...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Physical chemistry chemical physics: PCCP >Dimerisation of nitrile oxides: a quantum-chemical study
【24h】

Dimerisation of nitrile oxides: a quantum-chemical study

机译：丁腈氧化物的二聚化：量子化学研究

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

The [3 + 2] and [3 + 3] cyclodimerisation processes of small nitrile oxides, XCNO (X = F, Cl, Br, CN, CH3) are investigated by ab initio coupled cluster theory at the CCSD, CCSD(T) and MR-AQCC levels for the first time. The favoured dimerisation process is a multi-step reaction to furoxans (1,2,5-oxadiazole-2-oxides) involving dinitrosoalkene-like intermediates with diradical character. The rate determining step for all but the F-species is the first, corresponding to the C-C bond formation. The kinetic energy barrier depends on the nature of the substituent X, generally increasing with decreasing electronegativity and increasing 7t-donor ability of the substituent: F (ΔG_(298) = 0 kJ mol~(-1)) < Cl (72) < Br (90) < CH3 (104) < CN (114) (MR-AQCC(2,2)//UB3LYP/cc-pVTZ). Following initial C-C bond formation, three possible dinitrosoethylene diradical pathways are explored. Two of them are new, and one of them is a low-energy three-step path with implications for cycloreversion, tautomerism and detection of dinitrosoethylene intermediates. Alternative one-step, concerted [3 + 2] and [3 + 3] cyclodimerisation processes leading to l,2,4-oxadiazole-4-oxides and 1,4,2,5-dioxadiazines have kinetic energy barriers around 100-240 kJ mol~(-1) (CCSD//B3LYP), some 1.6 to 2.5 times higher than those leading to furoxans, supporting the experimental observations of furoxan formation as nitrile oxide loss channels during storage, trapping/re-vaporisation and reactions of nitrile oxides. Potential polymerisation initiation processes for NCCNO, involving the 1,2-dipolar NC substituent are also explored.
机译：在CCSD，CCSD（T）和CCSD上从头算耦合簇理论研究了小型腈氧化物XCNO（X = F，Cl，Br，CN，CH3）的[3 + 2]和[3 + 3]环二聚过程。 MR-AQCC首次达到水平。有利的二聚过程是对呋喃喃类化合物（1,2,5-恶二唑-2-氧化物）的多步反应，涉及具有二自由基特征的类似二亚硝基烯烃的中间体。除F物种外，所有其他物种的速率确定步骤都是第一步骤，对应于C-C键的形成。动能势垒取决于取代基X的性质，通常随着电负性的降低和取代基7t供体能力的增加而增加：F（ΔG_（298）= 0 kJ mol〜（-1））

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号