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Hi guys, its been a long time since I have last said anything on SDN. I have found that the further away I get from SDN, the better I do. Either way, I would like your help in something. I am taking my organic lab this quarter, and I have a midterm next week. I am trying to solve all the homework questions in the lab book, and I have a couple of questions that I have no idea how to do, because I just don't remember the material from Ochem 1, and I don't even know if it IS from ochem 1. They are pretty easy questions though, I can tell you that. Your help is greatly appreciated.
(1) The solubility of p-dibromobenzene (basically 1,4-dibromobenzene) in benzene is 80 micrograms/100 microliters at 25 C. Would you predict the solubility of this compound to be greater, less, or approximately the same in acetone solvent at this temperature? Explain.
I honestly have no idea what the exaplanation is, but I'm almost positive that it wouldn't be more soluble. It would be less soluble if we put it in acetone. Could it possibly be because the structure of benzene is a lot closer to the 1,4-dibromobenzene then the 2-propanone (acetone) is?
(2)Each of the solvents listed below are used in experiments in this text to extract organic compounds from aqueous solutions.
(a)Methylene Chloride
(b)Pentane
(c)Toluene
(d)Diethyl Ether
Now will the organic phase be the upper or lower layer when each of these solvents is mixed with water? Explain your answer for each case.
Now could this question possibly be as easy as getting the densities for each one of those and comparing it with the density of water assuming the heavier it is, the lower it will go, considering the fact that I already do have the densities tabulated in my textbook.
(3)A 36mg sample of an organic compound (MW = 84) is dissolved in 10ml of water. This aqueous solution is extracted with 5.0 ml of Hexane. Separation and analysis of the aqueous phase shows that it now contains 12mg of the organic compound. Calculate the partition coefficient for the compound.
Okay, now here I do know that the equilibrium constant, Kp is equal to the solubility of X in solvent 2 divided by the solubility of X in solvent 1.
We can get the moles by doing 36/84 for the organic compound. We can even get the density of the whole thing if we wanted to utilize density = mass/volume. But I am seriously lost though, I don't even know what this has to do with the lab we are taking.
(4)A qualitative method often used to determine whether an organic compound contains oxygen is to test its solubility in concentrated sulfuric acid. Almost all oxygen containing compounds are soluble in this acid. Explain.
I honestly have no clue here. I'm sure its really easy, but I have no clue🙁
(5) In the discussion of multiple extractions, it was suggested that in the example given, you might extend the relationship to the next step by using one-third of the total quantity of the ether solvent in three portions. The reason for increasing the number of extractions was to determine whether this expansion would increase the efficiency of the process even further. Now to determine if this next step isworth the effort, perform the calculations for the extraction of 100mg of P in 300 microliters of water with three 100 microliter portions of ether. Assume the partition coefficient is 3.5.
(a)Compare the amounts of P extracted from the water layer using one, two, or three extractions.
(b)Do you think that the additional amount of P extracted from the water layer using three extractions is justified? Might it be justified if P were valuable and you were working on the industrial scale of 100kg of P in 3000 Liters of water?
Thats it. I really would appreciate it if you guys could help me out. I finished my Ochem lectures a while back, and I left the labs till the end, and now I get lost sometimes because I haven't been over the material in a while.
Many thanks in advance🙂
george
(1) The solubility of p-dibromobenzene (basically 1,4-dibromobenzene) in benzene is 80 micrograms/100 microliters at 25 C. Would you predict the solubility of this compound to be greater, less, or approximately the same in acetone solvent at this temperature? Explain.
I honestly have no idea what the exaplanation is, but I'm almost positive that it wouldn't be more soluble. It would be less soluble if we put it in acetone. Could it possibly be because the structure of benzene is a lot closer to the 1,4-dibromobenzene then the 2-propanone (acetone) is?
(2)Each of the solvents listed below are used in experiments in this text to extract organic compounds from aqueous solutions.
(a)Methylene Chloride
(b)Pentane
(c)Toluene
(d)Diethyl Ether
Now will the organic phase be the upper or lower layer when each of these solvents is mixed with water? Explain your answer for each case.
Now could this question possibly be as easy as getting the densities for each one of those and comparing it with the density of water assuming the heavier it is, the lower it will go, considering the fact that I already do have the densities tabulated in my textbook.
(3)A 36mg sample of an organic compound (MW = 84) is dissolved in 10ml of water. This aqueous solution is extracted with 5.0 ml of Hexane. Separation and analysis of the aqueous phase shows that it now contains 12mg of the organic compound. Calculate the partition coefficient for the compound.
Okay, now here I do know that the equilibrium constant, Kp is equal to the solubility of X in solvent 2 divided by the solubility of X in solvent 1.
We can get the moles by doing 36/84 for the organic compound. We can even get the density of the whole thing if we wanted to utilize density = mass/volume. But I am seriously lost though, I don't even know what this has to do with the lab we are taking.
(4)A qualitative method often used to determine whether an organic compound contains oxygen is to test its solubility in concentrated sulfuric acid. Almost all oxygen containing compounds are soluble in this acid. Explain.
I honestly have no clue here. I'm sure its really easy, but I have no clue🙁
(5) In the discussion of multiple extractions, it was suggested that in the example given, you might extend the relationship to the next step by using one-third of the total quantity of the ether solvent in three portions. The reason for increasing the number of extractions was to determine whether this expansion would increase the efficiency of the process even further. Now to determine if this next step isworth the effort, perform the calculations for the extraction of 100mg of P in 300 microliters of water with three 100 microliter portions of ether. Assume the partition coefficient is 3.5.
(a)Compare the amounts of P extracted from the water layer using one, two, or three extractions.
(b)Do you think that the additional amount of P extracted from the water layer using three extractions is justified? Might it be justified if P were valuable and you were working on the industrial scale of 100kg of P in 3000 Liters of water?
Thats it. I really would appreciate it if you guys could help me out. I finished my Ochem lectures a while back, and I left the labs till the end, and now I get lost sometimes because I haven't been over the material in a while.
Many thanks in advance🙂
george
