198,750 research outputs found
Measurement of the ratio of prompt χ c to J / ψ production in pp collisions at √s = 7 TeV
Full text linkThe prompt production of charmonium χ c and J / ψ states is studied in proton-proton collisions at a centre-of-mass energy of √s = 7 TeV at the Large Hadron Collider. The χ c and J / ψ mesons are identified through their decays χ c → J / ψ γ and J / ψ → μ + μ - using 36 pb - 1 of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for χ c and J / ψ, σ (χ c → J / ψ γ) / σ (J / ψ), is determined as a function of the J / ψ transverse momentum in the range 2 < p T J / ψ < 15 GeV / c. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low p T J / ψ region
Reaction of 3-chloro-3-methyldiazirines with hydrogen atoms
No full textPT: J; CR: BINGHAM RC, 1975, J AM CHEM SOC, V97, P1285 BRADLEY GF, 1977, J CHEM SOC P2, P1214 BRASLAVSKY S, 1977, CHEM REV, V77, P473 CHADWELL HM, 1933, J AM CHEM SOC, V55, P1363 CLARK DT, 1969, T FARADAY SOC, V62, P393 CLARK DT, 1969, T FARADAY SOC, V62, P399 CLARK DT, 1969, T FARADAY SOC, V62, P405 CLOUGH PN, 1970, CAN J CHEM, V48, P2919 DYKSTRA CE, 1978, J AM CHEM SOC, V100, P1378 FIGUERA JM, 1978, J CHEM SOC F1, P809 FREY HM, 1966, ADV PHOTOCHEM, V4, P225 FREY HM, 1977, J CHEM SOC F1, P2010 GILBERT JC, 1979, TETRAHEDRON LETT, P4619 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4306 JAMIESON JWS, 1970, CAN J CHEM, V48, P3619 JENNINGS BM, 1976, J AM CHEM SOC, V98, P6416 JONES M, 1973, CARBENES, V1 JONES WE, CHEM BIOMED ENV INST JONES WE, 1973, CHEM REV, V73, P407 JONES WE, 1978, J CHEM SOC F2, V74, P831 LAU A, 1964, SPECTROCHIM ACTA, V20, P97 LIU MTH, UNPUBLISHED LIU MTH, 1973, CAN J CHEM, V51, P2393 LIU MTH, 1977, CAN J CHEM, V55, P3596 MAEDA Y, 1979, J AM CHEM SOC, V101, P837 MARTIN LR, 1979, INT J CHEM KINET, V11, P543 MEIER H, 1977, ANGEW CHEM INT EDIT, V16, P835 MOFFAT JB, 1978, CHEM DIAZONIUM DIA 1 MOSS RA, 1978, J CHEM SOC CHEM COMM, P775 SCHMITZ E, 1964, ANGEW CHEM INT EDIT, V3, P333 SCHMITZ E, 1971, 23RD INT C PUR ALL C, V2, P283 SCOTT PM, 1969, J PHYS CHEM-US, V73, P1513 SMITH NP, 1979, J CHEM SOC P2, P213 WITTER RA, 1973, J ORG CHEM, V38, P484; NR: 34; TC: 3; J9: J AMER CHEM SOC; PG: 2; GA: JN379Source type: Electronic(1
Benzylchlorocarbene: origins of Arrhenius curvature in the kinetics of the 1,2-H shift rearrangement
No full textBenzylchlorocarbene (1, BCC) was generated photochemically from benzylchlorodiazirine (2) in isooctane, methylcyclohexane (MCH), and tetrachloroethane (TCE) at temperatures from similar to 30 to -75 degrees C. At -70 degrees C in isooctane, the identified products included Z/E-beta-chlorostyrenes 4 (46.6%), alpha-chlorostyrene 5 (2.4%), 1,1-dichloro-2-phenylethane 6 (1.9%), a BCC-isooctane insertion product 8 (5.5%), carbene dimers 9 (3.8%), and azine 3 (30%). The significant incursion of intermolecular products 3, 8, and 9 implies that laser flash photolytic (LFP) kinetic data for the decay of BCC obtained at low temperature is biased and should not be employed in Arrhenius analyses. Accordingly, previously obtained curved Arrhenius correlations for BCC do not necessarily implicate quantum mechanical tunneling (QMT) in the 1,2-H shift rearrangement of BCC to 4. Similarly in MCH, where BCC affords a solvent insertion product in similar