Organic chemistry lab report - Friactional distillation
Methods and Background
Data Acquisition/ Presentation
I. Relevant Equations
II. Fractional Distillation of the Three Fractions
The purpose of this lab is to separate a mixture of ethyl acetate and butyl acetate using fractional distillation to make three fractions: one containing pure EtOAc, one containing pure BuOAc, and one containing a mixture of both compounds. These fractions are then analyzed using gas chromatography to determine how efficient fractional distillation is in separating the two liquids.
Boling point of any molecule is the temperature at which the pressure of the molecule equals the external vapor pressure. It depends on the molecular weight and the forces that hold the molecule together. Both EtOAc and BuOAc contain an ester group; however, BuOAc has higher molar mass than EtOAc. Hence, more energy is needed to break the intermolecular bonds and cause BuOAc to boil. Thus, BuOAc boils at 126oC whereas EtOAc boils at 77.1oC. Since the boiling points of both these volatile compounds do not differ by at least 40o-50oC, fractional
The volume of distillation vs. head temperature graph of both fractional distillation and simple distillation shows how fractional distillation is more useful in separating ethyl acetate and butyl acetate than simple distillation. The fractional distillation graph has a sharp steep slope around 14 mL, which is almost half-way through the distillation process. This sharp slope indicates a clear transition from EtOAc to BuOAc. Immediately after 14 mL of distillation, the temperature rose fast; thus indicating the separation of EtOAc from BuOAc. Furthermore, the GC graphs prove that the first fraction is completely EtOAc. Likewise, the third fraction is completely BuOAc. The second fraction has 22.2% EtOAc and 77.8% BuOAc. Simple distillation, on the other hand, did not give such accurate results. Even the first fraction in simple distillation contained mixtures of both EtOAc and BuOAc. Furthermore, the slope of the sim
Gilbert, J.C., Experimental Organic Chemistry, Saunders Publishing, New York, 2006, 4th Ed, pp. 123-125; 127-130; 192-202.
http://www.chadlandrie.com. (figure 1.)