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A Deep Insight into the Details of the Inter-Isomerization and Decomposition Mechanism of O-Quinolyl and O-Isoquinolyl Radicals. Quantum Chemical Calculations and Computer Modeling Faina Dubnikova, Carmen Tamburu, and Assa Lifshitz J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.6b07442 • Publication Date (Web): 01 Sep 2016 Downloaded from http://pubs.acs.org on September 4, 2016

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The Journal of Physical Chemistry

A Deep Insight into the Details of the Inter-isomerization and Decomposition Mechanism of o-Quinolyl and o-Isoquinolyl Radicals. Quantum Chemical Calculations and Computer Modeling

Faina Dubnikova, Carmen Tamburu and Assa Lifshitz* The Institute of Chemistry, Edmond J. Safra Campus, The Hebrew University of Jerusalem, Jerusalem 9190401 Israel *Corresponding author: [email protected], phone number +972 528 540 870

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ABSTRACT The isomerization of o-quinolyl ↔ o-isoquinolyl radicals and their thermal decomposition were studied by quantum chemical methods where potential energy surfaces of the reaction channels and their kinetics rate parameters were determined. A detailed kinetics scheme containing 40 elementary steps was constructed. Computer simulations were carried out to determine the isomerization mechanism and the distribution of reaction products in the decomposition.

The calculated mole percent of the stable products was compared to the

experimental values that were obtained in this laboratory in the past, using the single pulse shock tube. The agreement between the experimental and the calculated mole percents was very good. A map of the figures containing the mole-percent’s of eight stable products of the decomposition plotted Vs. T are presented. The fast isomerization of o-quinolyl → o-isoquinolyl radicals via the intermediate indene imine radical and the attainment of fast equilibrium between these two radicals, is the reason for the identical product distribution regardless whether the reactant radical is o-quinolyl or o-isoquinolyl. Three of the main decomposition products of o-quinolyl radical, are those containing the benzene ring, namely, phenyl, benzonitrile and phenylacetylene radicals. They undergo further decomposition mainly at high temperatures via two types of reactions: 1). Opening of the benzene ring in the radicals, followed by splitting into fragments. 2.) Dissociative attachment of benzonitrile and phenyl acetylene by hydrogen atoms to form hydrogen cyanide and acetylene.


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I. Introduction This investigation deals with the theoretical aspects of the thermal decomposition and inter-isomerization of quinolyl and isoquinolyl radicals. The latter are produced via H-atom ejection from quinoline and/or isoquinoline together with the production of quinolyl and isoquinolyl radicals. Quinolines can be seen as substituted naphathalenes, which are part of rich soot formation chemistry. Bio fuels may contain nitrogen compounds, which can be precursors for quinolyl radicals in real engines. The production of H-atoms via C−H bond cleavage, is the initiation step in the thermal decomposition mechanism of aromatic ring compounds such as benzene1,2, naphthalene3,4 and many others. There are also six-member aromatic rings containing nitrogen, such as pyridine, picoline, quinoline and isoquinoline that are also responsible for the production of hydrogen atoms. 5-15 It has also been suggested, in a few cases, that the first step in quinoline and isoquinoline decomposition was an H-atom transfer from carbon to an adjacent nitrogen atom to form singlet carbene,16 that is a pyridine ring containing carbon atom with a valence of two.

The

continuation of the overall decomposition, using this mechanism, involves high barriers, in a few steps even higher than 100 kcal/mol and it does not contribute to the processes over the temperature covered in this investigation. When the initial step is a H-atom ejection in the ring containg a nitrogen atom, the produced radical is, mainly, an ortho isomer, owing to its stabilization by the neighboring nitrogen.8,12-14 Such stabilization is caused by interaction of the unpaired electron on the carbon



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atom with the lone pair of the neighboring nitrogen.12-15 The second step is C−N or C−C bond cleavage via β-scission of the radical toward open ring isomers.14,15 Laskin and Lifshitz,15 in a previous work, studied the single-pulse shock-tube decomposition of quinoline and isoquinoline over the temperature range 1275-1700 K. Six products in this study were suggested as the result of a direct quinoline and isoquinoline decomposition.

