Homolytic addition of benzyl bromide to unsaturated compounds in conditions of metal-complex initiation

Radical addition of benzyl bromide to unsaturated compounds containing substituents of a different polar nature, CH₂=CHX (X=C₄H₉, SiMe₃, CF₃, CO₂Me, CN, H), was conducted in the presence of the Fe(CO)₅ + DMF (HMPA) system. Adducts were obtained and their structure was demonstrated by¹³C NMR and mass spectrometry.A. N. Nesmeyanov Institute of Organoelemental Compounds, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2347–2352, October, 1992.     

MNDO/3 study of the relative reactivity of ethylene derivatives upon addition to the benzyl radical

The transition states for the addition of a benzyl radical to substituted ethylenes CH₂=CHX were determined by the MNDO/3 method, where X=H, CF₃, CN, CH₃, C₄H₉, C(CH₃)₃, CO₂CH₃, and Si(CH₃)₃. The activation energies of the forward and back reactions were determined.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1676–1679, July, 1992.     

Reaction of benzyl chloride with propylene and trifluoropropene under metallocomplex initiation conditions

The reactions of benzyl chloride with propylene and 3,3,3-trifluoropropene in the presence of Fe(CO)₅ ` + DMF were studied. With propylene, the reaction stops at the addition stage with the simultaneous formation of dibenzyl. In the case of 3,3,3-trifluoropropene, a telomerization takes place, whereby the second growing radical C₆H₅CH₂CH₂CH(CF₃)CH₂HCF₃ practically completely isomerizes with a 1,5-migration into the radical C₆H₅HCH₂CH(CF₃)CH₂CH₂CF₃. To confirm the structure of the isolated compounds, chromato-mass-spectrometry and¹³C NMR were used.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1384–1388, June, 1991.     

Recovery of chromium hexacarbonyl after nucleophilic reactions of arenechromium tricarbonyl complexes

The arenechromium tricarbonyl complexes C₆H₄R₂Cr(CO)₃, (R = H, CHMe₂), obtained from arenes C₆H₄R₂ and Cr(CO)₆, react with nucleophiles (Nu = CH(CH₃)CN, CH(CH₃)CO₂-t-Bu), to form adducts which give, after treatment with CF₃CO₂H under carbon monoxide, the substituted cyclohexadienes C₆H₅R₂Nu (R = H, CHMe₂) and Cr(CO)₆ in good yield.     

Rare earth metal benzyl complexes bearing bridged-indenyl ligand for highly active polymerization of methyl methacrylate

The novel anionic bridged-indenyl rare earth metal benzyl complexes [{C₉H₆SiMe₂(CH₂)₂SiMe₂C₉H₆}Ln(CH₂C₆H₄-p-^tBu)₂][Li(THF)₄] (Ln = Y (1), Lu (2)) were synthesized by an acid-base reaction of C₉H₇SiMe₂(CH₂)₂SiMe₂C₉H₇ with one equiv. of rare earth metal trisbenzyl complexes, which were formed in situ from the reaction of anhydrous LnCl₃ with LiCH₂C₆H₄-p-^tBu in 1:3 molar ratio in THF. The complexes were characterized by elemental analysis, NMR spectroscopy, FT-IR spectroscopy, and X-ray structural analysis in the case of 2. Both complexes are active for the polymerization of methyl methacrylate (MMA) to afford high molecular weight and narrow molecular weight distribution PMMA. The molecular weights of PMMA could be controlled using 1 as a polymerization initiator in chlorobenzene at −40 °C.     

Relative kinetics of the homolytic addition of 2-phenyl-1,3-dioxolane to unsaturated compounds

The CH₂ = CHX olefins form a series relative to their reactivity in reactions with 2-phenyl-1,3-dioxolan-2-yl radicals, which qualitatively correlates with the electron-withdrawing capacity of substituent X: CN CO₂Me >> SiMe₃ C₄H₉. This behavior indicates that the dioxolanyl radical is nucleophilic.A. N. Nesmeyanov Institute of Organometallic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 7, pp. 1663–1666, July, 1992.     

