While reading of birch reduction I was confused as of why 1,4-cyclohexadiene is prefered over 1,3-cyclohexadiene, the latter which ought to have been the major product due to conjugation. One of the reason I felt could be of this outcome was "symmetry". The symmetry produced by the product could cancel the dipole forces acting on the cis- bonds, making the molecule stable. But is this sole reason sufficient to overpower the conjugation? Please explain. Edit: another possible reason I feel could be is the stereochemistry of the product. The product could facilitate more efficient structure in space about it's double bond (again symmetry), where as 1,3-cyclohexadiene formation could face issues of rotational barriers and might increase torsional strain on it.