Whereas four of them namely, acetylene, cyanoacetylene, benzene and

benzonitrile were produced directly from the ortho isomer of quinolyl and isoquinolyl, they where unable to explain the HCN and phenylacetylene formation on the basis of the ortho isomer decomposition. They therefore, assumed that two of that products, HCN and phenylacetylene, were produced from p-quinolyl or m-isoquinolyl radical decomposition. The key role in the same product distribution of both o-quinolyl and o-isoquinolyl isomers belongs to indene imine radical formation, as the common intermediate in quinolyl – isoquinolyl coupling. In this article we are using quantum chemical calculations and kinetics modeling suggesting some new mechanisms, where coupling of o-quinolyl–o-isoquinolyl radicals provides the six main products formation all from the ortho isomer.

II. Methods of calculations 1. Quantum chemical calculations. The quantum chemical calculations were carried out using the Gaussian-09 package17. The PBE0 (and uPBE0)18,19 hybrid density functional was used in conjunction with the Dunning correlation consistent polarized valence double ξ (cc-pVDZ) basis set.20 The PBE0 (and uPBE0) functional yields reliable results and is quite economic in computational time requirements for molecular systems as those discussed in this publication. The vibrational analysis of the


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structures was performed at the same level of theory in order to reliably characterize the optimized structures either as local minima or transition states. Relative energies include zero− point energy corrections (ZPE) of the corresponding species. All the calculated frequencies, the zero point energies and the thermal energies correspond to harmonic approximation. The calculations of intrinsic reaction coordinates (IRC) using internal coordinates were performed in order to examine whether the transition states under consideration connect the expected reactants and products. The basis set used was the same as the one used for the stationary point optimizations. These calculations were performed for all the transition states at the PBE0 (and uPBE0) level of theory. The energetics for local minima and transitions states was recalculated using coupled cluster theory CCSD(T).21,22

2. Rate constants calculations Rate constants were calculated from transition state theory, using the relation: k∞ = σ (kT/h) exp(∆S#R) exp(-∆H#/RT)

[1]

where σ is the degeneracy of the reaction coordinate and ∆S#(T) and ∆H#(T) are the temperature dependent entropy of activation and the energy barrier respectively. For unimolecular reactions,

∆H# = ∆E#, where ∆E# is the energy difference between the transition state and the reactant. ∆E# is equal to ∆E0total + ∆Ethermal where ∆E0total is obtained by taking the difference between the total energies of the transition state and the reactant and ∆Ethermal is the difference between the thermal energies of these species. From the analysis of the potential energy surfaces, values of preexponential factors and energy barriers could be calculated for each particular rate constant. Each rate constant was calculated using equation Eq. [1] at several temperatures in order to obtain the rate constant in terms of an Arrhenius equation, A exp (-Ea/RT).



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III. Isomerization and decomposition mechanism The decomposition and isomerization processes are shown in figures 1-4. Figure 1 shows the general map of the quinolyl ↔ isoquinolyl isomerization and decomposition based on the results of the quantum chemical calculations. The isomerization channel is marked as Channel [A] and the three decomposition channels are marked as Channels [B], [C] and [D]. Figure 2 shows the potential energy surface of Channel [A], including three arrows directed towards the products obtained from Channel [A]. Figure 3 shows the potential energy surface of Channel [B] containing its decomposition products where the origin is o-quinolyl radical. Figure 4 shows the two potential surfaces of Channel [C] and [D] and their decomposition products when starting from the o-isoquinolyl isomer.

1. Quinolyl ↔ isoquinolyl isomerization, Channel [A] Figures 1 and 2, show the channel describing the detailed isomerization process of oquinolyl ↔ o-isoquinolyl radicals. When starting from o-quinolyl, the isomerization process goes from o-quinolyl to o-isoquinolyl radical via the o-quinolyl ring opening to produce phenyl acrylonitrile (PhAN) radical, and then to form indene-imine radical by ring closure. The process ends in the isomerization to o-isoquinolyl radical.

Channel [A] which is the o-quinolyl radical

isomerization to o-isoquinolyl radical and the back reaction namely, the isomerization of oisoquinolyl to o-quinolyl radical, is defined as “the first generation of reactions”.

Place Figure 1 here Place Figure 2 here


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2. Reactions of Channel [B] The PhAN radical, in parallel to the ring closure to form indene-imine radical, undergoes decomposition along Channel [B] defined as “the second generation of reactions” shown in (Figs. 1 and 3).

Place Figure 3 here Starting from the PhAN radical produced in Channel [A], its first product is a cis isomer. In order for the H-atom (appears in figure 3 as bold colored in blue) to be able to migrate to the radical position in the benzene ring, the corresponding C−H bond in PhAN must be directed towards the benzene ring, namely to undergo a cis ↔ trans isomerization (Fig. 3). As can be seen in Fig. 1, the reaction has thus two parallel steps: (1) Ring closure to form indene-imine radical from cis-PhAN (Channel [A]) and (2) to undergo a cis ↔ trans isomerization of the cisPhAN radical.

The latter proceeds with some 40 kcal/mol activation energy whereas the

activation energy for the ring closure (1) is approximately 5 kcal/mol and is thus much faster than the initiation of Channel [B]. The detail description of the continued decomposition in Channel B and an H-atom attachment appears in the kinetics scheme that will be shown and discussed in the next chapter. 3. Reactions of Channels [C] and [D]. When the starting isomer is o-isoquinolyl, the open ring radical, o-vinyl benzonitrile (oVBN) in parallel to its ring closure, decomposes along Channels [C] and [D] defined also as “the second generation of reactions”. Except for the decomposition of o-VBN obtained in channel [A] to initiate Channel [C], the other two decomposition reactions from channels [B] and [D] begin with H-atom migration (Figs. 1 and 3).



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In Channel [D] (Fig. 4) the first product, o-VBN radical is neither a cis nor a trans isomer so that there are only two decomposition steps. In Channel [C] there is only one step. Since the isomerization process of the o-quinolyl ↔ o-isoquinolyl radicals is much faster than all the decomposition Channels [B], [C] and [D], the two radicals o-quinolyl and o-isoquinolyl radicals are practically at equilibrium almost the entire reaction time.

Place Figure 4 here The second generation of reactions proceeds in all channels, namely, [B], [C], and [D] and end in the production of one radical and one stable molecule each. In Channel [B] the stable molecule is cyanoacetylene and the radical is phenyl (Fig. 3). In Channel C, the stable molecule is acetylene and the radical is benzonitrile and in Channel [D], the stable molecule is HCN and the radical is phenylacetylene. These three processes end in what was previously defined as the second of generations of reactions. The radicals produced initiate a continuation of many reactions that are presented in detail in the reaction scheme (Table 1) that is a part of the present investigation. Table 2 presents the heat of formation and entropy values of the radicals shown in Figure 1 calculated at 298 K. These radicals participate in the main isomerization channel quinolyl – isoquionolyl.

4. The equilibrium quinolyl ↔ isoquinolyl In order to support the statement concerning the equilibrium between the radicals participating in Channel [A], we examined the results obtained using a kinetics scheme (that will be discusses in the next chapter), by running two different calculations. In one, the starting radical is o-quinolyl and in the second one o-isoquinolyl served as the starting reactant. In one calculation, we blocked the ring opening of o-isoquinolyl radical by multiplying its rate constant by 10-10 and in the second, we blocked the opening of the quinolyl radical in the same manner.


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We have then examined the ratios between the first decomposition products INT1B/INT1D (Fig. 1) where INT1B comes from o-quinolyl and INT1D comes from o-isoquinolyl radical. The calculation was performed in a number of reaction times at temperature of 1500 K. The use of several reaction times over the range of 2 msec. was done to make sure that the ratio INT1B/INT1D is independent of the extent of reaction. The results are shown in Table 3. As can be seen the ratios are independent on the origin of the open quinolyl radical from both sides of Channel [A]. These findings show unequivocally that the two quinolyl radicals are indeed at equilibrium almost the entire reaction time.

