It's IUPAC name is pent-2-one. According to the structure there are five carbon atoms present, so it's word root according to the IUPAC rule will be "pent". Then secondary suffix will be "one" ( ketone ).
						

							
Since keto group has more priority, we will number the principal chain from left to right .
The principal chain has 4 carbon and one almost group is present on the fourth carbon.
Therefore the iupac name would be
4-methoxy butan-1-one
						

							
5 -Methoxybutan-1-al is tbe required iupac name of the attached compound...Its apeejay paper 2015-16 right????
						

							
4 methoxy butanal..........main functional group is aldehyde and methoxy will be treated as a substituent
						

							
-CHO functional group has higher priority than -OCH3. 
the name is 4-Methoxybutanal.(4-Methoxy-1-butanal) since the number of aldehydic group is one it is not necessary to include that
						

							
See...as aldehyde  has more priority then ester so the ester will be name as prifix and the parent chain will contain 4 carbon so the name will 4 methoxy butanal.
						

							
4-Methoxybutan-1-al is the correct answer. Approve if it is correct.-------------------------++--------------------Regards Rohit
						

							
4-Methoxybutan-1-al is the IUPAC name of the given compound.
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With regards
Swastik Sharma