Synthesis of new α,α,β,β-tetrafluoroesters

Substituted phenyl iodides or diiodides reacted with ethyl iodotetrafluoroproponylate ICF₂CF₂CO₂Et, 1 in the presence of copper powder to give the coupled products 2 or 3 in good yields. Addition of 1 to ethylene and allyl acetate proceeded smoothly under thermal and radical conditions to give the corresponding adducts, which underwent elimination reaction to give β-vinyl and β-allyl α,α,β,β-tetrafluoroesters, CH₂CHCF₂CF₂CO₂Et, 4 and CH₂CHCH₂CF₂CF₂CO₂Et, 5, respectively. 1 also readily reacted with 1,5-hexadiene and 1-hexene with copper or palladium complex, followed by reduction to remove iodine to produce ω-alkenyl-α,α,β,β-tetrafluoroester CH₂CH(CH₂)₄CF₂CF₂CO₂Et 6 and α,α,β,β-tetrafluoroester C₄H₉CH₂CHICF₂CF₂CO₂Et.     

C-C bond formation by cyanide addition to dinuclear vinyliminium complexes

The diiron vinyliminium complexes [Fe₂{μ-η¹:η³-C(R′)C(H)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R=Me, R′ = SiMe₃ (1a); R = Me, R′ = CH₂OH (1b); R = CH₂Ph, R′ = Tol (1c), Tol = 4-MeC₆H₄; R = CH₂Ph, R′ = COOMe (1d); R = CH₂Ph, R′ = SiMe₃ (1e)) undergo regio- and stereo-selective addition by cyanide ion (from ), affording the corresponding bridging cyano-functionalized allylidene compounds [Fe₂{μ-η¹:η³-C(R′)C(H)C(CN)N(Me)(R)}(μ-CO)(CO)(Cp)₂] (3a-e), in good yields. Similarly, the diiron vinyliminium complexes [Fe₂{μ-η¹:η³-C(R′)C(R′)CN(Me)(R)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (R = R′ = Me (2a); R = Me, R′ = Ph (2b); R = CH₂Ph, R′ = Me (2c); R = CH₂Ph, R′ = COOMe (2d)) react with cyanide and yield [Fe₂{μ-η¹:η³-C(R′)C(R′)C(CN)N(Me)(R)}(μ-CO)(CO)(Cp)₂] (9a-d). The reactions of the vinyliminium complex [Fe₂{μ-η¹:η³-C(Tol)CHCN(Me)(4-C₆H₄CF₃)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (4) with NaBH₄ and afford the allylidene [Fe₂{μ-C(Tol)C(H)C(H)N(Me)(C₆H₄CF₃)}(μ-CO)(CO)(Cp)₂] (5) and the cyanoallylidene [Fe₂{μ-C(Tol)C(H)C(CN)N(Me)(C₆H₄CF₃)}(μ-CO)(CO)(Cp)₂] (6), respectively. Analogously, the diruthenium vinyliminium complex [Ru₂{μ-η¹:η³-C(SiMe₃)CHCN(Me)(CH₂Ph)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (7) reacts with to give [Ru₂{μ-η¹:η³-C(SiMe₃)CHC(CN)N(Me)(CH₂Ph)}(μ-CO)(CO)(Cp)₂] (8).Finally, cyanide addition to [Fe₂{μ-η¹:η³-C(COOMe)C(COOMe)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂][SO₃CF₃] (2e) (Xyl = 2,6-Me₂C₆H₃), yields the cyano-functionalized bis-alkylidene complex [Fe₂{μ-η¹:η²-C(COOMe)C(COOMe)(CN)CN(Me)(Xyl)}(μ-CO)(CO)(Cp)₂] (10). The molecular structures of 3a and 9a have been elucidated by X-ray diffraction.     

A shock-tube study of the kinetics of reaction of hydroxyl radicals with H2, CO,CH4, CF3H,C2H4, and C2H6

Concentration-time profiles have been measured for hydroxyl radicals generated by the shock-tube decomposition of hydrogen peroxide in the presence of a variety of additives. At temperatures close to 1300°K the rate constants for the reaction are found to be in the ratio 0.18:0.19:0.59:1.00:2.33:2.88 for the additives CO:CF₃H:H₂:CH₄:C₂H₄:C₂H₆, respectively.     