IV. The kinetics scheme In order to examine the overall kinetics behavior of the system, a kinetics scheme was constructed where the rate parameters of the elementary steps, the thermodynamic properties of the species involved and their geometrical structure are based on the results of the quantum chemical calculations as described in section II.

Bimolecular reactions and reactions that

proceed via variational transition state were estimated on the basis of similar reactions. The scheme that contains 40 elementary steps are shown in Table 1. The kinetics scheme contains a list of pre-exponential factor, activation energy and also enthalpy and entropy of the reactions at 1500 K. The scheme is divided into several sections starting with the first generation of product formation and continuing in additional higher generations whenever they are available. In order to compare the calculated mole percents to the experimental points (Figs. 5, 6), the kinetics scheme starts in the dissociation of the quinoline to H-atom and quinolyl radicals although the discussion of the overall process begins with oquinolyl. The experimental study had to begin with a stable molecule as it is impossible to run the experiments in the single-pulse shock tube with a radical as a starting reactant.



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Place Figure 5 here Place Figure 6 here The kinetics scheme shown in Table 1 describes the process when the starting material is o-quinoline.

Figure 5 shows the mole percent of eight stable reaction products, both

experimental and calculated. The experimental points for the hydrogen molecule could not be measured and are not shown.

Figure 6 shows the reactant’s total decomposition.

We have also constructed a kinetics scheme where the starting reactant is o-isoquinoline. We thus show in Fig 5. four pieces of information: the experimental mole percents when the starting reactants are quinoline (red points) and isoquinoline (blue points) and also the results of the quantum chemical calculation when the starting reactants again are quinoline (red lines) and isoquinoline (blue lines). The four pieces of information beautifully co-inside indicating again that the two quinolyl radicals, are indeed at equilibrium and it is immaterial what the starting isomer is. In addition, the excellent agreement between the experiment and the calculation clearly indicate that the structure of the kinetics scheme and the calculations are very reliable. It should be noted that molecules of quinoline and isoquinoline, unlike their radicals, are not at equilibrium, because formation of reactant’s isomer in molecular form from their radical requires the availability of hydrogen atoms in the system but its concentration is rather low.

V. Conclusion The present article describes a detailed investigation of the inter-isomerization of oquinolyl and o-isoquinolyl and their further decomposition, based on detail quantum chemical calculations and computer simulation. The calculated quantum chemical results and the results of the computer simulation are compared to the experimental results that were obtained in the past, in our laboratory, using the single pulse shock-tube technique. The ring opening of the


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pyridine ring in both quinoline and isoquinoline begins a series of decompositions shown and discussed in the 40 elementary reactions kinetics scheme. It is important to point out that the ortho isomers of both quinolyl and isoquinolyl radicals are the ones responsible for the production of the six main products. Diacetylene is the only one major product that is obtained from the decomposition of product molecules rather than from the sequences of quinolyl decomposition. The most important conclusions that can be reached from the very good agreement between the two sets of experimental results, and the two sets of the calculations is (1) both quinolyl and isoquinolyl radicals are in a state of equilibrium as of the very early stages of decomposition process and their inter-isomerization takes place via ring opening of the pyridine ring and then ring closure to indene-imine radical. (2) The agreement between the two set of experimental results and the two sets of calculations that compose the present article are very good.

Acknowledgment The present manuscript was supported financially by The Hebrew University of Jerusalem.

References 1. Van Scheppingen, W. B.; Cieplik, M. K; Louw, R. Gas-phase Hydrogenolysis of Benzene and Derivatives at Elevated Pressure; Methane Formation. Eur. J. Org. Chem. 2001, 11, 2101-2106. 2. Laskin, A.; Lifshitz, A. Thermal Decomposition of Benzene. Single-Pulse Shock-Tube Investigation. Proc. Combust. Inst. 1997, 26, 669-675. 3. Cieplik, M. K; Louw, R.; van Scheppingen, W. B. Thermal Hydrogenolysis of Polyaromatic Hydrocarbons and Activated Carbon at Elevated Temperatures and Pressures Eur. J. Org. Chem. 2001, 23, 4517-4524.



