Pyrene is a good luminescent probe as it can undergo fluorescence that has a long lifetime, 1/2 100 ns, and its fluorescence is highly dependent on the polarity of the solution it is in. Pyrene’s emission spectrum can provide information about the microenvironment it is in. The molecule is a rather large elongated pi-conjugated system, making it nucleophilic and impossible for it to have any affinity to a charged surface such as silica. Figure 1: Emission spectrum of small pyrene concentration in acetonitrile From the emission spectrum of pyrene in a specific solvent, there is a fixed ratio between the first and third intensity peaks. These ratios can be compared to ratios formed by other pyrene derivatives, as well as Dimroth’s ET
The net reaction is: This reaction has been studied extensively and occurs for a wide variety of ketones. In general, the halogenations of a ketone can be represented as follow: The main evidence for any mechanism is provided by kinetic studies to determine an experimental rate law. Following the rate law of chemical kinetics, the differential rate equation for the reaction could be written as follow: Where k = rate constant; a, b,c are the orders of the reaction of S, I3-, and H+ respectively. I3- ion is the only coloured species in the reaction mixture, a spectrophotometer can is used to measure the change in its concentration, by applying the Beer-Lambert Law Where A= absorbance, ε= molar absorption coefficient, [I3-]= concentration and /= optical path length, that is, the distance travelled by the light through the solution. The ideal wavelength for the measurement of
INTRODUCTION TO NUCLEAR REACTION: The main features of nuclear reactions include radioactive decay, nuclear fission and nuclear fusion. Radioactive decay: Energy is released in a radioactive decay in the form of the kinetic energy of the particle emitted (α and β), the kinetic energy of the daughter nucleus and the energy of the gamma-ray photon that may accompany the decay. The energy involved may be calculated by finding the mass defect of the reaction. The energy released is the energy equivalent of the mass defect of the reaction. Nuclear fission: Nuclear fission is the process in which a large nucleus breaks into two smaller nuclei that are almost equal in mass.
high melting point, hard, brittle, slightly soluble in water, conductor of electricity when melted or in solution Molecular solid - crystalline solid that has molecules arranged in a particular configuration. low melting point, generally insoluble in water, nonconductor of electricity. Metallic solid - crystalline solid that has atoms of metals arranged in a definite pattern. low to high melting point, malleable, ductile, conductor of electricity, insoluble in most solvents. Lesson 13.6 Changes of physical state: * necessary to draw a temperature-energy graph to see the change in temperature with a constant application of heat Heat of fusion - the amount of heat required to melt 1.00 g of substance.
Exothermic and endothermic reactions. First law of thermodynamics and enthalpies of reactions. Calculate standard enthalpies of formations (using the equation on page 191). Electromagnetic radiation, photoelectric effect and continuous and line spectra. Energy levels and electron configurations (including representation using orbital diagrams) of several common elements on the periodic table.
The technique of infrared spectroscopy, in both the solid and solution phases, has proved to be of very useful in these studies. In this experiment mononuclear metal carbonyl chemistry is observed with Molybdenum hexacarbonyl, [Mo(CO)6] (2). From there the synthesis pathway with each transition along the way being analyzed. This sequence of reactions is used to help one achieve a better understanding of the factors responsible in determining which ligands will be exchanged in a ligand substitution reaction involving an octahedral complex, and what might the dominant product stereochemistry be. Each of the three reactions are heated at reflux, cooled, and filtered, yielding their respective products.
How does a scanning electron microscope produce an image? a. bounces electrons off specimen b. passes electrons through specimen to a screen c. concentrates light to heavily illuminate specimen d. uses electromagnet to form image by attraction/repulsion 2. How does a transmission electron microscope produce its image? a. bounces electrons off specimen b. passes electrons through specimen to a screen c. concentrates light to heavily illuminate specimen d. uses magnetic waves to form image by attraction/repulsion 3. What is(are) the main difference(s) between electron microscopes and light microscopes?
An optimised imaging modality would result from a combination of these properties. One such emerging technique that achieves this is Cherenkov Luminescence Imaging (CLI). CLI harnesses Cherenkov radiation to image radionuclides using OI instruments2. Cherenkov radiation is a well known phenomenon that arises when charged particles, such as β- or β+ travel through an optically transparent material with a velocity that exceeds the speed of light in the material. As the particle travels through the medium it loses kinetic energy by polarizing the electrons of the given material.
Static electricity is produced from a process known as triboelectrification. To show how much static electricity an object has, it is determined by its position on the triboelectric series. Its position on this scale is determined by how tight the atom is holding the electrons. An atom is more positive in the triboelectric series if a material is more apt to give up electrons when in contact with another material. If a material is more apt to "capture" electrons when in contact with another material, it is more
Electromagnetism Everything is made out of atoms. Atoms consist of a nucleus (containing neutrons and protons) and a cloud of electrons surrounding the nucleus. Protons are positively charged and electrons are negatively charged. If an object has more protons than neutrons, then it is negatively charged. If an object has more electrons than protons, then it is positively charged.