Direct observation and reactivity of oxenium ions

Oxenium ions are poorly understood reactive intermediates of the formula R-O+. This body of work is an accumulated computational and experimental investigation into understanding the electronic configuration, spectroscopic signatures, spin-selective reactivity, and lifetimes of these short-lived intermediates. Chapter 1 overviews our attempts to find a photochemical precursor to oxenium ions, which ultimately led to the first direct detection of the short-lived parent phenyloxenium ion. Laser flash photolysis studies were performed on the phenyl hydroxylamine tetrafluoroborate salt to form the singlet phenyloxenium ion. These studies were performed by Jiadan Xue in the lab of Dr. David Lee Phillips. The lifetime for the phenyloxenium ion was found to be about 5 ns. Product studies from both thermolysis and photolysis with added traps suggest the formation of the phenyloxenium ion along with the phenoxy radical. In order to better understand the effect of structure on the electronic configuration of oxenium ions, Chapter 2 provides an in depth study of heteroaryl oxenium ions by high-level multireference CASSCF/CASPT2 calculations. 4-pyridinyl, pyrizidinyl, and pyrimidyl oxenium ions all have singlet-triplet gaps (ΔEST) of less than -4 kcal/mol, showing significantly changed electronics from the parent phenyloxenium ion. This small gap suggests the possibility that triplet states as well as open shell singlet states could be chemically relevant to these intermediates. In chapter 3, the synthesis of a photochemical precursor to the p-biphenylyl oxenium ion is described, and the ultrafast LFP experiments performed by Mingde Li in the lab of Dr. David Lee Phillips on this precursor suggest photolysis leads to the p-biphenylyl radical, as well as the p-biphenylyl oxenium ion as a closed shell singlet, open shell singlet, and a triplet state. Chapter 4 describes the synthesis of a photoprecursor to the m-dimethylamino phenyloxenium ion, which is computed to have a triplet ground state (+12 kcal/mol, B3LYP/cc-PVTZ). Photolysis of this precursor was studied using product studies as well as by matrix isolation EPR studies. The results obtained by matrix isolated EPR provide evidence that the ground state of the m-dimethylamino phenyloxenium ion is a ground state triplet

How a corn plant develops

There’s more than meets the eye in a field of growing corn. One way to look behind the scene is to consider the cornfield as a complex and constantly changing community. It is a manufacturing community, with many thousands of factories per acre. Every corn plant is a factory that produces dry matter. The corn plant is one of the most efficient factories in the world!https://lib.dr.iastate.edu/specialreports/1045/thumbnail.jp

North central regional potassium studies I. Field studies with alfalfa

Potassium (K)2 availability varies widely in soils of the North Central Region of the United States and the adjoining areas of Canada. Soils in the western part of the region generally contain adequate amounts of plant-available K, but in other parts of the region, soils vary from those with abundant supplies of available K to those that are very deficient. Present techniques for predicting crop requirements for K fertilizer on different soils based on the determination of all or a portion of the exchangeable K in the plow layer are often inadequate, even when applied within restricted soil areas. In view of the wide range of K availability in different soils of the region, more effective methods of assessing the K status of the soils must be developed if efficient use of K fertilizers is to be accomplished. Therefore, the major objective of this study was to investigate the relationship between crop yield response from K fertilizer or uptake of soil K by plants in the field and different laboratory indexes of plant-available K

Theoretical and Experimental Studies of Oxenium Ions

Theoretical and Experimental studies of Oxenium ions Patrick Hanway Iowa State University The geometries and energies of the phenyloxenium ion were computed at the CASSCF/CASPT2 multireference level of theory. The 1A1 was shown to be the ground state being 22 kcal/mol lower in energy than the 3A2 (n to p*) state. It was found that electron-withdrawing groups in the para position slightly stabilize the singlet compared to the triplet and electron-donating groups have the opposite effect. Electron-donating groups (NH2) in the meta position lead to nearly degenerate singlet triplet states. All the product studies suggest the formation of the phenyloxenium ion. The geometries and energies of heteroaryl oxenium ions were also computed using CASSCF/CASPT2. These results show that the 2- and 3-pyridyl oxenium ions have energies and states that are similar to the phenyloxenium ion. The 4-pyridyl, pyrimidinyl, and pyrizidinyl oxenium ions however have very different energetics from the phenyloxenium ion

Masculinity as Governance: police, public service and the embodiment of authority, c. 1700-1850

About the book: Public Men offers an introduction to an exciting new field: the history of masculinities in the political domain and will be essential reading for students and specialists alike with interests in gender or political culture. By building upon new work on gender and political culture, these new case studies explore the gendering of the political domain and the masculinities of the men who have historically dominated it. As such, Public Men is a major contribution to our understanding of the history of Britain between the Eighteenth and the Twentieth centuries

North central regional potassium studies III. Field studies with corn

Corn is sensitive to a deficiency of potassium (K),2 and yields of corn on K-deficient soils often are increased by K fertilizer applications. K deficiencies in corn have been observed or yield increases have been obtained from K fertilizer applications on many soils in the North Central Region of the United States. However, many other soils in the region have high levels of available K, and applications of K fertilizers on these soils have not increased corn yields. Therefore, it is important to have effective methods of estimating plant availability of K in different soils and to develop methods of predicting the yield response which can be expected from applications of K fertilizer for corn grown on different soils. The increases in yields of corn and other crops obtained from applications of K fertilizer have been shown in some studies to be inversely related to the level of exchangeable K in air-dry samples of the surface soil (5, 7). Therefore, this determination is commonly used in soil testing laboratories to estimate K availability. Other studies, however, have shown that the amount of exchangeable K in some soils is markedly changed by drying the soil (1, 2, 9, 17, 18). In some of these studies, the level of exchangeable K in undried soil samples provided a better estimate of K availability to plants than did the exchangeable K in dry soil samples (2,9,17). Matthews and Sherrell (18), on the other hand, studied the relation between exchangeable K in the soil and the yield of potatoes grown on sandy soils in Ontario, Canada and found a higher correlation with exchangeable K values for oven-dry soils than for undried soils