The aroma of Tuber gibbosum, a native Oregon truffle, was characterized using two distinct techniques. Volatile aroma constituents were identified by chemical analysis, and sensory characteristics were determined by examining response of the general populace to the truffle aroma. Truffle samples from four maturity ranges, as determined by microscopic examination of each specimen for spore maturity, were compared for amounts and types of aroma volatiles present. Aroma volatiles of frozen specimens of T. gibbosum were sampled using a headspace concentration technique. Volatile compounds were analyzed by gas chromatography/mass spectrometry/data system (GC/MS/DS) and the total volatile profile was found to contain up to 20 compounds, depending on sample treatment and maturity. Seven compounds were found to be the major aroma constituents and were selected for further investigation. These 7 compounds were identified from their mass spectra and the identities substantiated by determining their Kovats retention indices. Amounts of volatile compounds present in each sample were determined by capillary gas chromatographic (GO analysis using an internal standard of n-tridecane for quantitative determinations. The major aroma constituent for all the samples was oct-l-en-3-ol, representing about 50% of the total aroma profile. The other 7 major components were 8- and 6-carbon alchols, ketones and aldehydes. Quantitative data for all samples and components were analyzed statistically. A descriptive model for truffle maturity was derived based on the amounts of 5 of the 7 compounds, and the sum of the amounts of the 7 major constituents. A comparison of volatiles from ascorbic acid treated and untreated control truffle samples indicated an apparent reduction in the amounts of several compounds. The examination of public response to the aroma of T. gibbosum was conducted as part of a display on truffles at the Oregon Mycological Society Mushroom Show. The aroma of this truffle, and three other native Oregon truffles were rated for desirability and preference. Results indicate T. gibbosum was not the favored sample, but was liked by about 2/3 of the population. Comparison of responses by males and females showed no differences for individuals liking the truffle aromas. However, females rated the truffle aromas of 3 of the 4 species as more unpleasant than did males. / Graduation date: 1986