Syntheses, structures and reactivities of diindenyl-coordinated diiron bridging carbene complexes

Compound [Fe₂(μ-CO)₂(CO)₂(η⁵-C₉H₇)₂] (1) reacts with aryllithium reagents, ArLi (Ar = C₆H₅, p-CH₃C₆H₄, p-CF₃C₆H₄) followed by alkylation with Et₃OBF₄ to give the diindenyl-coordinated diiron bridging alkoxycarbene complexes [Fe₂{μ-C(OC₂H₅)Ar}(μ-CO)(CO)₂(η⁵-C₉H₇)₂] (2, Ar = C₆H₅; 3, Ar = p-CH₃C₆H₄, 4, Ar = p-CF₃C₆H₄). Complex 4 reacts with HBF₄ · Et₂O at low temperature to yield cationic bridging carbyne complex [Fe₂(μ-CC₆H₄CF₃-p)(μ-CO)(CO)₂(η⁵-C₉H₇)₂]BF₄ (5). Cationic 5 reacts with NaBH₄ in THF at low temperature to afford diiron bridging arylcarbene complex [Fe₂{μ-C(H)C₆H₄CF₃-p}(μ-CO)(CO)₂(η⁵-C₉H₇)₂] (6). The reaction of 5 with NaSC₆H₄CH₃-p under the similar conditions gave the bridging arylthiocarbene complex [Fe₂{μ-C(C₆H₄CF₃-p)SC₆H₄CH₃-p}(μ-CO)(CO)₂(η⁵-C₉H₇)₂] (7). Complex 5 can also react with carbonylmetal anionic compounds Na[M(CO)₅(CN)] (M = Cr, Mo, W) to produce the diiron bridging aryl(penta-carbonylcyanometal)carbene complexes [Fe₂{μ-C(C₆H₄CF₃-p)NCM(CO)₅}(μ-CO)(CO)₂(η⁵-C₉H₇)₂] (8, M = Cr; 9, M = Mo; 10, M = W). The structures of complexes 4, 6, 7, and 10 have been established by X-ray diffraction studies.     

Kinetics of reactions between methoxycarbonyl,methyl, and methoxy radicals formed in flash photolysis of dimethyl oxalate in gas phase

Flash photolysis of dimethyl oxalate produced the radicals CH₃, CH₃O, and COOCH₃. Thermally equilibrated methoxycarbonyl radicals did not decompose during radicalradical reactions in the presence of 40-torr cyclohexane in the temperature range 298–448 K. Cyclohexyl radicals were also generated during the flash photolysis of the reaction mixture. Rate coefficients of radical–radical reactions were calculated from the amounts of stable products determined by gas chromatography: CO, CO₂, CH₄, C₂H₄, C₂H₆, CH₂O, CH₃OH, CH₃OCH₃, HCOOCH₃, CH₃COOCH₃, CH₃OCOOCH₃, CH₃C₆H₁₁, and CH₃OC₆H₁₁. Calculations were performed using an iterative computer integration program. Absolute values of rate coefficients were based on the rate coefficient of the reaction between methyl radicals, k₁ = 2.7 × 10¹⁰ dm³ mol^?1 s^?1, measured with the same equipment. The rate coefficients for reactions (5)–(8) are:      

A SACM study of the cross-combination ratio of rate constants

An analysis of the cross-combination ratio of the rate constants in terms of the statistical adiabatic channel model allows to factorize into two contributions: one due to the motion along the reaction coordinates and another due to the reaction transitional modes. for the CH₃/CCl₃, CH₃/C₂H₃, CH₃/C₃H₅, CH₃/C₂H₅ and C₂H₅/C₃H₅ radical pairs were calculated.     

Reactivity of radicals CCl3(CH2CHR)n (R=H,CH3, Cl; n=1, 2) in addition reactions with unsaturated compounds

Using EPR spectroscopy, the rate constants for the addition of radicals CC1₃(CH₂· CH₂)_n, (R¹ for n=1 and R² for n=2), CCl₃CH₂CHCH₃ (R³), and CCl₃CH₂CHCl (R⁴) to unsaturated compounds CH₂=CHX (X=C₆H₅, COOCH₃, CN) and CH₂=C(CH₃)Y (Y=C₆H₅, COOCH₃) at 22C have been determined. The radicals R¹ and R² exhibit ambiphilic, and R⁴ electrophilic character towards the selected unsaturated compounds. It has been shown that the presence of the CCl₃ group in the -position of the radical center has little effect on the reactivity of the radical. Replacement of a hydrogen on the -carbon in radical R¹ by a CH₃ group or chlorine atom leads to a considerable reduction in the rate of addition of the radicals to the unsaturated compounds examined.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 548–554, March, 1991.     

