Q.Which one of the following names does not fit a real name?

Showing the 12 most recent of 14 on this concept.

1. CBSE 2026Set ANNUAL1 mark
   Q.Write the IUPAC name of (CH3)2CHNH2.

   ›Reveal solutionSolution

   (CH3)2CHNH2 is a three-carbon primary amine with the amine group on the middle (second) carbon, named by adding the suffix '-amine' to the parent alkane chain.

   The structure (CH3)2CH-NH2 has a propane backbone (3 carbons) with the -NH2 group attached to the middle carbon, C2.

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2. CBSE 2026Set ANNUAL1 markMCQ
   Q.IUPAC name of Neopentane is -

   (a) 2,2-dimethylpropane

   (b) 2-Methylbutane

   (c) 3-Methylbutane

   (d) 2-Ethylbutane

   ›Reveal solutionSolution

   Neopentane's IUPAC name is 2,2-dimethylpropane.

   Neopentane has the structure (CH3)4C — a central carbon attached to four -CH3 groups. To name it: find the longest continuous carbon chain. Picking any two of the outer methyls plus the central carbon plus one more methyl gives a 3-carbon chain (propane: C1-C2-C3), with the remaining two methyl groups both attached to the central carbon, C2. So the name is built as propane with two methyl substituents both at position 2: 2,2-dimethylpropane.

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3. CBSE 2026Set ANNUAL1 markMCQ
   Q.The IUPAC name of the compound is : CH2=CH-CH(CH3)-CH3

   (a) 1-Isopropyl ethene

   (b) 3-Methylbut-1-ene

   (c) 2-Vinyl propene

   (d) 1,1-Dimethyl-2-propene

   ›Reveal solutionSolution

   The IUPAC name of CH2=CH-CH(CH3)-CH3 is 3-Methylbut-1-ene.

   Step 1 — Identify the longest carbon chain containing the double bond:

   CH2=CH-CH(CH3)-CH3 has a 4-carbon main chain (but-ene) with one CH3 branch coming off the third carbon.

   Step 2 — Number the chain to give the double bond the lowest locant:

   C1(=CH2) = C2(H) − C3(H)(CH3) − C4(H3)

   The double bond is between C1 and C2, so it is but-1-ene, and the methyl substituent is on C3.

   Step 3 — Assemble the name:

   3-Methylbut-1-ene.

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4. CBSE 2025Set ANNUAL1 markMCQ
   Q.What is the IUPAC name of the following compound? Structure shown: CH3-CH=CH-CH2Br, drawn atom-by-atom as H-C(CH3)=CH-CH(H)(Br)

   (a) 1-Bromo-3-methyl prop-2-ene

   (b) 3-Bromo-1-methyl propene

   (c) 1-Bromobut-2-ene

   (d) 4-Bromobut-2-ene

   ›Reveal solutionSolution

   For CH3-CH=CH-CH2Br, numbering the 4-carbon chain from the bromine end gives the double bond and the substituent the lowest possible locant set, so the correct IUPAC name is 1-bromobut-2-ene.

   The structure is CH3-CH=CH-CH2Br (a straight 4-carbon chain with one C=C double bond and one Br substituent).

   Numbering from the CH3 end: C1(CH3)-C2=C3-C4(CH2Br) gives the double bond at position 2 and Br at position 4 -> locants {2,4}.

   Numbering from the CH2Br end: C1(CH2Br)-C2=C3-C4(CH3) gives Br at position 1 and the double bond at position 2 -> locants {1,2}. …

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5. CBSE 2025Set ANNUAL1 mark
   Q.The IUPAC name of CH2=CH-CH=CH2 is ______.

   ›Reveal solutionSolution

   CH2=CH-CH=CH2 is a 4-carbon chain with two C=C double bonds at positions 1 and 3, so its IUPAC name is buta-1,3-diene.

   Number the four carbons: C1(H2)=C2(H)-C3(H)=C4(H2). The parent chain has 4 carbons, so the base name is 'but-'. There are two carbon-carbon double bonds, so the suffix is '-die …

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6. CBSE 2023Set ANNUAL1 markMCQ
   Q.The IUPAC name of the compound CH3-CH(OH)-CH2-CH=CH-CH3 :

   (a) hex-2-en-4-ol

   (b) hex-4-en-2-ol

   (c) hex-2-en-4-al

   (d) hex-4-en-2-al

   ›Reveal solutionSolution

   The compound is a hexene bearing an -OH group; numbering the chain from the end closest to the -OH group (the senior/principal characteristic group) gives hex-4-en-2-ol.

   The given structure is CH3-CH(OH)-CH2-CH=CH-CH3, a straight chain of six carbons containing one C=C double bond and one -OH group. For IUPAC naming of an alcohol, the principal characteristic group (here -OH, named with the suffix -ol) must get the lowest possible locant when there is a choice, ahead of the locant for the double bond.

   Numbering from the left end (the end nearer -OH):

   C1(CH3) - C2(CH-OH) - C3(CH2) - C4(CH=) - C5(=CH) - C6(CH3)

   -OH is on C2, the double bond is between C4 and C5.

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7. CBSE 2023Set ANNUAL1 mark
   Q.Give the IUPAC name of the following compound.

   ›Reveal solutionSolution

   The compound is named 1-chloro-2,4-dinitrobenzene.

   The ring carries three substituents: one Cl and two NO2 groups. To assign the IUPAC name, the ring carbons are numbered so that the substituents get the lowest possible set of locants.

