Question

chain isomer of c4H8O in case of aldehyde group

Answer 1

There are a total of 15 isomers with the formula C4H8O (not counting the stereoisomers of the compounds with four different constituents on a carbon atom such as 3-buten-2-ol). 

1. Butanal HCOCH2CH2CH2CH3 (aldehyde) 
2. 2-Butanone (methyl ethyl ketone) CH3COCH2CH3 (ketone) 
3. cyclobutanol (ring compound) ---CH2CHOHCH2CH2--- 
4. 1,2-epoxy butane (epoxide) CH2OCHCH2CH3 
5. cis-2,3 epoxy butane 
6. trans-2,3 epoxy butane 
7. 2-buten-1-ol (crotyl alcohol) CH3CH:CHCH2OH 
8. 3-buten-1-ol (allylcarbiol) CH2:CHCH2CH2OH 
9. 3-buten-2-ol CH3CHOHCH:CH2 
10. methoxycyclopropane (ether) (ring compound) 
---CH2CH(OCH3)CH2--- 
11. allyl methyl ether CH3OCH2CH:CH2 
12. ethenyl ethyl ether (ethyl vinyl ether) CH3CH2OCH:CH2 
13. 1,4-epoxybutane (tetrahydrofuran) (ring compound) 
---OCH2CH2CH2CH2--- 
14. 1,2-epoxy-2-methylpropane (ring compound) H2COCH(CH3)(CH3) 
15. 2-methyl-2-propen-1-ol (methallyl alcohol) H2C:C(CH3)CH2OH...
Hope it helps u