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1.
《European Polymer Journal》1985,21(9):777-779
The polymerizability of styrene derivatives having alkylamino substituents, such as 1-(2-isopropylaminoethyl)-4-vinylbenzene (IPVB), 1-(2-diethylaminoethyl)-4-vinylbenzene (DEVB) and 1-(2-dimethylaminoethyl)-4-vinylbenzene (DMVB), was investigated in the range −96 to +25° with gamma-rays from a 60Co source. The glass transition temperatures were found to be −94° for IPVB, −102° for DEVB and −114° for DMVB. The polymer yield of these monomers prepared by 4 × 106 rad irradiation at −55° was 39.9, 10.4 and 4.9% respectively. On the other hand, the polymer yield of IPVB as a function of irradiation temperature (irradiation dose: 4 × 106 rad) was 2.4% at −96°, 27.4% at −78°, 39.9% at −55°, 35.7% at −37°, 36.4% at −24°, 54.8% at 0° and 71.3% at +25°. Such a trend of temperature-dependent polymer yield also decreased markedly in the order IPVB, DEVB and DMVB. The polymers prepared were soft and gummy, although polymers prepared by irradiating at the doses of 1 × 107 or above were hard and transparent. 相似文献
2.
ABSTRACT We examined the effect as donors of three aryl β-D-galactosides (i.e. p-nitrophenyl β-D-galactopyranoside, o-nitrophenyl β-D-galactopyranoside and phenyl β-D-galacto-pyranoside) on the regioselectivity and the yield of the synthesis of N-acetyllactosamine obtained from the transglycosylation reaction catalyzed by a crude preparation of β-D-galactosidase from Bacillus circulans at 25 °C, 37 °C and 55 °C, respectively. Using p-nitrophenyl β-D-galactopyranoside the reaction results were fully regiospecific at all the temperatures considered: the maximum molar yield (74%) was obtained at an incubation temperature of 55 °C. Using o-nitrophenyl β-D-galactopyranoside as the donor the reaction was still highly regioselective and the maximum molar yield (50%) was achieved at an incubation temperature also of 55 °C. Using phenyl β-D-galactopyranoside transglycolytic products appear only at an incubation temperature of 55 °C but at very low molar yield (about 14%) and lower regioselectivity. 相似文献
3.
Manoj Kumar Anant Deshpande Chintan Gupta A. K. Nath 《Journal of Chemical Sciences》2003,115(3):219-224
Multi-photon dissociation of Freon-22 (CF2HC1) at low temperatures has been carried out to separate the C-13 isotope using a TEA CO2 laser. Yield and enrichment of C-13 isotope in the product C2F4 are studied at 9P(22) laser line as a function of temperature (−50°C to 30°C). It is observed that at a given fluence when the temperature
is lowered the yield decreases and the enrichment factor of C-13 increases.
Room temperature irradiation of CF2HC1 towards the blue edge of C-13 absorption (i.e. at 9P(20) laser line) gives low yield of the product (C2F4) at a fluence, which produces the desired enrichment factor of 100. An increase in fluence gives very high yield of C2F4 but the enrichment factor is very low. Irradiating CF2HC1 at a temperature of −10°C enhances the enrichment factor to 100 and the yield obtained is comparable to that towards the
red edge of C-13 absorption (i.e. at 9P(26) laser line).
At a given enrichment factor higher enrichment efficiency is achieved when CF2HC1 is irradiated at lower temperature. 相似文献
4.
L. H. Klemm Joseph J. Karchesy Ross F. Lawrence 《Journal of heterocyclic chemistry》1978,15(5):773-775
Sulfur bridging of 2-phenylnaphlhalene ( 3 ) to form benzo[b ]naphtho[2,1-d]thiophene ( 5 ) (main product) and the isomeric benzo[b]naphtho[2,3-d]thiophene ( 4 ) is effected by means of hydrogen sulfide, benzene (solvent), and a sulfided cobaltous oxide-molybdic oxide-alumina (CMA-1) catalyst at 450–630° in a flow system (maximum yield 33% at 500°). The low yield is ascribed to decompositions of both 4 and 5 under reaction conditions. 相似文献
5.
