Preparation of β-Aminoisobutyric Acid from Glycine via the Wolff Rearrangement of Diazoethylketones

A description is given of the conversion of 3-diazo-1-phthalimidobutan-2-one (la) into B-phthalimidoisobutyranilide (Ila) via the Wolff rearrangement7, in aniline solution , and further rearrangement to B -aminoisobutyric acid. The same rearrangement in (-)-a-phenylethylamine solution is also described

Preparation of β-Aminoisobutyric Acid from Glycine via the Wolff Rearrangement of Diazoethylketones

A description is given of the conversion of 3-diazo-1-phthalimidobutan-2-one (la) into B-phthalimidoisobutyranilide (Ila) via the Wolff rearrangement7, in aniline solution , and further rearrangement to B -aminoisobutyric acid. The same rearrangement in (-)-a-phenylethylamine solution is also described

The Effect of the Type of Polyethylene on .the Grafting of Styrene onto Polyethylene. III. The Crosslinking Effect in the Grafting by Preirradiation in Vacuum

The graft-copolymerisation of styrene onto the free radicals trapped in vacuum-irradiated polyethylene was investigated. By an increase of the rigidity of the foils, the grafting rate is also increased, because the termination of the growing chains becomes more hindered. But further increase of the rigidity causes grafting to stop at comparatively low values. Crosslinking of the foils also increases this rigidity, while raising of grafting temperature partially eliminates its effect. Based on the experimental results, some kinetic and structural factors governing the grafting reactions are discussed and some former theories are revised

Calorimetric Investigation of Grafting of Styrene and Methylmethacrylate onto Air-Preirradiated Polyethylene

All existing and widely used methods for measuring reaction rate of polymerization processes suffer from basic disadvantages including indirect measurement, insufficient accuracy and limited applicability. Their unsuitability is especially pronounced in the investigation of graft copolymerization reactions in which the accuracy of measurement could be affected even by the different properties of individual polymer samples. In this work a new method, calorimetry, free of mentioned disadvantages is generally proposed for investigation of polymerization processes and particularly its application to radiation induced grafting of styrene and methylmethacrylate onto polyethylene is demonstrated. Experimental results showed the possibility of calorimetry to measure the grafting rate continuously and directly in the whole conversion range with the accuracy much better than with any other method used so far. It was concluded that styrene grafting is non-diffusion-controlled, whereas methylmethacrylate grafting is not diffusion- independent. With both monomers the reaction kinetics was found to be dependent on the type of polyethylene a s a consequence of different mechanisms, i. e. in the initiation step two different species, peroxy radicals and peroxides, take part. Its concentration is different in two types of polyethylene used. In the case of high density polyethylene both active species participate in the initiation process equally, according to their different nature. However, in low density polyethylene the concentration of peroxy radicals is negligible compared to that of peroxides and therefore peroxides have dominating role in the initiation step of grafting reaction. The change of the viscosity of reaction medium in the course of reaction as well as the structure of polymer in the case of high density polyethylene influence the kinetics of grafting reaction

The Effect of the Type of Polyethylene on .the Grafting of Styrene onto Polyethylene. III. The Crosslinking Effect in the Grafting by Preirradiation in Vacuum

The graft-copolymerisation of styrene onto the free radicals trapped in vacuum-irradiated polyethylene was investigated. By an increase of the rigidity of the foils, the grafting rate is also increased, because the termination of the growing chains becomes more hindered. But further increase of the rigidity causes grafting to stop at comparatively low values. Crosslinking of the foils also increases this rigidity, while raising of grafting temperature partially eliminates its effect. Based on the experimental results, some kinetic and structural factors governing the grafting reactions are discussed and some former theories are revised

Termination Reaction in the Anionic Polymerization of Methacrylonitrile

The anionic polymerization of methacrylonitrile initiated by triethylphosphine in dimethylformamide was studied. Experimental evidence for two mechanisms of termination reaction was obtained. By addition of water or alcohol in polymerizing system the rate of polymerization and molecular weight of polymethacrylon1itrile decrease, which proves the termination reaction to be bimolecular and proceed by interaction of the active carbanion with water or alcohol. The rate constant for termination of free anions with water was determined, k~,0 = 2.2 x 102 dm3 moP s-1• The termination reaction could not be excluded by purification and prolonged drying of all components of the system, which indicates that the second mechanism of termination is operative as well. Conductivity measurements gave evidence for a monomolecular spontaneous reaction leading to deactivation of the anion

Doses in the Vicinity of Mobile X-ray Equipment in a Children’s Intensive Care Unit

Most of the patients in the intensive care unit for children are newborns and infants having an infection of the central nervous system, with systemic septic and respiratory infections. Therefore, mobile X-ray equipment including mobile shields is routinely used for diagnosis of the respiratory tract, heart and endovascular cateterisation. The aim of this work was to determine the radiation exposure to the children in the vicinity of the exposed patient in the same or next room. Three measurement runs were carried out with thermoluminescence dosimetry system. The results show that the homogeneity of the irradiation field is adequate, the exposure of children to radiation in the vicinity of the exposed patient in the same or next room is very low, practically in the range of the lowest detectable dose. The entrance dose on the breast of the patient was found to be 0.07 mSv. Therefore, there is no basis for the risk estimation of genetic, leukemogenic and cancerogenic detriment

Calvet Microcalorymetry - a New Suitable Method for Investigation of Polymerization Reactions

The method of Calvet microcalorimetry was used to follow the course of the spontaneous polymerization of styrene. Comparison of this method with widely used point-by-point methods has been performed and the great advantages of calorimetry are shown. Calorimetry measures continuously and directly the reaction rate independently from the physical state of the sample using only one sample for the whole conversion range. The accuracy and sen,sitivity achieved are better than those achieved with other methods. On the basis of these advantages Calvet microcalorimetry can be recommended as very promising method for the investigation of polymerization kinetics

Doses in the Vicinity of Mobile X-ray Equipment in a Children’s Intensive Care Unit

Most of the patients in the intensive care unit for children are newborns and infants having an infection of the central nervous system, with systemic septic and respiratory infections. Therefore, mobile X-ray equipment including mobile shields is routinely used for diagnosis of the respiratory tract, heart and endovascular cateterisation. The aim of this work was to determine the radiation exposure to the children in the vicinity of the exposed patient in the same or next room. Three measurement runs were carried out with thermoluminescence dosimetry system. The results show that the homogeneity of the irradiation field is adequate, the exposure of children to radiation in the vicinity of the exposed patient in the same or next room is very low, practically in the range of the lowest detectable dose. The entrance dose on the breast of the patient was found to be 0.07 mSv. Therefore, there is no basis for the risk estimation of genetic, leukemogenic and cancerogenic detriment