N.m.r. studies on aromatic compounds. I—13C n.m.r. spectra of some mono- and disulpho-substituted hydroxycarboxylic acids

Carbon-13 n.m.r. spectra of 3-hydroxy-4-sulpho-2-naphthoic, 3-hydroxy-5-sulpho-2-naphthoic, 3-hydroxy-7-sulpho-2-naphthoic, 5-sulphosalicylic, 3-hydroxy-5,7-disulpho-2-naphthoic, 1-hydroxy-4,7-disulpho-2-naphthoic, and 3,5-disulphosalicylic acids were recorded with and without proton noise-decoupling. Analyses of the spectra were carried out for all compounds except 3-hydroxy-5-sulpho-2-naphthoic acid which dimerized. The fine splitting caused by long-range coupling was used in identifying the lines of the ¹³C n.m.r. spectra.     

Transition-metal-promoted reactions of boron hydrides. 17. Titanium-catalyzed decaborane-olefin hydroborations.

The titanium-catalyzed hydroboration reactions of decaborane with a variety of terminal olefins have been found to result in the exclusive, high-yield formation of monosubstituted decaborane 6-R-B(10)H(13) products, arising from anti-Markovnikov addition of the cage B6-H to the olefin. The titanium-catalyzed reactions are slow, often less than one turnover per hour; however, their high selectivities and yields coupled with the fact that they are simple, one-pot reactions give them significant advantages over the previously reported routes to 6-R-B(10)H(13) compounds. The catalyst also has extended activity with reactions carried out for as long as 13 days, showing little decrease in reactivity, thereby allowing for the production of large amounts of 6-R-B(10)H(13). The titanium-catalyzed reactions of decaborane with the nonconjugated diolefins, 1,5-hexadiene and diallylsilane, were found to give, depending upon reaction conditions and stoichiometries, high yields of either alkenyl-substituted 6-(CH(2)=CH(CH(2))(4))-B(10)H(13) (4) and 6-(CH(2)=CHCH(2)SiMe(2)(CH(2))(3))-B(10)H(13) (5) or linked-cage 6,6'-(CH(2))(6)-(B(10)H(13))(2) (6) and Me(2)Si(6-(CH(2))(3)-B(10)H(13))(2) (7) compounds, respectively. The unique tetra-cage product, Si(6-(CH(2))(3)-B(10)H(13))(4) (8), was obtained by the catalyzed reaction of 4 equiv of decaborane with tetraallylsilane. Sequential use of the titanium catalyst and previously reported platinum catalysts (PtBr(2) or H(2)PtCl(6).6H(2)O with an initiator) provides an efficient pathway to asymmetrically substituted 6-R-9-R'-B(10)H(12) species. The structures of compounds 5, 6, and 8, as well as a platinum derivative, (PSH(+))(2)-commo-Pt-[nido-7-Pt-8-(n-C(8)H(17))B(10)H(11)](2)(2-), of 6-(n-octyl)decaborane have been established by single-crystal crystallographic determinations.     

Chromic Oxidation of 2-Deoxy-d-Glucose. Comparative Study with Aldoses. I.

Abstract

A rate law for the oxidation of 2-deoxy-d-glucose (2DG) by Cr(VI) in perchloric acid has been derived. This rate law corresponds to the reaction leading to the formation of 2-deoxy-d-gluconic acid (2DGA). No cleavage to carbon dioxide takes place when a twenty-fold or higher excess of aldose over Cr(VI) is employed. Kinetic constants are interpreted in terms of the absence of an hydroxyl group at C-2 on the stability of the chromic ester formed in the first reaction step. Free radicals formed during the reaction convert Cr(VI) to Cr(V). The latter species was detected by EPR measurements.     

Mediated electrochemistry of horseradish peroxidase. Catalysis and inhibition.