The Bernthsen reaction between N-1-naphthyl-2-naphthylamine and 2-methylbutanoic acid and its anhydride at 200–230° for seven hours gives a low yield of 12- or 13-s-butyldibenz[a,h]acridine, instead of the expected 14-isomer. The parent molecule dibenz[a,h]acridine results from the same reaction conducted at 270° for thirteen hours. It is suggested that alkyl migration may have occurred in some other cases where the Bernthsen reaction was reported to yield 14-alkyldibenz[a,h]acridines. 相似文献
6.
Gelsemine Support Studies: Observation of an Unusual Free Radical Cyclization-Fragmentation Sequence
Treatment of vinylogous urethanes 9a and 9b with tri-n-butyl in hydride generated a tree radical that underwent cyclization-fragmentation to afford oxindole-ketones 10 and 11 in high yield. Vinylogous urethane 13 , gave only cyclization-reduction products 15 and 16 upon treatment with tri-n-butyltin hydride at 80 °C, but also afforded a low yield of cyclization-fragmentation product 14 upon treatment with tris(trimethyl-silyl)silane at 140 °C. 相似文献
7.
The reaction between indole and N-(2-haloacyl)pyridinium salts has been studied. With dioxan as solvent 1-(2-haloacyl)indole (2) was generally the product at low temperatures and 3-(2-haloacyl)indole (1) at high temperatures, as illustrated by the following α-bromopropionylation: Product ratio (1c/2a), 20° (0·01), 40° (0·8) and 60° (8·5). The fact that the a-bromobutyrylation at 60° gave 3-{N-(2-bromobutyryl)-1,4-dihydro-4-pyridyl}indole (6) as the main product, and 3-(2-bromobutyryl)indole (1d) only as a minor product, shows that the 3-acylation is affected by steric hindrance.At high reaction temperature (> 60°) the yield of1 decreased, owing to the formation of 3-indacylpyridinium salts (4). 相似文献
8.
A novel method for the preparation of diborane from aluminum,ethyl chloride,boron oxide and hydrogen
Chengwen Zhao Yijian Gu Zunhong Rui Zhongqiang Lin Huoming Yin Guangyu Lu Yusheng Tao 《Heteroatom Chemistry》1992,3(3):271-274
A novel method is described for the preparation of diborane from aluminum, ethyl chloride, boron oxide and hydrogen via three steps; deoxyalkylation of boron oxide, hydrogenation of triethylboron and liberation of diborane. The triethylboron was prepared from aluminum, ethyl chloride and boron oxide directly at 85–110°C in 88% yield, with aluminum trichloride as by-product in 95% yield. In the presence of triethylamine and a hydrogen pressure of 130 kg/cm2, the triethylboron was hydrogenated at 200°C for 2 hours to produce borane-triethylamine complex in 92% yield. The borane-triethylamine complex was treated again at 80°C with the aluminum trichloride collected from the first step to liberate diborane in 94% yield. The overall reaction yield was 76%. 相似文献
9.
Procedures for the dimerization of acrolein to form 3,4-dihydro-2H-pyran-2-carboxaldehyde by microwave induced synthesis have been developed. Significant rate-enhancement and yield increase were observed. 3,4-Dihydro-2H-pyran-2-carboxaldehyde was obtained in 91% yield under microwave irradiation for 5 minutes instead of 39% yield by reacting at 190 °C for 40 min or at 160 °C for 4 hr. 相似文献
10.
