An analysis of stable forms of CL-20: A DFT study of conformational transitions, infrared and Raman spectra

Kholod, Yana; Okovytyy, Sergiy I.; Kuramshina, G. M.; Qasim, Mohammad; Gorb, Leonid; Leszczyński, Jerzy

doi:10.1016/j.molstruc.2006.12.031

Cited by 77 publications

(87 citation statements)

References 19 publications

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“…Table 2 shows the infrared frequencies of raw CL-20 and prepared ε-CL-20 along with the literature Fig. 3(a), which is well comparable with α-CL-20 as reported in the literature 14,16 . We then recorded raw CL-20 and prepared ε-CL-20 spectrum using dispersed Raman spectrometer in the region of 100 cm -1 -4000 cm -1 as shown in Fig.…”

Section: Introductionsupporting

confidence: 81%

Preparation and Characterisation of ε-CL-20 by Solvent Evaporation and Precipitation Methods

Ghosh¹,

Venkatesan²,

Sikder³

et al. 2012

DSJ

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, et al. studied the crystal quality of ε-CL-20 obtained from different precursors and solvent systems.In the present study, it is focused to prepare and characterisation by both solvent evaporation and precipitation methods. The present evaporation method also relates for obtaining agglomeration free fine ε-CL-20 crystals by in-situ use of ultrasound to crystallisation solution. The obtained crystals were characterised using HPLC, FTIR, Raman, Powder XRD, SEM and DSC techniques. Particle size measurement of obtained ε-CL-20 was carried out using particle size analyser and true density by Helium gas pycnometer. EXPERIMENTAL WORKRaw CL-20 sample was obtained from Premier Explosive's Laboratories, India. All the solvents and allied chemicals used for the processes are of analytical grade with > 99 % purity. ε-CL-20 is prepared using both solvent evaporation and precipitation techniques. Raw CL-20 is dissolved in ethyl acetate solvent and then antisolvent, n-heptane is added into the solution to induce the crystallisation. For the effective recovery in the drowning-out crystallisation, the fraction of raw CL-20, ethyl acetate and n-heptane was applied as about from 1 : 15 : 35, AbSTRACT ε-CL-20 is prepared from raw CL-20 by solvent evaporation and precipitation methods. Experiments were also done using solvent evaporation coupled with in-situ ultrasonication method. Using precipitation method, ε-CL-20 is scaled up to 500 g batch. Raw CL-20 was assigned to α-CL-20. The chemical and polymorphic purity of prepared ε-CL-20 was found to be about 98 per cent and > 95 per cent, respectively. ε-CL-20 was obtained agglomeration free with well defined geometry in comparison with raw CL-20 and its crystal morphology is dominantly bi-pyramidal or lozenge crystal shapes. The obtained mean particle size of prepared ε-CL-20 by solvent evaporation method with and without in-situ ultrasonication and also by precipitation methods is about 30 µm -40 µm, 150 µm -200 µm and 150 µm -300 µm, respectively. The measured true density of prepared ε-CL-20 by precipitation method with 100 g and 500 g batch scale using Helium gas pycnometer was 2.038 g/cm 3 and 2.043 g/cm 3 , respectively. The lower value of calculated void percentage of ε-CL-20 (0.05-0.29%) indicate better crystal quality. Conclusively, prepared ε-CL20 has high true density with less percentage of voids, less total moisture content and free from agglomeration as compared with the starting raw CL-20 material.

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Section: Introductionsupporting

confidence: 81%

Preparation and Characterisation of ε-CL-20 by Solvent Evaporation and Precipitation Methods

Ghosh¹,

Venkatesan²,

Sikder³

et al. 2012

DSJ

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“…However, it is possible that debenzylation-nitration reaction could occur on the N-benzoyl groups (generated from benzyl groups) through nucleophilic substitution reaction of benzamide in the strong acidic media (although it is known as a difficult reaction). 28 Considering the large size of TADB and CL-20 [29][30][31] and corresponding transition state molecules, the reaction occurred on the external surface of the zeolites.…”

Section: Resultsmentioning

confidence: 99%

“…Considering the large size of TADB and CL-20 [29][30][31] and corresponding transition state molecules, the reaction occurred on the external surface of the zeolites.…”

mentioning

confidence: 99%

Synthesis of CL-20 from TADB in a One-Pot Method by Zeolite/HNO₃as a New Nitrolysis System

