Propyl Radicals Research Articles

Study of the potential energy surface of reactions in a system containing <i>i</i>-propyl and <i>n</i>-propyl radicals

The energy pathways of possible decomposition and isomerization reactions of iso-propyl (i-C3H7) and n-propyl (n-C3H7) radicals have been studied by computational methods of quantum chemistry. B3LYP, M062X, MP2, and CBS-QB3 methods are used to localize stationary points on the potential energy surface of a system containing propyl radicals. A number of intermediate compounds formed during the isomerization and decomposition of propyl radicals have been identified, and information has been obtained on their structure and thermochemical parameters. Based on the results of the research, a diagram of the energy levels of the system under consideration was constructed.

Study on the Mass Spectrometry Fragmentation Patterns for Rapid Screening and Structure Identification of Ketamine Analogues in Illicit Powders.

Ketamine analogues have been emerging in recent years and are causing severe health and social problems worldwide. Ketamine analogues use 2-phenyl-2-aminocyclohexanone as the basic structure and achieve physiological reactions similar to or even more robust than the prototype of ketamine by changing the substituents on the benzene ring (R1 and R2) and amine group (RN1). Therefore, the mass spectrometry (MS) fragmentation pathways and fragments of ketamine analogues have certain regularity. Eight ketamine analogues are systematically investigated by GC-QTOF/MS and LC-Q-Orbitrap MS/MS with the positive mode of electrospray ionization. The MS fragmentation patterns of ketamine analogues are summarized according to high-resolution MS data. The α-cleavage of carbon bond C1-C2 in the cyclohexanone moiety and further losses of CO, methyl radical, ethyl radical and propyl radical are the characteristic fragmentation pathways of ketamine analogues in EI-MS mode. The loss of H2O or the sequential loss of RN1NH2, CO and C4H6 are the distinctive fragmentation pathways of ketamine analogues in ESI-MS/MS mode. Moreover, these MS fragmentation patterns are first introduced for the rapid screening of ketamine analogues in suspicious powder. Furthermore, the structure of the ketamine analogue in suspicious powder is 2-(Methylamino)-2-(o-tolyl)cyclohexan-1-one, which is further confirmed by NMR. This study contributes to the identification of the chemical structure of ketamine analogues, which can be used for the rapid screening of ketamine analogues in seized chemicals.

Dynamically Formed Active Sites on Liquid Boron Oxide for Selective Oxidative Dehydrogenation of Propane

Boron oxide-based catalysts have been shown to be both active and selective for driving the oxidative dehydrogenation of propane (ODHP) without the use of metal promoters. However, this reaction occurs at temperatures where boron oxide melts, challenging experimental identification of the molecular structures within the boron oxide phase under reaction conditions and thus hindering the understanding of its active sites and reaction mechanism(s). By combining density functional theory computations, ab initio molecular dynamics simulations, in situ Raman characterization, and microkinetic modeling, we propose that dimerized di-coordinated boron sites (>B–B<)─dynamically formed in liquid boron oxide─are the active species for O2 activation under reaction conditions. The resulting peroxy-like species (>B–O–O–B<) is then responsible for propane activation but is a moderate oxidant for ODHP and thus inert to propene. These peroxy-like structures rapidly activate propane, homolytically cleaving the >B–O–O–B< bond, producing a propyl radical and a >B–O• dangling bond. These > B–O• originate from the >B–O–O–B< sites as well as the liquid B2O3 structure itself and play a critical role in the abstraction of H atoms from propane and propyl. In fact, microkinetic modeling reveals that the formation of adsorbed C3H7* radicals is the main rate-controlling step due to the highly endergonic adsorption of propane into the system. Otherwise, the only activated processes were found to be the dehydration steps that lead to water formation, which exhibit an intriguing dependence on the concentration of surface hydroxyl species. These findings provide significant insights into the ODHP mechanisms on boron-based catalysts and emphasize the importance of understanding the liquid nature of the oxide to account for its catalytic activity.

