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A three part study involving aspects of radical properties of various aromatic species was accomplished. Experiments to ascertain the importance of geometric and electronic effects on the intramolecular transfer of a pi-complexed radical to a terminal double bond was performed. Several 4-aryl-1-butenes were reacted in competition with 1-undecene with a variety of radical precursors at 70��C. The reactions were studied in both complexing and noncomplexing solvents. Most of the relative rates varied little from unity and no dependence on solvent was observed. A series of 21 phenacylarenes was subjected to mass spectrometry. The fragmentation process leading to arylmethyl radicals and benzoyl cations was measured by calculating the ratios of parent ion to benzoyl cation signal strength. In the case of the eleven homoaromatic compounds little overall correlation of these values to traditionally accepted arylmethyl radical stabilities was found. The degree of fragmentation for isomers of the same compound were found to be explicable in term of arylmethyl radical stabilities. Degrees of fragmentation of some compounds could be rationalized in terms of the bond order of the bond being broken, as calculated by AM1 methods. The ten heteroaromatic compounds showed little correlation of fragmentation with bond order. The degree of fragmentation was found to be dependent on many different variables of the individual molecules. No correlation with any one factor could be found. The relative rates of benzylic hydrogen atom abstraction from a series of substituted toluenes and cumenes under conditions of bromination by diethyl bromomalonate were determined at 70��C. A range of reactivity of 21.7 and 10.5 was found for the toluenes and cumenes respectively. The relative rates were found to correlate best with Hammett sigma plus constants. Hammett values of -0.89 and -0.73 were calculated for the substituted toluenes and cumenes. Reactivities for several alkyl benzenes having different steric requirements at the reaction site were also studied. The relative rates for these compounds indicate a relatively large radical to be the atom abstracting agent. The results of the Hammett correlations combined with the studies involving the steric properties of the abstracting radical suggest that diethyl malonyl radical is the hydrogen atom abstracting species. / Graduation date: 1997

Hydroxyl Radical (HO·) is a highly reactive radical species which is an important member of a class of chemical species known as Reactive Oxygen Species (ROS). Hydroxyl radical typically has an extremely short lifetime under most conditions and its highly reactive nature makes it hard to detect by conventional methods used for study of free radical kinetics. In this study we propose and develop an alternative method for relative reactivities and regioselectivities of hydroxyl radical reactions with aromatic compounds in organic solvents. Hydroxyl radical is generated by the thermolysis of a tert-butyl azohydroperoxide which dissociates to yield hydroxyl and tert-butyl radicals, nitrogen, and acetone. TMIO is used to trap the tert-butyl radical, but is less likely to trap hydroxyl radical, which is free to react with the target arene to yield a hydroxycyclohexadienyl species. These species undergo hydrogen abstraction with TMIO to yield phenols, which may be derivatized with an appropriate silylating agent (in this case BTFSA), and analyzed using gas chromatography with detection by flame ionization (GC-FID) and mass spectrometry (GC-MS). The reactivity and selectivity of reaction of hydroxyl radical with various aromatic compounds is determined at different temperatures to obtain relative reaction rates. In this work, the reactivities and selectivities for HO• reactions with simple arenes, such as toluene and naphthalene are investigated. / Department of Chemistry

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The scope and limitations of aromatic diazines undergoing nucleophilic substitution reactions occurring via a radical-chain Sʀɴ1 mechanism were investigated. The study was conducted on a series of mono- and dihalogenated aromatic diazines interacting with various ketone enolates in ammonia. Results indicate that this previously unrecognized reaction pathway in these nitrogen heterocycles is easily obtained and should prove of great synthetic utility in preparation of substituted diazines. / Ph. D.

