Quantum yield for photosubstitution of a co group in chromium hexacarbonyl by pyridine

The quantum yield of the photosubstitution of CO by pyridine in cyclohexane has a value of 0.67 ± 0.02 for [Cr(CO)₆] = 3.10^?4 mol l^? and [pyridine] = 10^? mol l^?1.     

Reactions of RSe− (R = Me,Ph) Groups in [RSeFe(CO)4I and [RSeCr(CO)5−]

The anionic [MeSeFe(CO)₄] and [MeSeCr(CO)₅] complexes were synthesized by reaction of [PPN][HFe(CO)₄] and [PPN][HCr(CO)₅] with MeSeSeMe respectively via nucleophilic cleavage of the Se-Se bond. The ease of cleavage of the Se-Se bond follows the nucleophilic strength of metal-hydride complexes. Methylation of [RSeCr(CO)₅^?] by the soft alkylating agent MeI resulted in the formation of neutral (MeSeMe)Cr(CO)₅ in THF at 0°C. In contrast, the [ICr(CO)₅^?] was isolated at ambient temperature. Reaction of [MeSeFe(CO)₄^?] or [MeSeCr(CO)₅^?] with HBF₄ yielded (CO)₃Fc(μ-SeMe)₂Fe(CO)₃ dimer and anionic [(CO )₅Cr (μ-SeMe)Cr(CO)₅^?] respectively, and no neutral (HSeMe)Fe(CO)₄ and (HSeMe)Cr(CO)₅ were detected spectrally (IR) even at low temperature. Reaction of NOBF₄ or [Ph₃C][BF₄] and [MeSeCr(CO)₅^?] resulted in the neutral monodentate (MeSeSeMe)Cr(CO)₅ complex. Addition of 1 equiv CpFe(CO)₂I to 2 equiv [MeSeCr(CO)₅^?] gave CpFe(CO)₂(SeMe) and the anionic [(CO)₅Cr(μ-SeMe)Cr(CO)₅^?] in THF at ambient temperature.     

Komplexchemie P-reicher Phosphane und Silylphosphane. XI [1]. Bildung,Reaktionen und Strukturen von Chromcarbonylkomplexen aus Reaktionen von Li(THF)2[η2-(tBu2P)2P] mit Cr(CO)5 · THF und Cr(CO)4 · NBD

Transition Metal Complexes of P-rich Phosphanes and Silylphosphanes. XI. Formation, Reactions, and Structures of Chromium Carbonyl Complexes from Reactions of Li(THF)₂[η₂-(^tBu₂P)₂P] with Cr(CO)₅ · THF and Cr(CO)₄ · NBD Reactions of Li(THF)₂[η²-(^tBu₂P)₂P] 1 with Cr(CO)₅ · THF yield Li(THF)₂Et₂O[Cr(CO)₄{η²-(^tBu₂P)₂P}η¹-Cr(CO)₅] 2 and the compounds [Cr(CO)₄{η²-(^tBu₂P)₂PH}] 3 , [Cr(CO)₅{η¹-(^tBu₂P)₂PH}] 4 , (^tBu₂P)₂PH 5 and ^tBu₂PH · Cr(CO)₅ 6 . The formation of 3, 4, 5 and 6 is due to byproducts coming from the synthesis of 1. 2 reacts with CH₃COOH under formation of 3 . After addition of 12-crown-4 1 with NBD · Cr(CO)₄ in THF forms Li(12-crown-4)₂[Cr(CO)₄-{η²-(^tBu₂P)₂P}] 7 (yellow crystals). 7 reacts with CH₃COOH to 3 – which regenerates 7 with LiBu – with Cr(CO)₅THF to compound 2 , with NBD · Cr(CO)₄ in THF to 2 and 3 (ratio 1 : 1). With EtBr, 7 forms [Cr(CO)₄{η²-(^tBu₂P)₂PEt}] 8 , and [Cr(CO)₄{η²-(^tBu₂P)₂PBr}] 9 with BrCH₂? CH₂Br. The compounds were characterized by means of ¹H, ¹³C, ³¹P, ⁷Li NMR spectroscopy, IR spectroscopy, elementary analysis, mass spectra, and 2, 3 and 4 additionally by means of X-ray diffraction analysis. 2 crystallizes in the space group P1 with 2 formula units in the elementary cell; a = 10.137(9), b = 15.295(12), c = 15.897(14) Å; α = 101.82(7), β = 91.65(7), γ = 98.99(7)°; 3 crystallizes in the space group P2_t/n with 4 molecules in the elementary unit; a = 11.914(6), b = 15.217(10), c = 14.534(10) Å; α = 90, β = 103.56(5), γ = 90°. 4 : space group P1 with 2 molecules in the elementary unit; a = 8.844(4), b = 12.291(6), c = 14.411(7) Å, α = 66.55(2), β = 89.27(2), γ = 71.44(2)°.     

