Cyclohexanone L-ascorbic acid ketal is synthesized from the reaction of L-isoascorbic acid and cyclohexanone with p-toluene sulfonic acid as catalyst,N,N-dimethyl acetamide(DMAc) as solvent and cyclohexane as water carrying agent.The optimal reaction conditions determined by orthogonal experiment are as follows:L-ascorbic acid 1.76 g(10 mmol),cyclohexanone 1.57 g(16 mmol),p-toluene sulfonic acid 0.38 g(2 mmol),DMAc 6 mL,cyclohexane 9 mL,reaction temperature 120～125℃ and reation time 2.5 h.The yield is 85.8% under these optimal conditions.The title compound is characterized by 1H NMR,FTIR and EI-MS.
Ascorbyl octyl aldehyde acetals are prepared from the reaction of ascorbic acid with octyl aldehyde using p-toluene sulfonic acid as catalyst,dimethyl acetamide as solvent,cyclohexane as dehydration agent. The acetals are obtained as a mixt. of two diastereomers(ratio,0.46∶0.54) based on the results of 1H-NMR spectroscopic analysis. The antioxidation activity of ascorbyl octyl aldehyde acetals in fresh tea seed oil is evaluated by peroxide value(POV) determination. The POV data show that ascorbyl octyl aldehyde acetals exhibits signifcant dose-effect relationship. The antioxidation activity of ascorbyl octyl aldehyde acetals is stronger than that of VC or PG but weaker than that of TBHQ,when their amount in fresh tea seed oil is respectively added according to the maximum allowed concentration as food additives in China.