to 44-53% yield, the curved Arrhenius correlation (Figure 1) cannot be readily interpreted. In polar solvents such as TCE, clean H-shift reactions of BCC are obtained even at -71 degrees C; an Arrhenius correlation of LFP kinetic data is linear from 3 to -71 degrees C (Figure 2), affording E-a = 3.2 kcal mol(-1) and log A = 10.0 s(-1). Therefore, QMT does not appear to play a major role in the 1,2-H shift rearrangement of BCC at ambient or near ambient temperature in solution.PT: J; CR: BONNEAU R, 1996, J AM CHEM SOC, V118, P3829 DEAN JA, 1992, LANGES HDB CHEM DIX EJ, 1993, J AM CHEM SOC, V115, P10424 DOX AW, 1941, ORG SYNTH, V1, P5 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 ISAACS NS, 1995, PHYSICAL ORGANIC CHE, P304 JACKSON JE, 1988, J AM CHEM SOC, V110, P5595 KAZANIS S, 1991, J PHYS CHEM-US, V95, P4430 KEATING AE, 1997, COMMUNICATION 0804 LAVILLA JA, 1989, J AM CHEM SOC, V111, P6877 LAVILLA JA, 1990, TETRAHEDRON LETT, V31, P5109 LIU MTH, 1984, TETRAHEDRON, V40, P887 LIU MTH, 1985, CHEM COMMUN, P982 LIU MTH, 1985, J ORG CHEM, V50, P3218 LIU MTH, 1990, J AM CHEM SOC, V112, P3915 LIU MTH, 1992, J AM CHEM SOC, V114, P3604 LIU MTH, 1992, J PHOTOCH PHOTOBIO A, V63, P115 LIU MTH, 1994, ACCOUNTS CHEM RES, V27, P287 LIU MTH, 1994, J PHOTOCH PHOTOBIO A, V84, P133 MODARELLI DA, 1992, J AM CHEM SOC, V114, P7034 MODARELLI DA, 1993, J AM CHEM SOC, V115, P470 MOSS RA, 1987, J AM CHEM SOC, V109, P4341 MOSS RA, 1990, J AM CHEM SOC, V112, P1638 MOSS RA, 1994, ADV CARBENE CHEM, V1, P59 MOSS RA, 1996, J AM CHEM SOC, V118, P12588 MOSS RA, 1997, CHEM COMMUN 0321, P617 MOSS RA, 1997, TETRAHEDRON LETT, V38, P7049 STORER JW, 1993, J AM CHEM SOC, V115, P10426 SUGIYAMA MH, 1992, J AM CHEM SOC, V114, P966 TOMIOKA H, 1984, J AM CHEM SOC, V106, P454 WHITE WR, 1992, J ORG CHEM, V57, P2841 WIERLACHER S, 1993, J AM CHEM SOC, V115, P8943 YEN VQ, 1962, ANN CHIM, V7, P785; NR: 33; TC: 8; J9: J ORG CHEM; PG: 7; GA: ZM109Source type: Electronic(1
Test Make Sense?
No full textCorresponding author Changyu Liu should be listed as the first corresponding author.No Full Tex
Electrochemical behavior of diazirines
No full textPT: J; CR: ENGEL PS, 1980, CHEM REV, V80, P99 FRY AJ, 1973, J ORG CHEM, V38, P2620 KITAJEV JP, 1965, COLLECT CZECH CHEM C, V30, P4178 LIU MTH, 1981, J CHEM SOC P2, P53 LUND H, 1966, COLLECT CZECH CHEM C, V31, P4175 MALACHESKY PA, 1969, ANAL CHEM, V41, P1493 MOFFAT JB, 1978, CHEM DIAZONIUM DIA 1 NICHOLSON RS, 1964, ANAL CHEM, V36, P706 SCHWARZ WM, 1965, J PHYS CHEM-US, V69, P30; NR: 9; TC: 2; J9: J CHEM SOC CHEM COMMUN; PG: 2; GA: NJ399Source type: Electronic(1
Spectroscopic detection of an arylchlorocarbene-ethyl acetate carbonyl ylide and subsequent oxirane formation
No full textLaser flash photolysis of 3-chloro-3-(p-nitrophenyl)diazirine (1) generates the corresponding ground-state singlet carbene (lambda-max = 310 nm), which reacts with ethyl acetate to form a carbonyl ylide of the ester (lambda-max = 490 nm). The absolute rate constant for ylide formation in CH2Cl2 is k = (2.85 +/- 0.17) X 10(6) M-1 s-1. Subsequent cyclization of the ylide to the corresponding oxirane (lambda-max = 350 nm) occurs with a rate constant of 1.26 x 10(6) S-1 (21-degrees-C) in ethyl acetate with Arrhenius activation parameters for oxirane formation of E(act) = 