A precise determination of the complex mechanism of catalysis and inhibition involved in the reaction of HRP with H(2)O(2) as substrate and an outersphere single electron donor ([Os(bpy)(2)pyCl](+)) as cosubstrate is made possible by a systematic analysis of the cyclic voltammetric responses as a function of the scan rate and of the substrate and cosubstrate concentrations, complemented by spectrophotometric steady-state and stopped-flow experiments. The bell-shaped calibration curve relating the electrochemical response to the concentration of H(2)O(2) is qualitatively and quantitatively explained by taking into account the conversion of the catalytically active forms of the enzyme into the inactive oxyperoxidase in addition to the primary catalytic cycle. These characteristics should be kept in mind in biosensor applications of HRP. The ensuing analysis and data allow one to predict biosensor amperometric responses in all practical cases. From a mechanistic standpoint, conditions may, however, be defined which render inhibition insignificant, thus allowing an electrochemical characterization of the primary catalytic cycle. At very low concentrations of H(2)O(2), its diffusion tends to control the electrochemical response, resulting in proportionality with H(2)O(2) concentration instead of the square root dependence characteristic of the classical catalytic currents. Intriguing hysteresis and trace crossings behaviors are also quantitatively explained in the framework of the same mechanism. As a consequence of the precise dissection of the rather complex reaction mechanism into its various elementary steps, a strategy may be devised for gaining a better understanding of the mechanism and reactivity patterns of each elementary step.     

Structural studies of metabolic products of dopamine. III. Crystal and molecular structure of (--)-adrenaline.

The crystal structure of (--)-adrenaline has been determined by X-ray methods, using 831 observed reflections collected by counter methods. The crystals are monoclinic, space group P2-1 with a=7.873(2), b=6.790(2), c=8.638(2) A and beta=98.01(2) degrees. Least-squares refinements yielded a conventional R-factor of 0.053. Standard deviations in bond lengths are 0.005-0.006 A and in bond lengths aree 0.005-0.006 A and in bond angles 0.4 degrees. The adrenaline molecules were found to exist as zwitterions in the crystals. The conformation of the adrenaline molecule corresponds closely to that usually encountered among the salts of the sympathomimetic amines. The crystals consist of molecular double layers parallel to (100). The molecules within a layer are linked through hydrogen bonds of the types N--H...O and O--H...O, whereas the layers are connected by van der Waals interactions.     

Nucleosides. Part LV. Efficient synthesis of arabinoguanosine building blocks

From guanosine ( 1 ) as starting molecule, protected arabinoguanosine derivatives such as phosphoramidite precursors and arabinoguanosine ( 18 ) itself were prepared in high yields. Inversion of the configuration at C(2′) was achieved by introduction of the (trifluoromethyl)sulfonyl residue and subsequent displacement by nucleophiles like acetate, bromide, and azide. The guanine moiety was protected at the amide function by the 2-(4-nitrophenyl)ethyl (npe) group on O⁶ and at the NH₂ function by the 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) group.     

Geminal systems. 16. Reactions of N-chloro-N-alkoxy-N-alkylamines with amines

Conclusions The reactions of N-chloro-N-alkoxy-N-tert-alkylamines with amines are characterized by nucleophilic substitution at the nitrogen atom with formation of the corresponding N-alkoxyhydrazines which are stable in the case of ethyleneimine and pyridine; give diazenes as in the case of MeNH₂, EtNH₂, and Me₂ or yield products of further transformations as in the case of NH₃, Me₂NH, and MeO(Me)NH. Nucleophilic substitution is repressed in the reaction with Et₂NH and Et₃ N by one-electron reduction with the formation of azoxy compounds.For Communication 15, see previous article [1].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2327–2334, October, 1981.     

Polyfluorocycloalkenes. Part XVIII. Aryl adducts of decafluorocyclohexene

Decafluorocyclohexene reacted slowly with aniline to give 1-phenylamino- 3-phenyliminoheptafluorocyclohex-2-ene, which was hydrolysed by hydrochloric acid to 3-phenylaminoheptafluorocyclohex-2-enone. Decafluorocyclohexene reacted stepwise with phenyl lithium, giving 1-phenylnonafluorocyclohexene and thence 1,2-diphenyloctafluorocyclohexene: the former product was attacked slowly by pentafluorophenyl lithium at ?40°C affording 1-pentafluorophenyl- 1-phenyloctafluorocyclohexene. Phenyl lithium reacted sluggishly with bis(pentafluorophenyl)octafluorocyclohexene to give 1-pentafluorophenyl-2-(2′,3′,5′,6′-tetrafluoro-1′-biphenylyl)octafluorocyclohexene and 1,2-bis(2′,3′,5′,6′-tetrafluoro-1′-biphenylyl)octafluorocyclohexene. 1,2-Diphenyloctafluorocyclohexene and 1,2-bis(pentafluorophenyl) octafluorocyclohexene were fluorinated by cobalt(III) fluoride to give the olefin, 1,2-bis(undecafluorocyclohexyl)octafluorocyclohexene.     

