Synthesis and Crystal Structure of 3-(4-Cyano-3-nitro-1H-pyrazol-5-yl)-4-nitrofurazan: Comparison of the Influence of the NO2 and CN Groups on Crystal Packing and Density
Round 1
Reviewer 1 Report
The Authors synthesized and characterized a new nitrofurazan derivative.
The paper is suitable for Molbank after some revisions. I ask the Authors to take into considration these points before the publication:
page 2, at the beginning of Paragraph 2 ‘Results and Discussion’ the sentences concerning the yield it seem wrong….dinitro product 5 (not 4) was isolated in 64% yield
page 2 after Scheme 1: after the description of synthetic method and before the illustration of the structure, a sentence with short comments about the ir and NMR evidence/concordance has to be inserted, since the abstract announces these characterizations. I ask the Authors not to be “neutral, but allied for peace”. Please, do the most you can for peace.
Figure 2, I propose a different organization: Since Tables 1, Table 2 and Figure 1 show the features of molecule 5 on the left and those of molecule 1 on the right, please do the same in Figure 2, putting ‘cisoid’ molecules in the first row and ‘transoid’ in the second one.
Since these molecules are announced as ‘explosophoric’, in the conclusion it is possible to add some parameters concerning their oxidation energy, in particular a comparison with molecule 1? (measured or extimated)
Author Response
Dear Mr. Shawn Huang
We are thankful for critical review of our manuscript and valuable suggestions.
All suggestions are taken into account and corresponding corrections are made in new version of our manucript.
English was also corrected. Changes made can be found in revised version of the manuscript.
Below are step-by-step answers to comments of Referee 1
Comment of Referee 1
The paper is suitable for Molbank after some revisions. I ask the Authors to take into considration these points before the publication:
page 2, at the beginning of Paragraph 2 ‘Results and Discussion’ the sentences concerning the yield it seem wrong….dinitro product 5 (not 4) was isolated in 64% yield
response
This is corrected.
Comment of Referee 1
page 2 after Scheme 1: after the description of synthetic method and before the illustration of the structure, a sentence with short comments about the ir and NMR evidence/concordance has to be inserted, since the abstract announces these characterizations. I ask the Authors not to be “neutral, but allied for peace”. Please, do the most you can for peace.
response
Following sentence is included on page 2 after Scheme 1.
" Product 5 has been characterized by IR, 1H, 13C and 14N NMR spectroscopy, as well as by MS and elemental analysis (see the Supporting Information)."
Comment of Referee 1
Figure 2, I propose a different organization: Since Tables 1, Table 2 and Figure 1 show the features of molecule 5 on the left and those of molecule 1 on the right, please do the same in Figure 2, putting ‘cisoid’ molecules in the first row and ‘transoid’ in the second one.
response
We changed Figure 2 as suggested by Referee and corresponding corrections are also done in the Caption to Figure 2.
Comment of Referee 1
Since these molecules are announced as ‘explosophoric’, in the conclusion it is possible to add some parameters concerning their oxidation energy, in particular a comparison with molecule 1? (measured or extimated)
response
Following sentence is added on page 7
"As expected, compound 5 exhibited a high detonation performance, and the calculated detonation velocity (D) and detonation pressure (P) were 7920 m×s-1 and 28.4 GPa, respectively, which exceeds the most widely used energetic material, TNT (D = 7450 m×s-1, P = 23.5 GPa)."
Reviewer 2 Report
In this report, synthesis and characterization of titled compounds are shown. The knowledge obtained this study is useful on organic synthesis.
However, there are some inadequacies. I think that the report is worthy of publication in the journal after some revisions about following points.
In Figure 2, the author indicates O-O interactions between nitro groups in compound 1. What is the type of the interaction? The author should show the authority (or reference) for existence of an attractive force there.
I think that the difference of conformations of compounds 1 and 5 is mainly attributed to the intermolecular H-bonds. The author should consider the value of intermolecular H-bonds in the discussion.
The crystal of compound 5 is obtained from HNO3 solution under dry conditions. Is the crystal including water molecules provided under wet conditions?
Author Response
Dear Mr. Shawn Huang
We are thankful for critical review of our manuscript and valuable suggestions.
All suggestions are taken into account and corresponding corrections are made in new version of our manucript.
English was also corrected. Changes made can be found in revised version of the manuscript.
Below are step-by-step answers to comments of Referee 2
Comment of Referee 2
In this report, synthesis and characterization of titled compounds are shown. The knowledge obtained this study is useful on organic synthesis.
However, there are some inadequacies. I think that the report is worthy of publication in the journal after some revisions about following points.
In Figure 2, the author indicates O-O interactions between nitro groups in compound 1. What is the type of the interaction? The author should show the authority (or reference) for existence of an attractive force there.
response
Those are peak-hole interactions of π-π type. An existence of attraction between two atoms (which are not covalently bonded) is based on the existence of the bond critical point located on the bond path between those atoms (Reference 36 in our manuscript). Following text on page 3 was added to provide more details.
"It allowed to find bond critical points (BCPs) not only for covalently bonded atoms, but also for some atomic pairs which are not covalently bonded. This is an indication of additional stabilization caused by attractive intramolecular noncovalent interactions."
Also, in new version of Fig. 2, critical points are better seen.
Comment of Referee 2
I think that the difference of conformations of compounds 1 and 5 is mainly attributed to the intermolecular H-bonds. The author should consider the value of intermolecular H-bonds in the discussion.
response
We agree that any crystal structure is defined by the interplay between intra- and intermolecular forces. Unfortunately we cannot calculate hypotetical crystal structures of transoid form of compound 5 and cisoid form of compound 1. However we can do it for isolated molecules. The obtained differences in energy (ca 1.5 kcal/mol) is not big enough and, of course, cannot be considered as the only reason of existence of observed conformations. Evidently, the system of intermolecular interactions also play its role in stabilization of observed conformation.
We replaced frase "molecular conformations observed in crystals are mainly determined by the preferences of isolated molecules" (on Page 5, line 131) with "molecular conformations observed in crystals are in part determined by the preferences of isolated molecules"
Comment of Referee 2
The crystal of compound 5 is obtained from HNO3 solution under dry conditions. Is the crystal including water molecules provided under wet conditions?
response
In the presence of water, hydrolysis of the nitrile group occurs. In this case, a mixture of product 5 with the corresponding amide and acid is obtained.
