以三甲胺硼烷为反应底物,通过两步法,合成了以不同烃基侧链咪唑硼烷为阳离子,二氰胺根和硝基氰胺根为阴离子的系列离子液体。采用1H和13C核磁、红外及高分辨质谱等表征方法,确认了所得离子液体的结构和组成,并测定计算了其性质。结果表...以三甲胺硼烷为反应底物,通过两步法,合成了以不同烃基侧链咪唑硼烷为阳离子,二氰胺根和硝基氰胺根为阴离子的系列离子液体。采用1H和13C核磁、红外及高分辨质谱等表征方法,确认了所得离子液体的结构和组成,并测定计算了其性质。结果表明：所得离子液体的分解温度均高于150℃,密度为1.04~1.27 g·cm-3,比冲为173.8~202.1 s。随着咪唑阳离子烃基侧链的增长,相应离子液体的密度减小,生成焓增大。二氰胺类离子液体同相应的硝基氰胺类离子液体相比,具有更短的点火延迟时间。其中,双烯丙基咪唑硼烷二氰胺离子液体具有良好的综合性能（粘度69 m Pa·s,分解温度180℃,生成焓753.6 k J·mol-1,点火延迟时间18 ms,比冲176.7 s）,有望作为一种绿色燃料应用于双组元液体自燃推进剂。展开更多
Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity a...Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity and selectivity of rare-earth compounds along with no residual impact on polymer product's performance,highly efficient catalytic reduction systems containing sodium borohydride(NaBH_(4))and rare-earth chloride(RECl_(3))were specifically designed for a telechelic carboxyl-terminated liquid fluoroeslastomer,aiming to facilitate the conversion of chainend carboxyl groups into hydroxyl groups and improvement in end-group reactivity.To achieve this,lanthanum chloride(LaCl_(3)),cerium chloride(CeCl_(3)),and neodymium chloride(NdCl_(3))were used separately to form catalytic reduction systems with NaBH_(4).The effects of solvent dosage,reaction temperature,reaction time length,and reductant dosage on carboxylic conversion were investigated,and the molecular chain structure,molecular weight,and functional group content of the raw materials and the products were analyzed and characterized by means of infrared spectroscopy(FTIR),proton nuclear magnetic resonance(^(1)H-NMR),fluorine-19 nuclear magnetic resonance(^(19)F-NMR),gel permeation chromatography(GPC),and chemical titration.Moreover,the catalytic activity and selectivity of the rare-earth chlorides,as well as the corresponding underlying interactions were discussed.Results indicated that the rare-earth-containing catalytic reduction systems studied in this work could efficiently convert the chain-end carboxyl groups into highly active hydroxyl groups,with a highest conversion up to 87.0%and differing catalytic reduction activities ranked as NaBH_(4)/CeCl_(3)>NaBH_(4)/LaCl_(3)>NaBH_(4)/NdCl_(3).Compared with the conventional lithium aluminum hydride(LiAIH_(4))reduction system,the NaBH_(4)/RECl_(3)systems provide multiple advantages such as mild reaction conditions,high conversion ratio with good selectivity,and environmental innocuity,and are potentially applicable as new reduction-catalysis combinations for the synthesis and functionalization of polymer materials.展开更多
看似简单实际却很复杂的乙硼烷(B_(2)H_(6),diborane)与氨(NH_(3))的反应已经困扰了硼化学家数十年。该反应在不同实验条件下可生成硼氢化二氢二氨合硼(III)([NH_(3)BH_(2)NH_(3)]BH_(4),diammoniate of diborane,DADB),氨硼烷(NH_(3)&#...看似简单实际却很复杂的乙硼烷(B_(2)H_(6),diborane)与氨(NH_(3))的反应已经困扰了硼化学家数十年。该反应在不同实验条件下可生成硼氢化二氢二氨合硼(III)([NH_(3)BH_(2)NH_(3)]BH_(4),diammoniate of diborane,DADB),氨硼烷(NH_(3)·BH_(3),ammonia borane,AB),氨基乙硼烷(NH_(2)B_(2)H_(5),aminodiborane,ADB)等化合物。从1923年起,化学家们对影响乙硼烷与路易斯碱反应的因素,如立体效应、诱导效应、溶剂效应、介电常数等进行研究,但一直无法根据上述影响因素准确预测产物。基于乙硼烷在THF中以THF·BH_(3)存在、路易斯碱与乙硼烷或THF·BH_(3)反应产物相同等实验事实,化学家们巧妙利用NH_(3)与THF·BH_(3)的反应,在温和的条件下研究了DADB、AB的生成机理,发现双氢键是控制反应的重要因素。利用AB与THF·BH_(3)的反应,实验和理论计算结果进一步揭示了基于双氢键的ADB的复杂形成机理。展开更多
