0.67 g of ground nutmeg was weighed into a clean, dry round-bottom flask 10 mL o
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0.67 g of ground nutmeg was weighed into a clean, dry round-bottom flask 10 mL of dichloromethane was added. A water-jacketed condenser was attached to the flask, and the mixture was heated to a gentle reflux for 45 min. The mixture was then cooled to room temperature and gravity filtration was performed. After removal of dichloromethane, 0.29 g of crude trimyristin was obtained. It was then recrystallized from hot 95% ethanol yielding 0.34 mmol of pure trimyrist in (MW 723.16 g/mo) with a melting point of 54-56 degree c. The purpose of refluxing is to recrystallize trimyristin from nutmeg saponify trimyristin extract trimyristin from nutmeg saponify nutmeg The dissolved trimyristin is best separated from dichloromethane by ization vacuum filtration acid-base extraction rotary evaporation If you did not observe any crystals of trimyristin after the recrystallization process, which of the following steps is least likely to aid crystal formation ? dropwise addition of hot solvent (95% ethanol) scratching the inner wall of the container with a glass rod addition of solid trimyristin as a "seed" crystal putting the solution back on the rotovap. Based on the quantity of crude trimyristin, what was the percent recovery of pure trimyristin from the recrystallization process? 85% 37 % 78 % 47 %Explanation / Answer
Ans. 7. Correct option C. Extract trimyristin from nutmeg. Nutmeg (ground, powdered form) has trimyristin in it. Treatment with dichloromethane extracts the lipid (trimyristin) from nutmeg into the organic solvent. Refluxing ensures that the solvent extract process is repeated several times for the same set of sample to maximize extraction.
Refluxing increases solvent extraction of trimyristin into the organic phase, it does not re-crystalize the lipid. It is not a saponification process because lipid is not reacted with an alkali.
Ans. 8. Correct option D. Rotatory evaporation. In this process, the more volatile solvent (dichloromethane) is evaporated leaving behind the lipid (solute).
Recrystallization. Recrystallization is a process in which a pure molecule is precipitated out in from of solid (crystals) due to change in solubility at different parameter (temperature, pH, etc.). It is used to separate the pure lipid from crude sample, not to separate the solvent from solutes.
The extraction process includes gravity filtration in which the reacted sample is allowed to stand undisturbed so that two phases are separated from each other. Vacuum filtration has not been not applied.
Ans. 9. Correct option D. 95% ethanol added to the crude sample removes the residual solvent from the crude solvent. Adding it does not cause recrystallization- for recrystallization the ethanol (as second solvent) must be evaporated using rotovap.
Scratching the inner walls of container with a glass rod and addition of solid trimyristin may act as nucleation for recrystallization.
Putting the solution to rotovap may remove residual solvents and may enhance recrystallization of pure solutes.
Ans. 10. Mass of trimyristin produced = moles x molar mass of trimyristin
= 0.34 x 10-3 moles x (723.16 g mol-1) ; [1 mmol = 10-3 mol]
= 0.2458744 g
% yield = (Mass of pure trimyristin / mass of crude trimyristin sample) x 100
= (0.2458744 g / 0.29 g) x 100
= 84.78 %
Correct option . A. 85%
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