Difluoroamino Groups Research Articles

Ethyl butyrates bearing nitro and difluoroamino groups

Difluoroamination and esterification reactions were utilized for the preparation of NF2-analogs of 2,2,2-trinitroethyl 4,4,4-trinitrobutanoate with replacing one or two nitro groups. Difluoroamino products possess promising properties as ingredients of metallized energetic materials.

THE AVAILABLE CURING AGENTS FOR POLY(3-DIFLUOROAMINOMETHYL-3-METHYLOXETANE/3,3-BIS-AZIDOMTHYLOXETANE) (PDB) OBTAINED THROUGH THE CURING REACTION STUDY OF PDB AND ISOCYANATE

The difluoroamino polymer poly(3-difluoroaminomethy l-3-methyloxetane/3,3-bis-azidomethylox-etane) (PDB) can be an excellent energetic binder in the composite solid propellant, while it has no practical application in curing yet. This study tried isophorone diisocyanate (IPDI), N-100, toluene diisocyanate (TDI), diphenyl methane diisocyanate (MDI), and naphthalene diisocyanate (NDI) to react with PDB, respectively. The ideal curing agent for PDB can form the carbamate structure (-NH-COO-), and the difluoroamino group (-NF<sub>2</sub>) was not destroyed in reactions. Fourier transform infrared, <sup>13</sup>C NMR, and <sup>1</sup>H nuclear magnetic resonance (NMR) was used to analyze the reactions between PDB and isocyanates. The curing reaction kinetics of PDB/TDI, the mechanical performance of PDB/TDI film, and the chemical changes in PDB/TDI reaction were studied separately. The results showed no carbamate structure formed during the reactions with aliphatic isocyanates (IPDI, N-100). In PDB/N-100 reaction, the -NF<sub>2</sub> was destroyed. Aromatic isocyanates (TDI, MDI, and NDI) have higher reactivity, formed carbamate structures in the curing reactions, and no -NF<sub>2</sub> was destroyed. Therefore, TDI, MDI, and NDI can be used as curing agents for PDB. The E<sub>α</sub> of PDB/TDI curing reaction was 42.4189 kJ/mol<sup>-1</sup>, and PDB/TDI films exhibit outstanding mechanical properties.

Theoretical insights on designing of difluoramino compounds

In order to screen out novel energetic compounds with excellent comprehensive properties and provide theoretical guidance for design researcher, a series of difluoroamino energetic compounds were designed by combining energetic molecular scaffolds and NF2 groups. The effect of energetic molecular scaffold, group number and connection position on the performance of difluoroamino energetic compounds was systematically studied, and its design basis was given. From results, we could draw a conclusion that none of the designed energetic compounds could simultaneously satisfy high density, high detonation, good stability, low sensitivity, high explosive power and high specific impulse. When designing a compound structure, the selection of the scaffold type and number of difluoroamino group should be considered comprehensively weighing each performance to meet the actual needs.

THEORETICAL INVESTIGATIONS ON DETONATION PERFORMANCE AND STABILITY OF THE DIFLUOROAMINO-PRISMANE DERIVATIVES

The difluoroamino derivatives of prismane were designed and calculated at the B3LYP/6-311G** level. The detonation performances, as well as the band gap, were investigated to look for high energy density compounds. Our calculations showed that difluoroamino group is an effective substitute group for increasing density and heats of formation. All compounds have large heats of formation, and there is a linear relationship between the heats of formation (HOFs) and the substituent numbers. Bond dissociation energies of trigger bonds are all over 200kJ/mol, which indicated that these prismane derivatives have good stability. More than three substituted groups made the detonation performances meet the requirement of energetic materials. Our calculations provided basic information for the further syntheses of title molecules.

