Question

4. a) In the reductive amination reaction why is the NaBH, only added 15 minutes after the amine and the aldehyde have been mixed, and not right away? b) What is a rotary evaporator (Rotovap) used for? c) In the Williamson Ether Synthesis, why did we use a reflux assembly and not just boil the reactants in a beaker or flask? d) Would you expect the melting point of a crude product to be higher or lower than the melting point of a recrystallized product? Why?

Answer 1

@ Reductive amination is a type of coupling seaction in which connession of Gabonyl group to amine group will happen win the Emine inter- mediate which is represcuted bella ľ NH3 NH MABHIQ NMy - Rla Rila la mine If we obscure the above reaction imine formation is the fullest step in the reaction. so aften that intue seduction faill happen by MABHA (so dumbaroky dente) If we add all to geather ie Aldehyde, wine, na BH4, instead of Reductive camination, Aldehuele reduction will happen to give corresponding alcohol as a product. RM + Nyt RunB44 to avoid Ahotely be reduction to give alcohol by mabuf, we must add first aldehyde to amine, then after half an hour, when Emine has been formed, we have to add Nabuu to get omine. in the main reason to add Mash outer 30 ming in to void allehuple reduction to alcohol by MG B Ml. Rotary evapointor und in chemical laboratories for efficient rewelled of diffeuent solvents from the laboratory samples by evaporation. In Robiny evoparator the pressure on the surface of the schent will be reduced so that Foiling point of the scheut also reduced. is at low temperatures we can exparate the high boiling temperature solvents. @ the products in williamson synthens de others which are having low boiling points and highly volatile instead of doing reaction in redan on if you do the reaction at open atmosphere condition the farmed an to the atmosphere because of its high wodatle indure. t on will lose your product if we do same in the delux cutition celling ondergeld, the vopout of faved fether will be condensed and will be stored in the flask. melting point of the couche product always lowed when compared with the laystalized product this is dere to the impurities present in the cande product mosses up to the crystalline lattice by blocking their formation and acute irregularities. Due to this in erride product the intalmolcadas bondy beame weakers, resulty Jower heat energy to break the bond which makes melting point belove lower where of in care of Crystall it won't happen and melting point higher.