2. This is 1-bromobutane.

3. It has a position isomer where the bromine atom is on a different carbon atom.

4. This is 2-bromobutane. These two compounds are position isomers.

5. This is butan-1-ol.

6. It has a position isomer where the hydroxyl group is on a different carbon atom.

7. This is butan-2-ol. These two compounds are position isomers.

8. This is 1,2-dichlorobenzene.

9. It has two position isomers where one of the chlorine atoms is on a different carbon atom.

10. This is 1,3-dichlorobenzene.

11. This is 1,4-dichlorobenzene. These three compounds are position isomers.

12. This is but-1-ene.

13. It has a position isomer where the double bond is between two different carbon atoms.

14. This is but-2-ene. These two compounds are position isomers.

15. This is butanal, an aldehyde.

16. It has a functional group isomer where the carbonyl group, C=O, is on a different carbon atom.

17. This is butanone, a ketone. These two compounds are functional group isomers.

18. These two compounds are functional group isomers of C 4 H 8 O.

19. This is butan-1-ol, an alcohol.

20. It has a functional group isomer involving the oxygen atom.

21. This is ethoxyethane, an ether. These two compounds are functional group isomers.

22. These two compounds are functional group isomers of C 4 H 10 O.

23. This is butene, an alkene.

24. It has a functional group isomer where the double bond is absent.

25. This is cyclobutane, a cyclic alkane. These two compounds are functional group isomers.

26. These two compounds are functional group isomers of C 4 H 8.