1 H NMR ( 300 MHz , CDCl 3 ) δ 1 . 31 ( 12 H , s ) , 1 . 87 - 2 . 04 ( 2 H , m ) , 2 . 75 ( 4 H , t , J = 7 . 6 Hz ) , 7 . 07 - 7 . 16 ( 1 H , m ) , 7 . 20 - 7 . 24 ( 1 H , m ) , 7 . 26 - 7 . 37 ( 5 H , m ) , 7 . 73 ( 2 H , d , J = 8 . 3 Hz ) .