Microfluidic continuous flow synthesis of 1,5-ditosyl-1,5-diazocane-3,7-dione using response surface methodology

3,3,7,7-tetrakis(difluoroamino) octahydro-1,5-dinitro-1,5-diazocine (HNFX) is a high-density energetic oxidizer with four difluoroamino groups (-NF2). In this study, 1,5-ditosyl-1,5-diazocane-3,7-dione, as an important intermediate for synthesis of HNFX, was successfully synthesized using Swern oxidation in a traditional batch reactor and a continuous flow microreactor, respectively. 1,5-dotosyl-1,5-diazocane-3,7-dione was characterized by HPLC, FTIR, 1H NMR, 13C NMR, Mass spectrometry, and X-ray crystal diffraction. Compared with the traditional batch reactor, the microreactor showed several advantages, including less reaction time, milder reaction temperature, higher yield and selectivity for 1,5-ditosyl-1,5-diazocane-3,7-dione. Moreover, the microreactor could ensure the safer and large-scale industrial production of 1,5-ditosyl-1,5-diazocane-3,7-dione. However, some solids produced in Swern oxidation which might block the channels (diameter of 0.3mm) in the microreactor. To overcome the challenges, the experimental device was modified to suit for Swern oxidation, contributing to wider application of the microreactor. Besides, response surface methodology (RSM) was introduced and an appropriate mathematical model was built to optimize experimental conditions. The optimum experimental parameters were recommended as 7.8℃ for the reaction temperature, 7.7mL/min for the flow rate, and 6% for the concentration of oxalyl chloride. The actual yield of 1,5-ditosyl-1,5-diazocane-3,7-dione was 89.7%, which was in great agreement with the highest predicted yield (90.1%).

Preparation, characterization and compatibility studies of poly(DFAMO/AMMO)

ABSTRACTPoly(3-difluoroaminomethyl-3-methyl oxetane (DFAMO)/3-azidomethyl-3-methyl oxetane (AMMO)) (PDA) can be used as an energetic pre-polymer in the binder systems of solid propellants and polymer-bonded explosives (PBXs). The cationic solution polymerization affords PDA using butane diol (BDO) and boron trifluride etherate (TFBE) as initiator and catalyst, separately. Its molecular structure is characterized and thermal decomposition behavior is investigated by thermogravimetric analysis (TG), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The copolymer has good thermal stability and exhibits a three-step mass-loss process with the first two steps mainly belonging to the thermal decomposition of difluoroamino and azido groups, respectively. DSC method is performed to evaluate the compatibility of PDA with some energetic components and inert materials. More than half of the selected materials are compatible with PDA, which including cyclotrimethylenetrinitramine (RDX), 2,4,6-trinitrotoluene (TNT), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB), pentaerythritol tetranitrate (PETN), ammonium perchlorate (AP), ammonium nitrate (AN), potassium nitrate (KNO3), aluminum powder (Al), aluminum oxide (Al2O3), 2-nitrodiphenylamine (NDPA) and 1,3-diethyl-1,3-diphenyl urea (C1).

Thermal decomposition and kinetics studies on poly(BDFAO/THF), poly(DFAMO/THF), and poly(BDFAO/DFAMO/THF)

Poly(3,3-bis(difluoroaminomethyl)oxetane/tetrahydrofuran), poly(3-difluoroaminomethyl-3-methyloxetane/tetrahydrofuran), and poly(3,3-bis(difluoroaminomethyl)oxetane/3-difluoroaminomethyl-3-methyloxetane/tetrahydrofuran) were synthesized via cationic bulk polymerization using boron trifluoride etherate/polyol mixture as catalyst system. Thermal decomposition behaviors of these polymers were investigated by thermogravimetric analysis/differential scanning calorimetry. Kinetics of thermolysis was studied by a model-free method. All of these polymers exhibited a two-stage mass-loss process. The elimination of HF with the activation energy at 95–110 kJ mol−1 dominated the first stage, while the second stage contained the thermolysis of the remaining polymer chain with monofluoroimino and cyano groups. Fourier transform infra red spectra of the degradation residues showed that the difluoroamino groups decomposed in a two-step HF loss at different temperatures. The existence of monofluoroimino groups was responsible for the two-stage thermolysis process.