D. Colin Phillips Sandra Spewock William M. Alvino 《Journal of polymer science. Part A, Polymer chemistry》1976,14(5):1137-1150
4-Aminophthalic acid has been polymerized in almost quantitative yield to low molecular weight polymer by electrochemical initiation at a platinum anode. Systems involving the acid, amine salt, and the ammonium salt have been explored; the acid and/or the amine salt of the acid provides the best means of obtaining polymer. Maximum molecular weight is attained in a very short time at low current densities (~2 hr at 50 mA). Thermogravimetric data indicate a temperature stability comparable to polyamide-imide polymers (400°C). Long reaction times and high current densities decrease molecular weight and polymer yield. 相似文献
11.
Protein Extraction and Enzymatic Hydrolysis of Ammonia-Treated Cassava Leaves (Manihot esculenta Crantz) 总被引:2,自引:0,他引:2
Lauris Urribarrí David Chacón Orlaidy González Alexis Ferrer 《Applied biochemistry and biotechnology》2009,153(1-3):94-102
In the present work, cassava leaves were treated with 0.5 kg ammonia/kg dry matter at 78 °C and 30% moisture content in a 2-kg reactor. Protein extraction was carried out with a calcium hydroxide solution (pH 10) for 30 min at several temperatures (30 °C, 45 °C, 60 °C, 75 °C, and 90 °C) and solid/liquid ratios (1:10 and 1:15) in a thermostatized bath. Soluble protein content of the extracts was determined by Lowry’s method. Dry substrate concentrations of 5%, 7.5%, and 10% and enzyme doses of 2 and 5 IU/g dry matter were used for the enzymatic hydrolysis in an orbital incubator at 50 °C and 100 rpm. Both cellulase and xylanase were used. Reducing sugars produced were determined with the dinitrosalicylic acid method. The highest protein extraction yield for the ammonia-treated leaves was 29.10%, which was 50% higher than with the untreated leaves (20%), and was obtained at 90 °C with a 1:10 solid/liquid ratio. The concentrate had a protein content of 36.35% and the amino acid profile was suitable for swine and poultry. The highest sugar yield was 54.72% with respect to theoretical and was obtained with 5% solids and an enzyme dose of 5 IU/g dry matter. This yield was 3.4 times higher than the yield of the untreated leaves (16.13%). These results indicate that cassava leaves have a great potential for animal feeding and ethanol production. Both protein extraction and sugar yields may be enhanced by optimizing the ammonia treatment. 相似文献
12.
Feng-Wen Wang Zhi-Bao Huo Yuan-Qing Wang Fang-Ming Jin 《Research on Chemical Intermediates》2011,37(2-5):487-492
Utilization of biomass has become a major topic of research around the world. One promising aspect of utilization is production of lactic acid from carbohydrate biomass. Our previous study showed that lactic acid can be formed from glucose and cellulose by alkaline hydrothermal reactions, but the yield of lactic acid was low, particular for cellulose. In this study, an efficient method for producing lactic acid from cellulose under hydrothermal conditions with NaOH in the presence of nickel was developed. Experiments were conducted in a batch reactor at 300 °C for 1?C4 min. Results showed that nickel could promote the yield of lactic acid from cellulose. The highest yield of 34.07% was obtained by adding 0.5 mmol nickel using 2.5 M NaOH solution at 300 °C for 1 min. 相似文献
13.
2,2'-联吡啶桥连的双-4,4'-联吡啶哑铃型化合物的合成 总被引:5,自引:0,他引:5
二甘醇2与对甲苯磺酰氯在CH_2Cl_2中,0 ℃~r.t.及Et_3N存在下反应得2- (羟乙氧基)乙醇对甲苯磺酸酯(3),收率88%。化合物3与对叔丁基苯甲酰氯在 CH_2Cl_2中0~5 ℃及吡啶存在下反应得2-(对叔丁基苯甲酰氧基乙氧基)乙醇对 甲苯磺酸酯(4),收率96%。4与对羟苯甲醇在乙腈中及CsF/K_2CO_3存在下70 ℃ 反应得2-(对叔丁基苯甲酰氧基乙氧基)乙氧苄醇(5),收率98%。5与NBS及 PPh_3在THF中,室温下反应得化合物2-(对 丁基苯甲酰氧基乙氧基)乙氧苄溴 (6),收率95%。6与4,4'-联吡啶在乙腈中,60 ℃反应1h得N-[2-(对叔丁基 苯甲酰氧基乙氧基)乙氧苄基]-4,4'-联吡啶六氟磷酸盐(7),收率85%。7与 α,α-二(溴甲基)-2,2'-联吡啶在乙腈中,油浴60 ℃反应36h,得到标题化 合物,产率为45%。 相似文献
14.