   Starting numbering at the carbon bearing Cl (position 1) and proceeding around the ring in the direction that reaches the two NO2 groups earliest, the positions come out as 1 (Cl), 2 (NO2), and 4 (NO2) — locant set {1,2,4}, which is lower than the {1,4,6} obtained numbering the …

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8. CBSE 2022Set TERM11 markMCQ
   Q.The IUPAC name of the following compound CH3-CH=C-CH2-CH3, with -CH2-CH2-CH3 attached to the C (the doubly-bonded carbon), is

   (a) 3-ethyl-2-hexene

   (b) 3-propyl-2-hexene

   (c) 3-propyl-2-pentene

   (d) 4-ethyl-4-hexene

   ›Reveal solutionSolution

   IUPAC naming picks the LONGEST chain that includes the double bond -- here that means extending through the propyl branch (6 carbons) rather than staying on the drawn backbone (5 carbons), leaving the remaining 2 carbons as an ethyl substituent.

   The compound is CH3-CH=C(-CH2-CH2-CH3)-CH2-CH3: a 5-carbon backbone (CH3-CH=C-CH2-CH3) with a propyl group (-CH2-CH2-CH3) attached to the double-bonded carbon (the third carbon).

   Step 1 -- find the longest chain THROUGH the double bond:

   • Staying on the drawn backbone gives 5 carbons (a pentene) with a 3-carbon propyl substituent -- NOT the longest option.
   • Extending the main chain through the propyl branch instead gives: CH3-CH=C-CH2-CH2-CH3, which is 6 carbons (a hexene), leaving the original CH2-CH3 (2 carbons) as an ethyl substituent on the double-bonded carbon. …

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9. CBSE 2022Set TERM11 markMCQ
   Q.[hexagon ring structure] is

   (a) Cyclopentane

   (b) Cyclohexane

   (c) Cyclobutane

   (d) none of these

   ›Reveal solutionSolution

   In skeletal (line-angle) structural formulas, a plain unlabelled polygon represents a cyclic saturated hydrocarbon with one carbon at each vertex -- a hexagon means 6 carbons, i.e. cyclohexane.

   In skeletal notation for cycloalkanes, each vertex of the polygon represents a carbon atom (with enough hydrogens implied to satisfy its 4 bonds), and each line/edge represents a single C-C bond, with no double bonds shown (a plain hexagon, unlike benzene, has no circle or alternating double bonds drawn inside it).

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10. CBSE 2022Set ANNUAL1 markMCQ
    Q.Match the following:

    (1) -NO2

    (2) -OCH3

    (3) -CH2-CH2-CH3

    (4) -NH2 with

    (i) Propyl

    (ii) Amino

    (iii) Methoxy

    (iv) Nitro

    (a) (1)-(iii), (2)-(ii), (3)-(iv), (4)-(i)

    (b) (1)-(iii), (2)-(iv), (3)-(i), (4)-(ii)

    (c) (1)-(iv), (2)-(iii), (3)-(i), (4)-(ii)

    (d) (1)-(ii), (2)-(i), (3)-(iv), (4)-(iii)

    ›Reveal solutionSolution

    Each group is matched to its standard IUPAC substituent name: nitro (-NO2), methoxy (-OCH3), propyl (-CH2CH2CH3), amino (-NH2).

    Match each numbered group to its lettered name:

    (1) -NO2 is the nitro group → (iv) Nitro

    (2) -OCH3 is the methoxy group (an -O-CH3 ether-type substituent) → (iii) Methoxy

    (3) -CH2-CH2-CH3 is a straight three-carbon chain, the propyl group → (i) Propyl …

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11. CBSE 2020Set ANNUAL1 mark
    Q.Write IUPAC name of CH3C(Cl)(C2H5)CH2CH3

    ›Reveal solutionSolution

    The central carbon of CH3-C(Cl)(C2H5)-CH2-CH3 carries a methyl, a chlorine, and two ethyl-type arms. The longest chain through it is 5 carbons (pentane), so the correct IUPAC name is 3-chloro-3-methylpentane -- not a 4-carbon (butane) parent name.

    The structure: CH3-C(Cl)(C2H5)-CH2-CH3. The substituted carbon in the middle is bonded to:

    • a methyl group (CH3),
    • a chlorine (Cl),
    • an ethyl group (C2H5 = CH2CH3), and
    • a -CH2CH3 chain (a second ethyl arm).

    Step 1 - longest chain: the IUPAC rule is to pick the LONGEST continuous carbon chain that includes the substituted carbon. Running from the terminal carbon of one ethyl arm, through the central carbon, out to the terminal carbon of the other ethyl arm gives CH3CH2-C-CH2CH3 = 5 carbons. That is a pentane parent, longer than any 4-carbon (butane) chain. The remaining methyl on the central carbon becomes a substituent.

    …

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12. CBSE 2020Set ANNUAL1 markMCQ
    Q.Write the IUPAC name of CH3-CH2-CH(OH)-CHO.

    (a) 1-formyl propanol

    (b) 1-hydroxy butanal

    (c) 2-hydroxy butanal

    (d) 3-hydroxy butanal

    ›Reveal solutionSolution

    CH3-CH2-CH(OH)-CHO is a 4-carbon aldehyde with an -OH group on the second carbon, so its IUPAC name is 2-hydroxybutanal.

    To name an aldehyde by IUPAC rules, the longest carbon chain containing the -CHO group is chosen as the parent chain, and numbering always starts from the carbon of the -CHO group (which is always C1, since -CHO can only be at a chain end).

    …

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