Design of organyl phosphate-based pro-drugs: comparative analysis of the antibiotic action of alkyl protecting groups with different degree of fluorination

Background. Molecular structures combining a phosphorus-containing counterpart and non-polar radicals are employed in design of pro-drugs as structural and functional groups necessary for transportation of drugs through cellular barriers. It is assumed that the carrier itself does not exhibit biological activity. However, the “organic phosphate – alkyl radical” complex may possess its own metabolic and pharmacological properties even in the absence of a drug moiety.The aim. To study the effect of fluorinated alkyl phosphates on the growth of bacterial test cultures in an agar medium and to identify conjugated metabolic markers using UV/visible spectroscopy.Materials and methods. The effect of six organyl phosphates on the growth of five types of bacteria under aerobic conditions was evaluated by the method of wells in an agar medium. For solutions containing cell metabolites of Pseudomonas aeruginosa, the absorption spectra were recorded at 250–280 nm. The principal component analysis (PCA) was used for multivariate comparative analysis of the spectra. Results. The studied organyl phosphates bearing the ethyl and propyl radicals are potential temporary carriers of the drug moiety, since they are capable of penetrating through cellular barriers. However, the fluorinated compounds exhibit bactericidal properties, the degree of which depends on the arrangement of fluorine atoms in the radical. The most active compounds are those exhaustively halogenated at the terminal carbon atom of the ethyl radical (-СН2-СF3), while non-fluorinated organyl phosphate is the least active. UV/visible spectra of P. aeruginosa cultivation products, according to PCA data, contain patterns reflecting the metabolic effects mediated by these structural features of the radicals.Conclusion. In terms of practical application of the studied compounds, the activity of a proantibiotic based on organyl phosphate with a non-fluorinated ethyl(propyl) radical will be determined only by the specificity of the drug moiety. Exactly the same molecule, but exhaustively fluorinated at the terminal carbon atom of the alkyl radical, is likely to be characterized by lower specificity and higher activity under the additive (or synergistic) action of metabolically active groups.

Photodissociation Dynamics of Astrophysically Relevant Propyl Derivatives (C3H7X; X = CN, OH, HCO) at 157 nm Exploiting an Ultracompact Velocity Map Imaging Spectrometer: The (Iso)Propyl Channel.

The photodissociation dynamics of astrophysically relevant propyl derivatives (C3H7X; X = CN, OH, HCO) at 157 nm exploiting an ultracompact velocity map imaging (UVMIS) setup has been reported. The successful operation of UVMIS allowed the exploration of the 157 nm photodissociation of six (iso)propyl systems─n/i-propyl cyanide (C3H7CN), n/i-propyl alcohol (C3H7OH), and (iso)butanal (C3H7CHO)─to explore the C3H7 loss channel. The distinct center-of-mass translational energy distributions for the i-C3H7X (X= CN, OH, HCO) could be explained through preferential excitation of the low frequency C-H bending modes of the formyl moiety compared to the higher frequency stretching of the cyano and hydroxy moieties. Although the ionization energy of the n-C3H7 radical exceeds the energy of a 157 nm photon, C3H7+ was observed in the n-C3H7X (X = CN, OH, HCO) systems as a result of photoionization of vibrationally "hot" n-C3H7 fragments, photoionization of i-C3H7 after a hydrogen shift in vibrationally "hot" n-C3H7 radicals, and/or two-photon ionization. Our experiments reveal that at least the isopropyl radical (i-C3H7) and possibly the normal propyl radical (n-C3H7) should be present in the interstellar medium and hence searched for by radio telescopes.

Site-Specific Carbon-Carbon Bond Fission in Photoexcited Propyl Radicals Leads to Isomer-Selective Carbene and Radical Products.

Although there have been many studies of C-H bond fission in the UV photochemistry of alkyl radicals, very little is known about the possible occurrence of C-C bond fission. Here, we report that upon excitation at 248 nm, gaseous 1-propyl radicals primarily undergo C-C bond fission, producing methylene (CH2) and ethyl radicals (C2H5), rather than the more energetically favored methyl (CH3) and ethylene (C2H4). In contrast, the exclusive C-C bond fission products from 2-propyl radicals were ethylidene (CHCH3) plus methyl radicals (CH3). The isomer-selective formation of high-energy carbene + radical products involves excited-state site-specific C-C bond fission at the radical carbon, with quantum yields comparable to those for C-H bond fission. Our observations suggest that a general feature of alkyl radical photochemistry is predissociation of the initially formed Rydberg states by high-lying valence states, yielding high-energy carbene plus alkyl radical products.

