Question

Which one of the following structures has the IUPAC name $3-\mathrm{ethynyl}-2-\mathrm{hydroxy}-4-\mathrm{methylhex}-3-\mathrm{en}-5-\mathrm{ynoic}\mathrm{acid}$?

• A.

  

• B.

  

• C.

  

• D.

  

Answer 1

The correct option is D

Explanation for the correct option:

Given IUPAC name is:

$3-\mathrm{ethynyl}-2-\mathrm{hydroxy}-4-\mathrm{methylhex}-3-\mathrm{en}-5-\mathrm{ynoic}\mathrm{acid}$

Determing the root word:

• Here, the root word is “hex”. hence, the chain will be having 6 carbon atoms.

Determing of names and positions of locants:

• There are three substituents that are attached at second, third and fourth position,
• At second we have ‘hydroxy’ , at third we have ‘ethynyl’ and at fourth we have ‘methyl’ group attached.

Determining the suffix:

The functional group here is Carboxyllic acid, so for that the suffix that we use is ‘oic acid’, and also we have a double bond and a triple bond at third and fifth position, so the suffix will be ‘ene’ and ‘yne’.

Hence, the compound will be,

and option (D) is the correct match.

Explanation for the incorrect options:

Option (A) The IUPAC name of the given compound is $3-\mathrm{ethyl}-4-\mathrm{ethynyl}-2-\mathrm{hydroxy}-\mathrm{hex}-2-\mathrm{en}-5-\mathrm{ynoic}\mathrm{acid}$.

Option (B) The IUPAC name of the given compound is $4-\mathrm{ethyl}-3-\mathrm{ethynyl}-2-\mathrm{hydroxy}-\mathrm{hex}-2-\mathrm{en}-5-\mathrm{ynoic}\mathrm{acid}$.

Option (C) The IUPAC name of the given compound is $4-\mathrm{ethynyl}-2-\mathrm{hydroxy}-3-\mathrm{methyl}-\mathrm{hex}-2-\mathrm{en}-5-\mathrm{ynoic}\mathrm{acid}$.

Hence, the correct option is (D).