1. Calculate percent recovery... not hard
2. When the first washing was done with NaOH, the strong attraction of the OH- pulled both compounds into the aqueous solution, leaving nothing to react with the acidification of the NaHCO3 layer.
OR
Appartently, you had benzoic acid, naphthalene, and 2-naphthol dissolved in ether. If you mistakenly extracted that solution with aqueous NaOH, then:
C6H5COOH + NaOH ===> C6H5COO-Na+ + H2O
C10H7OH + NaOH ===> C10H7O-Na+ + H2O
C10H8 + NaOH ===> No reraction
So both the benzoate and the 2-naphtholate would have gone into the water solution and the naphthalene remained in the ether solution. If you had extracted the ether solution with NaHCO3 solution next, only the naphthalene would be left in the ether solution, nothing would go into the NaHCO3 solution, and no crystals would be formed on acidification of the NaHCO3 solution.
3. p-tert-butylphenoxide anion (The sodium salt of p-tert-butylphenol)
4.Dichloromethane would sepaprate into the lower layer of the separatory funnel instead of the top, making extraction more difficult. Instead of using the funnel's stopcock, one would need to extract the top layer from above, leaving the bottom layer intact for further washes. (Check density)
The only change you would make is you would save the opposite layer. For example, if you were extracting an organic into the organic layer (tbme), you would save the top layer and discard the bottom (aqueous). If you used dichloromethane instead, you would save the bottom layer (MeCl2) and discard the top (aqueous).
5. Make a flowchart (http://i.imgur.com/gji6F.gif) also refer to (http://www.sas.upenn.edu/~zhall/flowchart.html) for details and cool stuff and unicorns and cute puppies
6. Lower/wider melting point range than expected implies less purtiy, nuff said
Wednesday, September 28, 2011
TECH 0705 Results: Seperating Acids and Neutral Compunds by Solvent Extraction
Results
SET 1:
Weight Before Extraction
p-Toluic Acid-0.513g
Acetanilde-0.256g
p-Tertbutylphenol-0.517g
Weight After Extraction
p-Toluic Acid-0.760g
p-Tertbutyl phenol-0.149g
Expected Melting Point Experimental Melting Point
p-Toluic Acid 180-182 174-180
SET 1:
Weight Before Extraction
p-Toluic Acid-0.513g
Acetanilde-0.256g
p-Tertbutylphenol-0.517g
Weight After Extraction
p-Toluic Acid-0.760g
p-Tertbutyl phenol-0.149g
Expected Melting Point Experimental Melting Point
p-Toluic Acid 180-182 174-180
p-Tertbutylphenol 98-101 91-98
SET 2:
Weight of initial acetanilide: 0.25606 g
Weight of initial p-toluic acid: 0.6079 g
Weight of initial p-tert-butylphenol: 0.5547 g
Mass of filter paper to filter out p-toluic acid: 0.013 g
Mass of test tube used to collect p-toluic acid: 7.934 g
Mass of filter paper to filter out p-tert-butylphenol: 0.006 g
Mass of test tube used to collect p-tert-butylphenol: 7.986 g
Mass of large test tube used to collect acetanilide: 38.7405 g
Weight of p-toluic recovery and test tube: 8.507 g
Weight of p-tert-butylphenol recovery and test tube: 8.172 g
Weight of acetanilide recovery and test tube: 39.141 g
Melting range of p-tert-buyltphenol: 82-89 C.
Melting range of p-toluic acid: 179-185 C.
Weight of initial p-toluic acid: 0.6079 g
Weight of initial p-tert-butylphenol: 0.5547 g
Mass of filter paper to filter out p-toluic acid: 0.013 g
Mass of test tube used to collect p-toluic acid: 7.934 g
Mass of filter paper to filter out p-tert-butylphenol: 0.006 g
Mass of test tube used to collect p-tert-butylphenol: 7.986 g
Mass of large test tube used to collect acetanilide: 38.7405 g
Weight of p-toluic recovery and test tube: 8.507 g
Weight of p-tert-butylphenol recovery and test tube: 8.172 g
Weight of acetanilide recovery and test tube: 39.141 g
Melting range of p-tert-buyltphenol: 82-89 C.
