Using a closed-system algal test to study the structure-activity relationships of halogen-substituted aliphatic esters

• Main Author: 洪萱芳
• Other Authors: Chen, Chung-Yuan
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/08046244899994245632

碩士 === 國立交通大學 === 環境工程系所 === 100 === This study presents the toxicity data of various halogen-substituted aliphatic esters to Pseudokirchneriella subcapitata. using a closed algal toxicity testing technique with no headspace. Three different response endpoints, i.e., final yield, growth rate, and the dissolved oxygen production were used to evaluate the toxicity of halogen-substituted aliphatic esters. We also use abiotic thiol reactivity (RC50) to establish the QSAR models. Halogen- substituted aliphatic esters toxicity mechanism are classified as electrophiles which are for a subgroup of the SN2 mechanistic domain. Between α-halo-carbonyl-containing compounds the order of reactivity is I>Br>Cl>F; but the toxicity of ethyl fluoroacetate (NO.1) is relatively high. The toxicity mechanism of ethyl fluoroacetate (NO.1) could be the inhibition of the Krebs cycle. Ethyl-2,3-di-bromopropionate(NO.14) with two halogens connect with two carbons which make the effect of the carbonyl group separated into a less pronounced overall electrophilicity as compared to ethyl bromoacetate(NO.3). Multi-halogenation at a single-carbon center (halogenated carbon) may sterically hinder their electrophilic reactivity which makes them less toxic than the chemical with only single bromine. The quantitative structure-activity relationship of halogen-substituted aliphatic esters toxicity with reactivity respect two outliers- Methyl 3-bromopropionate (NO.6) and ethyl tribromoacetate (NO.13). Methyl 3-bromopropionate (NO.6) has relatively high reactivity but low toxicity which seems more like nonpolar narcosis. The steric hindrance of ethyl tribromoacetate (NO.13) could not be presented by the ideal test which using pure glutathione to represent the target in vivo (RC50).