TLC was used to identify the actual unknown product as well as other products/reactants present in the filtered solution. The procedure was conducted by placing a TLC plate in a developing chamber that is filled with a small amount of solvent. The solvent cannot be too polar because it will cause spotted compounds on the TLC plate to rise up too fast, while a very non-polar solvent will not allow the spots to move. The polarity of the spots also determines how far it moves on the plate; non-polar spots are higher than polar ones. After spots on the TLC form, the Rf values are calculated and used to analyze the similarity of the compounds.
Water will act as initial solvent for caffeine extraction. This is due to water that slowly soluble with caffeine at ambient temperature but highly soluble when temperature is at 100°C. Then, methylene chloride is chosen as the extraction solvent, due to its miscibility with caffeine and immiscibility with water. As mentioned above, the immiscible pair is chose for the extraction part because to allow the aqueous and organic layers to be separated. Basically, the bottom layer is the aqueous layer while the upper layer is the organic compound.
This reaction was able to happen during designated lab time due to the fact that a phenol was used. Phenols or more reactive than unsubstitued benzene rings due to the presence of the alcohol on the benzene ring. The alcohol is considered an activating group due to the oxygen’s ability to donate its lone pairs into the benzene ring thus giving it more electrons and thus making it more nucleophilic and more likely to react with the introduced electrophilic species. As aforementioned, there are various products formed in this reaction the two major products formed though are the ortho and para products. It is debatable which product is more prominent due to steric reasons and the capability of each product to conduct in hydrogen bonding.
Since alkenes are immiscible with concentrated HBr, tetrabutylammonium bromide is used as a phase-transfer catalyst. It forms a complex with HBr and extracts it from the aqueous phase into the organic phase where the alkene is. This dehydrates the acid, making it more reactive so that the addition reaction is possible. Rapid stirring is required in order to maximize the surface area
When the aqueous layer was added to the vial, calcium chloride was then added to dry the solution. If the solution was dry enough, a large peak between 3300-3500 would have been present in the IR spectrum. In order to obtain the IR spectrum two Classification test were performed. The Bromine test and Permanganate test were used to determine if alkenes were indeed present in the solution. Both test were positive for the compound.
Week 1 a simple condensation reaction between benzaldeyde and hydroxylamine produced the product benzaldehyde oxime that was found to be in oil. The percentage yield of the experiment is 64%. The 36% loss can be due to the solution needing to be neutralised with glacial acid, there was no way to tell if the reaction was neutralised, to help increase yield the use of pH indictor paper to indicate whether the reaction was neutralised. As by using a rotary evaporator to remove the organic solvent may have caused small amounts of the product to evaporate off as it a low melting point solid, if the water bath temperature was too high would have caused to melt and evaporate off. As melting point was not measured was unable to tell whether the product is pure.
Rf is equal to the distance traveled by the substance divided by the distance traveled by the solvent. Since the solvent used in the developing chamber was hexanes—a non-polar molecule— the more nonpolar the substance was, the stronger it would stick to the plate. This means that the more polar a pigment was, the higher it climbed on the TLC plate and would therefore have a larger Rf. There are 3 major classes of pigments present in spinach: carotenes, xanthophylls, and chlorophylls. Since the solvent is nonpolar, we would expect carotene to have the lowest Rf, then xanthophylls, and chlorophylls would have the highest.
The experiment consisted of four main parts and in each part given acids and bases were different compared to previous one in terms of their strengths and weakness. In each reaction between the different type of acid and base we had unknown variables and to identify one of them the graph which represented dependence of pH of mixture on added substance was plotted. This graph allowed us to find out the volume of added substance in the equilibrium point. the equilibrium point of reaction is the point where the amount of base added was exactly the correct amount to have the moles of base completely react with the moles of acid and pH becomes 7 which represents neutralized environment. Since there is a 1:1 stoichiometry in the chemical reaction, as we know that for every one molecule of base that was needed to react with one molecule of acid.
Abstract The experiment was performed in order to compare the effectiveness of Simple and Fractional distillation in separation of solid impurities from liquid and liquids with difference in boiling point higher than 25⁰C. The distillation curves of both processes were graphed on each case and compared. The main source of possible error was discussed and the way to improve the experimental procedure was proposed. It was concluded that the Fractional distillation is more efficient procedure than Simple distillation in liquid separation. However, in case of separation of solid impurities from liquid or liquids with high difference in boiling points Simple distillation can be preferred.