Synthesis of new chiral gas chromatographic stationary phases with novel selectivities /
Both linear and cyclic carbohydrates were explored for their
| Main Author: | |
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| Format: | Thesis Book |
| Language: | English |
| Published: |
[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742536431&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Both linear and cyclic carbohydrates were explored for their use as potential chiral gas chromatographic stationary phases. A mixture of linear oligosaccharides was reacted with pentyl bromide and subsequently with trifluoroacetic anhydride. The derivatives of the linear oligosaccharides behaved as liquids and could be used as stationary phases without recourse to a carrier matrix. They possess chiral selectivities for a limited number of chiral compound classes indicating that chiral resolution could be achieved without inclusion complex formation. The derivatives of cyclic oligosaccharides, i.e. cyclodextrins, on the other hand, offer chiral selectivities that allow much broader application. Two classes of cyclodextrin derivatives were synthesized and characterized: liquid (Class I) and solid (Class 11) stationary phases. To prepare Class I stationary phases, cyclodextrin was liquified by partial substitution with nonpolar pentyl groups and subsequently modified with different chloroacetyl moieties on the secondary side to produce liquid monochloroacetyl (M), dichloroacetyl (D), and trichloroacetyl (T) pentyl cyclodextrins. The capacity factors (k'), selectivity values (a), and separation efficiencies of capillary columns coated with these three cyclodextrin derivatives were compared. The results clearly demonstrated that the chiral selectivities of these cyclodextrin derivatives could be simply altered by varying the number of chlorine atoms in the chloroacetyl moieties. In Class 11 stationary phases, the size and the type of the primary side substituents of cyclodextrin derivatives were varied. The capacity factors, selectivity values, and separation efficiencies of capillary columns coated with these five newly synthesized cyclodextrin derivatives were determined and compared. Although it was believed that only the secondary side of cyclodextrin is responsible for enantiodifferentiation, these Class 11 derivatized cyclodextrins, which possess identical secondary substituents, showed significantly different enantioselectivities. One of these Class H stationary phases, heptakis (2,3-di-0-methyl-6-0-vinyldimethylsilyl) []- cyclodextrin could be immobilized in the capillary column directly, without prior bonding to a polysiloxane backbone. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xiii, 114 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |