Substituent effects in benz[a]anthracene carbocations: a stable ion, electrophilic substitution (nitration, bromination), and DFT study.

Substituent effects in benz[a]anthracene carbocations: a stable ion, electrophilic substitution (nitration, bromination), and DFT study. Research Abstract Details 

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Substituent effects in benz[a]anthracene carbocations: a stable ion, electrophilic substitution (nitration, bromination), and DFT study. Abstract Text:

Kenneth K Laali,Maria A Arrica,Takao Okazaki,Ronald G Harvey,

A series of novel carbocations were generated from isomeric monoalkylated and dialkylated benz[a]anthracenes (BAs) by low-temperature protonation in FSO(3)H/SO(2)ClF. With the monoalkyl derivatives (5-methyl, 6-methyl, 7-methyl, and 7-ethyl) as well as the D-ring methylated analogues (9-methyl, 10-methyl, and 11-methyl), the C-7 or the C-12 protonated carbocations were observed (as the sole or major carbocation) in all cases. Protonation of the 12-methyl derivative (9) gave the C-7 protonated carbocation (9H+) as the kinetic species and the ipso-protonated carbocation (9aH+) as the thermodynamic cation. With the 12-ethyl derivative (10), relief of steric strain in the bay-region greatly favors ipso-protonation (10aH+). With 3,9-dimethyl (14), C-7 protonation (14H+) is strongly favored (with <10% protonation at C-12), and with 1,12-dimethyl (15) the sole species observed is the C-7 protonated carbocation (15H+). For 7-methyl-12-ethyl, 7-ethyl-12-methyl, and 7,12-diethyl derivatives (16, 17, and 18), two ipso-protonated carbocations were initially formed (C-7/C-12), rearranging in time to give the C-12 protonated carbocations exclusively (16aH+, 17aH+, and 18aH+). Protonation outcomes are compared with the computed relative energies by DFT. Charge delocalization paths in the resulting carbocations were deduced based on the magnitude of Deltadelta13C values. For the thermodynamically more stable C-12 protonated carbocations, the charge delocalization path is analogous to those derived based on computed NPA charges for the benzylic carbocations formed by 1,2-epoxide (bay-region) and 5,6-epoxide (K-region) ring opening. Nitration (and bromination) of the 4-methyl, 7-methyl, 7-ethyl, 3,9-dimethyl, and 1,12-dimethyl derivatives resulted in isolation and characterization of several novel derivatives. Excellent agreement is found between low-temperature protonation selectivities and the regioselectivities observed in model substitution reactions.

Substituent effects in benz[a]anthracene carbocations: a stable ion, electrophilic substitution (nitration, bromination), and DFT study. Publishing Authors By Initials

KK Laali,MA Arrica,T Okazaki,RG Harvey,

For similar biochemical phenomena, metabolism, and nutrition: biochemical phenomena: structure-activity relationship research abstracts see: biochemical phenomena, metabolism, and nutrition: biochemical phenomena: structure-activity relationship research

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Substituent effects in benz[a]anthracene carbocations: a stable ion, electrophilic substitution (nitration, bromination), and DFT study. Journal Published:

PUBLICATION TYPE: Research Support, N.I.H., Extr

Journal: The Journal of organic chemistry

VOLUME: 72

Page Numbers: 6768-75

Journal Abbreviation: J. Org. Chem.

ISSN: 0022-3263

DAY: 4

MONTH: 08

YEAR: 2007

Substituent effects in benz[a]anthracene carbocations: a stable ion, electrophilic substitution (nitration, bromination), and DFT study. Information

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LANGUAGE: eng

NlmUniqueID: 2985193

Substituent effects in benz[a]anthracene carbocations: a stable ion, electrophilic substitution (nitration, bromination), and DFT study. Keywords Mesh Terms:

KEYWORDS: Structure-Activity Relationship

MESH TERMS: chemistry

Chemical & Substance for Abstract: Substituent effects in benz[a]anthracene carbocations: a stable ion, electrophilic substitution (nitration, bromination), and DFT study. Information

Substance Name: Nitrogen

Registry Number: 7727-37-9

Grant and Affiliation Information for Substituent effects in benz[a]anthracene carbocations: a stable ion, electrophilic substitution (nitration, bromination), and DFT study.

AFFILIATION: Department of Chemistry, Kent State University, Kent, Ohio 44242, USA. klaali@kent.edu

Country: United States

AGENCY: United States NCI

GRANT: 2R15-CA078235-02A1

ACRONYM: CA

MEDLINETA: J Org Chem

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