347,078 research outputs found
Laser flash photolysis study of substituent effects on the rate of 1, 2-H migration in a series of benzylchlorocarbenes
No full textLaser flash photolysis of para-substituted 3-chloro-3-benzyldiazirines in isooctane produces the corresponding carbenes, which react with pyridine to form ylides or undergo 1,2-H migration to form the (Z)- and (E)-beta-chlorostyrenes. The rate for the 1,2-H migration is determined by plotting the pseudo-first-order rate constants for the growth of the ylide vs [pyridine] and extrapolating to zero pyridine concentration. In the case of (p-chlorobenzyl)chlorocarbene, the carbene decay can be monitored directly at 310 nm, whereas in [p-(trifluoromethyl)benzyl]chlorocarbene, the 285-nm trace may bc analyzed as the sum of the absorption of the carbene and of the product beta-chlorostyrenes. A Hammett plot of the logarithms of the rate constants for 1,2-H migration vs sigma(p) values gave a rho-value of -1.0, consistent with a hydride-like 1,2-H shift to the carbene center. The rate constants for the cyclopropanation of carbenes with tetramethylethylene (TME) were determined. In particular, the cyclopropanation of (p-chlorobenzyl)chlorocarbene with TME gave a negative activation energy of -4.7 kcal mol-1.PT: J; CR: BONNEAU R, 1989, J AM CHEM SOC, V111, P5973 BONNEAU R, 1989, J PHYS CHEM-US, V93, P4802 CARMICHAEL I, 1986, J PHYS CHEM REF DATA, V15, P1 DOYLE MP, 1987, J ORG CHEM, V52, P1619 EVANSECK JD, 1990, J PHYS CHEM-US, V94, P5518 GOULD IR, 1985, TETRAHEDRON, V41, P1987 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 HO GJ, 1989, J AM CHEM SOC, V111, P6875 HOUK KN, 1984, J AM CHEM SOC, V106, P4291 JACKSON JE, 1989, J AM CHEM SOC, V111, P6874 JONES M, 1980, REACTIVE INTERMEDIAT, V2 JONES WM, 1980, REARRANGEMENTS GROUN KIRMSE W, 1971, CARBENE CHEM LAVILLA JA, 1989, J AM CHEM SOC, V111, P6877 LIU MTH, 1908, J ORG CHEM, V52, P4223 LIU MTH, 1985, J CHEM SOC CHEM COMM, P982 LIU MTH, 1987, CHEM DIAZIRINES, CH5 LIU MTH, 1989, J AM CHEM SOC, V111, P6873 LIU MTH, 1989, J CHEM SOC CHEM COMM, V12 LIU MTH, 1990, J AM CHEM SOC, V112, P3915 LIU MTH, 1992, J PHOTOCH PHOTOBIO A, V63, P115 MORGAN S, 1991, J AM CHEM SOC, V113, P2782 MOSS RA, 1986, J AM CHEM SOC, V108, P7028 MOSS RA, 1990, J AM CHEM SOC, V112, P5642 SCHAEFER HF, 1979, ACCOUNTS CHEM RES, V12, P288; NR: 25; TC: 27; J9: J AMER CHEM SOC; PG: 4; GA: HT801Source type: Electronic(1
1, 2-H shift in benzylchlorocarbene: isotope effect and influence of the solvent
No full textLaser flash photolysis of 3-chloro-3-benzyldiazirine and 3-chloro-3-(phenyldideuteriomethyl)diazirine in isooctane over the 60 to -80-degrees-C temperature range gives rise to curved Arrhenius plots for both 1,2-H and 1,2-D migration in benzylchlorcarbene. The k(H)/k(D) values increase smoothly from 0.87 to 2.62 when the temperature increases from -60 to +30-degrees-C. The k(H)/k(D) value is approximately 4 for most of the temperatures studied if a solvent correction is applied. Quantum mechanical tunnelling or the influence of the solvent may be a possible explanation for these observations.PT: J; CR: BONNEAU R, 1989, J AM CHEM SOC, V111, P5973 BONNEAU R, 1992, J PHOTOCH PHOTOBIO A, V68, P97 DIX EJ, 1993, J AM CHEM SOC, V115, P10424 EVANSECK JD, 1990, J PHYS CHEM-US, V94, P5518 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 JACKSON JE, 1994, ADV CARBENE CHEM JONES M, 1980, REACTIVE INTERMEDIAT, V2 KIRMSE W, 1971, CARBENE CHEM LIU MTH, 1984, TETRAHEDRON, V40, P887 LIU MTH, 1990, J AM CHEM SOC, V112, P3915 LIU MTH, 1992, J PHOTOCH PHOTOBIO A, V63, P115 LIU MTH, 1992, J PHYS ORG CHEM, V15, P285 LIU MTH, 1994, RES CHEM INTERMEDIAT, V20, P195 MODARELLI DA, 1992, J AM CHEM SOC, V114, P7034 MOSS RA, 1992, TETRAHEDRON LETT, V33, P4287 MOSS RA, 1994, ADV CARBENE CHEM MUROV SL, 1973, HDB PHOTOCHEMISTRY NICKON A, 1993, ACCOUNTS CHEM RES, V26, P84 SALIS GA, 1968, J PHYS CHEM-US, V72, P752 SANDER W, 1994, UNPUB SCHAEFER HF, 1979, ACCOUNTS CHEM RES, V12, P288 SCHOLLER WW, 1989, HOUBEN WEYL METHODEN, P41 SHIMANOUCHI T, 1972, TABLES MOL VIBRATION, V1 SUGIYAMA MH, 1992, J AM CHEM SOC, V114, P966 WIERLACHER S, 1993, J AM CHEM SOC, V115, P8943; NR: 25; TC: 20; J9: J PHOTOCHEM PHOTOBIOL A-CHEM; PG: 5; GA: PV021Source 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
