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Article: Halide effects in the hydrolysis reactions of (±)-7β,8α-dihydroxy- 9α, 10α-epoxy-7,8,9,10-tetrahydrobenzo-[α]pyrene

TitleHalide effects in the hydrolysis reactions of (±)-7β,8α-dihydroxy- 9α, 10α-epoxy-7,8,9,10-tetrahydrobenzo-[α]pyrene
Authors
KeywordsChemicals And Cas Registry Numbers
Issue Date1998
PublisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/crt
Citation
Chemical Research in Toxicology, 1998, v. 11 n. 6, p. 630-638 How to Cite?
AbstractRates of reaction of (±)-7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10- tetrahydrobenzo[α]pyrene (DE-2) have been determined in 1:9 dioxane-water solutions containing 1.0 M KC1, 0.5 M KBr, and 0.1 M NaI over the pH range 4- 13. These pH-rate profiles are more complicated than those for reaction of DE-2 in 0.2 M NaC1O4 solutions and are interpreted in part by mechanisms in which halide ion attacks the diol epoxide as a nucleophile at intermediate pH, resulting in the formation of a trans-halohydrin. Reaction of DE-2 in these halide solutions at pH < ca. 5 occurs by rate-limiting carbocation formation, followed by capture of the intermediate carbocation by halide ion. The relative magnitudes of the rate constants for reaction of the intermediate carbocation with halide ions are estimated from product studies. The halohydrins are unstable intermediates and react quickly in subsequent reactions to yield tetrols in a ratio different than that formed from reaction of the carbocation with solvent. Nucleophilic attacks of 1.0 M CI- , 0.5 M Br-, and 0.1 M I- on DE-2 are the principal reactions in the pH range ca. 6-9, leading to intermediate trans-halohydrins that hydrolyze to tetrols. At pH ca. 9-11, halohydrin formed from attack of halide ion on DE-2 reverts back to epoxide, leading to a negative break in the pH-rate profile. The main product-forming reaction of DE-2 at pH 11.3 is the spontaneous reaction. At pH > 12, the rate of reaction of DE-2 increases due to a second- order reaction of HO- with DE-2.
Persistent Identifierhttp://hdl.handle.net/10722/91000
ISSN
2015 Impact Factor: 3.025
2015 SCImago Journal Rankings: 1.323
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorLin, Ben_HK
dc.contributor.authorDoan, Len_HK
dc.contributor.authorYagi, Hen_HK
dc.contributor.authorJerina, DMen_HK
dc.contributor.authorWhalen, DLen_HK
dc.date.accessioned2010-09-17T10:11:32Z-
dc.date.available2010-09-17T10:11:32Z-
dc.date.issued1998en_HK
dc.identifier.citationChemical Research in Toxicology, 1998, v. 11 n. 6, p. 630-638en_HK
dc.identifier.issn0893-228Xen_HK
dc.identifier.urihttp://hdl.handle.net/10722/91000-
dc.description.abstractRates of reaction of (±)-7β,8α-dihydroxy-9α,10α-epoxy-7,8,9,10- tetrahydrobenzo[α]pyrene (DE-2) have been determined in 1:9 dioxane-water solutions containing 1.0 M KC1, 0.5 M KBr, and 0.1 M NaI over the pH range 4- 13. These pH-rate profiles are more complicated than those for reaction of DE-2 in 0.2 M NaC1O4 solutions and are interpreted in part by mechanisms in which halide ion attacks the diol epoxide as a nucleophile at intermediate pH, resulting in the formation of a trans-halohydrin. Reaction of DE-2 in these halide solutions at pH < ca. 5 occurs by rate-limiting carbocation formation, followed by capture of the intermediate carbocation by halide ion. The relative magnitudes of the rate constants for reaction of the intermediate carbocation with halide ions are estimated from product studies. The halohydrins are unstable intermediates and react quickly in subsequent reactions to yield tetrols in a ratio different than that formed from reaction of the carbocation with solvent. Nucleophilic attacks of 1.0 M CI- , 0.5 M Br-, and 0.1 M I- on DE-2 are the principal reactions in the pH range ca. 6-9, leading to intermediate trans-halohydrins that hydrolyze to tetrols. At pH ca. 9-11, halohydrin formed from attack of halide ion on DE-2 reverts back to epoxide, leading to a negative break in the pH-rate profile. The main product-forming reaction of DE-2 at pH 11.3 is the spontaneous reaction. At pH > 12, the rate of reaction of DE-2 increases due to a second- order reaction of HO- with DE-2.en_HK
dc.languageengen_HK
dc.publisherAmerican Chemical Society. The Journal's web site is located at http://pubs.acs.org/crten_HK
dc.relation.ispartofChemical Research in Toxicologyen_HK
dc.subjectChemicals And Cas Registry Numbersen_HK
dc.titleHalide effects in the hydrolysis reactions of (±)-7β,8α-dihydroxy- 9α, 10α-epoxy-7,8,9,10-tetrahydrobenzo-[α]pyreneen_HK
dc.typeArticleen_HK
dc.identifier.emailLin, B:blin@hku.hken_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1021/tx9701743en_HK
dc.identifier.pmid9625731-
dc.identifier.scopuseid_2-s2.0-0031802933en_HK
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0031802933&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume11en_HK
dc.identifier.issue6en_HK
dc.identifier.spage630en_HK
dc.identifier.epage638en_HK
dc.identifier.isiWOS:000074301100006-

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