Physical Sciences and Mathematics Commons^™

Photochemical Generation Of Carbenes And Ketenes From Phenanthrene-Based Precursors Part I: Dimethylalkylidene Part Ii: Diphenylketene, Tarini S. Hardikar, Tarini Hardikar

Honors Theses

Previous studies have shown that the photolysis of phenanthrene-based cyclopropyl precursors can generate carbenes. In this work, a novel phenanthrene precursor was synthesized and photolyzed to generate the dimethylalkylidene carbene, which was subsequently trapped by cyclohexene. The car- bene was not prone to an internal rearrangement as some other carbenes are, and instead favored the intermolecular addition reaction. The precursor also underwent a rearrangement via pericyclic processes. A theoretical analysis of the potential energy surface of the system is presented using coupled cluster and density functional methods. Preliminary analysis for the precursor via time-resolved laser flash photolysis (LFP) was performed. …

Experimental And Computational Investigation Of Selected Β-Hydroxy Carbenes, Joseph D. Deangelo

Honors Theses

The photolytic precursor to the sterically hindered β-bis(tert)-butanol carbene, 3-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)-2,2,4,4-tetramethylpentan-3-ol was prepared in three steps from phenanthrene. Photolysis of the precursor generates the desired β-hydroxy carbene, an intermediate, which subsequently rearranges into two different observed products from an intramolecular C-H insertion and alkyl shift. Four intramolecular mechanisms were ultimately considered to account for the possible rearrangement pathways. Computational studies using density functional theory are also presented.

In addition, the photolytic precursors to two cyclic β-hydroxy carbenes, 1-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)cyclopropan-1-ol and 1-(1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl)cyclobutan-1-ol, were also prepared through different synthetic routes from phenanthrene. …

Intramolecular Chemistry Of Ss-Acetoxyethylidene And Photochemical Generation Of Vinylidenes, Jennifer M. Nguyen

Honors Theses

The parent carbene ß-acetoxyethylidene has been previously generated by the photolysis of its precursor, acetic acid 1a,9b-dihydro-1H-cyclopropa[l]phenanthren-1-yl methyl ester. Mechanistic studies on ß-acetoxyethylidene have indicated the possibilities of three rearrangement pathways to the formation of vinyl acetate: a proton shift, an acyl shift, and a cyclic rearrangement (see Figure 8). A deuterium labeling study involving the replacement of the hydrogens on the methylene carbon has indicated that the simple 1,2-H shift was the primary manner of rearrangement, with an 82% yield of product. However, a primary kinetic isotope effect may have occurred due to the greater strength of a C-D …