Enantiomers

Constitutional isomers

Diastereomers

Different conformations of the same compound

1,2−dichloro−1−pentene

1,3−dichloro−2−pentene

1,1−dichloro−1−pentene

1,4−dichloro−2−pentene

2

3

1

All equally

(a) −OH group exhibits +M effect and hence increases the electron density on the o and p positions

(b) Oxo cation is more stable than the carbocation

Both (a) and (b)

−OH group exhibits acidic character

22.44^o

90^o

9.4^o

0.44^o