A 5,5-dimethyl-1,3-cycloheptadiene |
B 6,6-dimethyl-1,3-cycloheptadiene |
C 6,6-dimethyl-1,4-cycloheptadiene |
D 3,3-dimethyl-1,4-cycloheptadiene |
Because of their symmetry, two of these isomers have five structurally distinct carbon atoms; the other two have eight such carbons.
One of the symmetrical dienes (X) has a uv absorption maximum near 250 nm.
The other symmetrical diene (Y) does not absorb uv light above 200 nm in wavelength.