The Experts below are selected from a list of 231 Experts worldwide ranked by ideXlab platform
Tamotsu Takahashi - One of the best experts on this subject based on the ideXlab platform.
-
Preparation of partially substituted 1-halo- and 1,4-dihalo-1,3-dienes via reagent-controlled desilylation of halogenated 1,3-dienes.
The Journal of organic chemistry, 2006Co-Authors: Zhiyi Song, Guangzhen Liu, Xiaozhong Liu, Tamotsu TakahashiAbstract:Depending on the desilylation reagents used, 1-halo-1,4-bis(trimethylsilyl)-1,3-Butadienes afforded either 1-halo-1-trimethylsilyl-1,3-Butadienes or 1-halo-4-trimethylsilyl-1,3-Butadienes in excellent yields with excellent selectivity, respectively, when treated with CF3COOH or with NaOMe. These monosilylated 1,3-Butadiene products could be further desilylated to generate their corresponding haloButadienes via the above reagent-controlled desilylation reaction. When 1,4-dihalo-1,4-bis(trimethylsilyl)-1,3-dienes were treated with MeONa/MeOH at room temperature, desilylation of both of the two trimethylsilyl groups took place to afford their corresponding 1,4-dihalo-1,3-dienes in excellent yields. The commonly used desilylation reagent CF3COOH did not work for these dihaloButadienes.
-
Synthesis of 1,1,4,4-Tetrabromo-2-butenes and Related Compounds via Desilylation−Bromination of Silylated 1,3-Butadiene Derivatives
The Journal of organic chemistry, 2004Co-Authors: Xiaozhong Liu, Fengyu Bao, Hongtao Fan, Tamotsu TakahashiAbstract:The combination of zirconocene-mediated coupling of silylated alkynes with a protonation-desilylation or bromination-desilylation process afforded otherwise unavailable Butadiene derivatives. When (E,E)-2,3-dialkyl-1,4-bis(trimethylsilyl)-1,3-Butadienes were treated with 3 equiv of Br(2) in CH(2)Cl(2), (E)-2,3-dialkyl-1,1,4,4-tetrabromo-2-butenes were obtained in excellent yields with perfect stereoselectivity.
-
synthesis of 1 1 4 4 tetrabromo 2 butenes and related compounds via desilylation bromination of silylated 1 3 Butadiene derivatives
Journal of Organic Chemistry, 2004Co-Authors: Xiaozhong Liu, Fengyu Bao, Hongtao Fan, Tamotsu TakahashiAbstract:The combination of zirconocene-mediated coupling of silylated alkynes with a protonation-desilylation or bromination-desilylation process afforded otherwise unavailable Butadiene derivatives. When (E,E)-2,3-dialkyl-1,4-bis(trimethylsilyl)-1,3-Butadienes were treated with 3 equiv of Br(2) in CH(2)Cl(2), (E)-2,3-dialkyl-1,1,4,4-tetrabromo-2-butenes were obtained in excellent yields with perfect stereoselectivity.
Sungseen Choi - One of the best experts on this subject based on the ideXlab platform.
-
Analytical method for determination of Butadiene and styrene contents of styrene-Butadiene rubber vulcanizates without pretreatment using pyrolysis-gas chromatography/mass spectrometry
Polymer Testing, 2014Co-Authors: Sungseen Choi, Hyuk-min KwonAbstract:Abstract Styrene-Butadiene rubber (SBR) vulcanizates were prepared using various emulsion SBRs (ESBRs) and solution SBRs (SSBRs) with different microstructures, and were pyrolyzed without pretreatment. Principal pyrolysis products of SBR vulcanizates are Butadiene and styrene. Butadiene and styrene contents of the SBR vulcanizates were determined using plots of the relative peak intensity ratio of Butadiene/styrene as a function of the molar ratio of Butadiene and styrene of the raw SBRs. The peak intensity ratio on the whole increased as the Butadiene content increased. The correlation was enhanced by correction with the Butadiene/styrene molar ratio of raw SBRs. For the plot of SSBR samples, the correlation was more enhanced by correction with the 1,2-unit/styrene molar ratio of raw SBRs. By using the corrected plots, Butadiene and styrene contents of unknown SBR vulcanizates could be determined.
