, and dehydration at 443 K follows Zaitsev’s rule. X is 2‑methylbutan‑2‑ol (tertiary), Y is 3‑methylbutan‑1‑ol (primary). The correct pair is option (D).

   The Lucas test (conc. HCl/ZnCl₂) is a classic way to distinguish alcohols by their reactivity with a strong acid‑Lewis acid mixture. Tertiary alcohols form a carbocation almost instantly, giving a cloudy emulsion of the alkyl chloride. Secondary alcohols react in a few minutes, primary alcohols hardly react at room temperature. So “turbidity instantly” means X must be a tertiary alcohol.

   Dehydration of an alcohol with conc. H₂SO₄ at 443 K follows an E1 or E2 mechanism depending on the alcohol class, but the major alkene product is always the more substituted one (Zaitsev’s rule). The question says “isomer Y of X undergoes dehydration” — it doesn’t specify the product, only that Y is an isomer of X that can be dehydrated under those conditions. That tells us Y is a different alcohol with the same formula C₅H₁₂O.

   Now let’s examine the options.

   1. Identify the tertiary alcohol among C₅H₁₂O isomers. The only tertiary alcohol with five carbons is 2‑methylbutan‑2‑ol:

   $\mathrm{CH_3CH_2C(CH_3)_2OH}$

   Its carbon skeleton is a four‑carbon chain with a methyl branch at C‑2 and the OH on that same carbon. No other C₅ alcohol is tertiary — 2,2‑dimethylpropan‑1‑ol is primary (OH on a primary carbon), and all the others are primary or secondary. So X must be 2‑methylbutan‑2‑ol.

   2. Check the options for X.

      • (A) gives X as 2,2‑dimethylpropan‑1‑ol — primary, no instant turbidity. Wrong.
      • (B) gives X as 2‑methylbutan‑2‑ol — tertiary, correct for X.
      • (C) gives X as 2,2‑dimethylpropan‑1‑ol — wrong.
      • (D) gives X as 3‑methylbutan‑1‑ol — primary, wrong. Only (B) has the correct X. But wait — we must also check Y.

   3. Identify Y from the options that pair with the correct X.

      In option (B), Y is 3‑methylbutan‑1‑ol:

   $\mathrm{(CH_3)_2CHCH_2CH_2OH}$

   This is a primary alcohol. Dehydration at 443 K with conc. H₂SO₄ will give an alkene — the major product is 2‑methylbut‑2‑ene (Zaitsev product). That’s perfectly plausible. So (B) seems consistent. …

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7. TG EAPCET 2025Set eng-2025-05-04-FN1 markMCQ
   Q.The condensed, bond line and complete formulae of n-butane are respectively (A) II, III, I (B) I, III, II (C) II, I, III (D) I, II, III

   ›Reveal solutionSolution

   The question asks for the correct matching of condensed, bond line, and complete formulae of n-butane. The condensed formula is $\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_3$, the bond line formula is a zigzag line of four vertices, and the complete formula shows all C–H bonds explicitly. The correct order is I, II, III, which corresponds to option (D).

   The problem is about recognising the three common ways to represent the same molecule — n-butane. Each representation carries the same structural information but at different levels of detail. The condensed formula groups atoms together, the bond line formula omits carbon and hydrogen labels (showing only the carbon skeleton as lines), and the complete formula draws every atom and bond explicitly. The trick is to match each given figure to its correct type.

   Let’s identify each representation step by step.

   1. Identify the condensed formula.

      The condensed formula of n-butane is $\text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_3$. It shows the carbon chain in a linear string, with hydrogens attached to each carbon. Among the given options, look for a structure that writes the atoms in a row without drawing bonds between every atom — that is I. So I is the condensed formula.

   2. Identify the bond line formula.

      In bond line notation, each vertex (or endpoint) represents a carbon atom, and hydrogen atoms are implied (each carbon forms four bonds, so missing bonds are filled by hydrogens). A straight chain of four carbons appears as a zigzag line with three segments and four vertices. That matches II. So II is the bond line formula.

