Answer
a. Structural isomers.
b. Structural isomers.
c. Same molecule.
Work Step by Step
a. The first molecule has a chain of 3 carbons, whereas the second has a chain of 4 carbons. Thus, they are different molecules.
b. The first molecule has 2 substituents, one on the second carbon and another on the third carbon, whereas the second has two substituents, one on the second carbon, and another on the fourth carbon. We cannot rotate the molecules to get the same result. Thus, they are different molecules.
c. The second representation is just a rotation of the first one.
