Hydration of nitriles: an examination in terms of No Barrier Theory

Nitriles pose an interesting problem to the explanatory powers of organic chemistry because, despite the favorable overall thermodynamics of hydrolysis to the corresponding amides, the reactions are inherently slow. The rate determining step is hydration of the nitrile to give the imidic acid, which quickly tautomerizes to the amide. In terms of Marcus Theory, the intrinsic barriers for acid and base‐catalyzed hydration are higher for nitriles than for amides, which are themselves slow reactions. It is remarkable that hydration of a nitrile, for which the free energy change is close to zero except for polyhaloacetonitriles, is much slower than hydration of an amide, which is energetically unfavorable. This can be explained by No Barrier Theory in terms of the high energetic cost of the geometrical distortions in “one thing at a time” corner species. There are no experimental equilibrium constants for this initial hydration step, so we have determined them computationally. The free energy change for the initial hydration is small; it is the fast and energetically downhill second step, tautomerization to the amide, which makes the overall hydrolysis of nitrile to amide thermodynamically favorable. Very few of the pK_a values needed in the acid and base‐catalyzed mechanisms are known, so we used linear free energy relations and treat the parent pK_a values as adjustable parameters. This procedure leads to pK_a values in accord with expectation based on such data as are available and permits calculation of rate constants in satisfactory agreement with experiment. Copyright © 2013 John Wiley & Sons, Ltd.     

本刊英文版Vol.30(2014),No.12论文摘要(英文)北大核心CSCD

Regularity of the Inverse of a Homeomorphism with Finite Inner Distortion Chang Yu GUO Abstract Let f:Ω→f（Ω）Rⁿ be a W^1,1-homeomorphism with L¹-integrable inner distortion.We show that finiteness of min{lip_f（x）,k_f（x）},for every x∈Ω\E,implies that f^-1∈W^1,nand has finite distortion,provided that the exceptional set E hasσ-finite H¹-measure.Moreover,f has finite distortion,differentiable a.e.and the Jacobian J_f>0 a.e.     

日本动画片中的物哀思想与死亡赞歌

日本动画片中洋溢的浓郁民族性一直是日本动画的显著特点,其中,物哀思想和对死亡的赞美充斥其中。日本动画片中体现物哀思想的唯美、颓废,死亡场面充满绝艳,美到让人窒息。这些带有病态特点的审美却成为吸引众多青少年的＂亮点＂,引人深思。如何批判的看待这一现象与如何借鉴日本动画片中民族性的表达对于我们当下的动画创作同样具有启迪和教训。     

广西贵县罗泊湾1号汉墓铜盆漆画新解

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王安石“不加赋而上用足”之说试析

“不加赋而上用足”是中国古代传统的理财良法，王安石变法以之为理财的指导思想，在具体实施过程中有所损益，使之切合时代需要，得以实现其“富国强兵”的目的。     

American put options with a finite set of exercisable time epochs

The ordinary American put option assumes that investors can exercise their right at any time epoch. However, due to limitations in actual trades, they are not totally free to exercise in time. In this paper, motivated by this practical situation, we consider American put options with a finite set of exercisable time epochs. Assuming that the underlying stock price process follows a discrete-time Markov process, the put option premium is derived. It is shown that, as for the ordinary American put, the option premium is decomposed into the corresponding European put premium plus the early exercise premium under the stationary independent increments assumption. Moreover, the option premium converges to the ordinary American put premium from below as the number of exercisable time epochs increases under regularity conditions. Some lower bound of the option premium is also obtained.     

以锑电极作参比电极测定废水中硫化物

提出了以锑电极作为参比电极与Ag2 S电极组成无液接测量电池测定废水中硫化物的新方法。并研究了电极的性能 ,测定条件及干扰物质的影响。方法的线性范围 1 .0× 1 0 - 2 mol/L～ 5 .0× 1 0 - 7mol/L[S2 - ],回收率为 99%～1 0 3%     

关于绍兴印山大墓墓主问题的探讨--兼说绍兴306号墓的国属问题

绍兴印山大墓出土遗物的年代约在春秋晚期至战国前期之间.在目前已知的同时代的南方墓葬中,印山大墓的体量最大,气势最为雄伟,结构最为奇特与复杂.结合越国历史,它绝对不可能是春秋时期的允常之墓,而只能是战国时期某位越王之墓,具体王名尚难确定.若参考诸位越王的传世铜器情况,以者旨于赐之墓的可能性较大.绍兴306号墓形制与印山大墓迥异,应该是徐墓,不是越墓.     

基于RS和GIS技术的近40a新疆昌吉州冰川变化分析

充分挖掘已有的地形图、冰川目录数据,并以三个典型研究区(乌鲁木齐河流域,玛纳斯河流域,博格达地区)为代表,利用多源、多时相的遥感数据和资料,借助遥感(RS)和地理信息系统(GIS)新技术对新疆昌吉州冰川的消融率进行分析和计算,经济、便利地获得了该区域冰川面积及其变化量.本研究方法具有很强的实用性和可操作性.     

浏阳河大桥0#块空间应力分析

对预应力混凝土连续箱梁在施工阶段各工况下0#块顶板、底板、腹板和横隔板作了空间应力分析,计算中计入了收缩、温度和时间效应的影响,对不同施工阶段作了对比分析,计算结果为该桥的设计提供了依据,对于同类桥梁0#块设计也具有重要的参考价值。