Stereochemistry of hexakis(dimethylamino)benzene and its dication

Jeffrey M. Chance, Bart Kahr, Andrzej B. Buda, John P. Toscano, Kurt Mislow

Research output: Contribution to journalArticle

Abstract

The crystal structures of hexakis(dimethylamino)benzene (4) and its dication bis(triiodide) (8) have been determined. Crystals of 4 are monoclinic, space group C2/c, a = 18.440 (6) Å, b = 9.461 (3) Å, c = 12.017 (4) Å, β = 104.74 (3)°, Z = 4. Like hexaisopropylbenzene, hexakis(dimethylsilyl)benzene, and hexakis(dichloromethyl)benzene, molecules of 4 adopt approximate C 6h symmetry in the crystal, but, unlike these otherwise closely related compounds, 4 does not manifest an orientational disorder. Reaction of 4 with iodine yields 8, crystals of which belong to the monoclinic system, space group P2/c, a = 16.243 (5) Å, b = 11.051 (4) Å, c = 20.358 (7) Å, β = 112.02 (3)°, Z = 4. Molecules of 8 have crystallographic C 2 symmetry and approximate D 2 symmetry, with the benzene ring in a twist conformation. Variable-temperature NMR studies on 1,3,5-tris(diethylamino)-2,4,6-tris(dimethylamino)benzene (9) and hexakis(diethylamino)benzene, two molecules that are structurally related to 4, show that pyramidal inversion of the nitrogen atoms requires 8.2 and 10.0 kcal mol -1, respectively. As shown by the interconversion of the diastereomers of 1,3,5-tris(ethylmethylamino)-2,4,6-tris(dimethylamino)benzene, which requires 16.0 kcal mol -1, barriers to rotation about the C ar-N bonds in this class of compounds are substantially higher than barriers to pyramidal inversion. According to AM1 calculations, the homomerization (topomerization) of 4 is not concerted but involves stepwise inversion of the dimethylamino groups. The calculated activation energy, 10.5 kcal mol -1, is in reasonable agreement with the experimentally observed barrier of 8.2 kcal mol -1 for 9. Variable-temperature NMR studies on 8 reveal a site exchange of the methyl groups which is rationalized by a pseudorotational motion of the twisted benzene ring.

Original languageEnglish (US)
Pages (from-to)3226-3232
Number of pages7
JournalJournal of Organic Chemistry
Volume53
Issue number14
StatePublished - 1988

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Stereochemistry
Benzene
Molecules
Nuclear magnetic resonance
Crystals
Crystal symmetry
Iodine
Conformations
Nitrogen
Activation energy
Crystal structure
Atoms
Temperature

ASJC Scopus subject areas

  • Organic Chemistry

Cite this

Chance, J. M., Kahr, B., Buda, A. B., Toscano, J. P., & Mislow, K. (1988). Stereochemistry of hexakis(dimethylamino)benzene and its dication. Journal of Organic Chemistry, 53(14), 3226-3232.

Stereochemistry of hexakis(dimethylamino)benzene and its dication. / Chance, Jeffrey M.; Kahr, Bart; Buda, Andrzej B.; Toscano, John P.; Mislow, Kurt.

In: Journal of Organic Chemistry, Vol. 53, No. 14, 1988, p. 3226-3232.

Research output: Contribution to journalArticle

Chance, JM, Kahr, B, Buda, AB, Toscano, JP & Mislow, K 1988, 'Stereochemistry of hexakis(dimethylamino)benzene and its dication', Journal of Organic Chemistry, vol. 53, no. 14, pp. 3226-3232.
Chance JM, Kahr B, Buda AB, Toscano JP, Mislow K. Stereochemistry of hexakis(dimethylamino)benzene and its dication. Journal of Organic Chemistry. 1988;53(14):3226-3232.
Chance, Jeffrey M. ; Kahr, Bart ; Buda, Andrzej B. ; Toscano, John P. ; Mislow, Kurt. / Stereochemistry of hexakis(dimethylamino)benzene and its dication. In: Journal of Organic Chemistry. 1988 ; Vol. 53, No. 14. pp. 3226-3232.
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title = "Stereochemistry of hexakis(dimethylamino)benzene and its dication",
abstract = "The crystal structures of hexakis(dimethylamino)benzene (4) and its dication bis(triiodide) (8) have been determined. Crystals of 4 are monoclinic, space group C2/c, a = 18.440 (6) {\AA}, b = 9.461 (3) {\AA}, c = 12.017 (4) {\AA}, β = 104.74 (3)°, Z = 4. Like hexaisopropylbenzene, hexakis(dimethylsilyl)benzene, and hexakis(dichloromethyl)benzene, molecules of 4 adopt approximate C 6h symmetry in the crystal, but, unlike these otherwise closely related compounds, 4 does not manifest an orientational disorder. Reaction of 4 with iodine yields 8, crystals of which belong to the monoclinic system, space group P2/c, a = 16.243 (5) {\AA}, b = 11.051 (4) {\AA}, c = 20.358 (7) {\AA}, β = 112.02 (3)°, Z = 4. Molecules of 8 have crystallographic C 2 symmetry and approximate D 2 symmetry, with the benzene ring in a twist conformation. Variable-temperature NMR studies on 1,3,5-tris(diethylamino)-2,4,6-tris(dimethylamino)benzene (9) and hexakis(diethylamino)benzene, two molecules that are structurally related to 4, show that pyramidal inversion of the nitrogen atoms requires 8.2 and 10.0 kcal mol -1, respectively. As shown by the interconversion of the diastereomers of 1,3,5-tris(ethylmethylamino)-2,4,6-tris(dimethylamino)benzene, which requires 16.0 kcal mol -1, barriers to rotation about the C ar-N bonds in this class of compounds are substantially higher than barriers to pyramidal inversion. According to AM1 calculations, the homomerization (topomerization) of 4 is not concerted but involves stepwise inversion of the dimethylamino groups. The calculated activation energy, 10.5 kcal mol -1, is in reasonable agreement with the experimentally observed barrier of 8.2 kcal mol -1 for 9. Variable-temperature NMR studies on 8 reveal a site exchange of the methyl groups which is rationalized by a pseudorotational motion of the twisted benzene ring.",
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AU - Chance, Jeffrey M.