-
Analysis of trace residual 1,3-Butadiene in poly(acrylonitrile-co-Butadiene-co-styrene)
Journal of Industrial and Engineering Chemistry, 2011Co-Authors: Sungseen Choi, Yun-ki KimAbstract:Abstract Residual 1,3-Butadiene in poly(acrylonitrile-co-Butadiene-co-styrene) (ABS) was extracted by solvent and using direct thermal desorption. Toluene and N,N-dimethylacetamide were used as the extraction solvents. The extracted 1,3-Butadiene was injected by headspace sampling to analyze using GC. The solvent extraction was found to be more efficient than the direct thermal desorption method. Solvent extraction with toluene was more efficient than that with N,N-dimethylacetamide. Calibration curves of the 1,3-Butadiene in toluene and N,N-dimethylacetamide showed good linear relationships. For the same concentration of 1,3-Butadiene, the peak area of 1,3-Butadiene in N,N-dimethylacetamide was larger than that in toluene. The experimental results were explained with the vapor pressure in the headspace and the compatibility of 1,3-Butadiene with the solvent.
-
Filler‐polymer interactions of styrene and Butadiene units in silica‐filled styrene–Butadiene rubber compounds
Journal of Polymer Science Part B: Polymer Physics, 2004Co-Authors: Sungseen Choi, Ik-sik Kim, Seung Goo Lee, Chang Whan JooAbstract:Styrene–Butadiene rubber (SBR) is a copolymer of styrene and Butadiene, and the Butadiene unit is composed of cis-1,4-, trans-1,4-, and 1,2-components. Filler-polymer interactions of each component of SBR in silica-filled SBR compounds were examined by microstructure analysis of the bound and unbound rubbers. The composition ratio of Butadiene and styrene units (Butadiene/styrene) of the bound rubber was higher than that of the compounded rubber. Of the Butadiene units, the 1,2-component of the bound rubber was more abundant than the cis-1,4- and trans-1,4-components. The filler-polymer interaction of the Butadiene unit with silica was stronger than that of the styrene unit, and the interaction of the 1,2-component was stronger as compared with the others. The Butadiene–styrene ratio of the bound rubber of the compounds containing the silane coupling agent was lower than for the compounds without the silane. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 577–584, 2004
Xiaozhong Liu - One of the best experts on this subject based on the ideXlab platform.
-
Preparation of partially substituted 1-halo- and 1,4-dihalo-1,3-dienes via reagent-controlled desilylation of halogenated 1,3-dienes.
The Journal of organic chemistry, 2006Co-Authors: Zhiyi Song, Guangzhen Liu, Xiaozhong Liu, Tamotsu TakahashiAbstract:Depending on the desilylation reagents used, 1-halo-1,4-bis(trimethylsilyl)-1,3-Butadienes afforded either 1-halo-1-trimethylsilyl-1,3-Butadienes or 1-halo-4-trimethylsilyl-1,3-Butadienes in excellent yields with excellent selectivity, respectively, when treated with CF3COOH or with NaOMe. These monosilylated 1,3-Butadiene products could be further desilylated to generate their corresponding haloButadienes via the above reagent-controlled desilylation reaction. When 1,4-dihalo-1,4-bis(trimethylsilyl)-1,3-dienes were treated with MeONa/MeOH at room temperature, desilylation of both of the two trimethylsilyl groups took place to afford their corresponding 1,4-dihalo-1,3-dienes in excellent yields. The commonly used desilylation reagent CF3COOH did not work for these dihaloButadienes.
-
Synthesis of 1,1,4,4-Tetrabromo-2-butenes and Related Compounds via Desilylation−Bromination of Silylated 1,3-Butadiene Derivatives
The Journal of organic chemistry, 2004Co-Authors: Xiaozhong Liu, Fengyu Bao, Hongtao Fan, Tamotsu TakahashiAbstract:The combination of zirconocene-mediated coupling of silylated alkynes with a protonation-desilylation or bromination-desilylation process afforded otherwise unavailable Butadiene derivatives. When (E,E)-2,3-dialkyl-1,4-bis(trimethylsilyl)-1,3-Butadienes were treated with 3 equiv of Br(2) in CH(2)Cl(2), (E)-2,3-dialkyl-1,1,4,4-tetrabromo-2-butenes were obtained in excellent yields with perfect stereoselectivity.
-
synthesis of 1 1 4 4 tetrabromo 2 butenes and related compounds via desilylation bromination of silylated 1 3 Butadiene derivatives
Journal of Organic Chemistry, 2004Co-Authors: Xiaozhong Liu, Fengyu Bao, Hongtao Fan, Tamotsu TakahashiAbstract:The combination of zirconocene-mediated coupling of silylated alkynes with a protonation-desilylation or bromination-desilylation process afforded otherwise unavailable Butadiene derivatives. When (E,E)-2,3-dialkyl-1,4-bis(trimethylsilyl)-1,3-Butadienes were treated with 3 equiv of Br(2) in CH(2)Cl(2), (E)-2,3-dialkyl-1,1,4,4-tetrabromo-2-butenes were obtained in excellent yields with perfect stereoselectivity.