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4. Laskin, A.; Tamburu, C.; Dubnikova F.; Lifshitz, A. Production of Major Reaction Productes in the Initial Steps of the Thermal Decomposition of Naphthalene. Experimental Shock-Tube Results and Computer Simulation. Proc. Combust. Inst. 2015, 35, 299-307. 5. Cieplik, M. K.; Louw, R.; Thermal Hydrogenolysis of Nitrogen-Containing (Hetero)arenes at Elevated Temperature and Pressure Eur. J. Org. Chem. 2004, 30113016. 6. Winkler, J. K.; Karow, W.; Rademacher, P. Gas Phase Pyrolysis of Heterocyclic Compounds, part3. Flow Pyrolysis and Annulation Reactions of Some Nitrogen Heterocycles, a Product Oriented Study. Arkivoc, 2000, 576-682 7. Wang, B.; Zhang, R. in Rate Constant Calculations for Thermal Reactions: Methods and Applications; Da Costa H., F., Eds.; John Wiley & Sons, 2012; pp 239-282. 8. Mackie, J.C.; Cloket III M.C.; Nelson P.F. Shock Tube Pyrolysis of Pyridine. J. Phys. Chem. 1990, 94, 4099-4106. 9. Jones, J.; Bacskay, G.B.; Mackie, J.C. The Pyrolysis of 3-Picoline: Ab initio Quantum Chemical and Experimental (Shock Tube) Kinetic Studies. Isr. J. Chem. 1996, 36, 239248 10. Ninomiya, Y.; Dong, Z.; Suzuki, Y.; Koketsu, J. Theoretical Study on the Thermal Decomposition of Pyridine. Fuel, 2000, 79, 449-457 11. Bruinsma, O. S. L; Tromp, P. J.J.; de Sauvage Nolting, H. J.J.; Moulijn, J. A.; Gas Phase Pyrolysis of Coal-related Aromatic Compounds in a Coiled Tube Flow Reactor 2. Heterocyclic Compounds, their Benzo and Dibenzo Derivatives. Fuel 1988, 67, 334-340. 12. Barckholtz, C.; Barckholtz,T.A.; Hada, C. M. C-H and N-H Bond Dissociation Energies of Small Aromatic Hydrocarbons J. Am. Chem. Soc. 1999, 121, 491-500. 13. Liu, R.; Huang, T. T. S.; Tittle, J.; Xia D.; A Theoretical Investigation of the Decomposition Mechanism of Pyridyl Radicals, J. Phys. Chem. A 2000, 104, 8368-8374. 14. Jones, J.; Bacskay, G. B.; Mackie J.C.; Dought, A. Ab lnitio Studies of the Thermal Decomposition of Azaaromatics: Free Radical versus Intramolecular Mechanism, J. Chem. Soc., Faraday Trans., 1995, 91, 1587-1592 15. Laskin, A.; Lifshitz, A. Thermal Decomposition of Quinoline and Isoquinoline. The Role of 1-Indene Imine Radical. J. Phys. Chem. A 1998, 102, 928-946