AU - Kahr, Bart

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AU - Mislow, Kurt

PY - 1988

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N2 - The crystal structures of hexakis(dimethylamino)benzene (4) and its dication bis(triiodide) (8) have been determined. Crystals of 4 are monoclinic, space group C2/c, a = 18.440 (6) Å, b = 9.461 (3) Å, c = 12.017 (4) Å, β = 104.74 (3)°, Z = 4. Like hexaisopropylbenzene, hexakis(dimethylsilyl)benzene, and hexakis(dichloromethyl)benzene, molecules of 4 adopt approximate C 6h symmetry in the crystal, but, unlike these otherwise closely related compounds, 4 does not manifest an orientational disorder. Reaction of 4 with iodine yields 8, crystals of which belong to the monoclinic system, space group P2/c, a = 16.243 (5) Å, b = 11.051 (4) Å, c = 20.358 (7) Å, β = 112.02 (3)°, Z = 4. Molecules of 8 have crystallographic C 2 symmetry and approximate D 2 symmetry, with the benzene ring in a twist conformation. Variable-temperature NMR studies on 1,3,5-tris(diethylamino)-2,4,6-tris(dimethylamino)benzene (9) and hexakis(diethylamino)benzene, two molecules that are structurally related to 4, show that pyramidal inversion of the nitrogen atoms requires 8.2 and 10.0 kcal mol -1, respectively. As shown by the interconversion of the diastereomers of 1,3,5-tris(ethylmethylamino)-2,4,6-tris(dimethylamino)benzene, which requires 16.0 kcal mol -1, barriers to rotation about the C ar-N bonds in this class of compounds are substantially higher than barriers to pyramidal inversion. According to AM1 calculations, the homomerization (topomerization) of 4 is not concerted but involves stepwise inversion of the dimethylamino groups. The calculated activation energy, 10.5 kcal mol -1, is in reasonable agreement with the experimentally observed barrier of 8.2 kcal mol -1 for 9. Variable-temperature NMR studies on 8 reveal a site exchange of the methyl groups which is rationalized by a pseudorotational motion of the twisted benzene ring.

AB - The crystal structures of hexakis(dimethylamino)benzene (4) and its dication bis(triiodide) (8) have been determined. Crystals of 4 are monoclinic, space group C2/c, a = 18.440 (6) Å, b = 9.461 (3) Å, c = 12.017 (4) Å, β = 104.74 (3)°, Z = 4. Like hexaisopropylbenzene, hexakis(dimethylsilyl)benzene, and hexakis(dichloromethyl)benzene, molecules of 4 adopt approximate C 6h symmetry in the crystal, but, unlike these otherwise closely related compounds, 4 does not manifest an orientational disorder. Reaction of 4 with iodine yields 8, crystals of which belong to the monoclinic system, space group P2/c, a = 16.243 (5) Å, b = 11.051 (4) Å, c = 20.358 (7) Å, β = 112.02 (3)°, Z = 4. Molecules of 8 have crystallographic C 2 symmetry and approximate D 2 symmetry, with the benzene ring in a twist conformation. Variable-temperature NMR studies on 1,3,5-tris(diethylamino)-2,4,6-tris(dimethylamino)benzene (9) and hexakis(diethylamino)benzene, two molecules that are structurally related to 4, show that pyramidal inversion of the nitrogen atoms requires 8.2 and 10.0 kcal mol -1, respectively. As shown by the interconversion of the diastereomers of 1,3,5-tris(ethylmethylamino)-2,4,6-tris(dimethylamino)benzene, which requires 16.0 kcal mol -1, barriers to rotation about the C ar-N bonds in this class of compounds are substantially higher than barriers to pyramidal inversion. According to AM1 calculations, the homomerization (topomerization) of 4 is not concerted but involves stepwise inversion of the dimethylamino groups. The calculated activation energy, 10.5 kcal mol -1, is in reasonable agreement with the experimentally observed barrier of 8.2 kcal mol -1 for 9. Variable-temperature NMR studies on 8 reveal a site exchange of the methyl groups which is rationalized by a pseudorotational motion of the twisted benzene ring.

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