Komplexchemie P-reicher Phosphane und Silylphosphane. VIII. Zur unterschiedlichen Tendenz der Bildung von Chromcarbonyl-Komplexen silylierter-alkylierter Phosphane und Diphosphane

Transition Metal Complexes of P-rich Phosphanes and Silylphosphanes. VIII. Concerning the Different Tendencies of Silylated and Alkylated Phosphanes and Diphosphanes to Form Chromium Carbonyl Complexes The influence of the substituents Me₃Si tBu and Me in phosphanes and diphosphanes on the formation of complex compounds with Cr(CO)₅THF is investigated. tBu(Me₃Si)P? P(SiMe₃)₂ 1 and (tBu)₂P? P(SiMe₃)₂ 2, resp., react with Cr(CO)₅THF 4 at ?18°C by coordinating Cr(CO)₅ to the P(SiMe₃)₂ group to give tBu(Me₃Si)P? P^IV(SiMe₃), · Cr(CO)₅ 1 a, tBu(Me₃Si)P^IV? P^IV(SiMe₃)₂ · Cr(CO)₄ 1b and (tBu)₂P? P^IV(SiMe₃)₂ · Cr(CO)₅ 2a . In the reaction of 1 with 4 using a molar ratio of 1:2 at first 1 a is formed which reacts on to yield completely 1 b. In a mixture of the dissolved compounds (Me₃Si)₃P 5, (tBu)₃P 6 and (tBu)₃P? P(SiMe₃)₂ 2 only 5 and 6 react with Cr(CO)₅THF yielding (Me₃Si)₃P · Cr(CO)₅ and (tBu)₃P · Cr(CO)₅, but 2 does not yet react. In a solution of (Me₃Si)₃P 5, P₂Me₄ 7 and (Me₃Si)₂P? PMe₂ 3 only 5 and 7 react with Cr(CO)₅THF (0.25 to 1.5 equivalents with respect to 3) to give (Me₃Si)₃P · Cr(CO)₅, P₂Me₄ · Cr(CO)₅ and P₂Me₄ · 2Cr(CO)₅. The formation of complexes with Cr(CO)₅THF of the phosphanes 5 and 6 is clearly favoured as compared to the silylated diphosphanes 2 and 3 (not to P₂Me₄); the PR₂ groups (R = tBu, Me in 2 or 3 ) don't have a strong influence.     

Synthesis of the pentacarbonyl(chalcocarbonyl)chromium(0) complexes,Cr(CO)5(CX) (X = S,Se)

The arene complexes, (η⁶-C₆H₆)Cr(CO)₂(CX) (X = S, Se), react with excess CO gas under pressure in tetrahydrofuran at about 60° C to produce the Cr(CO)₅(CX) complexes in high yield. The IR and NMR (¹³C and ¹⁷O) spectra of these complexes are in complete accord with the expected C_4v molecular symmetry. Like the analogous W(CO)₅(CS) complex, both compounds react with cyclohexylamine to give Cr(CO)₅(CNC₆H₁₁). However, while W(CO)₅(CS) undergoes stereospecific CO substitution with halide ions (Y^? to form trans-[W(CO)₄(CS)Y]^?, the two chromium chalcocarbonyl complexes apparently undergo both CO and CX substitution to afford mixtures of [Cr(CO)₅Y]^? and trans-[Cr(CO)₄(CX)Y]^?.     

The structure of copolymers of vinyl cyclohexane with styrene

Copolymerization of vinyl cyclohexane (monomer-1) with styrene was investigated in the presence of the stereospecific complex catalyst TiCl₃ + Al(iso-C₄H₉)₃. Monomer reactivity ratios were r₁ = 0·177 ± 0·051 and r₂ = 2·117 ± 0·370. The monomer unit distributions in the copolymers were estimated by comparison of the i.r.-spectra of copolymers and the isotactic homopolymers using absorption bands at 565 and 1084 cm^?1 which correspond to the vibrations of styrene blocks containing ? 5 styrene units and the band at 985 cm^?1 characterizing polystyrene crystallinity. The data indicate the tendency towards alternation in the copolymerization. Analysis of the experimental and literature data led to the conclusion that distribution of the units in copolymers of vinyl cyclohexane with α-olefins is determined by the nature of the α-olefin. The following activity series is proposed for α-olefins in their copolymerization with vinyl cyclohexane in the presence of catalytic systems based on titanium salts and organo-aluminium compounds: propylene >; 4-methylpentene-1 >; styrene >; 3-methylbutene-1 ～ vinyl cyclohexane.     

Photochemistry of Mn2(CO)10

Flash photolysis studies on Mn₂(CO)₁₀ in cyclohexane and THF show that the dominant photochemistry involves photolytic formation of 2 Mn(CO)₅ followed by recombination at rates near the diffusion-controlled limit. A second, relatively, long-lived intermediate is also observed and earlier observations of photodecomposition and photodisproportionation can be accounted for in terms of secondary photolysis of this intermediate. For the equilibrium: Mn₂(CO)₁₀ ? 2 Mn(CO)₅ △H ～ 36 kcal/mol, △S ～ 32 e.u., and K(25°C) ～ 10^?20 where the thermodynamic values have been estimated from kinetic measurements.     

Komplexchemie P-reicher Phosphane und Silylphosphane. IV. Bildung und Struktur der Chromcarbonylkomplexe des Tris(di-tert-butylphospha)heptaphosphanortricyclans, (t-Bu2P)3P7

Transition Metal Complexes of P-rich Phosphanes and Silylphosphanes. IV. Formation and Structure of the Chromium Carbonyl Complexes of Tris(di-tert-butylphospha)heptaphosphanortricyclane (t-Bu₂P)₃P₇ The reaction of (t-Bu₂P)₃P₇ 1 with Cr(CO)₅ · THF in a molar ratio of 1:1 yields yellow crystals of (t-Bu₂P)₃P₇[Cr(CO)₅] 2 having the Cr(CO)₅ group coordinated to a P^b atom (basal) of the three membered ring. With a molar ratio of 1:2 compounds 2 , (t-Bu₂P)₃P₇[Cr(CO)₅]₂ 3 , (t-Bu₂P)₃P₇[Cr(CO)₅][Cr(CO)₄] 4 and (t-Bu₂P)₃P₇[Cr(CO)₄]₂ 5 were obtained. In 3 (yellow crystals) one Cr(CO)₅ group is linked to a P^b atom, the other one to an exocyclic P^exo atom. On irradiation 3 loosing one CO group generates 4 (orange red crystals) with an unchanged Cr(CO)₅ group linked to the Pb atom and a five membered chelate-like ring containing an apical Pa atom, two equatorial P^a atoms, one P^exo atom and the Cr atom of the carbonyl group. Compound 5 (orange red crystals) contains two such five membered rings. (t-Bu₂P)₃P₇[Cr(CO)₄]₃ 6 (red needles) is formed with Cr(CO)₅ · THF in a molar ratio of 1 : 1. However, even with higher amounts of Cr(CO)₅ · THF and after extended reaction times, only 6 is formed; no further Cr carbonyl group could be attached to the P skeleton. With Cr(CO)₅ · NBD in a molar ratio of 1 : 1, (t-Bu₂P)₃P₇[Cr(CO)₄] 7 is produced from 1, and 5 with a molar ratio of 2 : 1. As in 4, the Cr(CO)₄ group in 7 (orange crystals) participates in a five membered chelate-like ring. It was not possible to generate 6 from 5 with an excess of Cr(CO)₄ · NBD and with extended reaction times. The molecular structures of the compounds were identified by investigating the ³¹P[¹H] NMR spec-tra and considering especially the coordination shift, and by crystal structure determinations of 2 and 4. Compound 2 crystallizes in the space group PI (no.2) with a = 1566.2(4) pm, b = 2304.1(5) pm, c = 1563.3(4) pm,α = 95.57(3)°, β = 108.79(3)°, γ = 109.82(4)° and Z = 4 formula units in the elementary cell. Compound 4 crystallizes in the space group P 2₁ /n (no. 14) with a = 1416.6(5) pm, b = 2573.6(5) pm, c = 1352.9(4) pm,β = 99.17(5)° and Z = 4 formula units in the elementary cell.     