Melting range of p-toluic acid: 179-185 C.
SET 3:
Mass of the acetanilide: 0.31 g.
Mass of the p-toluic acid: 0.57 g.
Mass of the p=tert-butylphenol: 0.45 g.
Isolating P-toluic Acid:
Mass of the filter paper: 0.0061 g.
Mass of dry p-toluic acid, test tube and filter paper: 5.476 g.
Mass of recovered p toluic acid: 0.084 g.
Measured melting point of p- toluic acid: 179.3-180.2 degrees Celsius
Actual melting point of p-toulic acid: 180-182 degrees Celsius
Isolating p-tert-butylphenol:
Mass of the filter paper: 0.0066 g.
Mass of the empty test tube: 5.324 g.
Mass of the dry p-tert-butylphenol, test tube, and filter paper: 5.64 g.
Mass of collected p-tert butylphenol: 0.3094 g.
Measured melting point of p-tert-butylphenol: 98.1 degrees Celsius
Actual melting point of p-tert-butylphenol: 98-101 degrees Celsius
Isolating Acetanilide
Mass of anhydrous Na2SO4: 1.003 g
Mass of 100 mL test tube: 5.288g.
Mass of dry acetinilide and test tube: 5.43 g.
Mass of recovered acetinilide: 0.142 g.
Measured melting point of acetanilide: 88.9 degrees Celsius
Actual melting point of acetinilide: 113-115 degrees Celsius
Mass of the acetanilide: 0.31 g.
Mass of the p-toluic acid: 0.57 g.
Mass of the p=tert-butylphenol: 0.45 g.
Isolating P-toluic Acid:
Mass of the filter paper: 0.0061 g.
Mass of dry p-toluic acid, test tube and filter paper: 5.476 g.
Mass of recovered p toluic acid: 0.084 g.
Measured melting point of p- toluic acid: 179.3-180.2 degrees Celsius
Actual melting point of p-toulic acid: 180-182 degrees Celsius
Isolating p-tert-butylphenol:
Mass of the filter paper: 0.0066 g.
Mass of the empty test tube: 5.324 g.
Mass of the dry p-tert-butylphenol, test tube, and filter paper: 5.64 g.
Mass of collected p-tert butylphenol: 0.3094 g.
Measured melting point of p-tert-butylphenol: 98.1 degrees Celsius
Actual melting point of p-tert-butylphenol: 98-101 degrees Celsius
Isolating Acetanilide
Mass of anhydrous Na2SO4: 1.003 g
Mass of 100 mL test tube: 5.288g.
Mass of dry acetinilide and test tube: 5.43 g.
Mass of recovered acetinilide: 0.142 g.
Measured melting point of acetanilide: 88.9 degrees Celsius
Actual melting point of acetinilide: 113-115 degrees Celsius
Thursday, September 15, 2011
TECH 0707: TLC Plates Post-Lab
Post-Lab
1a) The eluents in order of increasing polarity are hexane, toluene, dichloromethane, ethyl acetate and methanol.
1b) Hexane is very non polar so it causes the Rf the stock solution to stay low, and doen't allow for seperation of the compounds in the solution. Toulene and dichloromethane allows the compounds in the solution to seperate because it has an intermediate polarity and would thus give a range of Rf values based on the polarity of the individual compounds. Ethyl acetate and methanol are both very polar so they don't allow the compounds that are more non-polar to seperate out and would carry them all together towards the eluent front. This would then give a higher Rf value.
1c) Compound polarity and the polarity of the eluent determine how big of a Rf value you will get, if the compound is non-polar but is put into a very polar eluent, your Rf value will be higher because the stronger attraction from the eluent.
2) We chose to use toluene as the eluent because it seperated the compounds well. Hexane, ethyl acetate and methanol didn't allow the compounds to seperate at all so it would have been foolish to chose them as an eluent. The only other option was dichloromethane, which also seperated the compounds from the solution but we didn't choose it for arbitrary reasons.