Ion cyclotron resonance studies of some reactions of C+ ions

Product distributions and rate constants for the reaction of ground state C⁺ ions with O₂, NO, HCl, CO₂, H₂S, H₂O, HCN, NH₃, CH₄, H₂CO, CH₃OH, and CH₃NH₂ have been measured. Rate constants were obtained using ion cyclotron resonance trapped ion methods at JPL, and product distributions were obtained using a tandem (Dempster-ICR) mass spectrometer at the University of Utah. Rapid carbon isotope exchange has also been observed in C⁺-CO collisions.     

Hammett Correlation in the Accelerated Formation of 2,3-Diphenylquinoxalines in Nebulizer Microdroplets

The accelerated formation of 2,3-diphenylquinoxalines in microdroplets generated in a nebulizer has been investigated by competition experiments in which equimolar quantities of 1,2-phenylenediamine, C₆H₄(NH₂)₂, and a 4-substituted homologue, XC₆H₃(NH₂)₂ [X = F, Cl, Br, CH₃, CH₃O, CO₂CH₃, CF₃, CN or NO₂], or a 4,5-disubstituted homologue, X₂C₆H₂(NH₂)₂ [X = F, Cl, Br, or CH₃], compete to condense with benzil, (C₆H₅CO)₂. Electron-donating substituents (X = CH₃ and CH₃O) accelerate the reaction; in contrast, electron-attracting substituents (X = F, Cl, Br and particularly CO₂CH₃, CN, CF₃ and NO₂) retard it. A structure–reactivity relationship in the form of a Hammett correlation has been found by analyzing the ratio of 2,3-diphenylquinoxaline and the corresponding substituted-2,3-diphenylquinoxaline, giving a ρ value of −0.96, thus confirming that the electron density in the aromatic ring of the phenylenediamine component is reduced in the rate-limiting step in this accelerated condensation. This correlation shows that the phenylenediamine acts as a nucleophile in the reaction.     

Novel sandwich complexes of zirconium [C9H5(SiMe3)2](C5Me4R)ZrCl2 (R = CH3, CH2CH2NMe2): Synthesis and reduction behavior

Novel half-sandwich [C₉H₅(SiMe₃)₂]ZrCl₃ (3) and sandwich [C₉H₅(SiMe₃)₂](C₅Me₄R)ZrCl₂ (R = CH₃ (1), CH₂CH₂NMe₂ (2)) complexes were prepared and characterized. The reduction of 2 by Mg in THF lead to (η⁵-C₉H₅(SiMe₃)₂)[η⁵:η²(C,N)-C₅Me₄CH₂CH₂N(Me)CH₂]ZrH (7). The structure of 7 was proved by NMR spectroscopy data. Hydrolysis of 2 resulted in the binuclear complex ([C₅Me₄CH₂CH₂NMe₂]ZrCl₂)₂O (6). The crystal structures of 1 and 6 were established by X-ray diffraction analysis.     

A Theoretical Investigation of the Decomposition Reactions of Ethyl Formate in the S0 State

This study revisits the stability of the possible conformations and the decomposition reactions of ethyl formate in the S₀ state using the (U)MP2, MP4SDTQ, CCSD(T), and (U)B3LYP methods with various basis sets. The transition states of the decomposition channels to HCOOH + C₂H₄, CO + CH₃CH₂OH, CH₂O + CH₃CHO, HCOH + CH₃CHO, C₂H₆ + CO₂, and H₂ + CH₂CHOCHO are determined. The microcanonical rate constants derived from the RRKM theory are calculated for each of the decomposition reactions. The high‐pressure limit rate constants are calculated for the decomposition channels to HCOOH + C₂H₄, CO + CH₃CH₂OH, and CH₂O + CH₃CHO.     