The enthalpies of formation of CH3Mn(CO)5 and of CH3Re(CO)5, and the strengths of the CH3Mn and CH3Re bonds

From measurements of the heats of iodination of CH₃Mn(CO)₅ and CH₃Re(CO)₅ at elevated temperatures using the ‘drop’ microcalorimeter method, values were determined for the standard enthalpies of formation at 25° of the crystalline compounds: ΔH^o_f[CH₃Mn(CO)₅, c] = ?189.0 ± 2 kcal mol^?1 (?790.8 ± 8 kJ mol^?1), ΔH^o_f[Ch₃Re(CO)₅,c] = ?198.0 ± kcal mol^?1 (?828.4 ± 8 kJ mo^?1). In conjunction with available enthalpies of sublimation, and with literature values for the dissociation energies of MnMn and ReRe bonds in Mn₂(CO)₁₀ and Re₂(CO)₁₀, values are derived for the dissociation energies: D(CH₃Mn(CO)₅) = 27.9 ± 2.3 or 30.9 ± 2.3 kcal mol^?1 and D(CH₃Re(CO)₅) = 53.2 ± 2.5 kcal mol^?1. In general, irrespective of the value accepted for D(MM) in M₂(CO)₁₀, the present results require that, D(CH₃Mn) = $\text{1}\text{2}$D(MnMn) + 18.5 kcal mol^?1 and D(CH₃Re) = $\text{1}\text{2}$D(ReRe) + 30.8 kcal mol^?1.     

Kinetic determination of the metalmetal bond dissociation energy in bis(dicarbonyl η5-cyclopentadienyliron)

The ironiron bond energy in [C₅H₅Fe(CO)₂]₂ (I) has been determined by measuring the rate of disproportionation of the monoacetyl complex (AcC₅H₄)(C₅H₅)Fe₂(CO)₄ (II) to I and [AcC₅H₄Fe(CO)₂]₂ (III). The reaction follows first order kinetics in benzene solution in the temperature range of 60–100°C with activation parameters calculated as: ΔH^≠ = 26.9 ± 2.7 kcal mol^?1 and ▽s^≠ = 2.0 ± 3.2 cal mol^?1 deg^?1.     

The thermochemistry of carbonyl complexes of Cr,Mo and W with pyridine and acetonitrile

Microcalorimetric measurements at elevated temperatures of the heats of thermal decomposition and of iodination of a number of [M(CO)_nL_6-n] complexes (M = Cr, Mo, W; n = 3, 4; L = py, MeCN) have led to values for the standard enthalpies of formation of the following crystalline compounds (values given in kJ mol^?) at 25°C: fac-[Mo(CO)₃py₃](275 ± 12), fac-[Mo(CO)₃(NCCH₃)₃]  (410 ± 12), fac-[W(CO)₃py₃](250 ± 12), fac-[W(CO)₃(NCCH₃)₃](405 ± 12) and cis-[Cr(CO)₄py₂](505 ± 20). From these and other data, including estimated heats of sublimation, the bond enthalpy contributions of the various metalligand bonds in the gaseous metal complexes were evaluated as follows (values in kJ mol^?): D(Crpy) 102, D(Mopy) 146, DWPy) 173, D(Mo7z.sbnd;NCMe) 135 and D(WNCMe) 169. For a given metal the bond enthalpy contribution decreased in the order D(MCO) > D(Mpy) > D(Mz.sbnd;NCMe). This order is related to the σ- and π-bonding character of the ligand.     

Gas-phase chemistry of electron deficient organometallic anions: the reactions of [Cr(CO)3]− ˙ and [Cr(CO)4]− ˙ with aldehydes,ketones, esters and ethers

Reactions in the gas phase of the 13- and 15-electron radical anions [Cr(CO)₃]^{? ˙} and [Cr(CO)₄]^{? ˙} with a series of 27 aldehydes, ketones, esters and ethers have been examined. Sequential alkane eliminations and metal-bonded CO ligand displacements were the principal reactions identified for the RCHO/[Cr(CO)₃]^{? ˙} systems with the latter reaction also common to the RCHO/[Cr(CO)₄]^{? ˙} systems. While [Cr(CO)₄]^{? ˙} was generally unreactive towards ketones R · R'CO, the principal products identified for [Cr(CO)₃]^{? ˙}/ketone reactions were the metal-decarbonylated species, respectively [R · R'CO · Cr(CO)_x]^{? ˙} with x = 0–3, and [R · (R' - H₂)CO · Cr(CO)₂]^{? ˙}. The reaction of [Cr(CO)₃]^{? ˙} with esters RCOOR' proceeds via metal insertion into the alkoxy C? O bond to give end products of the type [R'O · Cr · R(CO)₂]^? and [R'O? Cr(CO)₃]^? while the sole ionic products of dialkyl ether/[Cr(CO)₃]^{? ˙} reactions were identified as the alkoxytricarbonylchromium species [RO · Cr(CO)₃]^?.     

