1 H - NMR ( 500 MHz , CDCl 3 , δ ) : 8 . 47 ( d , J = 1 . 5 Hz , 2 H ) , 7 . 89 ( dd , J = 8 . 5 Hz , 2 . 0 Hz , 2 H ) , 7 . 83 ( d , J = 1 . 5 Hz , 2 H ) , 7 . 80 - 7 . 78 ( m , 4 H ) , 7 . 74 ( d , J = 1 . 5 Hz , 2 H ) ,