The pyrolysis of acetaldehyde in the presence of nitric oxide

The kinetics of the acetaldehyde pyrolysis have been studied at temperatures from 450° to 525°C, at an acetaldehyde pressure of 176 torr and at 0 to 40 torr of added nitric oxide. The following products were identified and their rates of formation measured: CH₄, H₂, CO, CO₂, C₂H₄, C₂H₆, H₂O, C₃H₆, C₂H₅CHO, CH₃COCH₃, CH₃COOCH?CH₂, N₂, N₂O, HCN, CH₃NCO, and C₂H₅NCO. Acetaldehyde vapor was found to react with nitric oxide slowly in the dark at room temperature, the products being H₂O, CH₃COOCH₃, CO, CO₂, N₂, NO₂, HCN, CH₃NO₂, and CH₃ONO₂. The rates of formation of N₂ and C₂H₅NCO depend on how long the CH₃CHO-NO mixture is kept at room temperature before pyrolysis; the rates of formation of the other products depend only slightly on the mixing period. The pyrolysis of “clean” CH₃CHO–NO mixtures (i.e., the results extrapolated to zero mixing time, which are independent of products formed in the cold reaction) are interpreted as follows: (1) There are two chain carriers, CH₃ and CH₂CHO, their concentrations being interdependent and influenced by NO in different ways: the CH₃ radical is both generated and removed by reactions directly involving NO, whereas CH₂CHO is generated only indirectly from CH₃ but is also removed by direct reaction with NO. (2) An important mode of initiation by NO is its addition to the carbonyl group with the formation of which is converted into ; this splits off OH with the formation of CH₃NCO or CH₃ + OCN. (3) Important modes of termination are The steady-state equations derived from the mechanism are shown to give a good fit to the experimental rate versus [NO] curves and, in particular, explain why there is enhancement of rate by NO at higher CH₃CHO pressures and, at lower CH₃CHO pressures, inhibition at low [NO] followed by enhancement at higher [NO]. The cold reaction is explained in terms of chain-propagating and chain-branching steps resulting from the addition of several NO molecules to CH₃CHO and the CH₃CO radical. In the “unclean” reaction it is found that the rates of N₂ and C₂N₅NCO formation are increased by CH₃NO₂, CH₃ONO, and CH₃ONO₂ formed during the cold reaction. A mechanism is proposed, involving the participation of α-nitrosoethyl nitrite, CH₃CH(NO)ONO. It is suggested that there are two modes of behavior in pyrolyses in the presence of NO: (1) In the paraffins, ethers, and ketones, the effects are attributed to the addition of NO to a radical with the formation of an oxime-like compound. (2) In the aldehydes and alkenes, where there is a hydrogen atom attached to a double-bonded carbon atom, the behavior is explained in terms of addition of NO to the double bond followed by the formation of an oxime-like species.     

Efficient Cu‐catalyzed Atom Transfer Radical Addition Reactions of Fluoroalkylsulfonyl Chlorides with Electron‐deficient Alkenes Induced by Visible Light

Fluoroalkylsulfonyl chlorides, R_fSO₂Cl, in which R_f=CF₃, C₄F₉, CF₂H, CH₂F, and CH₂CF₃, are used as a source of fluorinated radicals to add fluoroalkyl groups to electron‐deficient, unsaturated carbonyl compounds. Photochemical conditions, using Cu mediation, are used to produce the respective α‐chloro‐β‐fluoroalkylcarbonyl products in excellent yields through an atom transfer radical addition (ATRA) process. Facile nucleophilic replacement of the α‐chloro substituent is shown to lead to further diverse functionalization of the products.     

Gas‐Phase Synthesis of the Benzyl Radical (C6H5CH2)

Dicarbon (C₂), the simplest bare carbon molecule, is ubiquitous in the interstellar medium and in combustion flames. A gas‐phase synthesis is presented of the benzyl radical (C₆H₅CH₂) by the crossed molecular beam reaction of dicarbon, C₂(X¹Σ_g⁺, a³Π_u), with 2‐methyl‐1,3‐butadiene (isoprene; C₅H₈; X¹A′) accessing the triplet and singlet C₇H₈ potential energy surfaces (PESs) under single collision conditions. The experimental data combined with ab initio and statistical calculations reveal the underlying reaction mechanism and chemical dynamics. On the singlet and triplet surfaces, the reactions involve indirect scattering dynamics and are initiated by the barrierless addition of dicarbon to the carbon–carbon double bond of the 2‐methyl‐1,3‐butadiene molecule. These initial addition complexes rearrange via multiple isomerization steps, leading eventually to the formation of C₇H₇ radical species through atomic hydrogen elimination. The benzyl radical (C₆H₅CH₂), the thermodynamically most stable C₇H₇ isomer, is determined as the major product.