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[综合交流] 一个反应活化能垒小于 20kcal/mol在常温常压下进行么?

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发表于 2018-6-23 13:34:12 | 显示全部楼层 |阅读模式
各位老师,大家好!请教一个审稿问题,主要做地质上甲基二苯并噻吩的甲基迁移转化机理。在文章中我提了一句话:“Generallyspeaking, when activation energy barrier is below 20 kcal/mol for one reactionsystem, it is very easy to take place under natural conditions”。首先,我根据20 kcal/mol 这个标准通过简单过渡态理论,计算出速率常数为 1.36×10-2 s-1;然后,我再以此速率常数(1.36×10-2 s-1)为基准,再次采用简单过渡态理论获取不同反应能垒下能进行的反应温度。现在,审稿意见回来了,评审提出了这个问题,感觉十分的不好回答,请教一下各位老师,我该怎么处理呢?有没有相关的文献支撑这个观点(我查阅了一些文献,都没有直接这么说,但一般做反应机理效果比较好的都是活化能垒非常低的,很多都小于20 kcal/mol ,此外我也课题的讨论了一下这个问题,也没有太确切的回答)?请各位老师给我指导为谢!审稿意见:Thediscussion on MDBT formation in natural (5.2) was based on the line of"Generally speaking, when activation energy barrier is below 20 kcal/molfor one reaction system, it is very easy to take place under natural conditions ." However, I am very confused by the derivation procedure.First, what is the natural conditions meaning in your work ? It means a low temperature and shallow depth burying? We need anaccurate value.  Second, I do not agree with the bound of activation energy barrier of 20kcal/mol for judgment whether the supposed reaction process can occur innatural conditions. The presence of clay minerals will catalyze the investigatedreaction pathways to some extent, and significantly reduce the activationenergy barrier. During catagenesis, the reactions with very high activation energybarrier also can occur, for example, the average activation energy barrier ofcracking reactions for most kerogen is about 60 kcal/mol.
Pathways
Energy barriers/kcal/mol
T/℃
P1
24.26
86.50
P2
76.93
830.90
P3
29.53
162.20
P4
17.69
-8.50
P5
12.42
-85.42
P6
32.37
202.80
P7
19.57
18.78
P8
38.04
283.64




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发表于 2018-6-24 11:32:56 | 显示全部楼层
让你说明你当前研究的反应是发生在什么具体外界情况下的(最最起码把温度写上),外环境可能产生什么影响。审稿人举例如果外界环境如果产生比如催化效应,20 kcal/mol(更常用的是21kcal/mol)的判断标准就不适用。
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 楼主| 发表于 2018-6-25 21:05:19 | 显示全部楼层
sobereva 发表于 2018-6-24 11:32
让你说明你当前研究的反应是发生在什么具体外界情况下的(最最起码把温度写上),外环境可能产生什么影响。 ...

谢谢Sob回复。我是这样回答的,不知道可不可以,是留着还是删除?
Thanks for your suggestion. First, 298.15 K and 1 bar are considered to be natural conditions in our work. Actually, the default temperature and pressure in Gaussian 09 code are also 298.15 K and 1 bar, respectively. According to our many years of experience and the reports of peers on various reaction systems , it has been generalized that when all activation energies between each individual pair of adjacent intermediates and state are reasonable (ca 20 kcal/mol), then the corresponding calculated mechanism is consistent with a reaction that can run at room temperature. Many publications have confirmed this point such as the publications from the Davies’s group and the Houk's group. Second, if a reaction system can react at normal temperature and pressure, it can be easier to occur under geological conditions of high temperature and pressure. This is why cracking reactions for most kerogen with an activation energy barrier of up to 60 kcal/mol can also occur. Lastly, the catalytic influence of clay minerals is an extremely complicated and actually interesting research topic in geochemistry. To design reliable strategy for the natural formation and occurrence of MDBTs on the molecular-scale, both quantum chemical methods and molecular simulation techniques would be applied to focus on the effects of clay mineral, water content, ultrahigh pressure, organic acid and metallic elements in future researches. Thank you again.
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发表于 2018-6-28 20:28:35 | 显示全部楼层
这个帖子非常好,能否可以列出 Davies’s group and the Houk's group的参考文献?学习啦。

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 楼主| 发表于 2018-6-29 10:37:23 | 显示全部楼层
vangogh 发表于 2018-6-28 20:28
这个帖子非常好,能否可以列出 Davies’s group and the Houk's group的参考文献?学习啦。

他们是大课题组,直接Google搜他们的课题组就行了。
https://davies-group.com/
http://www.chem.ucla.edu/houk/
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发表于 2018-6-30 23:00:34 | 显示全部楼层
多谢,如果能列出几篇,更好!
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