[noodlesoup]

hi guys,  i was working on my lab for ester synthesis via condensation rxn and got stuck by two questions:1/ the purpose of H2SO4 in the reaction? 2/why the mixture extracted with NaHCO3?  i was thinking about the reasons for them but they don't seem to be reasonable, so if you guys can share your insights, i really appreciate that. thanks.
btw, here is a short summary of the procedure;

in a 50mL round bottom flak containing 3-5 boiling chips, add 6.0 g of actetic acid and 6.0 g of an unknown alcohol. To this solution, add 0.5 mL of concentrated sulfuric acid.  After addtion of reagents is complete, attach a reflux condenser to the round bottom flask and gently reflux the mixture for 60 mins. then allow the mixture to cool and transfer the liquid to a separatory funnel and wash it with 2X 20 mL of water followed by a washing with 1X 20mL of a saturated NaHCO3 solution. Dry the organic layer over anhydrous Na2SO4. Decant the mixture into a 25mL round bottom flask and purify the product by distillation. obtain a mass of the final oil recovered after distillation.record odor of oil.

[macman104]

Give us your insights or talk us through your thoughts, and we'll help lead you after that.

[noodlesoup]

well, when i draw the mechanism for this reaction, i saw that H2SO4 acts as a strong acid to donate an H to the O in acetic acid so that the alcohol can react with the acetic acid through Nu and E attack.
i m not sure about the purpose of NaHCO3 though.

[cundi]

H2SO4 cat, is used to increase the electophilic behaviour of the acid. The alcohol atacks to CH3CO2H2+ and a molecule of water is formed.

Regarding to the use of NaHCO3.
It is used in the work-up of the reaction. It is not important in the mechanism.
Its role is eliminate er the excess of the acid employed  in the reaction (H2SO4 and AcOH). The corresponding salts are generated an eliminated in the aqueous layer. It is a very common work-up in reactions in which a acid is used as catalysts.
The ester formed is then extracted to the organic layer.

In a synthesis protocol it is important to distinguish the reactants of the own reaction and the "things" that are used in the work-up.