The reaction mechanism of o-aminophenol, acetic acid and phosphorus oxytrichloride in one-pot to form 2-methyl benzoxazole was studied by density functional theory. The geometries of the reactants, transition states, ...The reaction mechanism of o-aminophenol, acetic acid and phosphorus oxytrichloride in one-pot to form 2-methyl benzoxazole was studied by density functional theory. The geometries of the reactants, transition states, intermediates and products were optimized at the GGA/PW91/DNP level. Vibration analysis was carried out to confirm the transition state structure. Two possible reaction pathways were investigated in this study. The result indicates that the reaction Re→TS1→IM1→TSA2→IMA2→TSA3→IMA3→TSA4→IMA4→TSA5→P2 is the main pathway, the activation energy of which is the lowest. Re→TS1→IM1 is the rate-limiting step, with the activation energy being 221.54 kJ·mol^(-1) and the reaction heat being 10.06 kJ·mol^(-1). The dominant product predicted theoretically is in agreement with the experiment results.展开更多
目的系统评价我国学龄前儿童忽视状况,为预防和控制儿童忽视的发生提供参考。方法检索CNKI、CBM,VIP、万方、PubMed、Embase和Web of Science等中英文数据库公开发表的关于我国学龄前儿童忽视状况的相关文献。应用CMA V3.0软件进行Meta...目的系统评价我国学龄前儿童忽视状况,为预防和控制儿童忽视的发生提供参考。方法检索CNKI、CBM,VIP、万方、PubMed、Embase和Web of Science等中英文数据库公开发表的关于我国学龄前儿童忽视状况的相关文献。应用CMA V3.0软件进行Meta分析,按照性别、地区、城乡、时间段进行亚组分析。结果共纳入25篇文献,总样本量为39498人。Meta分析结果显示,我国学龄前儿童忽视率为36.36%(95%CI:31.78%~40.93%)。亚组分析结果显示:儿童忽视率中男童(34.78%)高于女童(32.12%);北方地区(37.56%)高于南方地区(31.68%);2015—2018年(48.74%)高于2011—2014年(42.33%)与2008—2010年(34.54%);农村(47.92%)高于城市(30.49%),差异有统计学意义(Q=38.418,P<0.01)。结论我国学龄前儿童忽视状况不容乐观,家庭、学校、社会应共同关注儿童忽视问题,对学龄前儿童给予足够重视,切实维护儿童身心健康。展开更多
基金Supported by the Scientific and Technological Research Program of Chongqing Municipal Education Commission(KJ1601215)the Ministry of Education "Chunhui Plan"(Z2016177)
文摘The reaction mechanism of o-aminophenol, acetic acid and phosphorus oxytrichloride in one-pot to form 2-methyl benzoxazole was studied by density functional theory. The geometries of the reactants, transition states, intermediates and products were optimized at the GGA/PW91/DNP level. Vibration analysis was carried out to confirm the transition state structure. Two possible reaction pathways were investigated in this study. The result indicates that the reaction Re→TS1→IM1→TSA2→IMA2→TSA3→IMA3→TSA4→IMA4→TSA5→P2 is the main pathway, the activation energy of which is the lowest. Re→TS1→IM1 is the rate-limiting step, with the activation energy being 221.54 kJ·mol^(-1) and the reaction heat being 10.06 kJ·mol^(-1). The dominant product predicted theoretically is in agreement with the experiment results.
文摘目的系统评价我国学龄前儿童忽视状况,为预防和控制儿童忽视的发生提供参考。方法检索CNKI、CBM,VIP、万方、PubMed、Embase和Web of Science等中英文数据库公开发表的关于我国学龄前儿童忽视状况的相关文献。应用CMA V3.0软件进行Meta分析,按照性别、地区、城乡、时间段进行亚组分析。结果共纳入25篇文献,总样本量为39498人。Meta分析结果显示,我国学龄前儿童忽视率为36.36%(95%CI:31.78%~40.93%)。亚组分析结果显示:儿童忽视率中男童(34.78%)高于女童(32.12%);北方地区(37.56%)高于南方地区(31.68%);2015—2018年(48.74%)高于2011—2014年(42.33%)与2008—2010年(34.54%);农村(47.92%)高于城市(30.49%),差异有统计学意义(Q=38.418,P<0.01)。结论我国学龄前儿童忽视状况不容乐观,家庭、学校、社会应共同关注儿童忽视问题,对学龄前儿童给予足够重视,切实维护儿童身心健康。
