Which of the following is not a proper iupac name?
a. 3-pentanone
b. 1-cyclopentanone
c. 2-pentanone
d. 1-pentanone

The IUPAC of 1-pentanone is not correct.

Explanation:

The structures of each of the given compounds with correct IUPAC names are shown in the figure.

In case of ketones there must be two alkyl groups attached to the carbonyl carbon. In case of aldehydes there must be atleast one hydrogen attached to carbonyl carbon.

Now if we are saying that 1-pentanone, it means we are actually naming the compound with wrong functional group. This is infact an aldehyde with the correct name as "pentanal".

Rest of the given IUPAC names are correct.

8 carbon atoms forming single bonds with 18 hydrogen atoms; a triple bond exists between the third and fourth carbon atom from the right

explanation: