We report on the preparation and selected properties of some new biodiesels which we synthesized from oils of plants growing in Northern Wisconsin and Minnesota. The composition and the low-temperature properties such as crystallization onset T c and end of melting T m investigated with the help of differential scanning calorimetry are presented. Some of these biodiesels exhibited remarkably good low-temperature characteristics. In order to further improve these properties, we use a variety of alcohols during the transesterification process, including isopropyl, 2-butyl, and isoamyl alcohols.
The product obtained upon collision-induced dissociation of sulfonated phenylalanine in the gas phase has been investigated by using infrared multiphoton dissociation spectroscopy with a free-electron laser. This confirms that the product formed by loss of ammonia from the amino acid is the α-lactone, as had been deduced previously based on qualitative analysis and electronic structure calculations. Spectroscopically, the structure is confirmed by the presence of the carbonyl stretching peak at 1915 cm À1 and supported by excellent agreement between the predicted and observed S-O stretching bands. The agreement between predicted relative intensities is not as good, but can be attributed to the nonlinear process of IRMPD.
The dissociation of anionic dipeptides Phe*Gly and GlyPhe*, where Phe* refers to sulfonated phenyl alanine, has been investigated by using ion trap mass spectrometry. The dipeptides undergo collision-induced dissociation (CID) to give the same products, indicating that they rearrange to a common structure before dissociation. The rearrangement does not occur with the dipeptide methyl esters. The structures of the b ions were investigated to determine the effect that having a remote, anionic site has on product formation. Comparison with the CID spectra for authentic structures shows that the b ion obtained from GlyPhe* has predominantly a diketopiperazine structure. The CID spectra for the Phe*Gly b ion and the authentic oxazolone are similar, but differences in intensity suggest a two-component mixture. Isotopic labeling studies are consistent with the formation of two products, with one resulting from loss of a non-mobile proton on the Gly α-carbon. The results are attributed to the formation of an oxazole and oxazolone enol product. Electronic structure calculations predict that the enol structure of the Phe*Gly b ion is lower in energy than the keto version due to intramolecular hydrogen bonding with the sulfonate group. Graphical Abstract ᅟ.
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