Which of the following is NOT a proper IUPAC name?
A)1-cyclopentanone
B)1-pentanone
C)2-pentanone
D)3-pentanone

Question

Quizplus · Accepted Answer

In IUPAC nomenclature, the carbonyl carbon of a ketone is assigned the lowest possible number. For pentanone, the carbonyl group can be at the 2-position (2-pentanone) or at the 3-position (3-pentanone) since numbering from either end of the chain gives the same result. "1-pentanone" is incorrect because the carbonyl group in a ketone cannot be at the terminal position (that would make it an aldehyde, not a ketone). "1-cyclopentanone" is correct because in cyclic ketones, the carbonyl carbon is automatically assigned the number 1.

Which of the Following Is NOT a Proper IUPAC Name