Bayat¹,

Hajighasemali²,

Mohajeri³

2016

Journal of the Brazilian Chemical Society

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Hexanitrohexaazaisowurtzitane is the most powerful non-nuclear explosive in the world. Herein, a greener and safer new one-pot method for the synthesis of CL-20 from tetraacetyldibenzylhexaazaisowurtzitane (TADB) has been developed through zeolite/98% HNO 3 . The H-ZSM-5 catalyst, with both Brønsted and Lewis acid sites, indicated higher catalytic activity. The reaction using H-ZSM-5 has been optimized with respect to reaction temperature, reaction time, amount of acid and amount of catalyst to substrate ratio. Keywords: debenzylation, nitrolysis, zeolite, tetraacetyldibenzylhexaazaisowurtzitane, CL-20Introduction 2 , 4 , 6 , 8 , 1 0 , 1 2 -H e x a n i t r o -2 , 4 , 6 , 8 , 1 0 , 1 2 -hexaazaisowurtzitane , first proposed by Willer 1 and synthesized by Nielsen et al., 2 has been subjected to extensive studies.3 It is a well-known caged nitramine with significantly higher density (e-form), 4 higher performance and minimum signature than the other nitramines (HMX, RDX); therefore, CL-20 has found numerous military applications. 5 All the processes for CL-20 synthesis are based on the same starting materials. 6 In the first step, the hexa substituted hexaazaisowurtzitane derivatives are formed in the condensation reactions (glyoxal and primary amines). Subsequently, CL-20 is prepared by debenzylation and nitration of hexaazaisowurtzitane derivatives. 9 have been introduced for the synthesis of CL-20 from TADB. The preparation of CL-20 in the final step requires the use of HNO 3 /H 2 SO 4 which has many disadvantages including formation of environmentally unfriendly wastes that are expensive to dispose of, strong acidic media, over nitration and safety problems. Presently, the environmental concerns would not allow such means of disposal; thus, there still remains a need to develop commercially valuable process and environment-friendly methods for preparation of CL-20. 10The synthesis of CL-20 from TADB by applying melamine hydrogen sulfate/HNO 3 11 and acidic ionic liquids/HNO 3 12 in the one-pot reactions is reported in the recent studies of these authors. Nevertheless, these methods (Table 1) are affected by the use of stoichiometric quantities of expensive reagents and the high temperature of reaction which is a drawback of industrial scales.Zeolites, with their unique advantages of high thermal and acid stability and high selectivity (through homogeneous pore shape and size with their defined cages and channels) have been considered at industrial scale. [13][14][15] Zeolite is applied in catalytic cracking, isomerization and alkylation, as well as in the nitration reactions, including nitration of xylene, 16 To the best knowledge of the authors of this article, no report is available in the literature where a zeolite was Synthesis of CL-20 from TADB in a One-Pot Method by Zeolite/HNO 3 as a New Nitrolysis System J. Braz. Chem. Soc. 1104 applied in nitrolysis of the substrate. In this study, the zeolite/HNO 3 as a nitrolysis system (nitro-debenzylation, nitro-deacetylation) was applied in order to prepar...

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“…Além dos polimorfos do CL-20 citados, existe ainda em alta pressão a estrutura ζ, que é uma fase reversível obtida a partir da fase γ. Quanto à estabilidade dos polimorfos CL-20, quando isolados apresentam estabilidade decrescente na ordem ε > γ > α > β, sendo o polimorfo ζ instável sob condições normais (Kholod et al, 2007).…”

Section: Hexanitrohexaazaisowurtzitanounclassified

“…Essa técnica foi empregada para confirmar a forma polimórfica do HMX estudado, uma vez que, segundo Mattos (2001), a identificação do polimorfo α-HMX é feita facilmente pela ausência da banda de absorção em 1145 cm -1 . Kholod et al (2007) descreveram que a identificação dos polimorfos do CL-20 também poderia ser conduzida com FT-IR ou Raman. Foltz et al (1994) estudaram transições de fase cristalina em polimorfos α, β, γ e ε do CL-20 em função da temperatura, descrevendo os resultados do estudo do equilíbrio de soluções em alta temperatura em ligação com FT-IR, permitindo a identificação da transição polimórfica.…”

Section: Ferreira Et Al (2009) Verificaram Que O Emprego De Fontesunclassified

Polimorfismo: caracterização e estudo das propriedades de uma fase cristalina

Silva¹,

Iha²

2010

JATM

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IntroduçãoPolimorfo (do grego "muitas formas") é o termo atribuído a uma das formas cristalinas em que uma mesma substância pode ser encontrada. As diferenças entre as formas envolvem igualmente a estrutura cristalina, número de átomos numa molécula de gás ou estrutura molecular de um líquido (Hawley, 1987).As chamadas "formas polimórficas" são muito mais comuns do que se pode imaginar e cotidianamente se interage com elas sem que se note. O exemplo clássico de polimorfismo é o carbono nas suas formas grafite e diamante. Todavia, substâncias ainda mais abundantes apresentam polimorfismo, tal como a água, que pode cristalizar-se exibindo, no mínimo, oito diferentes formas sólidas, cada qual com estrutura cristalina única.O pseudopolimorfismo se dá pela ocorrência de moléculas do solvente na estrutura cristalina que, não menos importante, é reportado com frequência em argilas de diversos fins (Cavani, Trifirò e Vaccari, 1991).A literatura não descreve apenas diferenças simples nos arranjos cristalinos de polimorfos, mas também mudanças significativas de solubilidade, processabilidade e estabilidades física e química entre diferentes polimorfos

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An analysis of stable forms of CL-20: A DFT study of conformational transitions, infrared and Raman spectra

Cited by 77 publications

References 19 publications

Preparation and Characterisation of ε-CL-20 by Solvent Evaporation and Precipitation Methods

Preparation and Characterisation of ε-CL-20 by Solvent Evaporation and Precipitation Methods

Synthesis of CL-20 from TADB in a One-Pot Method by Zeolite/HNO₃as a New Nitrolysis System

Polimorfismo: caracterização e estudo das propriedades de uma fase cristalina

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An analysis of stable forms of CL-20: A DFT study of conformational transitions, infrared and Raman spectra

Cited by 77 publications

References 19 publications

Preparation and Characterisation of ε-CL-20 by Solvent Evaporation and Precipitation Methods

Preparation and Characterisation of ε-CL-20 by Solvent Evaporation and Precipitation Methods

Synthesis of CL-20 from TADB in a One-Pot Method by Zeolite/HNO3as a New Nitrolysis System

Polimorfismo: caracterização e estudo das propriedades de uma fase cristalina

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Synthesis of CL-20 from TADB in a One-Pot Method by Zeolite/HNO₃as a New Nitrolysis System