Reactions of propyl radicals: A shock tube–VUV photoionization mass spectrometry study

The pyrolytic reactions of n-propyl and i-propyl radicals and their precursors have been investigated at elevated temperatures and pressures (600–900 K and 5–8 bar). The studies were performed in a miniature high repetition rate shock tube with synchrotron vacuum ultraviolet photoionization mass spectrometry yielding comprehensive datasets of temporal and photoionization energy dependencies of reagents and products. The propyl radicals were generated by pyrolysis of alkyl nitrites. In addition to the main decomposition path, NO elimination, the mass spectra allowed an alternative minor path via HNO elimination to be identified and quantified. For the n-propyl precursor the HNO elimination route accounted for 9% of the alkyl nitrite while for the i-propyl precursor it was 2.5%. These values are in good agreement with a recent study on i-butyl radicals in the same apparatus at similar conditions. The ratio of disproportionation/recombination was obtained for n-propyl from the relative concentrations of n-hexane and propene and for i-propyl from 2,3-dimethyl butane and propene. For n-propyl the ratio is 0.3 and 1.2 for i-propyl, both are independent of temperature and pressure over the experimental range. The disproportionation/recombination ratios are about a factor of 2 higher than prior evaluations that are based mainly on room temperature data. The experimental results are some of the first from the apparatus used and comments are made about the technique, challenges encountered, and suggestions for future developments.

Operando Photoelectron Photoion Coincidence Spectroscopy Unravels Mechanistic Fingerprints of Propane Activation by Catalytic Oxyhalogenation.

Herein, we demonstrate operando photoelectron photoion coincidence (PEPICO) spectroscopy as a pivotal technique for evidencing unprecedented mechanistic insights by isomer-selective radical detection within complex hydrocarbon-functionalization reaction networks, such as those of catalyzed propane oxychlorination and oxybromination. In particular, while the oxychlorination is surface-confined, we show that in oxybromination alkane activation follows a gas-phase reaction mechanism with evolved bromine and bromine radicals, favoring 2-propyl over 1-propyl radical formation, as evidenced by isomer-selective threshold photoelectron analysis. Furthermore, we provide new mechanistic insights into the cracking and coking pathways that are observed in oxybromination. The first entails propargyl radical formation from consecutive hydrogen abstraction of propyl radicals, ultimately yielding benzene. The second originates from C-C bond cleavage in propane to ethyl and methyl radicals, which produce CH4 and C2H4, or undergo chain-growth reactions, forming C4-C6 species.

Propane pyrolysis facilitated by phenyl radicals: A combined experimental and kinetic modeling study

Phenyl radicals generated from nitrobenzene were introduced as hydrogen abstraction agents to accelerate propylene formation from propane pyrolysis. Neat propane pyrolysis and propane pyrolysis facilitated by phenyl radicals were carried out between 550 °C and 650 °C. Our experiments showed that phenyl facilitated pyrolysis gave higher propane conversion over neat reactions, with yields of all main products increased. However, propylene selectivity in phenyl facilitated pyrolysis decreased in favor of methane and ethylene. Results from detailed kinetic modeling showed that the formation of normal propyl and isopropyl radicals was accelerated due to increased hydrogen abstraction of propane by phenyl radicals. Decreased propylene selectivity in phenyl facilitated pyrolysis was resulted from the increased rates of secondary reactions converting propylene into ethylene and methane. Our work demonstrates that a suitable free radical could facilitate propane pyrolysis for higher propylene yields. However, the balance between propylene yields and selectivity remains a major challenge.

