Figures (12)  Tables (3)

    • Figure 1. 

      PES for the isomerization and β-scission reactions of HNN(CH3)2 radical at CCSD(T)/CBS(D+T)//M06-2X/def2-TZVP level (unit: kcal/mol).

    • Figure 2. 

      The optimized molecular configurations of (a), (b) UDMH radicals at the M06-2X/def2-TZVP level of theory, and (c)–(e) MMH radicals at the CASPT2/aug-cc-pVTZ level of theory[31].

    • Figure 3. 

      Pressure-dependent rate constants for (a) R1, (b) R2, and (c) R3. (d) Branching ratios of all consumption reactions of HNN(CH3)2 radical at HPL.

    • Figure 4. 

      Pressure-dependent rate constants for (a) R1-R, (b) R4, and (c) R5. (d) Branching ratios of all consumption reactions of H2NN(CH3)CH2 radical at HPL.

    • Figure 5. 

      Comparison of the rate constants for the β-scission reactions of (a), (b) HNN(CH3)2, and (c) H2NN(CH3)CH2 radicals with those of MMH radicals with similar configurational characteristics[31].

    • Figure 6. 

      The optimized molecular configurations of (a)–(c) HNN(CH3)2 + NO2 at the M06-2X/def2-TZVP level of theory, and (d) NHN(H)CH3 + NO2 at the ωB97X-D/6-311++G(d,p) level of theory[12].

    • Figure 7. 

      PESs for the addition-dissociation reactions of HNN(CH3)2 with NO2 at CCSD(T)/CBS(D+T)//M06-2X/def2-TZVP level of theory (unit: kcal/mol).

    • Figure 8. 

      Pressure-dependent rate constants for the addition-dissociation reactions of HNN(CH3)2 radical with NO2.

    • Figure 9. 

      PESs for the addition-dissociation reactions of HNN(CH3)2 with NO at CCSD(T)/CBS(D+T)//M06-2X/def2-TZVP level of theory (unit: kcal/mol).

    • Figure 10. 

      (a) Rate constants, and (b) branching ratios for the addition-dissociation reactions of HNN(CH3)2 with NO at HPL.

    • Figure 11. 

      PESs for the isomerizartion and β-scission reactions of NN(CH3)2 at CCSD(T)/CBS(D+T)//M06-2X/def2-TZVP level of theory (unit: kcal/mol).

    • Figure 12. 

      Pressure-dependent rate constants for the consumption reactions of NN(CH3)2.

    • No. Reactions P (atm) A n Ea (cal/mol)
      1 HNN(CH3)2 = H2NN(CH3)CH2 HPL 1.2258E−15 8.1005 37,245
      2 HNN(CH3)2 = cis-HNNCH3 + CH3 HPL 1.3900E+12 0.78176 41,951
      3 HNN(CH3)2 = trans-HNNCH3 + CH3 HPL 2.1770E+12 0.72387 36,806
      4 H2NN(CH3)CH2 = H2NNCH2 + CH3 HPL 8.4385E+12 0.43102 29,575
      5 H2NN(CH3)CH2 = CH2NCH3 + NH2 HPL 1.6031E+13 0.18499 14,279
      6 HNN(CH3)2 + NO2 = NN(CH3)2 + cis-HONO 100 7.3949E+20 −2.7812 1,607.6
      4.2465E+04 1.8100 −4,564.2
      7 HNN(CH3)2 + NO2 = CH2NCH3 + ON(NH)(OH) 100 2.3499E+02 2.0956 22,579
      8 HNN(CH3)2 + NO2 = NN(CH3)2 + trans-HONO 100 1.0116E+45 −9.5853 39,906
      5.7045E+10 0.19569 20,318
      9 HNN(CH3)2 + NO2 = CH2NCH3 + NN(OH)2 100 3.9191E+03 1.6501 21,623
      10 HNN(CH3)2 + NO = NN(CH3)2 + HNO 100 1.7593E+03 2.2232 15,951
      11 HNN(CH3)2 + NO = HNN(CH3)CH2 + HNO 100 5.1298E+03 2.1753 24,033
      12 HNN(CH3)2 + NO = NN(CH3)2 + NOH 100 2.7881E+02 2.6552 41,967
      13 HNN(CH3)2 + NO = HNN(CH3)CH2 + NOH 100 2.4904E−01 3.3194 46,582
      14 NN(CH3)2 = HNN(CH3)CH2 HPL 3.7076E+10 0.99227 48,700
      15 NN(CH3)2 = N2 + C2H6 HPL 6.2976E+10 1.5546 36,030
      16 HNN(CH3)CH2 = HNNCH2 + CH3 HPL 3.5255E+12 0.29155 53,875

      Table 1. 

      List of the Arrhenius parameters for the rate constants of isomerization and β-scission reactions of UDMH radicals, as well as the H-abstraction reactions of the HNN(CH3)2 radical and subsequent decomposition reactions at HPL or 100 atm conditions.

    • Reactions Energy barrier (kcal/mol) Ref.
      trans-HNN(H)CH3 = H2NN(H)CH2 49.3 (52.98) This work ([31]a)
      HNN(CH3)2 = H2NN(CH3)CH2 (R1) 55.2 This work
      trans-HNN(H)CH3 = cis-HNNH + CH3 42.2 (39.84) This work ([31]a)
      HNN(CH3)2 = cis-HNNCH3 + CH3 (R2) 41.3 This work
      cis-HNN(H)CH3 = trans-HNNH + CH3 37.2 (35.19) This work ([31]a)
      HNN(CH3)2 = trans-HNNCH3 + CH3 (R3) 36.2 This work
      H2NN(H)CH2 = CH2NH + NH2 13.5 (13.75) This work ([31]b)
      H2NN(CH3)CH2 = CH2NCH3 + NH2 (R5) 14.0 This work
      a Results were obtained at the theory level of QCISD(T)/cc-pV∞Z//B3LYP/6-311++G(d,p); b Results were obtained at the theory level of QCISD(T)/cc-pV∞Z//CASPT2/aug-cc-pVTZ.

      Table 2. 

      Comparison of the energy barrier for the isomerization and β-scission reactions of UDMH radicals with those of MMH radicals with similar configurational characteristics.

    • Reactions Relative energy (kcal/mol) Ref.
      HNN(CH3)2 + NO2 = cis-ONON(H)N(CH3)2 −17.2 This work
      HNN(CH3)2 + NO2 = trans-ONON(H)N(CH3)2 −13.5 This work
      HNN(CH3)2 + NO2 = O2NN(H)N(CH3)2 −31.7 This work
      NHN(H)CH3 + NO2 = trans-ONON(H)N(H)CH3 −17.99 [12]
      NHN(H)CH3 + NO2 = O2NN(H)N(H)CH3 −33.84 [12]

      Table 3. 

      Relative energies of HNN(CH3)2 + NO2 at the CCSD(T)/CBS(D+T)//M062X/def2-TZVP level of theory and NHNHCH3 + NO2 at the RHF-UCCSD(T)-F12//ωB97X-D/6-311++G(d,p) level of theory[12].