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Reactions of chloro-s-triazine and c...

Lippa, Katrice A.

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Reactions of chloro-s-triazine and chloroacetanilide agrochemicals with reduced sulfur nucleophiles.

紀錄類型:	書目-語言資料,印刷品 : Monograph/item
正題名/作者:	Reactions of chloro-s-triazine and chloroacetanilide agrochemicals with reduced sulfur nucleophiles./
作者:	Lippa, Katrice A.
面頁冊數:	474 p.
附註:	Adviser: A. Lynn Roberts.
Contained By:	Dissertation Abstracts International63-03B.
標題:	Chemistry, Agricultural. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3046496
ISBN:	0493606866

Reactions of chloro-s-triazine and chloroacetanilide agrochemicals with reduced sulfur nucleophiles.
Lippa, Katrice A.

Reactions of chloro-s-triazine and chloroacetanilide agrochemicals with reduced sulfur nucleophiles. - 474 p.

Adviser: A. Lynn Roberts.

Thesis (Ph.D.)--The Johns Hopkins University, 2002.

Chloro-s-triazine and chloroacetanilide herbicides together represent approximately 40% of conventional agricultural pesticide usage in the U.S. Their high use and their recalcitrance towards most degradation processes renders them ubiquitous in environmental samples. These potentially (exo)toxic agrochemicals represent a source of nonpoint pollution to coastal marine environments in which bisulfide (HS<super>−</super>) and polysulfide (Sn<super> 2−</super>) sulfur species are present; these species may represent an important “reactive sink” for the abiotic transformation of such herbicides.

ISBN: 0493606866Subjects--Topical Terms:

1021829
Chemistry, Agricultural.

Reactions of chloro-s-triazine and chloroacetanilide agrochemicals with reduced sulfur nucleophiles.
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245 1 0 $a Reactions of chloro-s-triazine and chloroacetanilide agrochemicals with reduced sulfur nucleophiles.
300 $a 474 p.
500 $a Adviser: A. Lynn Roberts.
500 $a Source: Dissertation Abstracts International, Volume: 63-03, Section: B, page: 1508.
502 $a Thesis (Ph.D.)--The Johns Hopkins University, 2002.
520 $a Chloro-s-triazine and chloroacetanilide herbicides together represent approximately 40% of conventional agricultural pesticide usage in the U.S. Their high use and their recalcitrance towards most degradation processes renders them ubiquitous in environmental samples. These potentially (exo)toxic agrochemicals represent a source of nonpoint pollution to coastal marine environments in which bisulfide (HS<super>−</super>) and polysulfide (Sn<super> 2−</super>) sulfur species are present; these species may represent an important “reactive sink” for the abiotic transformation of such herbicides.
520 $a This dissertation work investigated the role that reduced sulfur species (relative to other chemical and biological reagents) exert on the fate of agrochemicals by examining the kinetics and mechanisms of reactions in well-defined aqueous solutions. The important structural features that control chloroazine and chloroacetanilide reactivity were delineated through laboratory kinetic investigations of structurally related analogs of these agrochemicals, complemented by computational molecular modeling techniques.
520 $a Polysulfides (Sn<super>2−</super>) were found to be more reactive than bisulfide (HS<super>−</super>) in reactions with chloroazines and chloroacetanilides (via SNAr and SN2 mechanisms, respectively). Rate constants for chloroazine reactions vary by more than seven orders of magnitude and are dependent on structural substituents (<italic>aza</italic> nitrogens, electron withdrawing or donating groups), in addition to the identity of the sulfur nucleophile. Chloroacetanilides are more than an order of magnitude more reactive than chloroazines towards either HS<super>−</super> or Sn<super>2−</super>. Both classes of agrochemicals form mercapto-substituted products (and also polymercapto-substituted products in the case of chloroacetanilides). In a natural sulfidic lake water studied, polysulfides are more important than HS<super>−</super> for the majority of reactions with chloroazines; both nucleophiles are important for chloroacetanilides. Half-lives range from minutes to weeks.
520 $a The α-anilide substituent of chloroacetanilides appears responsible for its activation towards reactions with strong sulfur nucleophiles. This is shown by a greater dependence on nucleophile polarizability (as seen in the Edwards correlation) relative to simple alkyl halides. In addition, there is a significantly lower enthalpic barrier (ΔH<super>&Dagger;</super>) observed for α-acetanilide-containing substrates. Furthermore, computational models of the transition states for the reactions of HS<super>−</super> with substrates containing α-acetanilide substituents demonstrate the presence of low-lying molecular orbitals that effectively distribute the electron density from the SN2 reaction center into the remainder of the molecule.
590 $a School code: 0098.
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650 4 $a Engineering, Environmental. $3 783782
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