Infrared spectroscopy of the n-propyl and i-propyl radicals in solid para-hydrogen

We report infrared spectra of the n- and i-propyl radicals isolated in solid para-hydrogen (p-H2). Propyl radicals were produced via 248 nm irradiation of matrices formed by co-deposition of p-H2 and either 1-iodopropane (forming n-propyl) or 2-iodopropane (forming i-propyl). Secondary photolysis was used to group spectral bands arising from the same species. In addition to those observed previously in either argon matrix or helium droplet spectra, we assign approximately 20 previously unreported bands. The assignment of features to propyl radicals is made via comparisons to VPT2+K anharmonic frequency computations. In separate measurements, propyl radicals were generated via the reaction between propene and hydrogen atoms produced within the p-H2 matrix. Because the barriers are between 700 and 1500 cm−1, the H + propene reaction is necessarily under tunneling control when carried out in solid p-H2 at 3.3 K. i-Propyl radicals were produced in ∼5–20 times greater abundance than n-propyl radicals, indicating that H atom addition to the terminal carbon is faster than addition to the central carbon. The Wentzl-Kramers-Brillouin approximation is applied to one-dimensional abinitio potentials to estimate the tunneling time constants for formation of n- and i-propyl. This model predicts the rate of addition to the terminal carbon (forming i-propyl) to be 17 times faster, in qualitative agreement with the experimental branching ratio.

Experimental Investigation on Pyrolysis of n-Decane Initiated by Nitropropane under Supercritical Pressure in a Miniature Tube

Adding an initiator is an effective method of promoting hydrocarbon pyrolysis and improving the heat sink of fuels. Nitropropane was proposed as an initiator with good performance, owing to its lower reaction activation energy for C–N bond cleavage. To study the effects of this initiator on hydrocarbon pyrolysis, a miniature tube reactor that can simulate a real heating procedure in an aeroengine was used to investigate the n-decane pyrolysis with and without nitropropane under experimental supercritical conditions. The results demonstrate that the nitropropane initiator promotes the pyrolysis of fuel as it flows through a tube with a large length–diameter ratio within a certain temperature range. The initial decomposition temperature of n-decane is reduced by approximately 100 K, and the increase in the conversion leads to a higher heat sink for n-decane, which can result in decreases in the fuel and reactor temperatures under the same heating condition and within the effective temperature range. A stronger promoting effect can be achieved by increasing the concentration of the nitropropane initiator. The variation laws for the n-decane pyrolysis reaction rate along the flow reactor are changed by the initiator, the presence of nitropropane greatly accelerates the pyrolysis reaction of fuel at a lower temperature, and the opposite tendency appears as the fuel temperature increases, which is caused by the consumption of the initiator. In addition, the selectivity of methane, propane, and alkenes, especially ethylene, increases because of the propyl radical generated by the C–N dissociation of nitropropane before the initiator is consumed.

Direct measurements of channel specific rate constants in OH + C3H8 illuminates prompt dissociations of propyl radicals

OH + molecules are an important class of reactions in combustion and atmospheric chemistry. Consequently, numerous studies have measured rate constants for these processes over an extended temperature range. A large majority of these experimental studies have utilized the decay of [OH] profiles (monitored either by absorption or laser-induced fluorescence) to obtain total rate constants. However, there are limited direct measurements of channel specific rate constants in this important class of reactions, particularly at combustion relevant temperatures. In the present experiments, we have directly measured site-specific rate constants for abstraction of the secondary CH bond in OH + C3H8 at high temperatures. Atomic resonance absorption spectrometry (ARAS) was used to monitor the formation of H-atoms from shock-heated mixtures of tert-butylhydroperoxide and C3H8 at high temperatures. Simulations for the experimental H-atom profiles are sensitive only to abstraction of the secondary CH bond leading to unambiguous measurements of the rate constants for this reaction. Over the T-range, 921 K < T < 1146 K, rate constants from the present experiments for OH + C3H8 → H2O + i-C3H7 can be represented by the Arrhenius expression,k=(3.935±1.387)×10−11exp(−1681±362K/T)cm3molecule−1s−1Simulations of the lower temperature data (T < 1000 K) indicate that the H-atom profiles are also influenced to a minor extent by the thermal dissociation of iso-propyl, i-C3H7 → H + C3H6, at short time-scales. Direct dynamics calculations were performed to examine in greater detail the potential role of prompt dissociations of i-C3H7 and n-C3H7 (formed from the title reaction) in interpreting the lower temperature (< 1000 K) data from the present work. These simulations suggest that prompt dissociation of propyl radicals does not influence the present experimental observations but has a minor influence on higher temperature combustion simulations.

DFT Studies of Carbon Structures Supported Vanadia Catalysts for Oxidative Dehydrogenation of Propane: Kinetic and Thermodynamic

The detailed mechanism for oxidative dehydrogenation of propane on the 1 VO4(CH3 )3 surface has been studied in depth with density functional theory (DFT) calculations at the B3LYP level and standard split-valance basis set, 6-31+G*. Monomeric vanadia specie was considered and modeled as catalysis. In addition, the mechanisms of the two complete catalytic cycle, involving the regeneration of the reduced catalyst using O2 gaseous have been reported. The reaction proceeds in two subsequent steps which at the first, one hydrogen abstracting by the vanadium of V= O1 group with about 48.35 cal/mol activation energy is the rate determining step. Subsequently, second intermediate has been formed through a bond formed between the propyl radical and O2 atom (V-O2). In continue, the O1 atom abstracts one hydrogen atom from the methyl group with a 131.63 kcal/ mol barrier to form propene by passing to second transition state. The results of our calculations have found that all the reactions involve vanadyl oxygen (V=O1), with the bridging oxygen (V-O-C) serving to stabilize the isopropyl radical intermediate.

Dealkanative Main Group Couplings across the peri-Gap.

Here, we highlight the ability of peri-substitution chemistry to promote a series of unique P-P/P-As coupling reactions, which proceed with concomitant C-H bond formation. This dealkanative reactivity represents an interesting and unexpected expansion to the established family of main-group dehydrocoupling reactions. These transformations are exceptionally clean, proceeding essentially quantitatively at relatively low temperatures (70-140 °C), with 100% diastereoselectivity in the products. The reaction appears to be radical in nature, with the addition of small quantities of a radical initiator (azobis(isobutyronitrile)) increasing the rate dramatically, as well as altering the apparent order of reaction. DFT calculations suggest that the reaction involves dissociation of a phosphorus centered radical (stabilized by the peri-backbone) to the P-P coupled product and a free propyl radical, which carries the chain. This unusual reaction demonstrates the powerful effect that geometric constraints, in this case a rigid scaffold, can have on the reactivity of main group species, an area of research that is gaining increasing prominence in recent years.

Pyrolysis of n-Butylbenzene at Various Pressures: Influence of Long Side-Chain Structure on Alkylbenzene Pyrolysis

This work investigates the pyrolysis of n-butylbenzene, which widely exists in transportation fuels and their surrogate mixtures. Both reactive and stable pyrolysis products were comprehensively detected with synchrotron vacuum ultraviolet photoionization mass spectrometry. Their mole fractions versus temperature were also evaluated at 30, 150, and 760 Torr. A kinetic model of n-butylbenzene pyrolysis was developed, and new data were used to validate the model. On the basis of the modeling analysis, the benzylic C–C bond dissociation that forms the benzyl radical and the propyl radical was found to be a key decomposition reaction of n-butylbenzene at all investigated pressures, whereas H abstraction provided increasing contributions with increasing pressure. Compared with small alkylbenzenes, such as toluene and ethylbenzene, n-butylbenzene demonstrates different pyrolysis characteristics and chemistry because of the existence of its long alkyl side chain. n-Butylbenzene has a higher pyrolysis reactivity ...

