The IUPAC name of the following compound is: HC\!\!C-CH2-CH(OH)-CH2-CH=CH2

Step 1: Identify the parent chain

Draw out the chain: $\ce{CH2=CH-CH2-CH(OH)-CH2-C\!\equiv\!CH}$

Count carbons: 7 carbons in a straight chain → parent = heptane. Functional groups present: double bond (alkene), triple bond (alkyne), and -OH (alcohol).

Step 2: Establish numbering — principal characteristic group gets lowest locant

The $\ce{-OH}$ group is the principal characteristic group (highest priority suffix). Number from the end that gives -OH the lowest locant:

• Numbering from the $\ce{CH2=CH}$ end: $\ce{CH2=CH}$ is C1-C2, $\ce{CH2}$ is C3, $\ce{CH(OH)}$ is C4, $\ce{CH2}$ is C5, $\ce{C\!\equiv\!CH}$ is C6-C7.
  • OH at C4, double bond at C1, triple bond at C6.
• Numbering from the $\ce{HC\!\equiv\!C}$ end: OH at C4, triple bond at C1, double bond at C6.

Both give OH at C4. Compare the set of locants for multiple bonds:

• First numbering: {1, 6} for double+triple → locant set {1,6}
• Second numbering: {1, 6} → same set.

When locant sets tie, give lower number to the double bond (alkene) over alkyne per IUPAC 2013: → Choose numbering where double bond is at C1 (not C6).

Step 3: Assemble the name

• Parent: hept-
• Double bond at C1: -1-en-
• Triple bond at C6: -6-yn-
• OH at C4: -4-ol
• Full name: Hept-1-en-6-yn-4-ol

Step 4: Why other options are wrong

• Options (a) and (b) use "hydroxy" as prefix — wrong when -OH is principal group.
• Option (c) "Hept-6-en-1-yn-4-ol" puts triple bond at lower locant — wrong, double bond gets preference over triple bond in locant assignment.

Key Points to Remember:

• Order of suffix suffix priority: -ol > -yne > -ene for lowest locant.
• When a tie in locant sets occurs between double and triple bond, give lower locant to the double bond.
• Never use "hydroxy-" as prefix when -OH is the principal characteristic group.