Authors: Andrew Nassif
Comments: 3 Pages.
Chemistry requires lots of conceptual thinking as well as analytical actions. Chemistry is a science of measurement. Like physics, it also requires much mathematical sequences in it. Chemistry is the bridge of science, because it is a sub-subject of every major field of science including physics and geology. Boyle describes chemistry as the subject of major bodies. Chang describes chemistry as the study of matter and the changes it undergoes. Chang's definition, is the most commonly used today. Chemistry was thought to be created by the greeks (atomism), however, it was created hundreds of years before as a way ancient Egyptians used herbs to create a remedy, or used the science of proper mechanics to build the pyramids using a special chemical combination as the glue that held bricks together. Cleopatra herself was an alchemist.
Gas to aqueous phase standard state (1 atm to 1 mol/L; 298.15 K) free energies of solvation (ΔGosolv) were calculated for a range of neutral and ionic inorganic and organic compounds using various levels and combinations of Hartree-Fock and density functional theory (DFT) and composite methods (CBS-Q//B3, G4MP2, and G4) with the IEFPCM-UFF, CPCM, and SMD solvation models in Gaussian 09 (G09). For a subset of highly polar and generally polyfunctional neutral organic compounds previously identified as problematic for prior solvation models, we find significantly reduced ΔGosolv errors using the revised solvent models in G09. The use of composite methods for these compounds also substantially reduces their apparent ΔGosolv errors. In contrast, no general level of theory effects between the B3LYP/6-31+G** and G4 methods were observed on a suite of simpler neutral, anionic, and cationic molecules commonly used to benchmark solvation models. Further investigations on mono- and polyhalogenated short chain alkanes and alkenes and other possibly difficult functional groups also revealed significant ΔGosolv error reductions by increasing the level of theory from DFT to G4. Future solvent model benchmarking efforts should include high level composite method calculations to allow better discrimination of potential error sources between the levels of theory and the solvation models.
Authors: Andrew Nassif
Comments: 5 Pages.
Chemistry is a branch of physical science that has to do with the study of the composition of matter and the study of everything composed of matter as well as based on the basis of atomism, fluid dynamics, and particle physics, as well as the action of measurements applied as a stoichiometry and a method in using chemistry. Chemistry in basically the central science, though it may be a branch of physical science, it is very distinct from physics. The world chemistry itself comes from the word alchemy which is derived from لكيمياء which is then derived from the greek word χημεία, this means he study of material, which is then translated to being the study of everything composed of matter. Ancient Egyptians themselves used synthetic chemistry as a study of herbs as well as using this branch of chemistry to help them plant crops in the fertile crust. Democritus's theory of atomism became the foundation of chemistry and elementary physics itself. Eventually Atomism brought forth ideas of models of the atoms around us and many generations later, the Quantum Mechanical Model was born. This is how the fundamental of chemistry came to be.
The partitioning behavior of disparlure ((7R,8S)-7,8-epoxy-2-methyloctadecane) - a sex pheromone of the gypsy moth, Lymantria dispar - between aqueous solutions and the organic solvents chloroform and n-heptane has been re-evaluated. Prior estimates from the literature of the aqueous-organic solvent partitioning coefficients (log P) for disparlure in these two solvent systems appear to have been underestimated by about 5-6 orders of magnitude. In the current work, we provide corrected log P(chloroform/water) and log P(heptane/water) values for disparlure of 9.87 and 9.15, respectively.
Authors: Andrew Nassif
Comments: 4 Pages.
Element must be heated to produce emitted light, this is due to its chemical reaction caused by
absorbed energy, which is required in order to emit light. This is why elements acquire being
heated in order to emit light. Sometimes absorbed energy can cause electromagnetic radiation,
also these spectrums are different waves of lights due to the different energy levels of a chemical