Thermal Decomposition, Kinetics and Compatibility Studies of Poly(3‐difluoroaminomethyl‐3‐methyloxetane) (PDFAMO)

AbstractThe thermal decomposition of poly(3‐difluoroaminomethyl‐3‐methyloxetane) (PDFAMO) with an average molecular weight of about 6000 was investigated using thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). The kinetics of thermolysis were studied by a model‐free method. The thermal decomposition of PDFAMO occurred in a two‐stage process. The first stage was mainly due to elimination of HF and had an activation energy of 110–120 kJ mol−1. The second stage was due to degradation of the polymer chain. The Fourier transform infrared (FTIR) spectra of the degradation residues showed that the difluoroamino groups decomposed in a two‐step HF loss at different temperatures. The remaining monofluoroimino groups produced by the incomplete elimination of HF were responsible for the two‐stage thermolysis process. The compatibility of PDFAMO with some energetic components and inert materials used in polymer‐bonded explosives (PBXs) and solid propellants was studied by DSC. It was concluded that the binary systems of PDFAMO with cyclotrimethylenetrinitramine (RDX), 2,4,6‐trinitrotoluene (TNT), 2,4‐dinitroanisole (DNAN), pentaerythritol tetranitrate (PETN), ammonium perchlorate (AP), aluminum powder (Al), aluminum oxide (Al2O3) and 1,3‐diethyl‐1,3‐diphenyl urea (C1) were compatible, whereas the systems of PDFAMO with lead carbonate (PbCO3) and 2‐nitrodiphenylamine (NDPA) were slightly sensitized. The systems with cyclotetramethylenetetranitroamine (HMX), hexanitrohexaazaisowurtzitane (CL‐20), 3‐nitro‐1,2,4‐triazol‐5‐one (NTO), ammonium nitrate (AN), magnesium powder (Mg), boron powder (B), carbon black (C. B.), diphenylamine (DPA), and p‐nitro‐N‐methylamine (PNMA) were incompatible. The results of compatibility studies fully supported the suggested thermal decomposition mechanism of PDFAMO.

Computational studies on thermodynamic properties, detonation properties and bond dissociation energies for polydifluoroaminopurine compounds

Abstract Density functional theory (DFT) was used to study the heat of formation (HOFs), electronic structure, energetic properties and thermal stability for a series of purine derivatives with difluoroamino groups. The isodesmic reaction method was employed to calculate the HOFs of the energies obtained from electronic structure calculations. Results indicated that the position of difluoroamino groups could influence the values of HOFs. The bond dissociation energies and bond orders of the weakest bonds were analyzed to investigate the thermal stability of the purine derivatives. Furthermore, the detonation velocities and pressure were evaluated by using the Kamlet–Jacobs equations based on the theoretical densities and detonation heat ( Q ). The cylinder wall velocities ( V ¯ ) were also calculated using the simplified calculational method. Compared with the conventional explosives, two purine derivatives may be regarded as the potential candidates for practical HEDCs.

Theoretical studies on four‐membered ring compounds with NF2, ONO2, N3, and NO2 groups

Density functional theory (DFT) method has been employed to study the geometric and electronic structures of a series of four-membered ring compounds at the B3LYP/6-311G** and the B3P86/6-311G** levels. In the isodesmic reactions designed for the computation of heats of formation (HOFs), 3,3-dimethyl-oxetane, azetidine, and cyclobutane were chosen as reference compounds. The HOFs for N(3) substituted derivations are larger than those of oxetane compounds with --ONO2 and/or --NF2 substituent groups. The HOFs for oxetane with --ONO2 and/or --NF2 substituent groups are negative, while the HOFs for N3 substituted derivations are positive. For azetidine compounds, the substituent groups within the azetidine ring affect the HOFs, which increase as the difluoroamino group being replaced by the nitro group. The magnitudes of intramolecular group interactions were predicted through the disproportionation energies. The strain energy (SE) for the title compounds has been calculated using homodesmotic reactions. For azetidine compounds, the NF2 group connecting N atom in the ring decrease the SE of title compounds. Thermal stability were evaluated via bond dissociation energies (BDE) at the UB3LYP/6-311G** level. For the oxetane compounds, the O--NO2 bond is easier to break than that of the ring C--C bond. For the azetidine and cyclobutane compounds, the homolyses of C--NX2 and/or N--NX2 (X = O, F) bonds are primary step for bond dissociation. Detonation properties of the title compounds were evaluated by using the Kamlet-Jacobs equation based on the calculated densities and HOFs. It is found that 1,1-dinitro-3,3-bis(difluoroamino)-cyclobutane, with predicted density of ca. 1.9 g/cm(3), detonation velocity (D) over 9 km/s, and detonation pressure (P) of 41 GPa that are lager than those of TNAZ, is expected to be a novel candidate of high energy density materials (HEDMs). The detonation data of nitro-BDFAA and TNCB are also close to the requirements for HEDMs.