   3. Identify the complete formula. …

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8. TG EAPCET 2025Set eng-2025-05-04-FN1 markMCQ
   Q.An alcohol X ($\mathrm{C_5H_{12}O}$) produces turbidity instantly with conc. $\mathrm{HCl/ZnCl_2}$. Isomer (Y) of X undergoes dehydration with conc. $\mathrm{H_2SO_4}$ at 443 K. X and Y respectively are (A) $\mathrm{(CH_3)_3C-CH_2OH}$ (2,2-dimethylpropan-1-ol) , $\mathrm{CH_3CH_2C(CH_3)_2OH}$ (2-methylbutan-2-ol) (B) $\mathrm{(CH_3)_2CHCH_2CH_2OH}$ (3-methylbutan-1-ol) , $\mathrm{CH_3CH_2C(CH_3)_2OH}$ (2-methylbutan-2-ol) (C) $\mathrm{CH_3CH_2C(CH_3)_2OH}$ (2-methylbutan-2-ol) , $\mathrm{(CH_3)_2CHCH_2CH_2OH}$ (3-methylbutan-1-ol) (D) $\mathrm{(CH_3)_3C-CH_2OH}$ (2,2-dimethylpropan-1-ol) , $\mathrm{CH_3CH_2CH(CH_3)CH_2OH}$ (2-methylbutan-1-ol)

   ›Reveal solutionSolution

   The key is that Lucas test (conc. HCl/ZnCl₂) instantly identifies a tertiary alcohol, and dehydration of an alcohol with conc. H₂SO₄ at 443 K follows Saytzeff’s rule. X must be a tertiary alcohol, and Y must be a primary alcohol that gives a single alkene. The correct pair is X = 2-methylbutan-2-ol and Y = 3-methylbutan-1-ol, which corresponds to option (C).

   The Lucas test is a classic way to distinguish between primary, secondary, and tertiary alcohols. When you add conc. HCl in the presence of ZnCl₂ (a Lewis acid catalyst), the alcohol undergoes an SN1 reaction to form an alkyl chloride. The rate depends entirely on the stability of the carbocation intermediate. Tertiary alcohols form a stable tertiary carbocation almost instantly, producing a cloudy emulsion of the insoluble alkyl chloride within seconds. Secondary alcohols take a few minutes, and primary alcohols do not react at room temperature at all. So if X produces turbidity instantly, X must be a tertiary alcohol.

   Now look at the molecular formula C₅H₁₂O. The only tertiary alcohol with five carbons is 2-methylbutan-2-ol: CH₃–CH₂–C(CH₃)₂–OH. That immediately narrows X down to either option (B) or (C), because only those list a tertiary alcohol as X. But wait — option (B) lists X as 3-methylbutan-1-ol (a primary alcohol), so that cannot be right. Option (C) correctly puts the tertiary alcohol as X. Let’s verify Y.

   Y is an isomer of X, so it also has formula C₅H₁₂O. Y undergoes dehydration with conc. H₂SO₄ at 443 K. Dehydration of an alcohol at this temperature follows an E1 or E2 mechanism depending on the alcohol, but the key point is that the major product is the most substituted alkene (Saytzeff’s rule). For a primary alcohol like 3-methylbutan-1-ol, dehydration gives a single alkene: 3-methylbut-1-ene? Actually, careful — 3-methylbutan-1-ol has the structure (CH₃)₂CH–CH₂–CH₂OH. Upon dehydration, the OH leaves from C1, and a proton is lost from C2, giving (CH₃)₂CH–CH=CH₂ (3-methylbut-1-ene). That is the only possible alkene because there is no other β-hydrogen that gives a different product. So Y = 3-methylbutan-1-ol fits perfectly.

   Watch out

   A common mistake is to think that 2,2-dimethylpropan-1-ol (neopentyl alcohol) is tertiary. It is not — the OH is on a primary carbon, even though the carbon is attached to three methyl groups. Neopentyl alcohol gives no turbidity with Lucas reagent at room temperature because it is primary. So option (A) and (D) are ruled out immediately.

   Let’s walk through the reasoning step by step.