6.68 +/- 0.19 kcal/mol and log A (s-1) = 11.08 +/- 0.15. The carbonyl ylide is also intercepted with the dipolarophile, diethyl fumarate, with a rate constant of (1.04 +/- 0.07) x 10(7) M-1 s-1. Additionally, solvent polarity effects on (p-nitrophenyl)chlorocarbene reactivity and spectroscopic evidence of oxirane formation (lambda-max = 350 nm) from the related acetone ylide of (p-nitrophenyl)chlorocarbene are presented.PT: J; CR: BONNEAU R, 1989, J CHEM SOC CHEM COMM, P510 BONNEAU R, 1990, J AM CHEM SOC, V112, P744 IBATA T, 1987, CHEM LETT, V28, P2135 LIU MTH, 1972, CAN J CHEM, V50, P3009 LIU MTH, 1987, TETRAHEDRON LETT, V28, P1011 LIU MTH, 1990, J CHEM SOC CHEM COMM, P1482 NAGARAJAN V, 1985, J PHYS CHEM-US, V89, P2330 PAUL H, 1978, J AM CHEM SOC, V100, P4520 PLATZ MS, COMMUNICATION REICHARDT C, 1988, SOLVENTS SOLVENT EFF, P352 SOUNDARARAJAN N, 1988, J AM CHEM SOC, V110, P7143 SOUNDARARAJAN N, 1988, TETRAHEDRON LETT, V29, P3419; NR: 12; TC: 14; J9: J AMER CHEM SOC; PG: 4; GA: GB298Source type: Electronic(1
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
Full text linkFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
Absolute rate constants for the reactions of some arylchlorocarbenes with acetic acid
No full textPT: J; CR: CLOSS GL, 1968, TOP STEREOCHEM, V3, P193 CLOSS GL, 1976, J AM CHEM SOC, V98, P8190 EISENTHAL KB, 1980, J AM CHEM SOC, V102, P6563 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 GRILLER D, 1982, J AM CHEM SOC, V104, P5549 HADEL LM, UNPUB CHEM PHYS LETT KIRMSE W, 1971, CARBENE CHEM, CH7 LIU MTH, 1972, CAN J CHEM, V50, P3009 NAGAI Y, 1962, B CHEM SOC JPN, V35, P132 SCAIANO JC, 1980, J AM CHEM SOC, V102, P7747 TURRO NJ, 1980, J AM CHEM SOC, V102, P7576 WONG PC, 1981, CHEM PHYS LETT, V83, P69 WONG PC, 1981, J AM CHEM SOC, V103, P5934 WONG PC, 1982, J AM CHEM SOC, V104, P5106 ZUPANCIC JJ, 1980, J AM CHEM SOC, V102, P5958 ZUPANCIC JJ, 1981, J AM CHEM SOC, V103, P2423 ZUPANCIC JJ, 1981, J AM CHEM SOC, V103, P944; NR: 17; TC: 17; J9: J ORG CHEM; PG: 2; GA: QM675Source type: Electronic(1
Insertion of phenylchlorocarbenes in the C-H bonds of alkanes: measurement of the rate constants by laser flash photolysis
No full textPhenylchlorocarbenes, produced by photolysis of the parent diazirines, have a very limited lifetime in alkane solvents. The rate of disappearance of p-methyl- and p-chlorophenylchlorocarbenes has been measured in iso-octane, cyclohexane and n-hexane as well as in benzene for comparison. The rate constants of several processes (dimerization, addition to the diazirine, reaction with the solvent, etc. ) contributing to the disappearance of the phenylchlorocarbenes have been determined. The rate of reaction with the solvent, which is much lower in benzene than in alkanes and depends strongly on the nature of the alkane, is assumed to be an insertion of the carbene in the C-H bonds of the solvent. Consequences of this reaction on the chemistry of carbenes produced by continuous irradiation (or thermolysis) of diazirines in alkanes are briefly discussed.PT: J; CR: BENSASSON R, 1971, T FARADAY SOC, V67, P1904 BONNEAU R, 1986, NOUV J CHIM, V10, P425 BONNEAU R, 1991, PURE APPL CHEM, V63, P289 DOYLE MP, 1988, TETRAHEDRON LETT, V29, P5863 GOULD IR, 1985, TETRAHEDRON, V41, P1587 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 LIU MTH, 1987, CHEM DIAZIRINES LIU MTH, 1990, J CHEM SOC CHEM COMM, P1482 LIU MTH, 1992, J AM CHEM SOC, V114, P3604 LIU MTH, 1992, J ORG CHEM, V57, P2483 LIU MTH, 1992, J PHOTOCH PHOTOBIO A, V63, P115 LUTZ H, 1973, J PHYS CHEM-US, V77, P1758 MORGAN S, 1991, J AM CHEM SOC, V113, P2782 MOSS RA, 1990, J AM CHEM SOC, V112, P5642 MOSS RA, 1990, KINETICS SPECTROSCOP; NR: 15; TC: 11; J9: J PHOTOCHEM PHOTOBIOL A-CHEM; PG: 10; GA: JQ196Source type: Electronic(1