Search Of High Active And Low Toxic Newly Synthesized Derivatives Of Piperidine For Regional Anesthesia

comparative assessment of local anesthetic activity of newly synthesized derivatives of piperidine for regional anesthesia, depending on their chemical structure. local anesthesia was determined by the method of “tail-flick” on white rats. For research of activity of the compound at the particular type of anesthesia the great important index is duration of complete anesthesia. The duration of complete anaesthesia of LAS-174 was similar to trimecaine, slightly higher than that of novocaine and a little bit less than lidocaine (p>0.05). Total duration of action of LAS-174 is higher than the novocaine and trimekain, and a few exceeding that of lidocaine (p>0.05). LAS-175 index of full anesthesia was 2 times higher than trimekain, 2.5 times than novocaine and a few more than lidocaine (p>0.05). By the total duration this compound exceeds the matched values of trimethoprim, lidocaine and novocaine in 3.4, 1.9 and 4.6 times, respectively. Replacement of the propyl radical to Amillic in the side chain at the 4-th carbon atom of the piperidine ring enhances local activity by the similar toxicity. In 1% solution duration of anesthesia of LAS-190 is similar to the trimecaine and slightly lower than the lidocaine. LAS-189 shows a weaker effect than trimekain and lidocaine (p>0.05). LAS-189 and 190 by the duration of anesthesia was more effective than novocaine, but this difference is not statistically significant. Replacement of the propyl radical (LAS-189) to the phenyl (LAS-190) contributes to increase of local anesthetic activity, especially for the total duration. Acute toxicity of LAS-189 is 750±of 35.56, LAS-190 - 1284±43,87. the Introduction of a cyclopropane radical at the triple bind of the piperidine ring leads to increased local anesthetic effect, weighting of the radical at the 4th carbon atom contributes to the growth of activity and lower toxicity.

NbOx/CeO2-rods catalysts for oxidative dehydrogenation of propane: Nb–CeO2 interaction and reaction mechanism

A series of NbOx/CeO2-rod catalysts were synthesized and employed as catalysts for oxidative dehydrogenation of propane (ODHP) reaction. Nb–CeO2 interaction and reaction mechanisms were studied with synchrotron-radiation-based techniques. Synchrotron radiation photoemission spectroscopy and resonant photoemission spectroscopy results demonstrate that the Nb5+ precursor preferentially interact with surface oxygen vacancies on CeO2 rods. Surface redox reactions occur between Nb5+ and Ce3+ (surface oxygen vacancy) to produce Nb4+ and Ce4+, resulting in decreased surface oxygen vacancy concentrations on CeO2 rods. CeO2 rods are active in catalyzing propane combustion at low temperatures (below 400°C) via the MvK mechanism. The loading of NbOx suppresses the surface reducibility of CeO2 rods, leading to decreased activity but greatly enhanced propene selectivity. The ODHP reaction catalyzed by CeO2 rods and NbOx/CeO2-rods catalysts at high temperatures (above 450°C) involves the radical mechanism, in which the gas-phase propyl radical was observed with synchrotron radiation VUV photoionization time-of-flight mass spectroscopy. These results greatly deepen the fundamental understanding of CeO2-based catalysts for ODHP reaction.

Combined Experimental and Computational Study on the Unimolecular Decomposition of JP-8 Jet Fuel Surrogates. I. n-Decane (n-C10H22).

Exploiting a high temperature chemical reactor, we explored the pyrolysis of helium-seeded n-decane as a surrogate of the n-alkane fraction of Jet Propellant-8 (JP-8) over a temperature range of 1100-1600 K at a pressure of 600 Torr. The nascent products were identified in situ in a supersonic molecular beam via single photon vacuum ultraviolet (VUV) photoionization coupled with a mass spectroscopic analysis of the ions in a reflectron time-of-flight mass spectrometer (ReTOF). Our studies probe, for the first time, the initial reaction products formed in the decomposition of n-decane-including radicals and thermally labile closed-shell species effectively excluding mass growth processes. The present study identified 18 products: molecular hydrogen (H2), C2 to C7 1-alkenes [ethylene (C2H4) to 1-heptene (C7H14)], C1-C3 radicals [methyl (CH3), vinyl (C2H3), ethyl (C2H5), propargyl (C3H3), allyl (C3H5)], small C1-C3 hydrocarbons [methane (CH4), acetylene (C2H2), allene (C3H4), methylacetylene (C3H4)], along with higher-order reaction products [1,3-butadiene (C4H6), 2-butene (C4H8)]. On the basis of electronic structure calculations, n-decane decomposes initially by C-C bond cleavage (excluding the terminal C-C bonds) producing a mixture of alkyl radicals from ethyl to octyl. These alkyl radicals are unstable under the experimental conditions and rapidly dissociate by C-C bond β-scission to split ethylene (C2H4) plus a 1-alkyl radical with the number of carbon atoms reduced by two and 1,4-, 1,5-, 1,6-, or 1,7-H shifts followed by C-C β-scission producing alkenes from propene to 1-octene in combination with smaller 1-alkyl radicals. The higher alkenes become increasingly unstable with rising temperature. When the C-C β-scission continues all the way to the propyl radical (C3H7), it dissociates producing methyl (CH3) plus ethylene (C2H4). Also, at higher temperatures, hydrogen atoms can abstract hydrogen from C10H22 to yield n-decyl radicals, while methyl (CH3) can also abstract hydrogen or recombine with hydrogen to form methane. These n-decyl radicals can decompose via C-C-bond β-scission to C3 to C9 alkenes.