Donald J. Burton - One of the best experts on this subject based on the ideXlab platform.
-
The stereospecific preparation of (E)-1-aryl-F-1,3-Butadienes
Journal of Fluorine Chemistry, 2013Co-Authors: Scot D. Pedersen, Donald J. BurtonAbstract:Abstract The Pd (PPh 3 ) 4 /Cu(I)I catalyzed cross coupling of ( Z )-1-tri- n -butylstannyl-1,2,3,4,4-pentafluoro-1,3-Butadiene with substituted aryl iodides provides a useful stereospecific route to ( E )-1-aryl-1,2,3,4,4-pentafluoro-1,3-Butadienes. Substituents, such as 4-nitro, 2-nitro, H, 3-CF 3 , 3-OCH 3 , 2-CH 3 , 1- i Pr react stereospecifically with the dienyl stannane synthon. Only with a bulky electron-withdrawing substuent, such as 2-CF 3 , did significant isomerization occur in isolation of the aryl diene. The bis-coupled product is formed stereospecifically with 1,4-diiodobenzene. The methodology could be extended to stereospecifically prepared the 1-triethylsilyl-1 E ,3 E ,-1,2,3,4,5,6,6-heptafluoro-1,3,5-hexatriene synthon.
-
coupling routes to hexafluoro 1 3 Butadiene substituted 1 3 fluorine containing Butadienes and fluorinated polyenes
Journal of Fluorine Chemistry, 2008Co-Authors: Donald J. Burton, Steven W Hansen, P A Morken, Kathryn J Macneil, Charles R Davis, Ling XueAbstract:Abstract Hexafluoro-1,3-Butadiene was readily prepared via a variety of self-coupling processes, such as Cu(0) mediated self-coupling of iodotrifluoroethene, Pd(0) catalyzed coupling of iodotrifluoroethene with the trifluorovinylzinc reagent, and CuBr 2 mediated coupling of the trifluorovinylzinc reagent. Perfluoro-2,3-dimethyl-1,3-Butadiene was readily synthesized by the reaction of pentafluoropropenyl-2-zinc reagent with either CuBr 2 or FeCl 3 . Alternatively, perfluoro-2,3-dimethyl-1,3-Butadiene was prepared by oxidation of the pentafluoropropenyl-2-copper reagent with dioxygen. Cu(0) mediated coupling of an ( E )-substituted α,β-difluoro-β-iodostyrene provided the first useful route to a ( Z )( Z )-1,4-diaryl-1,3-tetrafluoroButadiene. Extension of the Cu(0) mediated coupling methodology to a perfluorodienyl iodide demonstrated a useful stereospecific route to perfluoropolyenes.
Michael E. Jenkin - One of the best experts on this subject based on the ideXlab platform.
-
Ambient concentrations of 1,3-Butadiene in the UK.
Chemico-Biological Interactions, 2001Co-Authors: G.j Dollard, C.j Dore, Michael E. JenkinAbstract:Abstract This paper assesses the current knowledge of 1,3-Butadiene as an atmospheric pollutant, considers measurement techniques and reviews available data on 1,3-Butadiene monitoring and emissions estimates. Atmospheric chemistry, sources of emission, current legislation, measurement techniques and monitoring programmes for 1,3-Butadiene are reviewed. There have been comparatively few studies of the products of oxidation of 1,3-Butadiene in the atmosphere. However, on the basis of the available information, and by analogy with the oxidation mechanism for the widely-studied and structurally similar natural hydrocarbon isoprene (2-methyl-1,3-Butadiene), it is possible to define some features of the likely oxidation pathways for 1,3-Butadiene. The total UK 1,3-Butadiene emission to the atmosphere for 1996 has been estimated at 10.60 kTonnes. 1,3-Butadiene is a product of petrol and diesel combustion; consequently this total is dominated by road transport exhaust emissions (accounting for some 68% of the total). Off-road vehicles and machinery are responsible for 14% of the total UK emission. 1,3-Butadiene is used in the manufacture of numerous rubber compounds, and consequently emissions arise from both the manufacture and use of 1,3-Butadiene in industrial processes. Emissions from the chemical industry account for 18% of the UK total emission- 8% from 1,3-Butadiene manufacture and 10% from 1,3-Butadiene use. The United Kingdom Expert Panel on Air Quality Standards (EPAQS) has published a report on 1,3-Butadiene, and recommended a national air quality standard of 1.0 ppb (expressed as an annual rolling mean). This was adopted by the Government as part of the National Air Quality Strategy (NAQS) in 1997, and a target of compliance by 2005 was set. Work conducted for the review of the NAQS (1999) indicated that it was likely that all locations would be compliant with the national standard by the