OsII-Phthalocyaninate(2−): Darstellung und Eigenschaften von (Halogeno)-(carbonyl)phthalocyaninato(2−)osmat(II)

Os^II Phthalocyaninates(2?): Synthesis and Properties of (Halo)(carbonyl)phthalocyaninato-(2?)osmate(II) Soluble, blue tetra(n-butyl)ammonium (halo)(carbonyl)phthalocyaninato(2?)osmate(II), (ⁿBu₄N)[Os(X)(CO)Pc^2?] (X = Cl, Br, I) is obtained by the reaction of [Os(THF)(CO)Pc^2?] (THF: tetrahydrofurane) with (ⁿBu₄N)X in THF. In the cyclovoltammograms there are three reversible electrode processes at ?1.21 ± 0.01, 0.18 ± 0.04 and 0.65 ± 0.01 V assigned to the three redox pairs Pc^2?/Pc^3?, Os^II/Os^III and Pc^2?/Pc^3?. In the electronic absorption spectra only the intense B and Q regions are observed at ～ 15800 resp. 27500, 33000 cm^?1. The infrared and resonance Raman spectra closely resemble those of other phthalocyaninates(2?) of low valent osmium. In the infrared spectrum v(C? O) is detected at 1896 ± 4 cm^?1 and v(Os? X) at 260 (X = Cl), 175 (X = Br) or 143 cm^?1 (X = I).     

Kinetic study of the reactions of atomic chlorine with several volatile organic compounds at 240–340 K

The rate constant for the reactions of atomic chlorine with 1,4‐dioxane (k₁), cyclohexane (k₂), cyclohexane‐d₁₂(k₃), and n‐octane (k₄) has been determined at 240–340 K using the relative rate/discharge fast flow/mass spectrometer (RR/DF/MS) technique developed in our laboratory. Essentially, no temperature dependence for these reactions was observed over this temperature range, with an average of k₁ = (1.91 ± 0.20) × 10^?10 cm³ molecule^?1 s^?1, k₂ = (2.91 ± 0.31) × 10^?10 cm³ molecule^?1 s^?1, k₃ = (2.73 ± 0.30) × 10^?10 cm³ molecule^?1 s^?1, and k₄ = (3.22 ± 0.36) × 10^?10 cm³ molecule^?1 s^?1, respectively. The kinetic isotope effect of the reaction of cyclohexane with atomic chlorine has also been determined to be 1.14 by directly monitoring the decay of both cyclohexane and cyclohexane‐d₁₂ in the presence of chlorine atoms, which is consistent with the literature value of 1.20. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 386–398, 2006     

Fundamental metal carbonyl equilibria: III. A quantitative study of the equilibrium between dirhodium octacarbonyl and tetrarhodium dodecacarbonyl under carbon monoxide pressure. A correction

Previously reported (J. Organomet. Chem., 246 (1983) 309) experimental data for the equilibrium constants and thermodynamic parameters of the reversible reaction 2 Rh₂(CO)₈ ? Rh₄(CO)₁₂ + 4 CO have been re-evaluated using more reliable values for the solubility of carbon monoxide in hexane at lower than room temperature and introducing also a fugacity vs. pressure correction for carbon monoxide. The new values are: ΔH0 = 58.6 ± 10 kJ mol^?1 and ΔS⁰ = 305 ± 25 J mol^?1 K^?1     

Metallkomplexe mit anionischen Liganden von Elementen der 4. Hauptgruppe. VIII. Pentacarbonyl-trihalogenstannido-metallat(O)-Komplexe von chrom,molybdän und wolfram mit fluor- und jodhaltigen stannidliganden

