Preparation Of SO₃H-functionalized Ionic Liquid And Its Catalytic Synthesis Of Borneol From Turpentine

Turpentine resources is rich in China,and?-pinene is the main component of turpentine and the main active component of turpentine reaction.After deep processing of turpentine oil,many high value-added products can be obtained,and borneol is one of them.Borneol has a wide range of applications in medicine,flavors and fragrances,and cosmetics industries.Borneol is a pair of isomers.Borneol is more widely demanded on the market due to its excellent aroma.At present,the most widely used and most mature method to synthesize borneol is?-pinene esterification-saponification to synthesize borneol.Commonly used catalysts include boron,titanium,boron-titanium composite,solid super acid and so on.With the deepening of process research,the yield of borneol has been greatly improved,but the quality score of borneol is still low.Therefore,the research and development of a catalyst for the highly selective synthesis of borneol is of higher value for the subsequent production of borneol.Functionalized ionic liquids have a wide range of applications in organic synthesis as green solvents and catalysts.In this paper,nine different SO₃H-functionalized ionic liquids were prepared by a two-step method,which were directly used as catalysts in the study of turpentine esterification and saponification to synthesize borneol.(1)Nine ionic liquids[MIMBs]PTSA?[MIMBs]BF₄?[MIMBs]H₂PO₄?[MIMBs]HSO₄?[EIMBs]HSO₄?[PIMBs]HSO₄?[BIMBs]HSO₄?[Net₃B-SO₃H]HSO₄?[Bpy-SO₃H]HSO₄were prepared by a two-step method.The turpentine esterification-saponification reaction was used as a probe reaction to investigate the effect of ionic liquids on the synthesis of borneol.When the cations are the same,[MIMBs]HSO₄has the best selectivity for total borneol and normal borneol.When the anions are the same,[BIMBs]HSO₄has the best selectivity for total borneol and normal borneol.(2)[MIMBs]HSO₄was used to catalyze the reaction of turpentine esterification-saponification to synthesize Borneol,and the process conditions were optimized through single factor experiment and orthogonal experiment.The optimum process conditions are as follows:the amount of cyclohexane is 35 m L,the reaction temperature is 120?,the amount of catalyst is 6%of the mass of turpentine,the ratio of alkenoic acid is 1:2,and the reaction time is 9 h.At this time,the conversion rate was 100%,the selectivity of borneol was 45.13%,and the mass fraction of borneol was91.29%.The recurrence experiment and the catalyst life inspection are carried out under the optimized process of the orthogonal experiment,and the catalyst can be reused three times.With[BIMBs]HSO₄as the catalyst,the optimal process conditions are obtained through single factor and response surface optimization.The amount of cyclohexane is 40 m L,the reaction time is 9 h,the reaction temperature is 120?,the amount of catalyst is 8%of the mass of turpentine,and the ratio of enoic acid is 1:4.At this time,the conversion rate was 100%,the selectivity of borneol was47.21%.Under the response surface optimization process,the reproducibility experiment and the catalyst life inspection are carried out,and the catalyst can be reused three times.(3)The structure and acidity of the above-mentioned ionic liquids were studied by FT-IR,¹H NMR,¹³C NMR,TG,Hammett.The acidity of the ionic liquid has a great influence on its catalytic performance.The higher the acidity,the better the catalytic effect on the esterification-saponification of turpentine oil to synthesize bornhole.When the cations are the same,the acidity of the ionic liquid is related to the acidity of the anion source.When the anions are the same,explore the effect of imidazoles,pyridines,and quaternary ammonium salt ionic liquids on the synthesis of borneol.The main reason that affects the acidity of imidazoles,pyridines,and quaternary ammonium salt ionic liquids is the different types of hydrogen bonds in the three.