A versatile method for the synthesis of carbamates from an ‘in-situ’ generated polymer-supported chloroformate resin is presented. BTC (bis-trichloromethyl carbonate) is used as phosgene equivalent to afford a supported chloroformate, which, by sequential ‘one-pot’ reaction with a variety of alcohols and amines, furnishes the corresponding carbamates in high yields and purities. 相似文献
Conductance data for sodium nitrite, chloride, and acetate in water andN,N-dimethylformamide (DMF)-water mixtures (74.82D42.48) for the concentration range 0.001–0.04N, as well as the densities, viscosities, and dielectric constants of the solvent mixtures at 35°C, are reported. The data have been analyzed by the Fuoss (1975) equation. The existence of a maximum in the viscosity at a 13 mole ratio of DMF and water is indicated. The Walden products for all the three salts pass through a maximum while the equivalent conductances show a minimum with increasing DMF content. The maxima in the Walden product are attributed to the dehydration of ions by the cosolvent (DMF).Part I:Indian J. Chem.14A, 1015 (1976).Deceased. 相似文献
The usual methods for determining polychlorinated dibenzo-p-dioxins (PCDD), polychlorinated dibenzofurans (PCDF) and polychlorinated biphenyls (PCB) are generally expensive and time consuming. This fact has favored the development of faster and cheaper techniques, based on immunoassays and bioassays. This paper reviews these bioanalytical methods and their analytical importance at the present moment. 相似文献
The possible structures and isomerizations of H2C=C(OH)Li are studied theoretically by the gradient analytical method at RHF/6-31+G level. According to these results, reactions
of H2C=C(OH)Li with CH3+ and CH
3-
are investigated thoroughly. When H2C=C(OH)Li reacts with CH
3+
, HzC=C(OH)Li firstly changes from structure1 to structure4, and then combines with CH3+. In this reaction, the configuration of central carbon is retained. When H2C=C(OH)Li reacts with CH
3-
, structure1 firstly breaks its C-O bond to give contact ion-pair. Then through transition state16 which is similar to structure2, the attack of CH
3-
from the opposite side of-OH replaces-OH group and inverts the configuration of carbenoid carbon atom. All the results show that the ambident reactivity of carbenoid
has close relationship with the stability of special structures.
Project supported by the National Natural Science Foundation of China (Grant No. 29773025). 相似文献
The calorimeter allows the water absorbed dose, a measure of radiotherapy, to be measured according to its definition. Different detector types are used in the PTB calorimeter; this paper discusses heat conduction, convection and the radiolysis of the
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system for a ‘sealed’ detector. The ‘sealed’ detector allows the calorimeter to be operated at room temperature in the case of 60Co-γ-radiation. 相似文献
A transportable water calorimeter for the determination of the quantity of absorbed dose to water in radiotherapy beams has been developed at the PTB and is presented in detail in this investigation. Heat conduction effects occurring in the calorimeter are studied for different lateral sizes of high-energy photon beams, for different depth dose distributions of electron beams and for a scanned-beam irradiation with a heavy ion beam. The corresponding correction factors are calculated and arguments are given under which conditions these can adequately be applied. 相似文献
The International and European standards for radiation sterilization require evidence of the effectiveness of a minimum sterilization dose of 25 kGy but do not provide detailed guidance on how this evidence can be generated. An approach, designated VDmax, has recently been described and computer evaluated to provide safe and unambiguous substantiation of a 25 kGy sterilization dose. The approach has been further developed into a practical method, which has been subjected to field evaluations at three manufacturing facilities which produce different types of medical devices. The three facilities each used a different overall evaluation strategy: Facility A used VDmax for quarterly dose audits; Facility B compared VDmax and Method 1 in side-by-side parallel experiments; and Facility C, a new facility at start-up, used VDmax for initial substantiation of 25 kGy and subsequent quarterly dose audits. A common element at all three facilities was the use of 10 product units for irradiation in the verification dose experiment.
The field evaluations of the VDmax method were successful at all three facilities; they included many different types of medical devices/product families with a wide range of average bioburden and sample item portion values used in the verification dose experiments. Overall, around 500 verification dose experiments were performed and no failures were observed. In the side-by-side parallel experiments, the outcomes of the VDmax experiments were consistent with the outcomes observed with Method 1.
The VDmax approach has been extended to sterilization doses >25 and <25 kGy; verification doses have been derived for sterilization doses of 15, 20, 30, and 35 kGy. Widespread application of the VDmax method for doses other than 25 kGy must await controlled field evaluations and the development of appropriate specifications/standards. 相似文献