   1. Identify X from the Lucas test. Instant turbidity means a tertiary alcohol. Among C₅H₁₂O isomers, the only tertiary alcohol is 2-methylbutan-2-ol (CH₃CH₂C(CH₃)₂OH). So X must be this compound. …

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9. TG EAPCET 2025Set ap-2025-04-29-AN1 markMCQ
   Q.Which of the following sets are correctly matched? i. $P_2O_3$, $N_2O_4$ - acidic ii. $N_2O$, $NO$ - neutral iii. $SeO_3$, $TeO_3$ - basic iv. $As_2O_3$, $Sb_2O_3$ - amphoteric The correct option is (A) i, ii, iv only (B) i, ii, iii only (C) i, ii, iii, iv (D) ii, iii only

   ›Reveal solutionSolution

   The acidic or basic nature of oxides depends on the oxidation state and position of the element in the periodic table. Only sets i, ii, and iv are correctly matched; set iii is wrong because $SeO_3$ and $TeO_3$ are acidic, not basic. The correct option is (A).

   The classification of oxides as acidic, basic, amphoteric, or neutral is a cornerstone of inorganic chemistry. The key idea is simple: non‑metal oxides are generally acidic, metal oxides are generally basic, and elements on the borderline (metalloids) often give amphoteric oxides. But there’s a finer point — the same element can form different oxides with different acid‑base behaviour depending on the oxidation state. Higher oxidation states usually make the oxide more acidic.

   Let’s examine each pair one by one.

   1. Set i: $P_2O_3$ and $N_2O_4$ — acidic?

      Phosphorus and nitrogen are non‑metals. $P_2O_3$ (phosphorus trioxide) dissolves in water to give phosphorous acid ($H_3PO_3$), which is a weak acid. $N_2O_4$ is actually the dimer of $NO_2$; in water it forms a mixture of nitrous and nitric acids — clearly acidic. So this set is correctly matched.

   2. Set ii: $N_2O$ and $NO$ — neutral?

      Nitrous oxide ($N_2O$) and nitric oxide ($NO$) are both neutral oxides. They do not react with water to give an acid or a base, nor do they react with acids or bases under normal conditions. $N_2O$ is famously unreactive (laughing gas), and $NO$ is a radical that does not form a salt with water. This set is correctly matched.

   3. Set iii: $SeO_3$ and $TeO_3$ — basic? …

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10. TG EAPCET 2025Set ap-2025-04-29-FN1 markMCQ
    Q.What are X and Y in the following reaction sequence? Isopentane $\xrightarrow{\text{KMnO}_4}$ $\ce{C5H12O}$ (X) $\xrightarrow{\text{Y}}$ $\ce{C5H11Cl}$ (A) \chemfig{CH_3-CH_2-CH_2-CH(OH)-CH_3} ; Conc. HCl / ZnCl$_2$ (B) \chemfig{CH_3-CH_2-CH_2-CH_2-CH_2OH} ; HCl (C) \chemfig{(CH_3)_3C-OH} ; Conc. HCl (D) \chemfig{(CH_3)_2CH-CH(OH)-CH_3} ; Conc. HCl / ZnCl$_2$

    ›Reveal solutionSolution

    Isopentane (2-methylbutane) undergoes KMnO₄ oxidation to give a tertiary alcohol (2-methylbutan-2-ol), which then reacts with concentrated HCl in the presence of ZnCl₂ (Lucas reagent) to form the corresponding tertiary alkyl chloride. The correct pair is (C).

    The key here is recognising that isopentane is an alkane — it has no double bonds or functional groups. So how does KMnO₄, a strong oxidising agent, react with it? Normally, alkanes are inert to KMnO₄ at room temperature. But under vigorous conditions (hot, concentrated), KMnO₄ can oxidise the most substituted carbon — the tertiary carbon — to give an alcohol. This is a specific reaction: tertiary C–H bonds are weaker and more accessible to oxidation than primary or secondary ones.

    So the product X is a tertiary alcohol derived from isopentane. Isopentane is 2-methylbutane. Its structure is:

    $\ce{CH3-CH(CH3)-CH2-CH3}$

    The tertiary carbon is the one attached to three other carbons — that’s the second carbon (the one with the methyl branch). Oxidation at that carbon gives:

    $\ce{(CH3)3C-OH}$

    That’s 2-methylbutan-2-ol, a tertiary alcohol. Now, what about Y? The reaction sequence shows X → C₅H₁₁Cl. That’s a substitution of –OH by –Cl. For tertiary alcohols, the reaction with HCl is slow unless a catalyst is used. The classic reagent for converting tertiary alcohols to alkyl chlorides is Lucas reagent — concentrated HCl with ZnCl₂. ZnCl₂ helps to form a more stable carbocation intermediate, speeding up the reaction. Without ZnCl₂, tertiary alcohols do react with HCl, but the reaction is much slower and often requires heating. In exam contexts, the standard reagent for this conversion is conc. HCl / ZnCl₂.

