In the stilbene preparation above (problem 2), 3.0 g of stibene were obtained. What was the percent yield ? A student obtained 20. g of PhCH_2NEt_2 from 17 mL of PhCH_2Br and excess NHEt_2. What was the percent yield of the reaction? PhCH_2Br + 2 NHEt_2 rightarrow PhCH_2 NEt_2 + [H_2NEt_2] +^Br^-