Dany
Hazard to Others
Posts: 482
Registered: 3-8-2013
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On the misuse of the Kamlet-Jacobs equations
Two of the most important performance parameter for an explosive material is the detonation velocity (Dcj) and detonation pressure
(Pcj). High Dcj & Pcj are needed when one need a powerful explosive. Getting high detonation performance is not
an easy task. One should synthesize molecule with high crystal density and high detonation energy (Q) since Dcj and Pcj are very
sensitive to density and Q. however, in most cases high detonation energy result from introducing many explosophoric groups into the molecule which
increases the sensitivity of the explosive toward shock, impact and friction stimuli. So finding new species with high density is favorable over
species having very high Q. In this manner one can increase the detonation performance without deteriorating much the sensitivity.
In many case, the newly synthesized explosive material is available in small quantity (hundred of milligrams) so experimental determination of
Dcj and Pcj is impossible. Other factors, like sensitivity prevents scientist from scaling up the synthesis to multigram
quantity which is needed for experimental detonation performance. To solve this issue, scientist rely on predictive methods to predict detonation
performance of known and unknown (theoretical) energetic material. These methods may range from simple relationships to complicated thermochemical
code (e.g., CHEETAH, TIGER, EXPLO5).
One of the simplest but accurate relationships for Dcj and Pcj calculation is that of Kamlet-Jacobs [1]. For a given C-H-N-O
explosive these relationships are able to calculate detonation performance with few percent deviation from experimental measured one. A recent review
on the reliability of these relationships in detonation calculation is made by Politzer [2]. Molecular formula, crystal density, and heat of formation
is all what the user need to calculate Dcj and Pcj.
Recently, a paper [3] is published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal which deals with
theoretical study on an important drug called (S)-2-(2-oxopyrrolidin-1-yl)butanamide (Levetiracetam). The authors in this paper predicted the
molecular structure, harmonic force fields, vibrational wave numbers as well as the IR and Raman intensities of this pharmaceutically important
molecule. However, at the last section of the article, the authors made prdictions for the energetic properties of Levetiracetam!!! Since
Levetiracetam contain C-H-N-O element, they uses the predicted crystal density and heat of formation along with Kamlet-Jacobs equation to calculate
Dcj and Pcj. A fast examination of the molecule reveal without any doubt that the molecule is not energetic at all, since it
does not contain any explosophoric moiety. The calculated Dcj and Pcj for Levetiracetam are 2.68 km/s and 23.09 Gpa,
respectively. They came up with a conclusion that:(S)-2-(2-oxopyrrolidin-1-yl) butanamide is a potential low energy density material and worth
further investigations of the biological activity
This what i call the misuse of the Kamlet-Jacobs relationships. As one can notice the relationships cannot differentiate between an explosive molecule
and a non-explosive one, since the two groups may contain C-H-N-O elements. With this logic in head, all the amide organic compound are potentially
explosives because they contain C-H-N-O element! So here come the role of the user, by examining well the structure of the molecule and judging if the
molecule is explosive based on the explosophoric or energetic moiety in it. This article is published however there is any meaning in calculating the
detonation performance of an amide! which do not contain any energetic group.
References:
[1] M.J. Kamlet, S. J Jacobs, J. Chem. Phys. 48 (1968) 5–23.
[2] P. POLITZER and J. S. MURRAY, Central European Journal of Energetic Materials, 2011, 8(3), 209-220.
[3]S. Renuga, S. Muthu, Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 118 (2014)
702–715.
Dany.
Attachment: [3].pdf (1.6MB)
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DubaiAmateurRocketry
National Hazard
Posts: 841
Registered: 10-5-2013
Location: LA, CA, USA
Member Is Offline
Mood: In research
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I just saw a paper with screen shots of EXPLO5 simulator, it looks like an interesting and fun thing to use.
I wonder where can i download it ? Or other simulators ?
[Edited on 2-11-2013 by DubaiAmateurRocketry]
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