Organoplatinum complexes containing bis(diphenylphosphino)amine as ligand: uncommon case of N-H . . . I-Pt hydrogen bonding

The complex [PtMe(2)(dppa)], 1a, dppa = Ph(2)PNHPPh(2), which has previously been prepared as a mixture with the dimeric form [Pt(2)Me(4)(micro-dppa)(2)], was synthesized in pure form by the reaction of [PtCl(2)(dppa)] with MeLi. The aryl analogue [Pt(p-MeC(6)H(4))(2)(dppa)], 1b, was prepared by replacement of SMe(2) in cis-[Pt(p-MeC(6)H(4))(2)(SMe(2))(2)] with dppa. The reaction of the chelate complexes 1 with one equiv. of dppa afforded the complexes [PtR(2)(dppa-P)(2)], R=Me, 2a and R=p-MeC(6)H(4) 2b. The reaction of [PtR(2)(dppa)], 1, with neat MeI gave the organoplatinum(iv) complexes [PtR(2)MeI(dppa)], R=Me, 5a and R=p-MeC(6)H(4), 5b. The structure of 5a, determined by X-ray crystallography, indicated that the complex undergoes self-assembly by intermolecular N-H . . . I-Pt hydrogen bonding. MeI was also double oxidatively added to organodiplatinum(ii) complex cis,cis-[Me(2)Pt(micro-SMe(2))(micro-dppa)PtMe(2)], to give diorganoplatinum(iv) complex [Me(3)Pt(micro-dppa)(micro-I)(2)PtMe(3)], 4. The aryl analogue organodiplatinum(ii) complex cis,cis-[(p-MeC(6)H(4))(2)Pt(micro-SMe(2))(micro-dppa)Pt(p-MeC(6)H(4))(2)], 3b, was prepared by the reaction of cis-[Pt(p-MeC(6)H(4))(2)(SMe(2))(2)] with half equiv. of dppa, but 3b refused to react with MeI, probably because of the steric effects of the aryl ligands. The tetramethyl complex [PtMe(4)(dppa)], 6, was prepared either by reaction of 5a with MeLi or by replacement of SMe(2) in [Pt(2)Me(8)(micro-SMe(2))(2)] with dppa. All the complexes were fully characterized in solution by multinuclear NMR ((1)H, (13)C, (31)P and (195)Pt) methods and their coordination compared with that of the corresponding known dppm complexes.     

On the synthesis of ecdysone. IV. On insect hormones. The synthesis of the natural skin shedding hormone

Ecdysone ( 9 ), a hormone responsible for the skin shedding process of arthropoda, has been synthesized. (20S)-2β,3β-Diacetoxy-20-formyl-5β-pregn-7-en-6-one was prepared from the corresponding carboxylic acid and converted into ecdysone by a GRIGNARD reaction with 2-methyl-3-butyn-2-ol tetrahydropyran-2-yl ether, followed by hydrogenation of the triple bond, removal of the protecting groups, and hydroxylation in the 14α-position. C-22-isoecdysone was obtained as a by-product.     

Icosahedral carboranes. XVI. Preparation of linear poly-m-carboranylenesiloxanes

The first members of the series of poly-m-carboranylenesiloxanes were synthesized by the ferric chloride-catalyzed condensation of methoxy- and chloro-terminated monomers and generally obtained as insoluble crosslinked gums It has now been discovered that long-chain, linear polymers can be prepared by simple hydrolytic condensation of m-B₁₀H₁₀C₂(SiMe₂OSiMe₂Cl)₂ and m-B₁₀H₁₀C₂(SiMe₂OSiMe₂OSiMe₂Cl)₂ at ice bath temperature, as well as by acid-catalyzed condensation of the corresponding silanols. In addition, phenyl-substituted copolymers have been obtained which show outstanding thermo-oxidative stability at elevated temperature. These linear polymers are soluble waxes and liquids with molecular weights between 16,000 and 30,000; they are potentially useful as high-temperature liquids and coatings and can be cured at room temperature to form elastomers.     

