SOME CHEMICAL CONSTITUENTS OF THE BROWN ALGA, AGARUM CRIBOSUM AND THE EFFECT OF ELECTROSTATIC INTERACTIONS ON THE STEREOCHEMISTRY OF THE S(N)2' REACTION

<p>Part 1. Some Chemical Constituents of the Brown Alga, Agarum cribosum. Agarum cribosum was examined for major chemical constituents. Halogenated terpenes found in red algae were not present in this seaweed. The sterol content was determined by GC/MS analysis and six sterols were identified: fucosterol, 24-methylenecholesterol, cholesterol, 24-ketocholesterol, saringosterol, and desmosterol. The presence of desmosterol in brown algae had not been previously confirmed. A seventh sterol could not be identified from its mass spectrum. The fatty acid content was also determined by GC/MS analysis. The major fatty acids were C(,16:0), C(,16:1), C(,20:4) and C(,22:5). The sugar mannitol was isolated.</p><p>Part 2. The Effect of Electrostatic Interactions on the Stereochemistry of the S(,N)2' Reaction. The stereochemistry of the S(,N)2' reaction was studied using (trans-6-t-butyl-2-cyclohexen-1-yl) trimethylammonium tetrafluoroborate as a substrate for nucleophilic attack. The substrate was reacted with two nucleophiles, piperidine and sodium propanethiolate. To the extent that transition state electrostatic interactions can influence the direction of nucleophilic attack, it was expected that piperidine would attack anti to the leaving group while propanethiolate would attack syn. The experiments confirmed these predictions, piperidine attacking 80% anti and propanethiolate attacking 92% syn. It was concluded that transition state electrostatic interactions play a role in determining the direction of nucleophilic attack.</p>

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Dissertation

Year

1980

Author dc:creator

• NEWBURGER, JOAN DEBORAH

• Chemistry
• Organic

Repository record dc:identifier

https://scholars.unh.edu/dissertation/1255

OAI identifier oai:identifier

oai:scholars.unh.edu:dissertation-2254