3a) If a sample that is too large is applied while spotting the plate it may lead to poor seperation .
3b) If a spotted plate is put into a developing chamber that has an eluent level above the origin the compounds that were spotted on the plate may be dissolved in the eluent, with none left on the TLC plate.
3c) If you allow the plate to remain in the developing chamber until the eluent reaches the top of the plate you will not be able to have a eluent front to compare to the spots to give Rf values.
3d) If you remove the plate from the chamber when the eluent front has moved only halfway up the plate , you will not allow the plate to fully develop and the compounds to reach their polarities.
3e) If you develop the plate in an uncovered chamber you could allow the eluent to evaporate, and not travel up the TLC plate.
4) You could use a TLC plate to tell when the reaction is complete when the solution shows a compound that has a low polarity as indicated by the TLC plate.
1b) Hexane is very non polar so it causes the Rf the stock solution to stay low, and doen't allow for seperation of the compounds in the solution. Toulene and dichloromethane allows the compounds in the solution to seperate because it has an intermediate polarity and would thus give a range of Rf values based on the polarity of the individual compounds. Ethyl acetate and methanol are both very polar so they don't allow the compounds that are more non-polar to seperate out and would carry them all together towards the eluent front. This would then give a higher Rf value.
1c) Compound polarity and the polarity of the eluent determine how big of a Rf value you will get, if the compound is non-polar but is put into a very polar eluent, your Rf value will be higher because the stronger attraction from the eluent.
2) We chose to use toluene as the eluent because it seperated the compounds well. Hexane, ethyl acetate and methanol didn't allow the compounds to seperate at all so it would have been foolish to chose them as an eluent. The only other option was dichloromethane, which also seperated the compounds from the solution but we didn't choose it for arbitrary reasons.
3a) If a sample that is too large is applied while spotting the plate it may lead to poor seperation .
3b) If a spotted plate is put into a developing chamber that has an eluent level above the origin the compounds that were spotted on the plate may be dissolved in the eluent, with none left on the TLC plate.
3c) If you allow the plate to remain in the developing chamber until the eluent reaches the top of the plate you will not be able to have a eluent front to compare to the spots to give Rf values.
3d) If you remove the plate from the chamber when the eluent front has moved only halfway up the plate , you will not allow the plate to fully develop and the compounds to reach their polarities.
3e) If you develop the plate in an uncovered chamber you could allow the eluent to evaporate, and not travel up the TLC plate.
4) You could use a TLC plate to tell when the reaction is complete when the solution shows a compound that has a low polarity as indicated by the TLC plate.
OR
1. a) The five eluents could be arranged as follows in order of increasing polarity.
Hexane < Toluene < Dichloromethane < Ethyl acetate < Methanol
b) The effects of eluent polarity on the Rf value of each stock solution mixture compound.
Based on the experiment I could say that two of the compounds were either too polar or too non polar which means that either did not move from the origin at all (hexane- too non polar) or they went very close to the top of the plate (methanol – too polar).
The rest three compounds (dichloromethane, ethyl acetate and toluene) gave us pretty good separation by leaving two to three spots on the plate.
c) As stated in general chemistry II “Like dissolves like” means that polar compounds will interact will polar and non polar with non polar. Therefore, the Rf value will depend on plarity.
- We selected Toulene as our eluent because it gave us the best separation by leaving three spots on the plate. Dichloromethane gave us also three spots but in the middle of the experiment something did not work out very well and we decided to take it out of the list. The other compounds either did not separate at all or gave us one or two spots.