文摘以三甲胺硼烷为反应底物,通过两步法,合成了以不同烃基侧链咪唑硼烷为阳离子,二氰胺根和硝基氰胺根为阴离子的系列离子液体。采用1H和13C核磁、红外及高分辨质谱等表征方法,确认了所得离子液体的结构和组成,并测定计算了其性质。结果表明：所得离子液体的分解温度均高于150℃,密度为1.04~1.27 g·cm-3,比冲为173.8~202.1 s。随着咪唑阳离子烃基侧链的增长,相应离子液体的密度减小,生成焓增大。二氰胺类离子液体同相应的硝基氰胺类离子液体相比,具有更短的点火延迟时间。其中,双烯丙基咪唑硼烷二氰胺离子液体具有良好的综合性能（粘度69 m Pa·s,分解温度180℃,生成焓753.6 k J·mol-1,点火延迟时间18 ms,比冲176.7 s）,有望作为一种绿色燃料应用于双组元液体自燃推进剂。
文摘Herein the use of rare-earth compounds in catalytic reduction systems for the end-group functionalization of carboxyl-terminated low-molecularweight fluoropolymers was explored.Leveraging the high catalytic activity and selectivity of rare-earth compounds along with no residual impact on polymer product's performance,highly efficient catalytic reduction systems containing sodium borohydride(NaBH_(4))and rare-earth chloride(RECl_(3))were specifically designed for a telechelic carboxyl-terminated liquid fluoroeslastomer,aiming to facilitate the conversion of chainend carboxyl groups into hydroxyl groups and improvement in end-group reactivity.To achieve this,lanthanum chloride(LaCl_(3)),cerium chloride(CeCl_(3)),and neodymium chloride(NdCl_(3))were used separately to form catalytic reduction systems with NaBH_(4).The effects of solvent dosage,reaction temperature,reaction time length,and reductant dosage on carboxylic conversion were investigated,and the molecular chain structure,molecular weight,and functional group content of the raw materials and the products were analyzed and characterized by means of infrared spectroscopy(FTIR),proton nuclear magnetic resonance(^(1)H-NMR),fluorine-19 nuclear magnetic resonance(^(19)F-NMR),gel permeation chromatography(GPC),and chemical titration.Moreover,the catalytic activity and selectivity of the rare-earth chlorides,as well as the corresponding underlying interactions were discussed.Results indicated that the rare-earth-containing catalytic reduction systems studied in this work could efficiently convert the chain-end carboxyl groups into highly active hydroxyl groups,with a highest conversion up to 87.0%and differing catalytic reduction activities ranked as NaBH_(4)/CeCl_(3)>NaBH_(4)/LaCl_(3)>NaBH_(4)/NdCl_(3).Compared with the conventional lithium aluminum hydride(LiAIH_(4))reduction system,the NaBH_(4)/RECl_(3)systems provide multiple advantages such as mild reaction conditions,high conversion ratio with good selectivity,and environmental innocuity,and are potentially applicable as new reduction-catalysis combinations for the synthesis and functionalization of polymer materials.
文摘看似简单实际却很复杂的乙硼烷(B_(2)H_(6),diborane)与氨(NH_(3))的反应已经困扰了硼化学家数十年。该反应在不同实验条件下可生成硼氢化二氢二氨合硼(III)([NH_(3)BH_(2)NH_(3)]BH_(4),diammoniate of diborane,DADB),氨硼烷(NH_(3)·BH_(3),ammonia borane,AB),氨基乙硼烷(NH_(2)B_(2)H_(5),aminodiborane,ADB)等化合物。从1923年起,化学家们对影响乙硼烷与路易斯碱反应的因素,如立体效应、诱导效应、溶剂效应、介电常数等进行研究,但一直无法根据上述影响因素准确预测产物。基于乙硼烷在THF中以THF·BH_(3)存在、路易斯碱与乙硼烷或THF·BH_(3)反应产物相同等实验事实,化学家们巧妙利用NH_(3)与THF·BH_(3)的反应,在温和的条件下研究了DADB、AB的生成机理,发现双氢键是控制反应的重要因素。利用AB与THF·BH_(3)的反应,实验和理论计算结果进一步揭示了基于双氢键的ADB的复杂形成机理。
