Calculate extinction coefficients?

E = ε * c * d

ε = molar extinction coefficient [L/(mol *cm)]

c = molar concentration [mol/L]

d = layer thickness [1 cm]

ε = E/(c * d)

ε = 1.0/[(1.486 * 10⁻⁴ g/L/(138 g/mol)) * 1 cm] = 928670 L * mol⁻¹ * cm⁻¹

λ _max = 233 nm

But… how two methyl groups can fit at position 3 of the compound, i.e. at a C of the double bond, is very mysterious.