Ammonia → Phthalide
Reaction equation
N.[C:2]1([CH3:11])[C:3]([C:8]([OH:10])=[O:9])=[CH:4][CH:5]=[CH:6][CH:7]=1>>[C:2]1([CH3:11])[C:3]([C:8]([OH:10])=[O:9])=[CH:4][CH:5]=[CH:6][CH:7]=1.[C:8]1([C:3]2[C:2](=[CH:7][CH:6]=[CH:5][CH:4]=2)[CH2:11][O:10]1)=[O:9]Participants
Procedure
Next, the ammonia-treated crude o-toluic acid is subjected to fractionation so as to separate pure o-toluic acid from high boiling point components such as o-phthalimide, phthalide, etc. As to the fractionator, a packed column or a plate column having 10 ore more theoretical plates can be used. Preferably, a plate column or a packed column having 10 to 30 theoretical plates is used as the fractionator and operated at 100 to 300 Torr., preferably 150 to 250 Torr., and a reflux ratio of about 3 to 20. If the pressure is smaller than 100 Torr., an azeotrope of o-toluic acid and phthalide is produced, thus impairing the purity of o-toluic acid. A higher pressure elevates the bottom temperature of the fractionator, in which case o-toluic acid tends to decompose or polymerize. The fractionator should, therefore, be operated at the bottom temperature of lower than 250° C. Crude o-toluic acid treated with ammonia is fed to the fractionator at a point below the middle of the column and where at least two, preferably three, theoretical plates are allocated for the stripping section. For example, when a distillation column with 30 theoretical plates is used, it is preferable to allocate 3 to 7 theoretical plates in the stripping section.
Workup
- customto separate pure o-toluic acid from high boiling point components such as o-phthalimide, phthalide, etc. As to the fractionator
Sources & evidence
- ORD record
- ord-9e3473c00d644139b527632d45fb9c68
- Source dataset
- uspto-grants-1991_04
- Patent number
- US05011987
Reaction notes
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