Strain energies of cubane derivatives with different substituent groups

Homodesmotic reaction and isodesmotic reaction were designed for the computation of strain energies (SE) for a series of cubane derivatives. Total energies of the optimized geometric structures at the DFT-B3LYP/6-31G* level were used to derive the SE. The SE value of cubane is 169.13 kcal/mol for homodesmotic reaction, which is in good agreement with the experimental value. The variation of SE with respect to the number of substituents is similar for the homodesmotic reaction and isodesmotic reaction. The SE values of polynitrocubane and polydifluoroaminocubane increase slightly as up to four substituent groups being added to the cage skeleton. On contrary, the SE dramatically increases when the number of substituent groups m increases from 5 up to 8. For polynitratocubane, the SE decreases slightly at the beginning then increases as the number of group increases. For polyazidocubane, there are very small group effects on the SE. Among four types of substituent groups, the nitro group has greatest effect on the strain energy of caged cubane skeleton. The calculated SE value of octanitrocubane is 257.20 kcal/mol, while that of octaazidocubane is 166.48 kcal/mol via isodesmotic reaction. The azido group releases the strain energy of cubane skeleton when the number of azido groups is less than 7. The interactions among the substituted groups deviated from group additivity. The substituted groups withdraw electrons from the cubane, reducing the repulsion between C–C bonds and resulting the release the strain of the skeleton for isomers with fewer substituents. Group repulsions increase sharply with more and more nitro, nitrato and difluoroamino groups being attached to cubane, resulting large strains of the skeleton. The average negative charges of the substituted groups influence the strain energy of cubane derivatives.

Heat of formations and group interactions of polydifluoroaminoadamantanes: First-principle predictions

Both the heats of formation (HOFs) and the group interactions were predicted for a series of adamantane derivatives substituted with difluoroamino groups by using density functional theory (DFT) with 6-31G ∗ and 6-311G ∗∗ basis sets. The adamantane skeleton was chosen for as a reference compound in the isodesmic reactions designed for calculating the HOFs. The contribution of difluoroamino group to the heat of formation deviates from group additivity. The relationship between HOFs and molecular structures was discussed. It was found that the HOFs decrease more with each difluoroamino group attached to the tertiary carbon than to the secondary carbon of the adamantane skeleton, when the secondary carbon was substituted by one group only. However, the HOFs increase with the second difluoroamino group attached to the secondary carbon. The distance between difluoroamino groups influences the values of HOFs. The group interacting energies of polydifluoroaminoadamantane increase in the range of 8–70 kJ/mol with each difluoroamino group attached. The interaction of neighbor difluoroamino groups discords with the group additivity. The relative stability of the title compounds was assessed based on the calculated HOFs, the energy gaps between the frontier orbitals, and the bond order of C NF 2. The C NF 2 bond is greatly weakened with two NF 2 groups being attached to the same secondary carbon. The basis sets influence the HOFs when the substituent number is over 6 or when two substituted groups being attached to the same secondary carbon.