    Now let’s check the options:

    • (A) gives a secondary alcohol (pentan-2-ol) — not what we get from isopentane oxidation.
    • (B) gives a primary alcohol (pentan-1-ol) — also wrong. …

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11. TG EAPCET 2024Set ap-2024-05-08-FN1 markMCQ
    Q.Observe the following formula The groups/atoms in the plane of paper are (A) H, Cl, C (B) CH$_3$, Cl (C) H, CH$_3$, C (D) CH$_3$, C$_2$H$_5$, C

    ›Reveal solutionSolution

    In the wedge–dash 3D structure, the central carbon and the two substituents drawn with plain in-plane bonds — $\text{CH}_3$ and $\text{C}_2\text{H}_5$ — lie in the plane of the paper; option (D).

    For a tetrahedral carbon drawn in wedge–dash notation, exactly two bonds are drawn as plain lines lying in the plane of the paper (one wedge points toward the viewer, one dash points behind). The central carbon and the two atoms/groups attached by the plain in-plane bonds are what lie in the plane of the paper. …

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12. TG EAPCET 2024Set ap-2024-05-08-FN1 markMCQ
    Q.IUPAC name of neohexyl alcohol is (A) 3, 3–Dimethylbutan–2–ol (B) 3, 3–Dimethylbutan–1–ol (C) 2, 3–Dimethylbutan–1–ol (D) 2, 3–Dimethylbutan–2–ol

    ›Reveal solutionSolution

    Neohexyl alcohol refers to an alcohol where the alkyl group is a 2,2-dimethylbutyl group. Applying IUPAC rules to this structure yields 3,3-dimethylbutan-1-ol.

    The problem asks for the IUPAC name of "neohexyl alcohol". To solve this, we first need to understand what "neohexyl alcohol" represents in terms of its chemical structure, and then apply the standard IUPAC nomenclature rules for alcohols.

    Concept and Intuition

    The name "neohexyl alcohol" is a common name.

    • The "neo-" prefix in common nomenclature typically refers to an alkane structure where a carbon atom is bonded to four other carbon atoms (a quaternary carbon) at the second-to-last position of the main chain. For example, neopentane is 2,2-dimethylpropane.
    • The "hexyl" part indicates a total of six carbon atoms in the alkyl group.
    • "Alcohol" means the compound contains a hydroxyl ($-\text{OH}$) functional group.

    Combining these, a "neohexyl" group is a 6-carbon alkyl group with a specific branching pattern. Following the pattern of neopentyl (which is $(CH_3)_3C-CH_2-$), a neohexyl group would be $(CH_3)_3C-CH_2-CH_2-$. This structure has a total of 6 carbons.

    Once the structure is determined, we apply the IUPAC rules for naming alcohols:

    1. Identify the longest continuous carbon chain that contains the carbon atom bonded to the hydroxyl ($-\text{OH}$) group. This chain is the parent chain.
    2. Number the parent chain starting from the end that gives the carbon atom bearing the $-\text{OH}$ group the lowest possible number.
    3. Identify and name any substituents attached to the parent chain.
    4. Construct the full name by listing substituents alphabetically with their position numbers, followed by the parent alkane name, replacing the '-e' with '-ol', and indicating the position of the $-\text{OH}$ group.

    Step-by-step Derivation

    1. Determine the structure of neohexyl alcohol. As discussed, the "neohexyl" group is a 6-carbon alkyl group with a quaternary carbon at the second position from the end where the functional group attaches. The structure of the neohexyl group is:

    $\begin{array}{c} \text{CH}_3 \\ | \\ \text{CH}_3-\text{C}-\text{CH}_2-\text{CH}_2- \\ | \\ \text{CH}_3 \end{array}$

    Attaching an $-\text{OH}$ group to this alkyl group gives neohexyl alcohol:
    

    $\begin{array}{c} \text{CH}_3 \\ | \\ \text{CH}_3-\text{C}-\text{CH}_2-\text{CH}_2-\text{OH} \\ | \\ \text{CH}_3 \end{array}$

    2. Identify the longest carbon chain containing the $-\text{OH}$ group. Let's rewrite the structure to clearly show the chain: …

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