Q.Derive the structure of

Deriving Structures from IUPAC Names

Each name encodes the carbon skeleton, functional groups, and their positions. The key is to decode systematically: identify the parent chain/ring, number it correctly, then attach substituents.

(i) 2-Chlorohexane

Parent: hexane = 6-carbon saturated chain.

Numbering: Chloro substituent at C-2.

Structure: $\ce{CH3-CH(Cl)-CH2-CH2-CH2-CH3}$

(ii) Pent-4-en-2-ol

Parent: pent-4-ene = 5-carbon chain with C=C between C-4 and C-5.

Functional group: hydroxyl ($\ce{-OH}$) at C-2.

Structure: $\ce{CH3-CH(OH)-CH2-CH=CH2}$

(iii) 3-Nitrocyclohexene

Parent: cyclohexene = 6-membered ring with one C=C (between C-1 and C-2 by convention).

Substituent: nitro ($\ce{-NO2}$) at C-3.

Structure: A cyclohexene ring with $\ce{-NO2}$ on the third carbon from the double bond.

(iv) Cyclohex-2-en-1-ol

Parent: cyclohex-2-ene = 6-membered ring, C=C between C-2 and C-3.

Functional group: $\ce{-OH}$ at C-1 (gets priority in numbering).

Structure: Cyclohexene ring with hydroxyl at C-1 and double bond starting at C-2. …

The IUPAC name of an organic compound is a complete blueprint: it tells you the carbon skeleton, where to number from, and exactly where each functional group and substituent sits. The art lies in translating that name into a structural formula by following a disciplined sequence.

The general strategy:

1. Identify the parent chain or ring (the root word: hex = 6 carbons, pent = 5, cyclohex = 6-membered ring).
2. Identify the principal functional group (suffix: -ane = alkane, -en = alkene, -ol = alcohol, -al = aldehyde) and any substituents (prefixes: chloro, nitro, hydroxy).
3. Number the chain to give the principal functional group (or multiple bond, or substituent) the lowest possible locant.
4. Attach everything at the positions indicated by the numbers.

Let's build each structure.

(i) 2-Chlorohexane

Parent: Hexane → 6-carbon saturated chain.

Substituent: Chloro at position 2.

1. Draw a straight chain of 6 carbons:

2. Number from either end; we choose left-to-right as 1 through 6.

3. Attach $\ce{Cl}$ to carbon 2:

Structure:

(ii) Pent-4-en-2-ol

Parent: Pent = 5 carbons.

Functional groups: -en (double bond at position 4), -ol (hydroxyl at position 2).

1. Draw a 5-carbon chain:

2. The principal functional group is the alcohol ($\ce{-OH}$), so numbering must give it the lowest locant. Number from the end that puts $\ce{-OH}$ at carbon 2.

3. Place $\ce{-OH}$ at carbon 2 and a double bond between carbons 4 and 5:

Structure:

(iii) 3-Nitrocyclohexene

Parent: Cyclohexene → 6-membered ring with one double bond.

Substituent: Nitro ($\ce{-NO2}$) at position 3.

1. Draw a cyclohexane ring with one double bond. By convention, the double bond is between carbons 1 and 2 (cyclohex-1-ene is implied when no locant is given for the double bond in older nomenclature, but modern IUPAC would write cyclohex-1-ene; here "cyclohexene" implies the double bond starts at C1).

2. Number the ring so that the double bond gets the lowest locants: C1–C2 contains the double bond.

3. Attach $\ce{-NO2}$ at carbon 3.

Structure:

Or in a more standard depiction:

(The double bond is between C1 and C2; nitro group is on C3.)

(iv) Cyclohex-2-en-1-ol

Parent: Cyclohexene → 6-membered ring with one double bond.

Functional groups: -en (double bond at position 2), -ol (hydroxyl at position 1).

1. Draw a 6-membered ring. …