end of 2003. As a result, the review updated the air quality objective for 1,3-Butadiene, with the deadline for compliance being brought forward to 31/12/2003. The UK Hydrocarbon Monitoring Network provides continuous hourly measurements of 1,3-Butadiene at 13 sites, and has been operational since 1993. The dataset that is available allows spatial and temporal trends to be evaluated, and has proved to be invaluable in characterising the current ambient levels of 1,3-Butadiene in the UK. Hourly maximum concentrations of 1,3-Butadiene of up to 10 ppb (1 ppb=1 ppb, i.e. 1 vol. of 1,3-Butadiene in 1 000 000 000 vol. of air. 1 ppb of 1,3-Butadiene is ca. equal to 2.25 μg m−3 at 20°C) may be measured for several hours at the sites. Monthly mean concentrations are typically 0.1–0.4 ppbv. At most sites, these levels are driven by emissions from motor vehicles. Occasionally emissions of 1,3-Butadiene from industrial sources may elevate 1,3-Butadiene concentrations to several tens of ppb. Trend analysis of the data suggests that ambient concentrations of 1,3-Butadiene in the UK are declining at about 10% per year.
-
Ambient concentrations of 1,3-Butadiene in the UK.
Chemico-biological interactions, 2001Co-Authors: G.j Dollard, C.j Dore, Michael E. JenkinAbstract:This paper assesses the current knowledge of 1,3-Butadiene as an atmospheric pollutant, considers measurement techniques and reviews available data on 1,3-Butadiene monitoring and emissions estimates. Atmospheric chemistry, sources of emission, current legislation, measurement techniques and monitoring programmes for 1,3-Butadiene are reviewed. There have been comparatively few studies of the products of oxidation of 1,3-Butadiene in the atmosphere. However, on the basis of the available information, and by analogy with the oxidation mechanism for the widely-studied and structurally similar natural hydrocarbon isoprene (2-methyl-1,3-Butadiene), it is possible to define some features of the likely oxidation pathways for 1,3-Butadiene. The total UK 1,3-Butadiene emission to the atmosphere for 1996 has been estimated at 10.60 kTonnes. 1,3-Butadiene is a product of petrol and diesel combustion; consequently this total is dominated by road transport exhaust emissions (accounting for some 68% of the total). Off-road vehicles and machinery are responsible for 14% of the total UK emission. 1,3-Butadiene is used in the manufacture of numerous rubber compounds, and consequently emissions arise from both the manufacture and use of 1,3-Butadiene in industrial processes. Emissions from the chemical industry account for 18% of the UK total emission- 8% from 1,3-Butadiene manufacture and 10% from 1,3-Butadiene use. The United Kingdom Expert Panel on Air Quality Standards (EPAQS) has published a report on 1,3-Butadiene, and recommended a national air quality standard of 1.0 ppb (expressed as an annual rolling mean). This was adopted by the Government as part of the National Air Quality Strategy (NAQS) in 1997, and a target of compliance by 2005 was set. Work conducted for the review of the NAQS (1999) indicated that it was likely that all locations would be compliant with the national standard by the end of 2003. As a result, the review updated the air quality objective for 1,3-Butadiene, with the deadline for compliance being brought forward to 31/12/2003. The UK Hydrocarbon Monitoring Network provides continuous hourly measurements of 1,3-Butadiene at 13 sites, and has been operational since 1993. The dataset that is available allows spatial and temporal trends to be evaluated, and has proved to be invaluable in characterising the current ambient levels of 1,3-Butadiene in the UK. Hourly maximum concentrations of 1,3-Butadiene of up to 10 ppb (1 ppb=1 ppb, i.e. 1 vol. of 1,3-Butadiene in 1,000,000,000 vol. of air. 1 ppb of 1,3-Butadiene is ca. equal to 2.25 microg m(-3) at 20 degrees C) may be measured for several hours at the sites. Monthly mean concentrations are typically 0.1-0.4 ppbv. At most sites, these levels are driven by emissions from motor vehicles. Occasionally emissions of 1,3-Butadiene from industrial sources may elevate 1,3-Butadiene concentrations to several tens of ppb. Trend analysis of the data suggests that ambient concentrations of 1,3-Butadiene in the UK are declining at about 10% per year.