- a.) If we apply too much of the sample on the plate, we are risking of getting not very good results because we might not be able to distinguish the spots and they might get mixed up if the distance between them is very small. Moreover, we will get poor separation.
b.) If we put the plate in the chamber with eluent level above the level of the plate, we risk the sample to dissolve from the plate into the eluent layer.
c.) If we forget and leave the plate in the chamber until the eluent front reaches the top of the plate, then the mixture compound may keep moving along the plate which will lead us to not valid Rf measurements.
d.) If we remove the plate from the chamber before it reaches the eluent front, then we might not be able to see the full process of separation. This will also lead us to not valid Rf values.
e.) If we leave the chamber open and keep developing the plate, then the eluent will evaporate in the air and will not allow proper separation of the plate which again will lead to wrong Rf values if any at all.
4. If you prepared benzhydrol by the reduction of benzophenone with sodium borohydride, we could use TLC to decide when the reaction was completed by performing the same experiment with compounds that will give separation and mark the spots. Then do the experiment again with sodium borohydride and spot it. The result will be on the same spot as benzhydrol.
TECH 0707: TLC Plates Results
Results
I was assigned to do the Thin-Layer Chromatography on dichloromethane as a reagent for the first part of the lab. The middle set of dots on my TLC plate was due to error, while spotting the plate my capillary tube must have touched the TLC plate intentionally.
The distance between the origin and eluent front of dichloromethane was 6.0 cm.
From other team members TLC Plates: Hexane didn't move the eluent very far from the origin and didn't seperate so we decieded it is non-polar. Ethyl acetate and Methanol did move the eluent far up closer to the eluent front, thus showing that it is more polar, but also didn't seperate the compounds within the mixture. Toluene was the only other eluent that seperated the mixture of Biphenyl, Benzhydrol, and Benzophenone into it's individual compounds. So as a group we decided to use Toulene as being thMy assigned compound for this section of the lab was biphenyl. I spotted the stock solution on the left side of the TLC plate and biphenyl on the right side. After the plate had been developed, it appears that toluene takes much longer to evaporate than dicholoromethane. The distance between the origin and the topmost spot was 3.8 cm and the distance between the origin and the eluent front was 5.4 cm.
e best for seperating the mixtures later in this lab since my TLC plate had an error (the middle dots).
My unknown solution was #13 , and Toluene was used as the eluent. The left-most set of spots is the stock solution and the right-most set of spots is the unknown. Based on the results of the TLC plate, my unknown solution was comprised of Biphenyl and Benzhydrol. The distance between the origin and the eluent front is 5.8 cm, the distance between the origin and Biphenyl is 4.5 cm, and the distance between th origin and Benzhydrol is .5 cm.
TECH 0708: Adsorption Column Chromatography Post-Lab
Post-Lab
2. As hexane was added to the column, Acetylferrocene did progress down the column although very slowly. It wasnt until TBME was added that acetylferrocene went down the column at a more rapid pace.
3. Had hexane been the only eluent added to the column, the ferrocene would have come out of the column but since the acetylferrocene is more polar, it has a stronger attractive force to the alumna and wouldn't proceed down the column bed.
4. If you had used TBME as the only eluent added, you wouldn't achieve seperation, both the ferrocene and acetylferrocene would proceed down the column bed together since ferrocene is more non-polar and holds less attraction to the absorbant,alumna.
3. Had hexane been the only eluent added to the column, the ferrocene would have come out of the column but since the acetylferrocene is more polar, it has a stronger attractive force to the alumna and wouldn't proceed down the column bed.
4. If you had used TBME as the only eluent added, you wouldn't achieve seperation, both the ferrocene and acetylferrocene would proceed down the column bed together since ferrocene is more non-polar and holds less attraction to the absorbant,alumna.
TECH 0708: Adsorption Column Chromatography Results
Results
After the hexane was added to the pipet, yellow was the first color to separate out of the solution, as was expected since ferrocene is less polar. It seperated out fairly quickly once the hexane had reached the 50/50 ferrocene/ acetylferrocene mixture. Acetylferrocene gradually does seperate out with hexane and moves down the column bed much more slowly than ferrocene and is dark orange in color. As the ferrocene moves down the column, the yellow and dark orange colors do seperate. Air was used to force the hexane down the pipet at a faster rate, it worked well to move the hexane as well as ferrocene down the column.
