Q.Write the IUPAC name of CH3-CH2-CH(CH3)-CH2-CH3.

Showing the 12 most recent of 96 on this concept.

1. CBSE 2026Set A1 markMCQ
   Q.The IUPAC name of CH3CH2COCH2CH3 is

   (a) Diethyl ketone

   (b) 3-Pentanone

   (c) 2-Pentanone

   (d) Methyl propyl ketone

   ›Reveal solutionSolution

   Number the five-carbon chain to give the C=O the lowest locant: the ketone carbon is C-3, so the IUPAC name is pentan-3-one (3-pentanone).

   Structure: CH3-CH2-CO-CH2-CH3. The longest chain containing the carbonyl has 5 carbons -> pentanone. Numbering from either end places the carbonyl carbon at position 3. Hence the IUPAC name is pentan-3-one (3-pentanone). (Diethyl ketone is the common/trivial name, not the IUPAC name.)

   ✓Final answer

   (b) 3-Pentanone (pentan-3-one).

2. CBSE 2026Set ANNUAL1 markMCQ
   Q.IUPAC name of [a benzene ring with an -OC2H5 (ethoxy) group attached] is

   (a) Benzyl ethoxide

   (b) Benzene ethoxide

   (c) Ethoxybenzene

   (d) Ethoxybenzoyl

   ›Reveal solutionSolution

   Simple ethers with one aromatic and one alkyl group are IUPAC-named as 'alkoxy' + 'benzene', treating the -OR group as a substituent on the ring.

   The compound is a benzene ring bearing an ethoxy substituent (-O-C2H5). Following IUPAC substitutive nomenclature for ethers, the smaller/simpler group's oxygen chain is named as an 'alkoxy' prefix attached to the parent (here benzene):

   -OC2H5 = ethoxy group

   So the compound is Ethoxybenzene (common name: phenetole).

   'Benzyl ethoxide' and 'Benzene ethoxide' are not valid IUPAC names (benzyl would mean a -CH2-C6H5 group, not directly relevant here, and 'ethoxide' misnames the functional class), and 'Ethoxybenzoyl' incorrectly implies an acyl (-COR) group, which is absent.

   ✓Final answer

   (c) Ethoxybenzene.

3. CBSE 2026Set ANNUAL1 markMCQ
   Q.IUPAC name of CH3COOH is:

   (a) Ethanol

   (b) ethanoic acid

   (c) Ethanal

   (d) ethane

   ›Reveal solutionSolution

   CH₃COOH is acetic acid, IUPAC name ethanoic acid.

   CH₃COOH is a two-carbon carboxylic acid, commonly called acetic acid. In IUPAC nomenclature, carboxylic acids are named by replacing the "-e" of the corresponding alkane name with "-oic acid". The two-carbon alkane is ethane, so CH₃COOH becomes ethanoic acid.

   ✓Final answer

   (b) ethanoic acid.

4. CBSE 2026Set ANNUAL1 markMCQ
   Q.The IUPAC name of Formic acid is :

   (a) Methanoic acid

   (b) Ethanoic acid

   (c) Ethandioic acid

   (d) Methandioic acid

   ›Reveal solutionSolution

   Formic acid, HCOOH, is the one-carbon carboxylic acid, named methanoic acid by IUPAC rules.

   Formic acid has the structure H–COOH (a single carbon bearing the carboxyl group). To name a carboxylic acid by IUPAC nomenclature:

   1. Select the longest carbon chain including the –COOH carbon.
   2. Replace the terminal '-e' of the corresponding alkane name with '-oic acid'.

   Here the chain has just one carbon (methane), so the name becomes methanoic acid.

   • Ethanoic acid (option b) is acetic acid, CH₃COOH (two carbons).

   • Ethandioic acid / methandioic acid (options c, d) refer to oxalic acid, HOOC–COOH (a dicarboxylic acid), not formic acid.

   ✓Final answer

   (a) Methanoic acid.

5. CBSE 2026Set ANNUAL1 markMCQ
   Q.The IUPAC name of isobutyl chloride is

   (a) 2-chlorobutane

   (b) 1-chloro-2-methyl propane

   (c) 2-chloro-2-methyl propane

   (d) 1-chlorobutane

   ›Reveal solutionSolution

   Isobutyl chloride has the structure (CH3)2CH-CH2-Cl. Number the longest chain (propane, 3 carbons) so the substituent (Cl) gets the lowest locant, then name the methyl branch.

   Structure of isobutyl chloride: (CH3)2CH-CH2-Cl

   This can be redrawn as: Cl-CH2-CH(CH3)-CH3

   Step 1: Identify the longest carbon chain containing the point of attachment of Cl. That's a 3-carbon (propane) chain: C1(CH2Cl)-C2(CH, bearing a methyl branch)-C3(CH3).

   Step 2: Number the chain to give Cl the lowest possible locant. Numbering from the Cl end: C1 = CH2Cl, C2 = CH(CH3), C3 = CH3.

   Step 3: Cl is on C1 (chloro at position 1); the methyl branch is on C2 (2-methyl).