Chemistry of the diazeniumdiolates. 3. Photoreactivity

We have found O(2)-substituted diazeniumdiolates, compounds of structure R(2)N-N(O)=NOR' that are under development for various possible pharmaceutical uses, to be rather photosensitive. With R = ethyl and R' = methyl, benzyl, or 2-nitrobenzyl, the observed product distributions suggest that two primary pathways are operative. A minor pathway involves the extrusion of nitrous oxide (N(2)O) with simultaneous generation of R(2)N(*) and R'O(*), which may then form amines, aldehydes, and alcohols. The major reaction pathway is an interesting photochemical cleavage of the N=N bond to form a nitrosamine (R(2)NN=O) and an oxygen-substituted nitrene (R'ON). The intermediacy of the O-nitrene was inferred from the production of abundant oxime, via rearrangement of the O-nitrene to a C-nitroso compound (R'ON --> O=NR'), and subsequent tautomerization to the more stable oxime. Involvement of the O-nitrene was confirmed by trapping with 2,3-dimethyl-2-butene to form the aziridine and with oxygen to generate the nitrate ester. 2-Nitro substitution on the benzyl derivative had surprisingly little effect on the reaction course. For each compound examined, minor amounts of nitric oxide (NO), presumably produced by secondary photolysis of the nitrosamine, were observed. Time-resolved infrared experiments provided additional support for the above reaction pathways and confirmed that the nitrosamine is a primary photoproduct. We have also found that the relative contributions of the reaction pathways can be altered in certain derivatives. For example, when R' = 2,4-dinitrophenyl, the contribution of the nitrosamine/O-nitrene-forming pathway was diminished. Pharmacological implications of these results are discussed.     

Mass spectral fragmentation patterns of heterocycles. IV . Tetracyclic phenothiazines. IX. Electron impact promoted mass spectral fragmentation of pyrrolo[3,2,1-kl]phenothiazine

The mass spectral fragmentation patterns of pyrrolo[3, 2, 1-kl]phenothiazine ( 1 ) and its 1, 10-dideuterioderi-vative [2] are reported. The site of deuterium substitution in 2 was established by examination of its ¹³C nuclear magnetic resonance spectrum. The heteroaromatic stability of 1 to electron impact is exemplified by the occurrence of the molecular ion as the base peak and the formation of a reasonably intense M²⁺ ion. An intense M-1 ion is also observed. The more abundant fragment ions appear to result from sulfur ionization. Fragment ions arising from ionization of the nitrogen constitute only a small fraction of the total ion current. Proposed fragmentation pathways of 1 are supported by the detection of appropriate metastable ions, exact mass measurements, and electron impact spectrum of 2 .     

Polyoxometalate HIV-1 protease inhibitors. A new mode of protease inhibition.

Nb-containing polyoxometalates (POMs) of the Wells-Dawson class inhibit HIV-1 protease (HIV-1P) by a new mode based on kinetics, binding, and molecular modeling studies. Reaction of alpha(1)-K(9)Li[P(2)W(17)O(61)] or alpha(2)-K(10)[P(2)W(17)O(61)] with aqueous H(2)O(2) solutions of K(7)H[Nb(6)O(19)] followed by treatment with HCl and KCl and then crystallization affords the complexes alpha(1)-K(7)[P(2)W(17)(NbO(2))O(61)] (alpha(1)()1) and alpha(2)-K(7)[P(2)W(17)(NbO(2))O(61)] (alpha(2)()1) in 63 and 86% isolated yields, respectively. Thermolysis of the crude peroxoniobium compounds (72-96 h in refluxing H(2)O) prior to treatment with KCl converts the peroxoniobium compounds to the corresponding polyoxometalates (POMs), alpha(1)-K(7)[P(2)W(17)NbO(62)] (alpha(1)()2) and alpha(2)-K(7)[P(2)W(17)NbO(62)] (alpha(2)()2), in moderate yields (66 and 52%, respectively). The identity and high purity of all four compounds were confirmed by (31)P NMR and (183)W NMR. The acid-induced dimerization of the oxo complexes differentiates sterically between the cap (alpha(2)) site and the belt (alpha(1)) site in the Wells-Dawson structure (alpha(2)()2 dimerizes in high yield; alpha(1)()2 does not). All four POMs exhibit high activity in cell culture against HIV-1 (EC(50) values of 0.17-0.83 microM), are minimally toxic (IC(50) values of 50 to >100 microM), and selectively inhibit purified HIV-1 protease (HIV-1P) (IC(50) values for alpha(1)()1, alpha(2)()1, alpha(1)()2, and alpha(2)()2 of 2.0, 1.2, 1.5, and 1.8 microM, respectively). Thus, theoretical, binding, and kinetics studies of the POM/HIV-1P interaction(s) were conducted. Parameters for [P(2)W(17)NbO(62)](7)(-) were determined for the Kollman all-atom (KAA) force field in Sybyl 6.2. Charges for the POM were obtained from natural population analysis (NPA) at the HF/LANL2DZ level of theory. AutoDock 2.2 was used to explore possible binding locations for the POM with HIV-1P. These computational studies strongly suggest that the POMs function not by binding to the active site of HIV-1P, the mode of inhibition of all other HIV-1P protease inhibitors, but by binding to a cationic pocket on the "hinge" region of the flaps covering the active site (2 POMs and cationic pockets per active homodimer of HIV-1P). The kinetics and binding studies, conducted after the molecular modeling, are both in remarkable agreement with the modeling results: 2 POMs bind per HIV-1P homodimer with high affinities (K(i) = 1.1 +/- 0.5 and 4.1 +/- 1.8 nM in 0.1 and 1.0 M NaCl, respectively) and inhibition is noncompetitive (k(cat) but not K(m) is affected by the POM concentration).     

