No description available.

<p> 1,1-Bis(4-(trifluoromethyl)phenyl)germacyclobutane and 1,1-bis(3,5-bis(trifluoromethyl)phenyl)germacyclobutane have been prepared, and their photochemistry studied by steady state and nanosecond laser flash photolysis (NLFP) techniques. Photolysis of the two compounds in the presence of methanol leads to the formation of products resulting from reaction of the alcohol with two germanium-containing reactive intermediates, the germenes and germylenes.</p> <p> The reactivities of the two germenes with nucleophiles such as alcohols, carboxylic acids, and amines have been examined by NLFP techniques, and the results are compared to analogous data for 1,1-diphenylgermene and 1,1-diphenylsilene. Germene reactivity is shown to increase with increasing electron-withdrawing power of the substituents, consistent with a mechanism initiated by nucleophilic attack at germanium. The increased electrophilicity of the substituted 1,1-diarylgermenes results in kinetic behavior indistinguishable from that of 1,1-diphenylsilene, indicating that germenes and silenes form a mechanistic continuum in their reactions with nucleophiles.</p> / Thesis / Master of Science (MSc)

<p> 2-Trifluoromethylnorbornene has been synthesized from norbornene. The UV photoelectron spectra and optical UV absorption spectra of norbornene, 2-methylnorbornene and 2-trifluoromethylnorbornene have been studied, and indicate that the π,π* state is the lowest excited singlet state. Direct photolysis of 2-trifluoromethylnorbornene with 193 nm light yields 1-trifluoromethyl-2-norcarene (in 90% yield) by formal [1,3]-sigmatropic rearrangement. Chlorobenzene-sensitized photolysis affords the photoreduction products, exo-and endo-2-trifluoromethylnorbornane, decane isomers, and several products of higher molecular weight.</p> <p> By comparing the photochemistry of 2-trifluoromethylnorbornene to those previously reported for norbornene and 2-cyanonorbornene as well as on the basis of spectroscopic evidence, it is proposed that the π,π* state is the lowest energy excited singlet state in 2-trifluoromethylnorbornene. Trifluoromethyl substitution has the effect of significantly raising the energy of the π,R(3s) Rydberg state in simple alkenes without altering the high energy or the localized character of the π,π* state.</p> <p> 7-Trifluoromethylbicyclo[4.2.0]oct-7-ene (86) was synthesized from bicyclo[4.2.0]oct-7-ene (84). By comparing the UV photoelectron spectroscopy and optical spectra of 86, 84, 97, it is concluded that the π,π* state is the lowest excited singlet state in 86. Direct photolysis with 193 nm light yields three diene isomers derived from formal electrocyclic π,π* ring opening, and cyclohexene derived from fragmentation. Comparison of spectroscopic and photochemical results for this compound to those of bicyclo[4.2.0]oct-7-ene (84) and 7-methylbicyclo[4.2.0]oct-7-ene (97) indicate that ring-opening is non stereospecific and arises largely from the π,π* singlet state. Fragmentation arises largely from the Rydberg excited state.</p> / Thesis / Master of Science (MSc)

