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Solubility book (3rd Edn)
Purify cinnamic acid by recrsyalizing from hexane then determine solublity by NMR of cinnamioc acid in boiling hexane. Purifying the solute will determine if the low recrystallization yield in
was due to an impurity or not.
About 3 grams of cinnamic acid and 100mL of hexane were added into an Erlenmeyer flask and put on hot plate until the contents of the flask were boiling. The boiling liquid was transferred to a NMR tube (tried to avoid getting any solid into the vial at first) and an NMR was taken of the cinnamic acid in hexane. The supernatant that was formed in the flask was transferred into a flattened round-bottom flask until crystals formed.
According to the NMR, the solubility of the cinnamic acid in boiling hexane is 0.128M
Characterization of 291A
amount: 0.3808g was obtained.
appearance: white crystals.
showed trace amounts of hexane, which was not desired but the amount that was detected should not affect the results of the recrystallization done in
H NMR: (
MHz, CDCl3, δ, ppm) 6.447 (d, J=16) 6.479 (d, J=16)
The recrystallization had to be repeated because
gave a yield that was approximately 65%.
A solubility of 0.16M was calculated from
and now that result seems more likely than before due to the NMR reading.
If the solubility of 0.13M is correct, the yield of cinnamic acid from hexane should be approximately 85%.
After taking the NMR of the cinnamic acid in boiling hexane, the calculation showed that the solubility is 0.13M
hot plate to 200C
12:08 - Added 3.0075g trans-cinnamic acid into 125mL Erlenmeyer flask
12:12 - Added approximately 100mL n-hexane into same Erlenmeyer flask and set on hot plate
12:20 - turned down hot plate to 140C to prevent the contents of flask from evaporating
12:31 - Added approximately 0.7mL CDCl3 into a one dram vial
12:35 - titurated solution with a pipette in the Erlenmeyer flask then transferred approximately 200microLiters of supernatant into the vial
12:37 - transferred contents of vial into NMR tube
12:38 - Poured supernatant of erlenmeyer flask into a flattened round-bottom flask
12:43 - crystals formed inside the flattened round-bottom flask.
12:49 - Took NMR of cinnamic acid in hexane
11:44 - filtered the purified cinnamic acid crystals in hexane via the suction method
11:46 - mass of empty vial 11.7688g
11:55 - Added the purified cinnamic acid into the vial
12:02 - mass of vial with pure cinnamic acid 12.1496g
12:03 - total cinnamic acid in vial 0.3808g (291A)
12:16 - put small amount of cinnamic acid and CDCl3 into small vial
12:18 - transferred contents of vial into NMR tube
12:40 - took NMR of the cinnamic acid and found trace amounts of hexane in the purified crystals
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