Polymerizations of substituted cyclopropanes. II. Anionic polymerization of 1,1-disubstituted 2-vinylcyclopropanes

Among the four 1,1-disubstituted 2-vinylcyclopropanes, diethyl 2-vinylcyclopropane-1,1-dicarboxylate (Ia), 2-vinylcyclopropane-1,1-dicarbonitrile (Ib), ethyl 1-cyano-2-vinylcyclopropanecarboxylate (Ic), and 1,1-diphenyl-2-vinylcyclopropane (Id), Ib and Ic polymerized well with sodium cyanide in N,N-dimethylformamide. Ib was most reactive and a polymer (IIb) from Ib exhibited an inherent viscosity of 1.05 dl/g (concentration of 1.0 g in 100 ml of 95% H₂SO₄). All experimental results indicated that the polymerization proceeded by ring opening and that the structure of the polymers had pendant vinyl groups. The polymer IIc from Ic was soluble in common solvents like acetone, but IIb was soluble only in 95% H₂SO₄. Reactions of those compounds with benzenethiolate ion in ethanol yielded addition products that supported the ring-opening polymerization of those monomers. In the postulated mechanism of polymerization cyanide ion attacks the carbon of a cyclopropane ring with electron-releasing vinyl group and the resulting anion is thereby stabilized by two electron-withdrawing substituents. The propagation takes place by the reaction of the anion with another monomer molecule.     

New reactions of pyrroles. I. pyridylethylpyrroles

Pyrroles with unsubstituted 2- and/or 5-positions are found to react with 4-vinyl-pyridine, giving hitherto unreported 2- and 2,5-di- pyridylethylpyrroles. Pyrrole-2-carboxylic acids can also react to give the same products by displacement of the carboxyl group. Pyridylethylation at an available 3- and/or 4-position was not observed. Catalytic reductions and alkylations of the resulting piperidylethylpyrroles are also reported.     

Functionalization of polystyrene. III. Synthesis of polymeric thiol reagents

The synthesis of polymer-bound thiol reagents, supported on macroporous 4% divinylbenzene co-polymer (Amberlite XE-305), via three synthetic approaches is described: (i) Alkylation or acylation of XE-305 with 3-nitro-4-halogen-substituted benzyl chloride or benzoyl halide yielding 3-nitro-4-halobenzene-bound species, followed by substitution of the activated polymeric halogen atom with sulfur (see Scheme 1). (ii) Formation of a thiol ether by a direct substitution of an active polymeric halogen by reaction with benzylthiol, followed by chlorination, thiolation, and reduction (see Scheme 2). (iii) Attachment of a prepared tailor-made disulfide to aminomethyl function of a polymeric support, followed by reduction (see Scheme 3). The polymers were tested for their free-thiol content by 5, 5′-dithiobis(2-nitrobenzoic acid) (Ellman's reagent¹²) in DMF. Their thiolytic activity was investigated in the removal of 2-nitrophenylsulphenyl (Nps) group from Nps-protected amino acid (Scheme 4). Site-site interaction between the polymer-bound thiol with its activated halide precursor to yield polymeric sulfide during displacement reaction, and the interconversion of the polymeric thiols into polymeric disulfides at equilibrium or during reaction with Nps-amino acids, observed, and is attributed to the flexibility of the polymeric matrices.     