   Step 4: Assemble the IUPAC name: 1-chloro-2-methylpropane.

   ✓Final answer

   (b) 1-chloro-2-methyl propane.

6. CBSE 2026Set ANNUAL1 mark
   Q.Write IUPAC name of the following compound:

   ›Reveal solutionSolution

   Numbering the 6-carbon chain from the -COOH carbon (C1) puts the ketone at C4 and the terminal bromine at C6, giving 6-bromo-4-oxohexanoic acid.

   The drawn structure is a straight 6-carbon chain: BrCH2-CH2-CO-CH2-CH2-COOH, i.e. a terminal -CH2Br at one end and -COOH at the other, with a ketone in between.

   • The carboxylic acid (-COOH) is the senior group and is numbered C1.
   • Numbering from that end: C1 (COOH), C2 (CH2), C3 (CH2), C4 (the ketone C=O), C5 (CH2), C6 (the terminal CH2Br).
   • Parent chain = 6 carbons = hexanoic acid; the ketone is cited as the prefix 'oxo' at C4, and 'bromo' at C6 (bromo before oxo alphabetically).

   Name: 6-bromo-4-oxohexanoic acid.

   ✓Final answer

   6-Bromo-4-oxohexanoic acid, i.e. HOOC-CH2-CH2-CO-CH2-CH2Br.

7. CBSE 2026Set ANNUAL1 markMCQ
   Q.The IUPAC name of CH3COOH is

   (a) Acetic acid

   (b) Formic acid

   (c) Ethanoic acid

   (d) Methanoic acid

   ›Reveal solutionSolution

   CH3COOH = ethanoic acid (IUPAC).

   CH3COOH has two carbon atoms and a −COOH group. In IUPAC nomenclature, a two-carbon carboxylic acid is 'ethan' (two carbons) + 'oic acid' = ethanoic acid. Its common (trivial) name is acetic acid. Formic acid / methanoic acid is HCOOH.

   ✓Final answer

   (C) Ethanoic acid.

8. CBSE 2026Set ANNUAL1 markMCQ
   Q.The IUPAC name of CH3−CH(OH)−CH3 is

   (a) Propan-1-ol

   (b) Propan-2-ol

   (c) n-propyl alcohol

   (d) Isopropyl alcohol

   ›Reveal solutionSolution

   CH3−CH(OH)−CH3 = propan-2-ol.

   The chain has three carbons (propane). The −OH group is attached to the central (second) carbon. Numbering to give the OH the lowest locant places it at position 2, so the IUPAC name is propan-2-ol (common name isopropyl alcohol).

   ✓Final answer

   (B) Propan-2-ol.

9. CBSE 2026Set ANNUAL1 markMCQ
   Q.The structure of a valuable organic compound used as solvent in many chemical industries is shown below (a central carbon bearing a CH₃ group above, a CH₃ group to the left, an OH group below, and a –CH₂–OCH₃ group to the right). The IUPAC name of the organic compound is

   (a) 1-methoxy-2-methylpropan-2-ol

   (b) 3-methoxy-2-methylpropan-2-ol

   (c) 1-methoxy-3-methylpropan-3-ol

   (d) 2-methoxy-2-methylpropan-2-ol

   ›Reveal solutionSolution

   The structure is (CH₃)₂C(OH)CH₂OCH₃; the parent is propan-2-ol with a 2-methyl and a 1-methoxy substituent, giving 1-methoxy-2-methylpropan-2-ol — option (A).

   The central carbon bears two $CH_3$ groups, an $OH$, and a $-CH_2-OCH_3$ group, so the molecule is

   $(CH_3)_2C(OH)-CH_2-OCH_3.$

   Naming:

   • The longest carbon chain containing the –OH is three carbons (propane): $C1 = CH_2(OCH_3)$, $C2 = C(OH)(CH_3)$, $C3 = CH_3$.

   • The principal characteristic group is $-OH$, so it becomes the suffix -ol and gets the lowest locant. $OH$ is on $C2$ → propan-2-ol.

   • Substituents: a methyl group on $C2$ (the second $CH_3$) and a methoxy ($-OCH_3$) group on $C1$.

   • Arranged alphabetically (methoxy before methyl): 1-methoxy-2-methylpropan-2-ol.

   ✓Final answer

   (A) 1-methoxy-2-methylpropan-2-ol.

10. CBSE 2025Set 56/5/11 markMCQ
    Q.The IUPAC name for $CH_3 - CH_2 - N(CH_3) - CH_2 - CH_2 - CH_3$ is : (A) N-methylpentan-2-amine (B) N-ethyl-N-methylpropan-1-amine (C) N,N-diethylpropan-1-amine (D) N,N-dimethylpropan-1-amine

    ›Reveal solutionSolution

    The compound is a secondary amine with an ethyl and a methyl group on the nitrogen, and a three-carbon chain as the parent. The correct IUPAC name is N-ethyl-N-methylpropan-1-amine, which corresponds to option (B).

