1 H - NMR ( 500 MHz , CDCl 3 , δ ) : 7 . 76 - 7 . 72 ( m , 4 H ) , 7 . 30 - 7 . 12 ( m , 10 H ) , 7 . 10 - 7 . 02 ( m , 10 H ) , 6 . 98 ( t , J = 8 . 5 Hz , 2 H ) , 6 . 91 ( t , J = 8 . 5 Hz , 2 H ) , 6 . 76 - 6 . 71 ( m , 4 H ) , 6 . 61 - 6 . 53 ( m , 4 H ) , 6 . 41 ( t , J = 8 . 5 Hz , 2 H ) , 2 . 17 - 2 . 16 ( m , 6 H )