Browsing by Subject "Hydrocarbons -- Analysis"
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Item Baylis-Hillman-type C-C bond formation and olefin diamination reaction(Texas Tech University, 2003-12) Pei, WeiThis thesis described new methodologies for Baylis-Hillman-type C-C bond formation and olefin diamination reaction. The Baylis-Hillman-type reaction was developed using a,â-unsaturated cycloketone and S-ethyl thioacrylate as the Michael-type acceptors with diethylaluminum iodide alone as the promoter. Direct diamination of enones was developed using N,N-dichloro-2-nitrobenzenesulfonamide (2-NSNCI2) as the electrophilic nifrogen source. The Baylis-Hillman-type reaction between a,â-unsaturated cycloketone or a,â-unsaturated S-ethyl thioacrylate and aldehydes has been achieved using diethylaluminum iodide as the promoter without the direct use of any Lewis bases. The reaction showed a good scope of substrates, and aldehydes which failed to give desired Baylis-Hillman products under our previous TiCl4-based conditions can be successfully used as the electrophiles to give good yields. The reactions proceeded to completion at 0 °C in CH2CI2 within 7-24 hours without the protection by inert gases. These processes involve the conjugate addition of Et2AlI to a,â-unsaturated substrates followed by carbonyl coupling. Releasing CH3CH3 is believed to act as a strong driving force and make the reactions irreversible. New electrophilic imidazolination reaction of enones was developed using 2-NsNCl2 as the electrophilic nitrogen source without any catalyst. It showed faster reaction rates and higher chemical yields than the reaction using analogous nitrogen source, 4-TsNCl2, under similar conditions. Molecular sieves and temperature played important roles to control the formation of desired products, l-o-nitrobenzenesulfonyl-3-dichloromethyl- 4,5-imidazolines and l-o-nitrobenzenesulfonyl-3-trichloromethyl-4,5-imidazolines. A [2+3] cycloaddition reaction was proposed as one step for the reaction to explain the regio- and stereoselectivity. a,â-Differentiated 1,2-vicinal diamines have been efficiently synthesized with good to excellent yields (87 - 96%) by using the new electrophilic imidazolination reaction of alkenes. The hydrolysis of imidazolines was performed by treatment with 6 A'' HCl in THF at 70 °C or in CHCI3 at 50 °C without epimerization.Item Characterization of the brood cuticular hydrocarbons of the fire ant Solenopsis Invicta and their possible role in brood recognition by workers(Texas Tech University, 2004-12) Al Diri, IssamChromatography and mass spectrometry analysis were used to identify and quantify 14 cuticular hydrocarbons in the developmental stages of S. invicta. The following quantitative and qualitative differences in hydrocarbons were observed among brood components. Cuticular hydrocarbons consisted of saturated n-alkanes and methylalkanes, ranging from C23 to C29. The total amount of cuticular hydrocarbons was greatest in prepupae and least in pupal stages. While the total amount of cuticular hydrocarbons was several magnitudes greater in components of sexual brood, as expected since sexual forms are larger than worker forms, the ratio of n-alkanes to methylalkanes in worker brood was generally higher than its counterparts in sexual brood. Discriminant function analysis of the brood subcastes using the five most abundant hydrocarbons within and among colonies showed that the brood subcastes clustered together based on their respective developmental stage, with n-heptacosane being the major component responsible for the observed clustering. Finally, several bioassays were conducted to determine whether cuticular hydrocarbons play a role in brood recognition. Worker retrieval response toward pupae immersed in hexane for 5 min was significantly lower than that towards a control. Immersing pupae in boiling water for 3 sec. also induced a similar response to that caused by hexane. Several concentrations of cuticular extracts in hexane of sexual prepupae applied to a paraffin dummy failed to induce any retrieval response by workers. In addition, manipulation of the composition of brood cuticular hydrocarbons did not seem to affect worker response toward the brood. Taken together, the results suggest that a chemical signal other than cuticular lipids is involved in brood recognition.