Effect of diazirine concentration on the reaction of 3-benzyl-3-chlorodiazirine with methanol
No full textPT: J; CR: GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 GRILLER D, 1982, J AM CHEM SOC, V104, P5549 LIU MTH, 1984, J CHEM SOC CHEM COMM, P1062 LIU MTH, 1985, J CHEM SOC CHEM COMM, P982 LIU MTH, 1985, J ORG CHEM, V50, P3218 LIU MTH, 1985, TETRAHEDRON LETT, V26, P3071 LIU MTH, 1986, J CHEM SOC PERK T 2, P1233 LIU MTH, 1986, J PHYS CHEM-US, V90, P75 LIU MTH, 1987, CHEM DIAZIRINES, V1, CH5 TOMIOKA H, 1984, J AM CHEM SOC, V106, P454 TOMIOKA H, 1986, J CHEM SOC CHEM COMM, P1364; NR: 11; TC: 5; J9: J CHEM SOC PERKIN TRANS 2; PG: 3; GA: L7207Source type: Electronic(1
Termolecular trapping of benzylchlorocarbene by methanol
No full textPT: J; CR: GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 GRILLER D, 1982, J AM CHEM SOC, V104, P5549 KIRMSE W, 1971, CARBENE CHEM LIU MTH, UNPUB LIU MTH, 1982, CHEM SOC REV, V11, P127 MOSS RA, 1973, CARBENES, V1 MOSS RA, 1975, CARBENES, V2 TOMIOKA H, 1984, J AM CHEM SOC, V106, P454 TURRO NJ, 1982, J AM CHEM SOC, V104, P1754; NR: 9; TC: 14; J9: J CHEM SOC CHEM COMMUN; PG: 3; GA: TF969Source type: Electronic(1
Energy barrier for 1,2-hydrogen migration in benzylchlorocarbene
No full textPT: J; CR: BODOR N, 1972, J AM CHEM SOC, V94, P9103 BURNETT SM, 1983, CHEM PHYS LETT, V100, P124 GRAHAM WH, 1965, J AM CHEM SOC, V87, P4396 JONES WM, 1980, REARRANGEMENTS GROUN, V1, P95 KIRMSE W, 1967, CHEM BER, V100, P1491 KIRMSE W, 1971, CARBENE CHEM KYBA EP, 1977, J AM CHEM SOC, V99, P8330 LIU MTH, 1982, CHEM SOC REV, V11, P127 LIU MTH, 1983, TETRAHEDRON LETT, V24, P5713 LIU MTH, 1984, TETRAHEDRON, V40, P887 MOSS RA, 1973, CARBENES, V1 MOSS RA, 1975, CARBENES, V2 POPLE JA, 1983, J AM CHEM SOC, V105, P6389 SCHAEFER HF, 1979, ACCOUNTS CHEM RES, V12, P288 SU DTT, 1978, J AM CHEM SOC, V100, P1972 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; NR: 18; TC: 34; J9: J CHEM SOC CHEM COMMUN; PG: 3; GA: AMG08Source 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
Reactive intermediates in the photolysis and thermolysis of 3-chloro-3-benzyldiazirine
No full textPT: J; CR: BRADLEY GF, 1977, J CHEM SOC P2, P1214 DOLBY LJ, 1966, J ORG CHEM, V31, P110 ENGEL PS, 1980, CHEM REV, V80, P99 GRILLER D, 1983, J ORG CHEM, V48, P1359 HEGARTY AF, 1978, CHEM DIAZONIUM DIA 2, P511 JENNINGS BM, 1976, J AM CHEM SOC, V98, P6416 LIU MTH, 1974, J CHEM SOC P2, P937 LIU MTH, 1981, J CHEM SOC P2, P53 LIU MTH, 1982, CHEM SOC REV, V11, P127 MO YK, 1976, CARBONIUM IONS, V5, P2135 NAIDAN VM, 1972, ZH ORG KHIM, V8, P2172 SCHAEFER HF, 1979, ACC CHEM RES, V12, P88 SCHMITZ E, 1979, ADV HETEROCYCL CHEM, V24, P63 SMITH NP, 1979, J CHEM SOC P2, P213 SMITH RAG, 1975, J CHEM SOC P2, P686 TOMIOKA H, UNPUB TURRO NJ, 1980, J AM CHEM SOC, V102, P7576; NR: 17; TC: 12; J9: TETRAHEDRON; PG: 6; GA: SG656Source type: Electronic(1
Berotha taiwanica U. Aspock, Liu & H. Aspock 2013
No full textBerotha taiwanica U. Aspöck, Liu & H. Aspöck, 2013 Berotha taiwanica U. Aspöck, Liu & H. Aspöck, 2013: 224. Type locality: China (Taiwan: Dalin). Diagnosis. This species is characterized by the male’s extremely tiny bristle-bow complex of fused gonocoxites, gonapophyses and gonostyli 10 (= paramere-mediuncus complex). Distribution. China (Taiwan). Remarks. This species was sufficiently described in U. Aspöck et al. (2013), a re-description is unnecessary in this paper.Published as part of Li, Di, Aspöck, Horst, Aspöck, Ulrike & Liu, Xingyue, 2018, A review of the beaded lacewings (Neuroptera: Berothidae) from China, pp. 235-257 in Zootaxa 4500 (2) on page 243, DOI: 10.11646/zootaxa.4500.2.5, http://zenodo.org/record/529757
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