Q.Write down the possible isomers of C4H9NO2 and give their IUPAC names.

Step 1. C4H9NO2 first splits into the NITROALKANE family (R-NO2, four carbons) and the functionally-isomeric ALKYL NITRITE family (R-O-N=O, four carbons) -- both share this same molecular formula.

Step 2. Within the nitroalkanes, CHAIN isomerism gives a straight-chain and a branched skeleton: 1-nitrobutane (CH3CH2CH2CH2-NO2, straight chain) and 1-nitro-2-methylpropane / 2-methyl-1-nitropropane ((CH3)2CH-CH2-NO2, branched).

Step 3. POSITION isomerism on the straight chain moves -NO2 along it: 1-nitrobutane vs 2-nitrobutane (CH3CH2CH(NO2)CH3); on the branched skeleton, moving -NO2 to the central carbon gives the fourth nitroalkane, 2-methyl-2-nitropropane ((CH3)3C-NO2, tertiary).

Step 4. Each of these four nitroalkanes has a corresponding FUNCTIONAL isomer among the alkyl nitrites, built on the identical four carbon skeletons but with the nitrogen bonded through oxygen instead: n-butyl nitrite (CH3CH2CH2CH2-O-N=O), sec-butyl nitrite (CH3CH2CH(CH3)-O-N=O), isobutyl nitrite ((CH3)2CH-CH2-O-N=O), and tert-butyl nitrite ((CH3)3C-O-N=O).

Step 5. Altogether, C4H9NO2 has 8 distinct constitutional isomers spanning these two functional families.

Enumerate the nitroalkane skeleton-and-position variants first (chain and position isomerism within R-NO2), then pair each one with its functionally-isomeric alkyl nitrite (same skeleton, R-O-N=O) to reach the full isomer count.

• Listing only the four nitroalkanes and stopping there -- the question's own isomerism vocabulary (chain, position AND functional) signals that the alkyl-nitrite functional isomers must also be included for a complete answer.