Rearrangement of alkylchlorocarbenes: 1,2-H shift in free carbene, carbene-olefin complex, and excited states of carbene precursors
No full textPhotolysis of alkylchlorodiazirines (1) in the presence of olefins gives a cyclopropane (3) by addition of the generated carbene to the olefin and a vinyl chloride derivative (2) resulting from a 1,2-H shift rearrangement. This rearrangement may occur either in the carbene or in some excited state, precursor of the carbene (RIES mechanism), or in a ''carbene + olefin complex'' on the way to the formation of 3 (COC mechanism). Results obtained by time-resolved photoacoustic calorimetry as well as by thermolysis and photolysis of ClCH2C(N-2)Cl and CH3(CH2)(2)C(N-2)Cl in the presence of tetramethylethylene clearly indicate that both the RIES and COC mechanisms play a role but with efficiencies which greatly depend on the nature of the diazirine. Reexamination of the results previously obtained with benzylchlorodiazirines indicates that, for this class of diazirines, the RIES mechanism is temperature dependent and has a very low efficiency at room temperature and below, whereas the nonlinearity of the plots [3]/[2] vs [olefin] is mainly due to the COC mechanism.PT: J; CR: BIGOT B, 1978, J AM CHEM SOC, V100, P8575 CHANG KT, 1979, J AM CHEM SOC, V101, P5082 FREY HM, 1966, ADV PHOTOCHEM, V4, P225 GANZER GA, 1986, J AM CHEM SOC, V108, P1517 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 HEIHOFF K, 1987, BIOCHEMISTRY-US, V22, P1422 HOUK KN, 1984, J AM CHEM SOC, V106, P4291 HOUK KN, 1984, J AM CHEM SOC, V106, P4293 JACKSON JE, 1994, ADV CARBENE CHEM, V1 KANABUSKAMINSKA JM, 1987, J AM CHEM SOC, V109, P5267 LAVILLA JA, 1989, J AM CHEM SOC, V111, P6877 LAVILLA JA, 1989, J AM CHEM SOC, V111, P712 LAVILLA JA, 1990, TETRAHEDRON LETT, V31, P5109 LIU MTH, 1987, J ORG CHEM, V52, P4223 LIU MTH, 1989, J CHEM SOC CHEM COMM, P12 LIU MTH, 1990, J AM CHEM SOC, V112, P3915 MODARELLI DA, 1991, J AM CHEM SOC, V113, P8985 MODARELLI DA, 1992, J AM CHEM SOC, V114, P7034 MOSS RA, 1993, J CHEM SOC CHEM COMM, P1597 MOSS RA, 1994, ADV CARBENE CHEM, V1 MULDER P, 1988, J AM CHEM SOC, V110, P4090 MULLERREMMERS PL, 1985, J AM CHEM SOC, V107, P7275 NI T, 1989, J AM CHEM SOC, V111, P457 NICKON A, 1993, ACCOUNTS CHEM RES, V26, P84 RUDZKI JE, 1985, J AM CHEM SOC, V107, P7849 SKELL PS, 1969, J AM CHEM SOC, V91, P7131 TOMIOKA H, 1984, J AM CHEM SOC, V106, P454 TURRO NJ, 1982, J AM CHEM SOC, V104, P1754 WARNER PM, 1984, TETRAHEDRON LETT, V25, P4211 WESTRICK JA, 1987, BIOCHEMISTRY-US, V26, P8313 WHITE WR, 1992, J ORG CHEM, V57, P2841 WIERLACHER S, 1993, J AM CHEM SOC, V115, P8943 YAMAMOTO N, 1994, J AM CHEM SOC, V116, P2064; NR: 33; TC: 30; J9: J AMER CHEM SOC; PG: 9; GA: UG695Source type: Electronic(1
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