Metal Complexes with Anionic Ligands of Elements of the Main Group IV. VIII Pentacarbonyltrihalogenostannidometalate(O) Complexes of Chromium, Molybdenum, and Tungsten with Fluorine and Iodine Containing Trihalogenostannido Ligands In methylenechloride [As(C₆H₅)₄][SnF₃] readily reacts with the metalhexacarbonyls forming the arsoniumsalts of the pentacarbonyltrifluorostannidometalate(O) complexes, [M(CO)₅SnF₃]^? (M ? Cr, Mo, W). Exclusively by the reaction of the intermediately formed complex Cr(CO)₅THF only one pure triiodostannidometalate(O) Complex, [N(C₂H₅)₄][Cr(CO)₅SnJ₃], could be isolated. The trihalogenostannidometalate(O) complexes [M(CO)₅SnClX₂]^? (X ? F: M ? Cr, Mo, W; X ? J: M ? Cr) could be prepared by SnX₂-insertion reactions of the [M(CO)₅Cl]^? complexes. The bonding properties of the halogenostannide ions are discussed on the bases of the IR spectra of their metalate(O) complexes.     

Uber die Reaktionen der Hexacarbonyle der VI. Nebengruppe mit Zinn (II)- und Germanium (II)-halogeniden

On Reactions of Subgroup. VI. Hexacarbonyls with Tin(II) and Germanium (II) Halides The neutral complexes M(CO)₅SnX₂ and M(CO)₅GeCl₂ (M = Cr, Mo, W; X = Cl, Br, J) have been prepared by a photochemical reaction between M(CO)₆ and SnX₂, or CsGeCl₃ in THF. The reaction of these compounds with [N(CH₃)₄]X (X = Cl, Br, J) in THF was found to lead to a series of anions [M(CO)₅SnX₃]^? or [M(CO)₅GeCl₃]^? (M = Cr, Mo, W; X = Cl, Br, J), some of which have previously been prepared. The physical properties and IR-spectra of the above compounds are discussed.     

Rate constant of the gas-phase reaction between Fe atoms and CO2

The rate constant of the gas-phase reaction Fe(a ⁵ D ₄) + CO₂ at 1180–2380 K and a total gas density of (7.0–10.0) × 10^?6 mol/cm³ behind incident shock waves is k(Fe + CO₂) = 1.4 × 10^{14.0 ± 0.3}exp[?(14590 ± 1100)/T] cm³ mol^?1 s^?1, as determined by resonance atomic absorption photometry. Using thermochemical data available from the literature, the rate constant of the reverse reaction was calculated to be k(Fe + CO) = 9.2 × 10^{11.0 ± 0.3} (T/1000)^0.57exp[?(490 ± 1100)/T] cm³ mol^?1 s^?1. The results are compared with data reported earlier.     

Beiträge zur chemie des bors LXXX. Pentacarbonylchromkomplexe von diorganylmethylthioboranene und von 2-diäthylboryl-5-methylthiophen

Substitution of THF by diorganylmethylthiboranes in (CO)₅Cr · THF yields the rather unstable complexes (CO)₅Cr · CH₃SBR₂ (R = CH₃, C₆H₅). In contrast to the σ-thiophene complex (CO)₅Cr · SC₄H₄ the pentacarbonylchromium complex of the σ-S-bonded 2-diethylboryl-5-methylthiopene is quite stable due to interaction of the boryl group with CO ligands.     

An FTIR study of the Cl-atom-initiated reaction of glyoxal

The kinetics and mechanism of Cl-atom-initiated reactions of CHO? CHO were studied using the FTIR detection method to monitor the photolysis of Cl₂–CHO? CHO mixtures in 700 torr of N₂–O₂ diluent at 298 ± 2 K. The observed product distribution in the [O₂] pressure of 0–700 torr combined with relative rate measurements provide evidence that: (1) the primary step is Cl + CHO? CHO → HCl + CHO? CO with a rate constant of [3.8 ± 0.3(σ)] × 10^?11 cm³ molecule^?1 s^?1; (2) the primary product CHO? CO unimolecularly dissociates to CHO and CO with an estimated lifetime of ≤ca. 1 × 10^?7 s; (3) alternatively, the CHO? CO reacts with O₂ leading to the formation of CO, CO₂, and most likely the HO radical, but no stable products containing two carbon atoms; (4) the HO₂ radical, formed in the secondary reaction CHO + O₂ → HO₂ + CO, reacts with the CHO? CHO with a rate constant ca. 5 × 10^?16 cm³ molecule^?1 s^?1 to form HCOOH and a new transient product resembling that detected previously in the HO₂ reaction with HCHO.