非平面多環芳香化合物因其獨特的結構，性能和在材料科學中的應用引起了有機化學家的濃厚興趣。此論文討論了由於引入七元環或空間位阻效應而導致扭曲的多環芳香化合物，重點強調其合成，化學性質和潛在的應用。第1章介紹了常見的非平面多環芳香烴及其有代表性的兩類分子，即芳香碗和螺烯。它們分別因包含五元環或空間原子擁擠效應而偏離平面結構。本章論述了芳香碗及螺烯的合成，分子和超分子的結構及其應用。第2章詳細闡述了關於一類空間過度擁擠的庚富瓦烯衍生物的合成，表徵及順反異構化的研究。庚富瓦烯衍生物在光異構化和熱異構化過程中具有異常高的選擇性和大的分子結構變化。這些結果表明空間過度擁擠的庚富瓦烯衍生物是一類可被潛在應用為分子開關或者分子機器的化合物。第3章闡述了一種新的具有負曲率且與六苯並蔻等π電子的多環芳烴分子。向六苯並蔻（HBC）分子中引入七元環，我們得到了一種新穎的馬鞍狀大π分子。相比先前報導的[7]圈烯，該分子的具有較小的平均高斯曲率但卻有大的分子剛性。第4章闡述了另一種同六苯並蔻等π電子體系的非平面六苯並苝衍生物。空間原子的過度擁擠導致六苯並苝衍生物存在手性扭曲和反式折疊兩種構象。在升溫條件下該兩種構象之間可相互轉變並達致平衡。該結果連同進一步的熱力學和動力學研究加深了我們對六苯並苝的構象認知。手性扭曲的分子之間同時存在著面對面和邊對面的π-π相互作用，其可被用作場效應晶體管中的半導體材料。研究表明，分子彎曲的π體系在決定前線分子軌道能級和π-π相互作用中起到至關重要作用，因此在設計新的有機半導體材料時必須加以考慮。 / Non-planar polycyclic aromatic molecules are of great interests to organic chemists because of their unique structures, properties and useful applications in materials science. Detailed in this thesis are studies toward non-planar polycyclic aromatic molecules, which are forced out of planarity either by embedded seven-membered rings or by the steric strain from atom crowding, emphasizing on their synthesis, chemical properties and potential applications. / Chapter 1 introduces nonplanar polycyclic aromatic hydrocarbons (PAHs) with focus on two representative groups of non-planar PAHs, namely aromatic bowls and helicenes, which are forced out of plane by five-membered rings and atom crowding respectively. Here aromatic bowls and helicenes are reviewed in terms of synthesis, molecular and supramolecular structures as well as applications. / Chapter 2 details a comprehensive study on synthesis, characterization and syn/anti isomerism of overcrowded heptafulvalene derivatives. It was found that the heptafulvalene derivatives have achieved unusually high selectivity in both photo-isomerization and thermal isomerization. The predominance of syn isomer in the photo-isomerization has been clearly explained with DFT calculations in terms of the arrangement of the excited state and ground state potential energy surfaces. Another interesting finding is that the energy barrier of thermal syn-to-anti isomerization is directly related to the rigidity and crowdedness of the seven-membered rings. These findings suggest that overcrowded heptafulvalene derivatives are promising candidates for molecular switches and machines. In addition, a correction of the previously claimed synthesis of hexabenzooctalene is also introduced in this chapter. / Chapter 3 presents a new negatively curved polycyclic aromatic molecule that is π-isoelectronic to the well-known hexa-peri-hexabenzocoronene (HBC). Embedding a seven-membered ring into HBC leads to a novel saddle-shaped π-molecule, whose π-backbone is slightly less curved than the previously reported [7]circulene in terms of the average Gauss curvature, but surprisingly much more rigid than [7]circulene. The resulting heptagon-embedded PAH molecules not only are of theoretical interests in relation to aromaticity and curved π-orbitals but also can serve as segments, models and, in principle, synthetic precursors for graphitic carbon networks containing negative curvature, such as graphene containing heptagonal defects and toroidal carbon nanotubes / In Chapter 4, another type of curved π-molecule that has the same number of Clar's aromatic sextets as HBC is presented. Overcrowded fjord regions in novel derivatives of hexabenzoperylene (HBP) lead to both chiral twisted and anti-folded conformers, which are found to isomerize to each other at elevated temperature to reach an equilibrium. This finding along with the study on the thermodynamics and kinetics of the thermal isomerization has improved the early understandings on the conformation of HBP. It is found that the chiral twisted molecule exhibit both face-to-face and edge-to-face π-π interactions leading to a semiconducting film, which functions as the active layer in field effect transistors. The study reveals that the curvature of π-face plays a role in determining the frontier molecular orbital energy levels and π-π interactions and thus needs to be considered when one designs new organic semiconductors. / Chapter 5 is conclusion and outlook. / Detailed summary in vernacular field only. / Luo, Jiye. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / Abstract --- p.i / 中文摘要 --- p.iii / Acknowledgement --- p.iv / Table of Contents --- p.vi / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Curved PAHs with non-hexagonal rings --- p.3 / Chapter 1.1.1 --- Curved PAHs with four-membered rings --- p.3 / Chapter 1.1.2 --- Curved PAHs with five-membered rings --- p.5 / Chapter 1.1.3 --- Curved PAHs with seven-membered rings --- p.17 / Chapter 1.2 --- Curved PAHs with steric strain from atom crowding --- p.20 / Chapter 1.2.1 --- General Properties --- p.20 / Chapter 1.2.2 --- Synthetic methodologies --- p.21 / Chapter 1.2.3 --- Large PAHs containing multiple helicene structures --- p.28 / Chapter Chapter 2 --- Switching and Cyclization of Overcrowded Heptafulvalene Derivatives --- p.43 / Chapter 2.1 --- Introduction --- p.43 / Chapter 2.2 --- Results and Discussion --- p.46 / Chapter 2.3 --- Conclusion --- p.64 / Chapter 2.4 --- Experimental --- p.65 / Chapter Chapter 3 --- Heptagon-Embedded Hexabenzocoronene of Negative Curvature --- p.94 / Chapter 3.1 --- Introduction --- p.94 / Chapter 3.2 --- Results and Discussion --- p.95 / Chapter 3.3 --- Conclusion --- p.102 / Chapter 3.4 --- Experimental --- p.103 / Chapter Chapter 4 --- Hexabenzoperylene: Synthesis, twisted/anti isomerization and semiconductor applications --- p.118 / Chapter 4.1 --- Introduction --- p.118 / Chapter 4.2 --- Results and Discussion --- p.120 / Chapter 4.3 --- Conclusion --- p.134 / Chapter 4.4 --- Experimental --- p.134 / Chapter Chapter 5 --- Conclusion and Outlook --- p.153 / Appendix --- p.155

No description available.

No description available.