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16. Ling, L.; Zhang, R.; Wang, B.; Xie K. Pyrolysis Mechanisms of Quinoline and Isoquinoline with Density Functional Theory. Chin. J. Chem. Eng. 2009, 17, 805-813. 17. Frisch, M. J.; Trucks, G.W.; et al. Gaussian 09, version B.01; Gaussian, Inc.; Wallingford CT, 2009. 18. Perdew, J. P.; Burke, K.; Ernzerhof, M., Generalized Gradient Approximation Nade Simple. Phys. Rev. Lett. 1997, 78, 1396-1396. 19. Adamo, C.; Barone, V. Toward Reliable Density Functional Methods without Adjustable Parameters: The PBE0 Model. J. Chem. Phys. 1999, 110, 6158-6170. 20. Dunning, T. H. Gaussian-Basis Sets for Use in Correlated Molecular Calculations .1. The Atoms Boron through Neon and Hydrogen. J. Chem. Phys. 1989, 90, 1007-1023. 21. Pople, J. A.; Head-Gordon, M.; Raghavarchari, K. Quadratic Configuration Interaction a General Technique for Determining Electron Correlation Energies. Chem. Phys. Lett., 1987, 87, 5968-5975. 22. Scuseria, G. E.; Schaefer, III, H. F. Is Coupled Cluster Singles and Doubles (CCSD) more Computationally Intensive than Quadratic Configuration-Interaction (QCISD). J. Chem. Phys., 1989, 90, 3700-3703 23. Westly, F.; Herron, J.T.; Cvetanovich, R. J.; Hampson, R.F.; Mallard, W.G. NISTChemical Kinetics Standard Reference Data Base 17, Version 5.0, National Institute of Standards and Technology. Washington, DC, 1985. 24. Kiefer, J. H.; Mizerka, L.J.; Patel, M. R.; Wei, H. C. A Shock-Tube Investigation of Major Pathways in the High-Temperature Pyrolysis of Benzene. J. Phys. Chem. 1985, 89, 2013-2019. 25. Fahr, A.; Stein, S. E. Gas-Phase Reactions of Phenyl Radicals with Aromatic Molecules J. Phys. Chem. 1988, 92, 4951-4955. 26. Lifshitz, A.; Cohen, Y.; Braun-Unkhoff, M., Frank, P. Thermal Decomposition of benzonitrile: a Combined Single-Pulse Shock Tube – Aras Investigation. Proc. Combust. Inst. 1997, 26, 659-667. 27. Herzler, J.; Frank, P. High-Temperature Reactions of Phenylactylene. Ber. Bunsen-Ges.. 1992, 96, 1333-1338.



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TABLES

Table 1. Kinetic scheme of production of hydrogen atoms and o-quinolyl and oisoquinolyl radicals and their reactions. Geometrical structures were obtained from the quantum chemical calculations No

E≠ ∆Sr ∆Hr Ref. kcal/mol (1500) (1500) cal/(K kcal/mol mol) Production of o-quinolyl and o-isoquinolyl radicals Reaction

A s-1

1*

1.00E+16

98.00

34.5

103.00

23

1.00E+14

13.91

6.4

─4.47

15

1.00E+16

96.00

31.6

96.70

8

1.00E+14

13.91

3.6

-10.77

2, 24

1.40E+15

101.40

28.1

107.48

23

+H N

N

2** +H

+ H2

N

N

3*

+H

N

N

4**

+H N

5*

N

+ H2

H2 +Ar → H˙ + H˙ + Ar

Channel [A] o-quinolyl → o-isoquinolyl radicals isomerization (Figs. 1 and 2) 6

2.73E+14

33.91

11.4

25.43

1.80E+12

4.89

─8.7

─25.85

2.28E+14

28.96

9.2

23.02

1.27E+12

9.48

─14.2

─27.33

N N

7 N

N

8 N

N

9 N N

Channel [B] Production of phenyl radical and cyanoacetylene from PhAN radical (Figs. 1 and 3) and their further reactions


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10

N

2.72E+13

40.35

0.3

─2.55

8.48E+12

25.52

1.7

─7.85

1.30E+16

55.78

23.5

47.24

5.66E+15

70.97

12.5

62.49

3.08E+15

46.78

39.6

42.57

1.00E+15

106.00

35.5

112.82

2, 24

5.00E+11

9.34

1.0

9.82

25

N

11

N

12

N

N

+ HC C C N H C

13

CH

HC HC

C CH

H C

14

CH

HC

H C CH + C2H2

HC C HC C CH

15* +H

16** +

+

N

N

Channel [C] Production of benzonitrile radical and acetylene from o-VBN radical (Figs. 1 and 4) and their further reactions 3.95E+15 48.43 34.8 40.28 17 + C2H2 N

