36 research outputs found
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