Theoretical Studies on the Heats of Formation and the Interactions among the Difluoroamino Groups in Polydifluoroaminocubanes

The heats of formation (HOFs) were calculated for a series of polydifluoroaminocubanes by using density functional theory (DFT), Hartree-Fock, and MP2 method with 6-31G basis set as well as semiempirical methods. The cubane skeleton was not broken in the process of designing isodesmic reactions; i.e., the cubane skeleton was chosen for a reference compound. The contribution of difluoroamino group to the heat of formation deviates from group additivity. The semiempirical MO (MNDO, AM1, and PM3) methods did not produce accurate and reliable results for the HOFs of the title compounds. The relationship between HOFs and molecular structures was discussed. It was found that the HOFs decreased dramatically initially and then gradually with each difluoroamino group attached to the cubane skeleton. The distance between difluoroamino groups influences the values of HOFs. The interacting energies of polydifluoroaminocubanes are in the range 14-20 kJ/mol. The interaction of neighbor difluoroamino groups discords with the group additivity. The average interaction energy between the nearest-neighbor NF(2) group in the most stable conformer of octadifluoroaminocubane is 13.94 kJ/mol at the B3LYP/6-31G level. The NF(2) group can rotate freely around the C-N bond. The relative stability of the title compounds was accessed on the basis of the calculated HOFs, the energy gaps between the frontier orbitals, and the bond order of C-NF(2). These results provide basic information for the molecular design of novel high energetic density materials.

99/02677 Fuel and synthesis gas from waste

Density functional theory (DFT) was used to study the heat of formation (HOFs), electronic structure, energetic properties and thermal stability for a series of purine derivatives with difluoroamino groups. The isodesmic reaction method was employed to calculate the HOFs of the energies obtained from electronic structure calculations. Results indicated that the position of difluoroamino groups could influence the values of HOFs. The bond dissociation energies and bond orders of the weakest bonds were analyzed to investigate the thermal stability of the purine derivatives. Furthermore, the detonation velocities and pressure were evaluated by using the Kamlet–Jacobs equations based on the theoretical densities and detonation heat (Q). The cylinder wall velocities (V¯) were also calculated using the simplified calculational method. Compared with the conventional explosives, two purine derivatives may be regarded as the potential candidates for practical HEDCs.

Interaction of polynitro compounds with difluoroamine

Difluoroamine does not react with tetranitromethane and fluoro-, chloro-, and bromotrinitromethanes in DMF and in acidic media (CF3COOH, ClSO3H, FSO3H, and oleum), but reacts with α-fluoro- and α-(difluoroamino)-α,α-dinitrotoluenes to give substitution products of the difluoroamino group for both the nitro groups,viz., PhC(NF2)2F and PhC(NF2)3, respectively.

Reaction of 3-amtnofurazans with elemental fluorine

1. Aminofurazans are fluorinated by elemental fluorine selectively at the amino group with the formation of N,N-difluoroamino derivatives as the main products. The reaction can be accompanied by oxidative dimerization to the corresponding azo compounds. 2. The difluoroamino group in a series of furazans exhibits the properties of an R substituent.

Difluoroamination of N-acetonylphthalimide

1. A method was developed for the preparation of N-[2,2-bis(difluoroamino)propyl] phthalimide by reacting N-acetonylphthalimide with difluoroamine in the presence of weak oleum. 2. The insertion of difluoroamino groups in the N-alkyl substituent of phthalimide substantially retards the hydrolysis of the latter in acid medium.

ChemInform Abstract: REACTION OF PENTAFLUOROGUANIDINE WITH ELECTROPHILIC REAGENTS

AbstractPentafluor‐guanidin (I) bildet mit Chlorsulfonsäurefluorid (II) in äquimolaren Mengen bei ‐78°C die Verbindungen (III).

Reaction of pentafluoroguanidine with electrophilic reagents

1. Pentafluoroguanidine reacts easily with electrophilic reagents: chlorine fluorosulfate, peroxydisulfuryl fluoride, and nitryl chloride. 2. In bis(difluoroamino)fluorochloroaminomethyl and bis(difluoroamino)fluorosulfatemethyl fluorosulfates the difluoroamino groups are easily replaced by fluorosulfate groups uncer the influence of either chlorine fluorosulfate or peroxydisulfuryl fluoride.

Detonation rates of compounds that contain difluoroamino groups

1. The detonation rates of compounds with difluoroamino groups, and specifically C4H8N2F4, C5H8N2F4, and C5H8N4F8, and also of their solutions in tetranitromethane, were measured. 2. A comparison was made of the detonation rates of compounds that contain difluoroamino groups and of nitro compounds that resemble them, and it was established that the indicated detonation rates are close.