Once the ferrocene was through the column, the acetylferrocene moved more slowly when TBME was added to the column, than the speed at which the ferrocene moved down the column with hexane. Some of the Acetylferrocene / TBME that was collected accidently spilled. We were also told to stop collecting the acetylferrocene eluent when the drops were clearer although not completly colorless.
After spotting TLC plates at different ratios of eluents, as a group we determined that the best separation of the ferrocene and acetylferrocene came from a 25% Ethyl Acetate/ 75% Toluene mix.
Once the ferrocene was through the column, the acetylferrocene moved more slowly when TBME was added to the column, than the speed at which the ferrocene moved down the column with hexane. Some of the Acetylferrocene / TBME that was collected accidently spilled. We were also told to stop collecting the acetylferrocene eluent when the drops were clearer although not completly colorless.
After spotting TLC plates at different ratios of eluents, as a group we determined that the best separation of the ferrocene and acetylferrocene came from a 25% Ethyl Acetate/ 75% Toluene mix.
TECH 0701: Melting Points
Conclusion
In this experiment, we need to be careful when measuring the melting point of compounds because if we put too much of the sample into the capillary tube there would be poor heat transfer and if the compound is not a very fine powder, we would not get very good heat transfer. Mistakes can occur when measuring the melting point because there might be some king of changes in the compound such as sagging or shrinking and one can take it as the start of melting which actually is not. Another process that we must be aware of when taking the melting point of a compound is called sweating. Sweating is not melting. Sweating refers to process when we might have traces of moist due to not very well drying of the tubes.
All these possible errors can occur and this would lead us to wrong results.
OR
Within this lab we observed the characteristics of melting points and how they could be used to identify an unknown substance.
When we melted benzoic acid the melting point we had found was between 123-125 degrees celcius which is higher than what the literature had stated and when we had melted mandelic acid, we had observed it starting to melt earlier than the literature had stated although it did complete melting at the accepted temperature.
It was determined that for the unknown substance #14 the melting point had started at 153 degrees celcius and had completely melted at 155 degrees celcius. Given this range, we know that the unknown substance could be benzilic acid which has a melting point between 150-154 degrees celcius or adipic acid which has a melting point between 152-154 degrees celcius. Based on my results of melting the unknown compound with benzilic acid and then with adipic acid I am led to believe that unknown compound #14 was adipic acid. When melted together with adipic acid, the unknown had a narrower range of when it began to melt and when it completed melting as well as it's melting point had not been lowered due to an impurity as was the case of when the unknown had been mixed together with benzilic acid and had melted.
In this experiment, we need to be careful when measuring the melting point of compounds because if we put too much of the sample into the capillary tube there would be poor heat transfer and if the compound is not a very fine powder, we would not get very good heat transfer. Mistakes can occur when measuring the melting point because there might be some king of changes in the compound such as sagging or shrinking and one can take it as the start of melting which actually is not. Another process that we must be aware of when taking the melting point of a compound is called sweating. Sweating is not melting. Sweating refers to process when we might have traces of moist due to not very well drying of the tubes.
All these possible errors can occur and this would lead us to wrong results.
OR
Within this lab we observed the characteristics of melting points and how they could be used to identify an unknown substance.
When we melted benzoic acid the melting point we had found was between 123-125 degrees celcius which is higher than what the literature had stated and when we had melted mandelic acid, we had observed it starting to melt earlier than the literature had stated although it did complete melting at the accepted temperature.
It was determined that for the unknown substance #14 the melting point had started at 153 degrees celcius and had completely melted at 155 degrees celcius. Given this range, we know that the unknown substance could be benzilic acid which has a melting point between 150-154 degrees celcius or adipic acid which has a melting point between 152-154 degrees celcius. Based on my results of melting the unknown compound with benzilic acid and then with adipic acid I am led to believe that unknown compound #14 was adipic acid. When melted together with adipic acid, the unknown had a narrower range of when it began to melt and when it completed melting as well as it's melting point had not been lowered due to an impurity as was the case of when the unknown had been mixed together with benzilic acid and had melted.
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