甘油硝酸酯类化合物红外光谱和热力学性质的理论研究.pdf

doi10. 3969/ j. issn. 1001-8352. 2018. 06. 004 Theoretical Prediction of Infrared Spectra and Thermodynamic Properties of Glyceryl Nitrates ❋ ZHANG Wenjing①, XUE Chuang①, WANG Guixiang①, GAO Pin② ①School of Chemical Engineering,Nanjing University of Science and Technology Jiangsu Nanjing,210094 ②National Quality Supervision and Inspection Center for Industrial Explosive Materials Jiangsu Nanjing,210094 [ABSTRACT] Glyceryl nitrates are one type of compounds with wide applications in military, medicine, etc. In this study, 6 glyceryl nitrates including NG, DGTN, DGPN, DGHN, TriGPN, and TetraGHN were investigated at the B3LYP/ 6-31G∗level of density functional theory. The infrared spectra were obtained and assigned. The frequencies scaled by a factor of 0. 96 were then used to calculate the thermodynamic properties based on the principle of statistic thermodynamics. The thermodynamic properties are correlated with the number of ONO2and CH2OCH2CHONO2 groups in a linear manner, obviously showing a good group additivity character. [KEYWORDS] glyceryl nitrates; IR spectra; thermodynamic properties; density functional theory [CLASSIFICATION CODE] TQ560. 71;O64 甘油硝酸酯类化合物红外光谱和热力学性质的理论研究 张文静① 薛 闯① 王桂香① 高 贫② ①南京理工大学化工学院 江苏南京,210094 ②国家民用爆破器材质量监督检验中心 江苏南京,210094 [摘 要] 甘油硝酸酯类化合物广泛应用在军事、医学等方面。 用密度泛函理论方法,在 B3LYP/6-31G∗水平下, 对 NG、DGTN、DGPN、DGHN、TriGPN 和 TetraGHN 6 种甘油硝酸酯类化合物进行了研究,获得它们的红外光谱并作 归属。 对谐振频率以 0. 96 进行标度,基于统计热力学原理,计算了它们的热力学性质。 热力学性质与硝酸酯基和 CH2OCH2CHONO2基之间具有线性关系,表现出很好的基团加和性。 [关键词] 甘油硝酸酯;红外光谱;热力学性质;密度泛函理论 Introduction Solid propellants are the propulsion power behind rockets, missiles and launch vehicles. They are gene- rally a type of high energy composite materials, which eject as hot gaseous products on combustion from the nozzle to produce forward thrust to propulsion units. Properties of propellants play an important role in the development of aerospace industry and the survival capacity and combat efficiency of missiles. An ongoing effort in energetic materials community is to design new propellantswithhighperanceanddesirable mechanical and safety properties. Such properties are adjustable via ulations of oxidizers, plasticizers, metallic fuels, polymer binders, and other high energy additives. Nitrate ester is an important kind of organic compounds with excellent plasticizing properties and 第 47 卷 第 6 期 爆 破 器 材 Vol. 47 No. 6 2018 年 12 月 Explosive Materials Dec. 2018 ❋ 收稿日期2018-06-26 基金项目国家自然科学基金21403110 作者简介张文静1993 － ,女,硕士研究生,主要从事有机含能化合物的理论研究。 E-mail523538001＠ qq. com 通信作者王桂香1978 － ,女,副教授,主要从事含能材料的理论计算研究。 E-mail wanggx1028＠163. com widely used as components of industrial explosives dynamites and smokeless powders. One of the oldest classes of fielded energetic materials used both in gun and rocket propellants, is based on various stocks of nitrocellulose NC and plasticized most often with ni- troglycerine NG [1-3]. Methyl nitrate MN, ethy- lene glycol dinitrate EGDN, pentaerythritol tetrani- trate PETN, etc. , have also been receiving a lot of investigations[4-21]. EGDN, diethylene glycol dinitrate DEGDN, NG, etc. , have been paid considerable attentions in synthesis and analysis. Their structures, heats of ation, pyrolysis mechanism, mechanical properties, etc. , have been studied theoretically by the semi-empirical molecular orbital MO , ab initio MO , density functional theory DFT, and molecular dynamics MD, etc. Vibrational spec- tra and thermodynamic properties of