<p> Fluorosulphonic acid has been employed to generate cyclohexadienyl cations by protonation of weak bases in order to study the affect of uv light on such systems which are variably substituted. Differing substitution has been obtained by selecting polymethylbenzenes, cyclohexadienones and polymethylphenols as cation precursors. </p> <p> The photoisomerization of the 1,2,4,5-te-tramethylcyclohexadienyl cation to the 1,2,4,5-tetramethylbicyclo-[3 .1.O.] hexenyl cation has been studied by nmr methods and is discussed mechanistically in terms of competitive electrocyclic and [ δ2a + π2a] mechanisms of ring closure. Investigations of a similar 1,2,3,5-tetrarnethylcyclohexadienyl cation failed to uncover an analogous photoisomerization. This result is briefly discussed in relation to the demonstrated instability of the supposed photo-product which has been produced by a non photo chemical route. </p> <p> Both the 1-hydroxy-6,6-dimethyl- and 1-hydroxy-4 1 4 dimethylcyclohexadienyl cations have been generated from the corresponding cyclohexadienones by low temperature protonation in FS03H. Photoisornerization of these systems produced the same 2-hydroxy-6,6-dimethylbicyclo[3.l.0.] hexenyl cation which underwent further photorearrangement to various protonated phenols, the nature of which depended upon the frequency of irradiation. </p> <p> A number of protonated polymethylphenols have been investigated with respect to their site(s) of protonation in fluorosulphonic acid and their tendency to undergo photochemical reaction. Several members of this series have been shown to rearrange photochemically to isomeric phenols through a bicyclo[3.l.O.] hexenyl cation intermediate. A necessary criterion for this reaction has been established as protonation of a methyl bearing ring carbon. </p> <p> An exceptional example of the phenol photo- isomerization was the photo-conversion of protonated 2,4,6-trimethy·lphenol·to protonated 1,3,5-trimethyl. bicyclo[3.1.o] hex-3-en-2-one. This, as well as additional evidence led to the conclusion that a significant amount of meta protonation occurred with this phenol. </p> / Thesis / Master of Science (MSc)

<p> The photoadditions of 3-phenyl-2-cyclohexenone to bicyclo [2.2.1] hepta- 2,5-diene, bicyclo [2.2.1] hept-2-ene and cyclopentene have been studied. In all cases cis fused cyclobutane products were obtained. Quenching and sensitization experiments indicated a singlet excited state to be active in photocycloaddition. Phosphorescence and fluorescence emission were observed from 3-phenyl-2-cyclohexenoneo Energy transfer to the lowest triplet of 3-phenyl-2-cyclohexenone was evident from the quenching of Michler's ketone phosphorescence. Two norbornene dimers were detected in the photolysis of 3-phenyl-2-cyclohexenone and norbornene giving evidence for a higher triplet excited state of the enone. The photoaddition of 3-methyl-2-cyclohexenone to cyclopentene was studied for comparison and both cis and trans fused adducts were obtained. In photolyses with bicyclo [2.2.1] hepta-2,5-diene or cyclopentene, 2-phenyl-2-cyclohexenone was unreactive. </p> / Thesis / Master of Science (MSc)

When subjected to ultraviolet radiation in the presence of an alkene, s-triazolo[4,3-b]pyridazine (STP) undergoes an unusual 3 + 2 photocycloaddition wherein the alkene adds to the 1 and 8 positions of STP with concommitant N4-N5 bond cleavage yielding 5,6-disubstituted-6,7-dihydro-7-methylene (and 7-cyanomethyl)-5H-pyrrolo[1,2-b]-s-triazoles. Amides and esters of indole-3-carboxylic acid have been synthesized by a novel reaction employing the ultraviolet irradiation of 3-diazo-4-oxo-3,4-dihydroquinoline (QDA) in the presence of amines or alcohols respectively. QDA, when irradiated, is postulated to undergo an internal Wolff Rearrangement to Indole-3-ketene which can add any amine or alcohol to form the corresponding amide or ester in modest to good yield.

An investigation was made of the photoreduction of indigo carmine dye and flavin mononucleotide (FMN) by an illuminated sugar beet leaf homogenate in the presence of 2,6-dichlorophenolindophenol dye (DPIP) and ascorbic acid. DPIP and ascorbate were absolutely required for the reaction. Reconstitution experiments indicated a requirement for a heat-labile factor present in the supernatant fluid following centrifugation of the leaf homogenate. This factor activated the photoreduction of indigo carmine more than 20 times. The photoreduction of FMN was activated 2 times by this factor. Studies on the stoichiometry of indigo carmine photoreduction revealed that one mole of ascorbate was photooxidized for each mole of indigo carmine photoreduced. It is postulated that the DPIP-ascorbate couple serves to prevent reoxidation of reduced indigo carmine by either reacting with the photochemical [OH] system or by depleting the O_2 content of the solution.

No description available.

No description available.

No description available.