《Arabian Journal of Chemistry》2022,15(2):103577
The oxidative coupling of methane (OCM) is an attractive route to convert natural gas directly into value-added chemical products (C2+). This work comparatively investigated SiO2- or La2O3-supported Na2WO4-MnxOy (denoted as NWM) catalysts in powder and fiber forms. The powder catalysts were prepared using a co-impregnation method and the fiber catalysts were prepared successfully using an electrospinning technique. The NWM/La2O3 fiber catalysts were activated at low temperature (500 °C) and had a 4.7% C2+ yield, with the maximum C2+ yield of 9.6% at 650 °C, while the NWM/SiO2 fiber catalyst was activated at 650 °C and had a maximum C2+ yield of 20.4% at 700 °C. The XPS results in the O 1s region indicated that NWM/La2O3 had a lower binding energy than NWM/SiO2, suggesting that the lattice oxygen species is easily released from the catalyst surface and creates vacancy sites that enhance performance. The stability test of the catalysts indicated that the La2O3-containing catalysts had excellent activity and high thermal stability, while the SiO2-containing catalysts had a higher C2+ yield when the prepared catalysts were compared at 700 °C. Considering the same component catalysts, the fiber catalysts achieved higher performance because their heat and mass transfer properties were enhanced. 相似文献
15.
Radiation polymerization of large crystals of chloroprene formed within the temperature range -130 to -180°C has yielded the stereoregular trans-1,4-poly(2-chloro-1,3-butadiene). The monomer was found to have a glass transition temperature of ca. -180°C. Polymerization of monomer rapidly cooled to below -180°C was difficult and gave only structurally irregular polymer in low yield. 相似文献
16.
J. S. Amato V. J. Grenda T. M. H. Liu E. J. J. Grabowski 《Journal of heterocyclic chemistry》1979,16(6):1153-1155
Reactions of 2-(4′-fluorophenyl)imidazole ( 1 ) and related compounds under various nitrating conditions are discussed. With 90% nitric acid in 20% oleum at ?10°, 1 affords 2-(4′fluorophenyl)-4(5)-nitroimidazole ( 2 ) in 80% yield. Reaction of 2 with the same reagents at 25° affords 2-(4′-fluoro-3′-nitrophenyl)-4(5)-nitroimidazole ( 4 ) in 90% yield, whereas with 90% nitric acid in acetic acid at 95°, 2 affords 4,5-dinitro-2-(4′-fluorophenyl)imidazole ( 5 ) in 80% yield. Reaction of 1 with 70% nitric acid in concentrated sulfuric acid at 25° affords 2-(4′-fluorophenyl)-5-hyroximinoimidazolin-4-one ( 6 ), which rearranges and hydrolyzes to 5-(4′-fluorophenyl)-1,2,4-oxadiazole-3-carboxylic acid. A discussion of these reactions is presented. 相似文献
17.