some nitrates have been studied by using ab initio or density functional s[12-13,15,18,20].However, previous studies on some of nitrate esters little involve polyglycerine polyni- trates to systematically study their IR spectra and ther- modynamic properties. IR spectrum, as is well known, is not only the basic property of compounds, but also an effective measure to analyze substances. Therefore, it is of great importance to predict IR spectra for both theoreticalandpracticalreasons.Thermodynamic properties, such as heat capacity, entropy, and enthal- py, are important parameters for compounds and are necessary in predicting reactive properties of chemical reactions at different temperatures. Accurate prediction of thermodynamic properties is important in developing models for chemical reactions in which experimental data are incomplete or inaccurate. For example, based on thermodynamic properties, accurate prediction of △fHθ mcan be achieved and help us predict detonation properties of explosives[22]. Studies[13,15,20,23]have shown that the DFT-B3LYP [24-25]in combination with the 6-31G∗[26]basis set is able to produce accurate molecular structures, infrared vibrational frequencies, and thermodynamic properties[15]. Therefore, in this paper, 6 glyceryl ni- trates such as NG, DGTN, DGPN,DGHN,TriGPN and TetraGHN, see Fig. 1 are studied using this DFT . Their IR spectra are assigned by the vibra- tional analysis and vibrational frequencies are used to uate thermodynamic parameters according to the statistical thermodynamic theory.The results of this study can be helpful for further studies on other physi- cal, chemical, and energetic properties of these com- pounds. 1 Computational s Six glyceryl nitrates are studied at the B3LYP/6- 31G∗level with the Gaussian 03 program package. Since the DFT-calculated harmonic vibrational frequen- cies are usually larger than the experimentally observed values, they are scaled using a factor of 0. 96 as was done before[27]. On the basis of the principle of statis- tical thermodynamics[28], standard molar heat capacity Co p,m, standard molar entropy S o m,and standard molar enthalpy Ho m from 200 to 800 K are derived using a self-compiled program. Fig. 1 Illustration of the molecular structures of glyceryl nitrates 22 爆 破 器 材 第 47 卷第 6 期 2 Results and discussion 2. 1 Infrared spectra Vibrational analysis is necessary as a part of theo- retical prediction of thermodynamic properties and can provide the motions responsible for the vibrational modes. Tab. 1 presents the calculated IR spectra of the glyceryl nitrates. Due to the complexity of vibrational modes, the vibrational spectra of the title compounds are difficult to be completely assigned, therefore, only some typical vibrational modes are analyzed and dis- cussed. Tab. 1 shows that, the calculated frequencies of NG are closed to the values in Ref. [3], e. g. the cal- culated frequencies 812. 4-833. 6, 1 271. 9-1 278. 9, 1 696. 9-1 703. 2 cm －1 are in accord with the experi- mental values 842. 0, 1 276. 0 and 1 651. 0 cm －1. This demonstrates the dependability of theoretical com- putation results. The trivial discrepancy is perhaps due to the intermolecular interactions existed in experimen- tal samples. Data in Tab. 1 show that there are three main characteristic regions. There are two intense characte- ristic peaks in their IR spectra. One is in 1 684. 2- 1 728. 