    The key to naming amines under IUPAC rules is to identify the longest continuous carbon chain attached to the nitrogen — that becomes the parent alkane name, with the suffix "-amine". The other groups on the nitrogen are treated as substituents, prefixed with "N-" to show they are attached to the nitrogen atom, not to the carbon chain.

    Let's break this down step by step.

    1. Draw the structure from the given condensed formula.

       The formula is $CH_3 - CH_2 - N(CH_3) - CH_2 - CH_2 - CH_3$.

       The nitrogen has three bonds: one to an ethyl group ($-CH_2CH_3$), one to a methyl group ($-CH_3$), and one to a propyl group ($-CH_2CH_2CH_3$). So the molecule is:

            CH3
             |
       CH3-CH2-N-CH2-CH2-CH3
       

       The nitrogen is connected to three different alkyl groups: ethyl, methyl, and propyl.

    2. Identify the parent chain.

       The IUPAC rule for amines: the parent chain is the longest continuous carbon chain attached directly to the nitrogen. Here, the chain on the right is $CH_2-CH_2-CH_3$ — that's three carbons, a propyl group. The chain on the left is $CH_2-CH_3$ — two carbons, an ethyl group. The methyl group ($CH_3$) is just one carbon.

       So the longest chain is the three-carbon chain (propyl). The parent name becomes propan-1-amine (since the nitrogen is at the end of the chain, carbon 1).

    3. Name the substituents on the nitrogen.

       The other two groups attached to the nitrogen are an ethyl group ($-CH_2CH_3$) and a methyl group ($-CH_3$). Since they are on the nitrogen, not on the carbon chain, they are prefixed with "N-".

       Alphabetically, ethyl comes before methyl. So we write N-ethyl-N-methyl.

    4. Combine the parts.

       The full name is: N-ethyl-N-methylpropan-1-amine.

    Tip

    A common shortcut: if the nitrogen has two small alkyl groups and one longer chain, the longest chain is always the parent. The "N-" prefixes tell the reader exactly where those groups are — without them, the name would imply the groups are on the carbon chain, which would be a different compound.

    Watch out

    A frequent mistake is to pick the wrong parent chain. Some students might see the ethyl group on the left and think the parent is pentane (five carbons), but that would ignore the rule that the longest chain attached to nitrogen is the parent. Here, the propyl chain is the longest, so the parent is propan-1-amine, not pentan-2-amine. Option (A) is wrong for exactly this reason.

    Now check the options:

    • (A) N-methylpentan-2-amine — this would imply a five-carbon parent chain with the nitrogen on carbon 2, which is not the longest chain attached to N.
    • (B) N-ethyl-N-methylpropan-1-amine — matches our name exactly.
    • (C) N,N-diethylpropan-1-amine — would require two ethyl groups on N, but we have one ethyl and one methyl.
    • (D) N,N-dimethylpropan-1-amine — would require two methyl groups on N, but we have one methyl and one ethyl.

    ✓Final answer

    The correct IUPAC name is N-ethyl-N-methylpropan-1-amine, which is option (B).

11. CBSE 2025Set X11 markMCQ
    Q.The IUPAC name of $\text{H}_3\text{C}-\underset{\underset{\text{Br}}{|}}{\text{CH}}-\text{CH}_2-\underset{\overset{\text{O}}{||}}{\text{C}}-\text{H}$

    (a) 3–bromobutyraldehyde

    (b) 2–bromopropanaldehyde

    (c) 3–bromobutanal

    (d) 2–bromobutanal

    ›Reveal solutionSolution

    The compound is $\text{CH}_3\text{-CH(Br)-CH}_2\text{-CHO}$, a 4-carbon aldehyde with bromine on C-3 → 3-bromobutanal.

    The structure is $\text{H}_3\text{C-CH(Br)-CH}_2\text{-CHO}$.

    • The principal functional group is the aldehyde (–CHO), so it gets the lowest locant. Numbering starts at the carbonyl carbon: C1 = CHO, C2 = $\text{CH}_2$, C3 = CH(Br), C4 = $\text{CH}_3$.
    • Longest chain = 4 carbons → butanal.
    • Bromine substituent is on C-3 → 3-bromo.

    Hence the IUPAC name is 3-bromobutanal. (Options with "butyraldehyde"/"propanaldehyde" use non-IUPAC or wrong chain length.)

    ✓Final answer

    (c) 3–bromobutanal

12. CBSE 2025Set D1 markMCQ
    Q.The IUPAC name of CH3COOC2H5 is

    (a) Methyl propanoate

    (b) Ethyl ethanoate

    (c) Acetoethane

    (d) Ethoxyethane

    ›Reveal solutionSolution

    CH3COOC2H5 = ethyl ethanoate (common name ethyl acetate).

    The compound is an ester derived from ethanoic acid (CH3COOH) and ethanol (C2H5OH). An ester R-COO-R' is named as 'alkyl alkanoate':

    • The alkyl group from the alcohol part (C2H5) -> ethyl
    • The acyl part CH3COO- comes from ethanoic acid -> ethanoate

    So the IUPAC name is ethyl ethanoate. Its common name is ethyl acetate.

    ✓Final answer

    (b) Ethyl ethanoate.