Various nucleophiles were subjected to SRNl (nucleophilic substitution via a radical chain mechanism) conditions with representative carboaromatic and heteroaromatic substrates. Upon 5-25 min of near-UV irradiation, the carbanions of 2-benzyl-4,4-dimethyl-2-oxazoline, ethyl phenylacetate, t-butyl acetate, N,N-dimethylacetamide and dimethyl methylphosphonate underwent reactions with both 2-bromopyridine and iodobenzene in an S_R_N1 manner to give yields of good substitution products. The S_R_N1 reaction between N,N-dimethylacetamide enolate ion and 2-chloroquinoline occurred even without photostimulation. Due to incomplete ionization and the lack of homogeneity of the reaction mixture, potassio-2,4,4-trimethyl-2-oxazoline reacted with 2-bromopyridine to give low yield of the substitution product through a photostimulated S_R_N1 pathway. However, the reaction of this carbanion with iodobenzene afforded moderate yield of the substitution product, which was found to be formed via both S_R_N1 and AE mechanisms. The dimethyl phosphite anion reacted slowly with 2-bromopyridine and failed to react with 2-chloroquinoline and chloropyrazine under the influence of near-UV light. This unusual trend of reactivity was attributed to the inability of the product radical anion to restore an electron to the aromatic substrate, a necessary step in the propagation of the S_R_N1 cycle. Treatment of t-butyl α-trimethylsilylacetate with KNH₂ caused cleavage of the C-Si bond. t-butyl acetate and hexamethyldisiloxane were obtained upon quenching. Methylene triphenylphosphorane, sulfur and selenium stabilized carbanions of 1,3-dithiane, 2-phenyl-1,3-dithiane, dimethyl sulfone, t-butyl α-phenylthioacetate, bisphenylthiomethane and t-butyl α-phenylselenoacetate, failed to react with 2-bromopyridine and iodobenzene. The carbanion of dimethyl sulfone remained unreactive towards iodobenzene even upon attempted entrainment by a catalytic amount of acetone enolate. The dianion of phenylacetic acid reacted with iodobenzene to give biphenylacetic acid and benzene upon irradiation. Similar results were obtained with p-bromotoluene as substrate where substitution occurred only at the para position of the dianion. A non-chain mechanism was proposed to described both of these reactions. The dianion of phenylacetic acid also reacted with 2-bromopyridine to give a complex mixture under photostimulated conditions. 2-Benzylpyridine, bis(2-pyridyl)phenylmethane, p-(2-pyridyl)phenylacetic acid, potassio α-bis(2-pyridyl)phenylacetate, and 2-aminopyridine were found as products. Based on experiments performed with several probable intermediates of this reaction, and S_R_N1 mechanism can account for formation of all products. Preliminary results showed that the reaction of phenylacetamide dianion with iodobenzene also gave rise to the para substituted product. The dianion of 1,3-phenylacetone was found to react with iodobenzene to give 1,1,3-triphenylacetone via a mechanism other than an S_R_N1 pathway. / Ph. D.

The acld-oata17zed oyclodehydrat1on reaction of 2-benzylphenyl l-naphthyl ketone gives two products! 9-(1-naphthyl)anthracene, the expected product and in addition lO-phenyl-l,2-benzanthracene. This second product is the one expected it the ketone were subjected to the conditions of an .Elba reaction. The effect of substituents on the course of this reaction was investigated by synthesizing six 2-benzylphenyl 1- and 2-naphthyl ketones and subjecting each of them to the acid catalyzed reaction and to Elba reaction conditions. Of the six ketones, two had unsubstituted benzyl groups, two had 3'-methyl groups in the benzyl group and the remaining two had ,'-tr1fluoromethyl groups. The original finding was confirmed and the other ketones that cyoilzed by either treatment gave the expected products. When 2-(3'-methylbenzyl) 2-naphthl1 ketone was subjected to Elbs reaction conditions, 9-(2-naphthyl)anthraoene, the product of aromatic oyclodehydrat1on, was obtained. An explanation oft the unusual experimental results is suggested. The results of treat1ng the ketones w1th alumina and w1th l1qu1d hydrogen fluoride are reported. / Ph. D.