3 cm －1 range, attributed to the N��O asymmet- ric stretch of ONO2groups. In this region, their cen- tral positions move towards higher frequency as the number of ONO2groups increases. For instance, the vibration frequencies of DGTN, DGPN and DGHN are 1 698. 9-1 713. 1, 1 706. 1-1 723. 6 and 1 704. 1- 1 728. 3 cm －1, respectively. Moreover, their central positions also basically move towards higher frequency as the number of CH2OCH2CH ONO2 increases. Besides, the difference between the fre- quencies of the isomers is small, indicating that the straight chain length, the space orientation of groups, and the branch chain have little influences on frequen- cies. Another intense band locates at 1 271. 9-1369. 4 cm －1, corresponding to the N ��O symmetric stretch of ONO2groups and out of plane bend of CH bonds. In this region, the main frequencies increase with the increasingnumberofCH2OCH2CH ONO2 groups, but with the increase of ONO2 groups, the main frequencies may increase and de- crease. Finally, the weak peaks at less than 1 129. 0 cm －1 are mainly caused by the stretching vibration of ONO2, CONO2and COCH2 bonds, which belongs to the fingerprint region and can be used to identify isomers. 2. 2 Thermodynamic properties Thermodynamic properties of the title compounds ranging from 200 to 800 K are calculated and presented in Tab. 2. Tab. 1 Key vibrational frequencies of glyceryl nitrates computed at the B3LYP/6-31G∗levela cm －1 CompoundνsONO2νsCOνsN��O and νbCHνasN��O NG 812. 4,816. 1, 833. 6 842. 0b 887. 5,997. 3 1 271. 9, 1 278. 9 1 276. 0b 1 696. 9,1 697. 7, 1 703. 21 651. 0b DGTN806. 5,813. 2,823. 6880. 4,992. 0,1 138. 0 1 274. 6,1 296. 1, 1 303. 3 1 698. 9,1 703. 3,1 706. 1, 1 713. 1 DGPN791. 4,797. 7,822. 0 953. 3,1 003. 1, 1 126. 4 1 288. 3,1 296. 4, 1 313. 0 1 706. 1,1 708. 3,1 718. 2, 1 723. 6 DGHN 772. 4,789. 3,797. 0, 817. 4 956. 7, 982. 9, 1 000. 9,1 113. 0 1 282. 3,1 288. 5,1 290. 1, 1 309. 0,1 311. 6,1 318. 0 1 704. 1,1 708. 2, 1 722. 5,1 726. 1,1 728. 3 TriGPN 809. 5,811. 9,825. 0, 838. 9 894. 2,1 001. 1,1 011. 4, 1 129. 0 1 282. 1,1 282. 4,1 285. 7, 1 290. 4,1 364. 2 1 684. 2,1 697. 1,1 717. 2 TetraGHN 818. 1,821. 9, 841. 1 869. 4,894. 7,1 005. 8, 1 012. 8,1 123. 0 1 278. 9,1 279. 1,1 286. 8, 1 294. 9,1 369. 4 1 689. 1,1 697. 2,1 697. 3, 1 712. 3 a,νsONO2 ONO2stretch; νsCO CONO2and COCH2 stretches; νsN��O and νasN��O N��O symmet- ric and asymmetric stretches of nitro groups; νbCH CH out of plane bend. b,values taken from Ref [3] are in parentheses. 32 Theoretical Prediction of Infrared Spectra and Thermodynamic Properties of Glyceryl Nitrates 2018 年 12 月 ZHANG Wenjing,et al 万方数据 Tab. 2 Thermodynamic properties of the title compounds at different temperaturesa Compounds para- meters T/ K 200. 00298. 15300. 00400. 00500. 00600. 00700. 00800. 00 Co p,m 163. 39214. 55215. 49262. 21300. 25330. 21353. 78372. 55 NGSom459. 49534. 31535. 64604. 22666. 98724. 48777. 22825. 73 Ho m －958. 038－958. 031－958. 031－958. 022－958. 011－957. 999－957. 986－957. 972 Co p,m 261. 08342. 34343. 84420. 56484. 55535. 73576. 50609. 32 DGTNSom631. 70751. 09753. 21862. 89963. 861 056. 901 142. 661 221. 86 Ho m －1 430. 757 －1 430. 746 －1 430. 746 －1 430. 731 －1 430. 714 －1 430. 695－1 430. 673－1 430. 651 Co p,m 300. 59393. 75395. 45480. 46549. 92604. 69647. 82682. 15 DGPNSom684. 69822. 19824. 64950. 381 065. 351 170. 651 267. 231 356. 06 Ho m －1 710. 429 －1 710. 416 －1 710. 416 －1 710. 399 －1 710. 379 －1 710. 357－1 710. 333－1 710. 308 Co p,m 340. 92445. 73447. 61540. 