Dai Xiaoxuan Identification of an organic solid 1. Through the analysis for the melting point of sample 313, it was determined that the range for this sample to melt was between 131.5 degrees Celsius and 132.0 degrees Celsius. Upon observation, only two other samples had similar range of melting points those being sample 466, belonging to Rahul and having a melting point range between 129.5 degrees Celsius and 133.0 degrees Celsius, and sample 396, belonging to Margaux and having a melting point range between 129.0 degrees Celsius and 133.3 degrees Celsius. The TLC results also showed high similarity. In both trials, my sample rose about 0.7 centimeters and had a retention factor of about 0.14. The other samples had moved around 0.5 centimeters and had a retention factor of about 0.1. The co-spotted solution moved about 0.4 centimeters and had a retention factor of about 0.8. The mixed melting point analysis yielded results very close to that of the pure compound. The melting point range of the 313 and 466 mixture was between 130.5 degrees Celsius and 132.5 degrees Celsius and that of the mixture between 313 and 396 was between 130.5 degrees Celsius and 132.0 degrees Celsius. This data suggests that the compound is trans-cinnamic acid, which is an organic acid with a benzene ring attached to an ethene group, which is in turn attached to a carboxylic acid group:
2. From Sigma Aldrich, the best price for trans-cinnamic acid is item number W228818 which sells 25 kilograms for 887.00 dollars meaning it sells for 0.04 dollars per gram of acid, which is the best price. Some other information provided include a picture of its molecular structure as described above, a synonym for the acid being trans-3-Phenylacrylic acid, its empirical formula being C9H8O2, its molecular weight being 148.16 grams and its CAS (Chemical Abstracts Service) number, the specific number assigned to a compound used for easy identification purposes for all chemicals in chemical literature, being 140-10-3. 3. I would use ethyl acetate as a developing solvent to obtain more useful information in the next trial because both hexane and dichloromethane are not very polar solutes and since the retention factor is only 0.05, his means that the solute is quite polar a so more polar solvent might yield a better movement and ethyl acetate is quite polar. 4. MSDS stands for Material Safety Data Sheet, which is essentially a data sheet that gives all the pertinent information and properties of a particular substance so that it may be used properly. These exist to catalog substances and to include safe use for the substance as well as possible hazards. Toxicity is measured in relative to milligram of the substance per kilogram of the user's bodyweight and the effects on the user. The toxicity also varies whether the substance is orally ingested, applied to the skin, inhaled as dust, inhaled as vapor, or inhaled as gas. The MSDS also provides toxicity for other animals in addition to humans. Acetaminophen's lowest lethal dose to humans when ingested orally is 143 mg/kg
whereas benzoic acid's is 500 mg/kg meaning that it takes more benzoic acid than acetaminophen to kill a human. 5. A.
B. Diphenymethane is in the first lane because it is the less polar compound of the two. The more polar a solute is, the less it will travel when using a nonpolar developing solvent. If a polar developing solvent was used, the other would be in the first lane C. a) No b) No c) Yes d) No e) No
D. Since silica gel is polar, the more polar solute (the diphenylmethanol) will bind to it strongly unless a very polar developing solvent is used where the more polar solute will be found in the mobile phase if that is the case. E. Diethyl ether is fairly nonpolar. In order to make the spots move less, use an even less polar dissolving solvent like hexane or dichloromethane. F. First you dissolve your samples in dichloromethane. Then prepare the TLC plate by noting the starting lane. Than spot the samples in their own lanes your and co-spot them in a third lane prepare the developing chamber with developing solvent an a wick. Place the TLC plate into the chamber and wait until the solvent reaches about 1 centimeter from the top. Remove the plate and observe under UV. 6. A. Unless human error was involved, the three compound are all different. If there was error in melting point determination, 1 and 2 are most likely the same. If there was error in TLC, then 2 and 3 are most likely the same. B. a: 92-98 degrees celsius