Azulene-1-carbaldehydes which have Me substituents at C(3) and C(8) and no substituent at C(6) react with excess dimethyl acetylenedicarboxylate (ADM) in decalin at 200° to yield exclusively the Diels-Alder adduct at the seven-membered ring (cf. Scheme 3). The corresponding 1-carboxylates behave similarly (Scheme 4). Azulene-1-carbaldehydes which possess no Me substituent at C(8) (e.g. 11 , 12 in Scheme 2) gave no defined products when heated with ADM in decalin. On the other hand, Me substitutents at C(2) may also assist the thermal addition of ADM at the seven-membered ring of azulene-1-carbaldehydes (Scheme 6). However, in these cases the primary tricyclic adducts react with a second molecule of ADM to yield corresponding tetracyclic compounds. The new tricyclic aldehydes 16 and 17 which were obtained in up to 50% yield (Scheme 3) could quantitatively be decarbonylated with [RhCl(PPh3)3] in toluene at 140° to yield a thermally equilibrated mixture of four tricycles (Scheme 8). It was found that the thermal isomerization of these tricycles occur at temperatures as low as 0° and that at temperatures > 40° the thermal equilibrium between the four tricycles is rapidly established via [1,5]-C shifts. The establishment of the equilibrium makes the existence of two further tricycles necessary (cf. Scheme 8). However, in the temperature range of up to 85° these two further tricycles could not be detected by 1H-NMR. When heated in the presence of excess ADM in decalin at 180°, the ‘missing’ tricyclic forms could be evidenced by their tetracyclic trapping products ‘anti’- 45 and ‘anti’- 48 , respectively (Scheme 9). 相似文献
18.
The decomposition of η6-(2-lithiochlorobenzene)tricarbonylchromium(0) (I) was found to follow first order kinetics with kdec 5.1 x 10-3 min-1 at 0°C, the half life of I being 136 min at 0°C. While this dependence strongly suggests intermediacy of η6-(benzyne)tricarbonylchromium, trapping experiments were successful in only low yield. 相似文献
19.
Hitoshi Yamaoka Isamu Obama Koichiro Hayashi Seizo Okamura 《Journal of polymer science. Part A, Polymer chemistry》1970,8(2):495-503
Radiation-induced postpolymerization of nitroethylene in 2-methyltetrahydrofuran glass has been studied and discussed in reference to the results obtained from ESR measurements. No postpolymerization occurred at the temperature below ?150°C. In the temperature range between ?135°C and ?78°C, the polymer yield decreased with increasing postpolymerization temperature. The polymer yield increased linearly with the increase of the preirradiation dose in the range below 0.9 × 106 r. The mean value for chain initiation was estimated to be about 1.3. The following correlations were observed between the results of the postpolymerization and ESR measurements. The postpolymerization started in the temperature range between ?140°C and ?135°C, where the ESR spectrum due to the anion radicals of nitroethylene disappeared. The polymer yield of the postpolymerization decreased with the photoirradiation at ?196°C before warming the samples in parallel with the photobleachability of the anion radicals observed in the glassy mixture by the ESR method. It was concluded from these results that the radiation-induced postpolymerization was initiated by the anion radicals of nitroethylene formed by the capture of electons. 相似文献
20.
Xiaoning Guo Caihong Hao Guoqiang Jin Huai‐Yong Zhu Xiang‐Yun Guo 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(7):2004-2008
Copper is a low‐cost plasmonic metal. Efficient photocatalysts of copper nanoparticles on graphene support are successfully developed for controllably catalyzing the coupling reactions of aromatic nitro compounds to the corresponding azoxy or azo compounds under visible‐light irradiation. The coupling of nitrobenzene produces azoxybenzene with a yield of 90 % at 60 °C, but azobenzene with a yield of 96 % at 90 °C. When irradiated with natural sunlight (mean light intensity of 0.044 W cm−2) at about 35 °C, 70 % of the nitrobenzene is converted and 57 % of the product is azobenzene. The electrons of the copper nanoparticles gain the energy of the incident light through a localized surface plasmon resonance effect and photoexcitation of the bound electrons. The excited energetic electrons at the surface of the copper nanoparticles facilitate the cleavage of the N O bonds in the aromatic nitro compounds. Hence, the catalyzed coupling reaction can proceed under light irradiation and moderate conditions. This study provides a green photocatalytic route for the production of azo compounds and highlights a potential application for graphene. 相似文献