N

18

H C

HC

C N

19

H C

HC

CH

C

62.17

8.47E+12

23.29

1.5

-9.20

9.59E+14

41.97

27.6

51.49

4.78E+15

49.07

59.0

42.00

CH HC HC

C

20

13.3

C C N

HC C

HC

67.57

CH

HC C

1.06E+15

C N

C C N

HC C CH HC

HC C

H C

CH + HC C C N

HC

21

C C N H HC C CH HC

HC C C

H C

C C

C N + C2H2

C N



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22

HC CH

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1.91E+14

66.53

13.3

62.87

1.08E+16

46.44

47.5

43.77

5.00E+16

115.00

32.9

109.22

26

2.50E+10

10.30

-1.6

6.22

25

1.17E+14

31.09

22.9

23.51

6.41E+14

34.45

29.6

26.02

CH HC C C

C

C N

N

23

CH

HC CH

HC C C

CH

+ C2H2 C

HC C C C N

N

24* +H N

N

25**

+

+ N

N

N

26 H

N

+ H

C

C

N

N

27 H

+ HCN

C N

Channel [D] Production of phenylacetylene radical and HCN from o-VBN radical (Figs 1 and 4) and their further reactions 1.61E+13 33.12 0.7 13.17 28 N

N

29

9.92E+14

35.59

35.8

26.12

9.36E+14

65.20

12.6

59.6

8.81E+12

21.29

3.6

─11.70

4.84E+14

45.55

35.4

64.32

+ HCN N

30

HC

H C

CH

HC C

C

C C CH

CH

31

HC

H C

CH

HC

C

CH

HC

C C C CH

32

HC

HC

C

HC C C CH

CH

HC HC C

H C CH + HC C C CH

HC C C CH


Page 17 of 25

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33


HC

H C

CH

HC

HC

1.61E+15

44.24

59.1

36.00

1.93E+14

66.57

12.6

62.61

2.50E+15

46.33

59.1

41.0

5.00E+16

113.50

31.3

107.86

26

3.00E+10

9.9

─3.2

4.86

27

1.03E+14

41.39

28.5

37.43

3.92E+15

33.28

32.0

39.58

1.13E+14

40.12

23.9

39.51

H C C C C CH + C2H2

C C C CH

34

HC CH CH HC C C C CH

C CH

35

CH

HC CH CH

C

HC C

C

HC C C C CH

+ C 2H 2 CH

36* +H C

C

CH

37**

CH

+

+ C

N

N

CH

38 H C

40

HC C

CH

+ H CH

C CH

39 H C

C

+ C2H2 CH

H C CH

HC C

C CH + H

* estimated ** only pre-exponential factor is estimated. The empty spaces in the “reference” column refers to our quantum chemical calculations



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Table 2. Heat of formation and entropy values of the radicals shown in Figure 1 calculated at 298 K. These radicals participate in the main isomerization channel quinolyl - isoquionolyl radical ∆H0f (298 K) kcal/mol S (298 K) cal/(K mol) o-quinolyl 99.0 82.8 phenyl acrylonitrile (PhAN) 123.9 92.1 Indene-imine 98.1 84.6 o-vinyl benzonitrile (o-VBN) 119.9 91.4 o-isoquinolyl 100.1 82.9


Page 18 of 25

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Table 3. The ratio of the concentrations of INT1B/INT1D (Fig. 1), where both quinoline and isoquinoline were used as reactants TIME

Transition Transition from ofrom oisoquinolyl quinolyl is blocked is blocked 10 0.87 0.88 20 0.88 0.88 30 0.89 0.90 40 0.92 0.92 50 0.95 0.96 60 1.00 1.00 70 1.05 1.06 80 1.11 1.12 90 1.19 1.20 100 1.27 1.28 200 2.46 2.56 400 6.23 6.75 600 10.97 11.99 800 15.97 17.43 1000 20.90 22.65 1200 25.63 27.52 1400 30.07 32.05 1600 34.24 36.19 1800 38.15 40.05 2000 41.78 43.58



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A Deep Insight into the Details of the ... - ACS Publications

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