JennyHale-16

Measuring the solubility of 8-bromo-octanoic acid in ethanol, methanol and THF
This solubility was originally attempted in an earlier experiment but I ran out of solid.

Method
Three 2 mL screw cap vials were taken and labelled with their planned contents. Three 1.6 mL microcentrifuge tubes were labelled with the planned contents and the masses recorded. 300 μL of each solvent was added to it's respectively labelled vial. Narrow spatula scoops of 8-bromo-octanoic acid were added to the ethanol and the solution vortexed in 10 second intervals until the solution became saturated. The compound is particularly soluble and so the preparation of solutions in methanol and THF was abandoned due to the amount of solid available. //[Do you think Sigma-Aldrich would sponsor me about 5-10 g of this compound so I can complete the measurements in methanol and THF? - JH]// The saturated solution was centrifuged for 1 minute at 13 200 rpm/16 100 rcf in an Eppendorf 5415D centrifuge. 200 μL supernatant was transferred to it's respectively labelled eppendorf. The solution was dried by speedvac initially for 3 hours. At this point the sample was still liquid and was returned to speedvac for a further hour after measuring the mass. After that hour, the sample was still liquid and had lost less than 1 mg in mass. The sample was returned to speedvac. It seems possible that the sample has become too warm to solidify as it has a low melting point. If it is failing to solidify, I will try putting it in the fridge. I anticipate that all the ethanol has evaporated and it is just liquid 8-bromo-octanoic acid remaining.**[Yes it does not take much solvent to lower the m.p. of compounds with m.p. close to room temp. I would trust the evaporation to constant weight. My main concern for this compound is that it is a primary alkyl halide and may react with nucleophilic solvents like methanol and ethanol. If you can take an NMR of the remaining solid that would resolve the issue. You might be able to do it by TLC also. JCB]** The sample was placed in the freezer for 20 minutes and became a white solid. This was returned to speedvac for 10 minutes.

Results
The results can be found in the spreadsheet [|JennyHale-16]

Discussion
The result of the solubility measurement was 4.39 M. I had anticipated the solubility being a lot higher from the amount of solid I was able to add to make a saturated solution. However if there had been a reaction between the alkyl halide and the solvent then that may explain the result. A check by TLC or NMR would confirm what the product is. I will try and get a TLC done and see if I can get an NMR run.

Log
03.03.09 Tuesday Lab clock has broken as has my watch, so accurate times could not be recorded. This is just the oder of work and vortex times were counted in my head. 300 μL solvent added to vials 4 Narrow spatula scoopfuls added to ethanol. Sample vortexed for 40 seconds in 10 second intervals. 4 Narrow spatula scoopfuls added to ethanol. Sample vortexed for 40 seconds in 10 second intervals. 2 Narrow spatula scoopfuls added to ethanol. Sample vortexed for 50 seconds in 10 second intervals. 2 Narrow spatula scoopfuls added to ethanol. Sample vortexed for 30 seconds in 10 second intervals. 2 Narrow spatula scoopfuls added to ethanol. Sample vortexed for 40 seconds in 10 second intervals. 2 Narrow spatula scoopfuls added to ethanol. Sample vortexed for 1 minute in 10 second intervals. 2 Narrow spatula scoopfuls added to ethanol. Sample vortexed for 1.5 minutes in 10 second intervals. 2 Narrow spatula scoopfuls added to ethanol. Sample vortexed for 1.5 minutes in 10 second intervals. 2 Narrow spatula scoopfuls added to ethanol. Sample vortexed for 2 minutes in 10 second intervals. Left to stand for a few minutes and found to be saturated on return. Centrifuged for 1 minute Transferred 200 μL supernatant to Eppendorf. Placed on speedvac to dry.