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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The syntheses and photochromic properties of several substituted and condensed benzo[e]dimethyl-dihydropyrenes

Wang, Yunxia 01 May 2017 (has links)
The symmetric multistate photo-switchable molecule 72, which contains two DHP units with a dibenzocyclophane as a spacer, was successfully synthesized by different routes using aryne-furan type Diels-Alder reactions. In the course of making 72, the intermediate furan 79 was synthesized, which upon deoxygenation gave photo-switchable furan 82. In a study of substitution effects on benzo[e]pyrene 21, the substituents phenyl, acetyl, nitro and phenylethynyl were attached to the 4,5-positions. The acetyl and nitro groups were introduced by direct substitution of 21, while coupling methodology were used for the phenyl and phenylethynyl groups. In the later case, a Suzuki coupling was used on bromide 69, followed by bromination, or a Sonogashira coupling was used on the bromoiodide 100, and then an aryne-furan Diels-Alder reaction and deoxygenation were used to give the final substituted benzo[e]pyrenes 105 and 103. The successful synthesis of the phenylbenzo[e]pyrene 105 enabled us to access the monosubstituted tris-pyrene system 120 through the reaction of bromophenylpyrene 107 and furan 79. The thermal return reactions (cyclophanediene to dihydropyrene) were studied on the benzo[e]pyrene derivatives and multistate photoswitch systems. Although the activation energies and enthalpies do not change much with substitution, the thermal return rates do appear to decrease with an electron withdrawing substituent. Photochromic studies were performed on 72 and 120. They both opened in a stepwise manner with one DHP ring opening and then the other, though the intermediate could not be isolated. A simple comparison of the photo opening and closing rates relative to benzo[e] pyrene 21 was performed under excess light conditions. All the derivatives of 21 synthesized in this thesis had faster visible opening rates than the parent 21; the UV closing rates did not change much however. / Graduate
2

Imaging studies of photochemistry of the stratospheric bromine and chlorine compounds

Kim, Hahkjoon 16 August 2006 (has links)
This dissertation focuses on the photodissociation dynamics of stratospheric bromine and chlorine radical intermediates (BrO, ClO) along with reservoir species (ClONO2), which are known to play an important role at stratospheric ozone depletion. The experiments were carried out using a newly built velocity-map ion imaging apparatus which is an improvement over traditional translational spectroscopy studying photodissociation dynamics. The apparatus combines a collision-free molecular beam source with a laser-based pump-probe technique; i.e., single state pumping followed by a state-selective resonantly enhanced multiphoton ionization. Intense molecular beams were prepared using a custom-built flash pyrolytic source. The current research involves the development of fundamental properties of target species such as bond enthalpies and heats of formation, the chemical identification of photofragments, and their relative branching ratios, the excited states dynamics that lead to final products, partitioning of the available energy and finally the wavelength dependence of all these properties.
3

Photolysis of some carbohydrate dithiobis (thioformates)

Stout, Edward Irvin, 1939- January 1973 (has links)
No description available.
4

A comparison of photochemistry at rural sites in the Southeastern United States and Southeastern China

Pearson, James Richard 08 1900 (has links)
No description available.
5

A study of the photochemical rearrangements of 2-methoxy-3-keto-9-methyl- -hexahydronaphthalene

Liles, Donald Taylor 05 1900 (has links)
No description available.
6

Formal intramolecular photoredox reactions of anthraquinones mediated by water

Hou, Yunyan 26 May 2011 (has links)
The formal intramolecular photoredox reaction initially discovered for the parent 2- (hydroxymethyl)-9,10-anthraquinone (HMAQ) in aqueous solution was extended to a variety of anthraquinone derivatives 2.1-2.9, biphenyl anthraquinones 3.1-3.4 and acenequinones 4.1-4.4. The purpose of the study was to explore the generality of the unique photochemical reaction involving HMAQ, understand the mechanism of the reaction and develop potential applications. All the anthraquinones studied (except for 2.4) undergo the formal intramolecular photoredox reaction with a range of quantum yields (PHI =0.02-0.7). Mechanistic studies based on the parent compound HMAQ were carried out by product studies, isotope effects, solvent deuterium isotope effects, pH effect, triplet quenching studies, and laser flash photolysis. It was found that the formal intramolecular photoredox reaction involves a highly polarized triplet excited state in which the electron density of the benzylic CH20H moiety is transferred to the central anthraquinone ring. This highly polarized triplet excited state is subsequently trapped adiabatically by protonation at the anthraquinone carbonyl oxygen. / Graduate
7

The atmospheric photochemical stability of CC1F2NO, CC12FNO, CC1F2NO2 and CC12FNO2 /

Fazekas, George B. January 1982 (has links)
Thesis (M.S.)--Rochester Institute of Technology, 1982. / Typescript. Includes bibliographical references (leaves 82-85).
8

A precision radiation integrator for photochemical research,

Shriver, George Edward, January 1934 (has links)
Thesis (Ph. D.)--New York, University, 1934. / Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: p. 54-55.
9

A precision radiation integrator for photochemical research,

Shriver, George Edward, January 1934 (has links)
Thesis (Ph. D.)--New York, University, 1934. / Vita. eContent provider-neutral record in process. Description based on print version record. Bibliography: p. 54-55.
10

Mechanistic organic photochemistry

Blinn, James Robert. January 1979 (has links)
Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographies.

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