64615. 42673. 73719. 19755. 05 DGHNSom752. 42908. 34911. 101 053. 031 182. 031 299. 611 407. 021 505. 49 Ho m －1 990. 101 －1 990. 086 －1 990. 086 －1 990. 067 －1 990. 045 －1 990. 020－1 989. 994－1 989. 966 Co p,m 358. 91468. 72470. 79577. 40667. 57740. 24798. 45845. 50 TriGPNSom816. 77980. 42983. 321 133. 671 272. 541 400. 921 519. 561 629. 36 Ho m －1 903. 477 －1 903. 462 －1 903. 462 －1 903. 442 －1 903. 418 －1 903. 391－1 903. 362－1 903. 330 Co p,m 454. 65595. 05597. 71734. 84851. 29945. 391 020. 921 082. 08 TetraGHNSom976. 171 183. 691 187. 381 378. 491 555. 401 719. 241 870. 862 011. 31 Ho m －2 376. 195 －2 376. 176 －2 376. 175 －2 376. 150 －2 376. 120 －2 376. 085－2 376. 048－2 376. 008 a,UnitsCo p,m J/ molK; S o m J/ molK; H o m a. u. Tab. 2 shows that all the thermodynamic functions increase evidently with the rise of temperature. The reasonable interpretation of this result is that transla- tional, vibrational and rotational movements strengthen as the temperature increases, so the thermodynamic functions Ho m and So m, contributed from these three movements, increase evidently.As for translational Co p,mand rotational C o p,m, they are constant under some approximations. Only vibrational heat capacity depends on temperatures.The vibrational movement is weak when temperature is low, so the main contributions to Co p,m come from the translation and rotation of mole- cule, while with the rise of the temperature, the vibra- tional movement is intensified and therefore makes more contributions to Co p,m, which leads to the increase in Co p,mvalues. In addition, Co p,mand S o mlinearly increase with the number of ONO2groups and CH2OCH2 CHONO2 groups NG, DGTNa, TriGPNa, Te- traGHNa, n ＝0,1,2,3, while Ho mlinearly decreases. Fig. 2 provides the linear relations between the substi- tuent number of CH2OCH2CH ONO2 n and the calculated thermodynamic functions at 298. 15 K, respectively. The correlation coefficients are all bigger than 0. 998 9. On this condition, Co p,m, So m, and H o m change on average by 126. 79 J/ mol K, 217. 75 J/ molK, and －472. 72 kJ/ mol, re- spectivelywhenmoreCH2OCH2CH ONO2 groups are introduced. Fig. 2 Relationships between the thermodynamic functions and the number of CH2OCH2CHONO2 n at 298. 15 K 3 Conclusions From theoretical calculations and analyses of the IR spectra and thermodynamic properties of glyceryl ni- 42 爆 破 器 材 第 47 卷第 6 期 万方数据 trates at the B3LYP/6-31G∗level, the following con- clusions are drawn 1 The calculated and assigned IR spectra have three strong characteristic regions. Two of them corres- pond to the N��O asymmetric and symmetric stretches of the ONO2groups and the out of plane bend of the CH bonds.The third mainly corresponds to the stretching vibration of the ONO2, CONO2and COCH2 bonds; 2 Thermodynamic properties in the range from 200 to 800 K are calculated. All the thermodynamic fuctions increase evidently with the rise of temperature. 参 考 文 献 [1] ZHENG J, HOU L F, YANG Z X. The progress and prospects of high energy propellants[J]. Journal of Solid Rocket Technology, 2001, 241 28-34. 郑剑,侯林法,杨仲雄. 高能固体推进剂技术回顾与展 望[J]. 固体火箭技术,2001, 241 28-34. [2] PANG A M, ZHENG J. Prospect of the research and de- velopment of high energy solid propellant technology[J]. Journal of Solid Rocket Technology, 2004, 274 289- 293. 庞爱民,郑剑. 高能固体推进剂技术未来发展展望 [J]. 固体火箭技术,2004, 274 289-293. [3] BUSZEK R J, SOTO D, DAILEY J M, et al. 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