Evaluation of enteric coated tablet sensitive to pancreatic lipase. I. In vitro disintegration test.

We designed a new enteric coated preparation which is pH independent and functions by pancreatic lipase activity in the duodenum. Triolein (TO) and trilaurin (TL) were selected as lipase sensitive components and ethylcellulose (EC) was used as the support film for TO and TL. Tablets (330 mg, d = 10 mm) containing a model drug, sulfamethizole (SMZ), were coated with 1% each of TO, TL and EC solution by the fluidized bed coating technique. Disintegration tests were carried out in the media including JPXI 1st fluid (pH 1.2, JP-1), 2nd fluid (pH 6.8, JP-2) and JP-2 with gall powder and pancreatic lipase (JP-2-GL). The lag time of disintegration of the tablet (TOTL-Tab) coated 5-7 mg/tab with TO, TL and EC was about 10 min and all of the tablets disintegrated completely within 30 min in JP-2-GL. However, in the other media, which did not contain lipase, TOTL-Tab did not disintegrate for at least 2 h. It was confirmed that TO and TL in the coating film were digested by lipase. In addition, the tensil strength of the film decreased quickly after incubation in JP-2-GL. These results suggest that the application of TO, TL and EC to tablet coating is useful for an enteric release preparation sensitive to pancreatic lipase, even if patients have low gastric acidity or are taking antacids.     

Deuteron N.M.R. relaxation studies of phospholipid membranes

Bilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), specifically deuteriated at various positions of the sn-2-chain, have been studied by N.M.R. relaxation methods. Analysis of the experiments, employing a density matrix treatment based on the stochastic Liouville equation, provides new information about the dynamic organization of the different membrane phases (liquid-crystalline, intermediate and gel phases). The complex molecular dynamics are characterized by a super-position of inter- and intramolecular motions, comprising overall reorientation of phospholipid molecules and trans-gauche isomerization of individual chain segments. In addition, there is evidence for two-site rotational jumps of the sn-2-chains in the plane of the membrane. The results clearly demonstrate the particular advantage of N.M.R. relaxation studies in characterizing complex chemical and biological systems.     

Oxidation of ethyne and But-2-yne. 2. Master equation simulations

The aim of this study is to improve understanding of the tropospheric oxidation of ethyne (acetylene, C2H2) and but-2-yne, which takes place in the presence of HO and O2. The details of the potential energy hypersurface have been discussed in a previous article [Maranzana et al., J. Phys. Chem. A 2008, 112, XXXX]. For both molecules, the initial addition of HO radical to the triple bond is followed by addition of O2 to form peroxyl radicals. In both reaction systems, the peroxyl radicals take two isomeric forms, E1 and E2 for ethyne and e1 and e2 for but-2-yne. Energy transfer parameters (alpha = 250 cm-1) for the ethyne system were obtained by simulating laboratory data for N2 buffer gas, where O2 was not present. In simulations of C2H2 + HO when O2 is present, E1 reacts completely and E2 reacts almost completely, before thermalization. Radical E1 produces formic acid ( approximately 44%) and E2 gives glyoxal ( approximately 53%), in quite good agreement with experiments. For but-2-yne, pressure-dependent laboratory data are too scarce to obtain energy transfer parameters directly, so simulations were carried out for a range of values: alpha = 200-900 cm-1. Excellent agreement with the available experimental yields at atmospheric pressure was obtained with alpha = 900 cm-1. Two reaction channels are responsible for acetic acid formation, but one is clearly dominant. Biacetyl is produced by reactions of e1 and, to a minor extent, e2. The peroxyl radical e2 leads to less than 8% of all products. Vinoxyl radical (which has been reported in experiments involving C2H2 + HO) and products of its reactions are predicted to be negligible under atmospheric conditions.