Combined Experimental and Computational Study on the Unimolecular Decomposition of JP-8 Jet Fuel Surrogates. II: n-Dodecane (n-C12H26).

We investigated temperature-dependent products in the pyrolysis of helium-seeded n-dodecane, which represents a surrogate of the n-alkane fraction of Jet Propellant-8 (JP-8) aviation fuel. The experiments were performed in a high temperature chemical reactor over a temperature range of 1200 K to 1600 K at a pressure of 600 Torr, with in situ identification of the nascent products in a supersonic molecular beam using single photon vacuum ultraviolet (VUV) photoionization coupled with the analysis of the ions in a reflectron time-of-flight mass spectrometer (ReTOF). For the first time, the initial decomposition products of n-dodecane-including radicals and thermally labile closed-shell species-were probed in experiments, which effectively exclude mass growth processes. A total of 15 different products were identified, such as molecular hydrogen (H2), C2 to C7 1-alkenes [ethylene (C2H4) to 1-heptene (C7H14)], C1-C3 radicals [methyl (CH3), ethyl (C2H5), allyl (C3H5)], small C1-C3 hydrocarbons [acetylene (C2H2), allene (C3H4), methylacetylene (C3H4)], as well as the reaction products [1,3-butadiene (C4H6), 2-butene (C4H8)] attributed to higher-order processes. Electronic structure calculations carried out at the G3(CCSD,MP2)//B3LYP/6-311G(d,p) level of theory combined with RRKM/master equation of rate constants for relevant reaction steps showed that n-dodecane decomposes initially by a nonterminal C-C bond cleavage and producing a mixture of alkyl radicals from ethyl to decyl with approximately equal branching ratios. The alkyl radicals appear to be unstable under the experimental conditions and to rapidly dissociate either directly by C-C bond β-scission to produce ethylene (C2H4) plus a smaller 1-alkyl radical with the number of carbon atoms diminished by two or via 1,5-, 1,6-, or 1,7- 1,4-, 1,9-, or 1,8-H shifts followed by C-C β-scission producing alkenes from propene to 1-nonene together with smaller 1-alkyl radicals. The stability and hence the branching ratios of higher alkenes decrease as temperature increases. The C-C β-scission continues all the way to the propyl radical (C3H7), which dissociates to methyl (CH3) plus ethylene (C2H4). In addition, at higher temperatures, another mechanism can contribute, in which hydrogen atoms abstract hydrogen from C12H26 producing various n-dodecyl radicals and these radicals then decompose by C-C bond β-scission to C3 to C11 alkenes.

Electronic states of alkyl-radical-functionalized C20 fullerene using density functional theory

The structures and electronic states of alkyl-radical-functionalized C20 fullerenes (denoted by C20–R) have been investigated using density functional theory (DFT). The different alkyl radicals investigated were methyl, ethyl, propyl, and butyl radicals. The DFT calculation indicated that the alkyl radical binds to the carbon atom of C20 in the on-top site, thus forming a strong C–C single bond. The binding energies of the alkyl radicals to C20 were calculated to be 83.9–86.6 kcal/mol at the CAM-B3LYP/6-311G(d,p) level. The electronic states of the C20–R complex are discussed on the basis of the theoretical results.