Exp266

=media type="custom" key="9944269"= =Researcher= Evan Curtin and Jean-Claude Bradley =Objective= To determine the melting point of [|4-benzyltoluene] to clarify [|discrepancies in melting point data]. =Procedure= The sample of a few grams in a sealed bottle or tube was frozen then allowed to warm back up and an attempt to measure the melting point from the appearance of the sample was made. =Results= Pic1 showing the bottle as received with 10g of 4-benzyltoluene Pic2 showing the sealed bottle about to enter the 0C ice bath Pic3 showing the sealed bottle with frozen contents and bath temp at -18C Pic4 showing the tube with frozen sample and internal thermometer allowed to heat up Pic5 showing the sample frozen at -14C after 16 days in freezer Pic6 showing the still frozen sample in an ice water bath

media type="custom" key="9865711" =Discussion= Allowing the sample to warm to room temperature after freezing gave inconclusive results. Instead of a plateau at the melting point, the sample appeared to melt as low as about -10C but solid was still present at +7C. Failure to solidify after 2 days at -15C suggested that the melting point should be below this value. However, after 16 days the sample did freeze and slow warming identified the melting point at about 4-6C. An H NMR of the sample was consistent with the reported purity >98%. It was also consistent with the H NMR reported for compound 3b in ([|Manih2008] ). This compound was reported as yellow crystals melting at 97-98 C in that reference. =Conclusion= After 2 days in the freezer the sample remains unfrozen at -15C. However, after 16 days the sample was found frozen at -14C. Immersion in an ice bath and very slow heating over a few hours revealed that complete melting happened at 4-6 C. =Log=
 * HNMR of Sample**
 * [Also take C NMR at some point to compare with above ref JCB]**

2011-06-03
11:20 - Removed 4-benzyltoluene container from package, observed that it is a liquid at room temperature (25C) - pic 1 11:31 - Wrapped in parafilm, put in 0C bath. - pic 2 11:34 - No change in viscosity of the sample 11:52 - Moved sample to an acetone bath, slowly added dry ice. Sample was not frozen at -5C (bath temperature) 12:00 - unclear when sample froze but after letting heat up to -18C sample still frozen - pic 3 12:10 - Transferred ~2mL of sample into a test tube, put thermometer into the sample directly, wrapped the open end of the tube with parafilm (around the thermometer). 12:20 - Froze the sample inside the test tube, this happened completely around -30 to -35C. Removed from bath, observed as the sample warmed. Sample warmed too quickly to get accurate data. 12:41 started pic4 series of 6 about one per minute 12:51 - Froze sample again inside the test tube, observed some freezing around 0C. Let sample warm inside an acetone/dry ice bath. Sample was solid at -11C. Sample started melting at -9C. Over time, the sample melted, but the temperatures continued to rise.

2011-06-06
11:00 put the sample in freezer 12:00 sample still liquid with internal thermometer reading of -15C

2011-06-08
9:00 sample in freezer after 2 days still a liquid and not viscous - internal thermometer reading of -15C

2011-06-22
11:55 - Sample in freezer is solid, internal temperature reading -14C. 11:56 - Took pic5 showing frozen sample 11:58 - Put sample in ice/water bath. Temperature of bath -1C internal temperature 2C 11:59 - Took pic6 showing still frozen sample at internal temperature 2C 12:04 - Internal temperature 2C, external temperature -1C 12:20 - Internal temperature 2.5C, external temperature 0C, sample is solid. 12:47 - Internal temperature 3C, external temperature 0C, sample is solid. 13:10 - Internal temperature 3C, external temperature 0C, sample still solid. 13:55 - Internal temp 3C external temp 0C. Sample solid. 14:05 - internal temp 4C external temp 0c some liquid formed. 14:14 - internal temp 4C external temp 0C some liquid, mostly solid in the sample. 14:43 - internal temp 4C external temp 0C some liquid, mostly solid in the sample. 14:54 - internal temp 5C external temp 0C. Slightly more liquid formed in the sample, but most of the sample is solid. 15:12 - Internal temp 5C external temp 3C. More liquid formed, still mostly solid. 15:19 - Internal temp 5.5C External temp 4C. The sample is roughly half liquid and half solid. 15:22 - Internal temp 6C, external temp 4C. The sample is nearly all liquid. 15:23 - Internal temp 6.5C. External temp 5C. The sample is completely melted.

2011-06-23
11:36 - Mixed some of the sample with CDCl3, put in NMR tube. 12:53 - Took HNMR spectra using 300MHz varian NMR.