Crystal structure of 4,5-dibromophenanthrene

The synthesis and crystal structure of the title compound, C14H8Br2, is described. The molecule is positioned on a twofold rotation axis and the asymmetric unit consists of half a molecule with the other half being generated by symmetry. The presence of two large bromine atoms in the bay region significantly distorts the molecule from planarity and the mean planes of the two terminal rings of the phenanthrene system are twisted away from each other by 28.51 (14)°. The torsion angle between the two C—Br bonds is 74.70 (14)° and the distance between the two Br atoms is 3.2777 (13) Å. The molecules pack in layers in the crystal, with the centroids of the central rings of the phenanthrene units in adjacent layers separated by a distance of 4.0287 (10) Å. These centroids are shifted by 2.266 (6) Å relative to each other, indicating slippage in the stacking arrangement. Furthermore, the distance between the centroids of the terminal and central rings of the phenanthrene units in adjacent layers is slightly shorter at 3.7533 (19) Å. While all of the molecules within each layer are oriented in the same direction, those in adjacent layers are oriented in the opposite direction, leading to anti-parallel stacks

Influence of Substituents on the Through-Space Shielding of Aromatic Rings

A series of naphthalene derivatives, bearing a methyl group and a substituted phenyl ring in a 1,8-relationship, have been synthesized. The chemical shifts of the protons of the methyl group, which are pointed toward the shielding zone of the phenyl ring, were monitored as the phenyl substituents were varied. This work indicates that the shielding effect of the phenyl ring is not so severely altered by the substituents as to significantly influence the chemical shift of the methyl group. Nonetheless, within the small changes observed experimentally, there appears to be a tendency for electron-withdrawing X to shift the methyl signal downfield, whereas electron-donating X-groups cause a more upfield shift. Polarization and field effects are discussed as possible causes for this phenomenon. Chemical shifts computed for selected members of the series, using the recently published procedures of Rablen and Bally, are in agreement with the experimentally observed trends

Influence of Substituents on the Through-Space Shielding of Aromatic Rings

A series of naphthalene derivatives, bearing a methyl group and a substituted phenyl ring in a 1,8-relationship, have been synthesized. The chemical shifts of the protons of the methyl group, which are pointed toward the shielding zone of the phenyl ring, were monitored as the phenyl substituents were varied. This work indicates that the shielding effect of the phenyl ring is not so severely altered by the substituents as to significantly influence the chemical shift of the methyl group. Nonetheless, within the small changes observed experimentally, there appears to be a tendency for electron-withdrawing X to shift the methyl signal downfield, whereas electron-donating X-groups cause a more upfield shift. Polarization and field effects are discussed as possible causes for this phenomenon. Chemical shifts computed for selected members of the series, using the recently published procedures of Rablen and Bally, are in agreement with the experimentally observed trends

Influence of Substituents on the Through-Space Shielding of Aromatic Rings

A series of naphthalene derivatives, bearing a methyl group and a substituted phenyl ring in a 1,8-relationship, have been synthesized. The chemical shifts of the protons of the methyl group, which are pointed toward the shielding zone of the phenyl ring, were monitored as the phenyl substituents were varied. This work indicates that the shielding effect of the phenyl ring is not so severely altered by the substituents as to significantly influence the chemical shift of the methyl group. Nonetheless, within the small changes observed experimentally, there appears to be a tendency for electron-withdrawing X to shift the methyl signal downfield, whereas electron-donating X-groups cause a more upfield shift. Polarization and field effects are discussed as possible causes for this phenomenon. Chemical shifts computed for selected members of the series, using the recently published procedures of Rablen and Bally, are in agreement with the experimentally observed trends

Influence of Substituents on the Through-Space Shielding of Aromatic Rings

A series of naphthalene derivatives, bearing a methyl group and a substituted phenyl ring in a 1,8-relationship, have been synthesized. The chemical shifts of the protons of the methyl group, which are pointed toward the shielding zone of the phenyl ring, were monitored as the phenyl substituents were varied. This work indicates that the shielding effect of the phenyl ring is not so severely altered by the substituents as to significantly influence the chemical shift of the methyl group. Nonetheless, within the small changes observed experimentally, there appears to be a tendency for electron-withdrawing X to shift the methyl signal downfield, whereas electron-donating X-groups cause a more upfield shift. Polarization and field effects are discussed as possible causes for this phenomenon. Chemical shifts computed for selected members of the series, using the recently published procedures of Rablen and Bally, are in agreement with the experimentally observed trends

Influence of Substituents on the Through-Space Shielding of Aromatic Rings

A series of naphthalene derivatives, bearing a methyl group and a substituted phenyl ring in a 1,8-relationship, have been synthesized. The chemical shifts of the protons of the methyl group, which are pointed toward the shielding zone of the phenyl ring, were monitored as the phenyl substituents were varied. This work indicates that the shielding effect of the phenyl ring is not so severely altered by the substituents as to significantly influence the chemical shift of the methyl group. Nonetheless, within the small changes observed experimentally, there appears to be a tendency for electron-withdrawing X to shift the methyl signal downfield, whereas electron-donating X-groups cause a more upfield shift. Polarization and field effects are discussed as possible causes for this phenomenon. Chemical shifts computed for selected members of the series, using the recently published procedures of Rablen and Bally, are in agreement with the experimentally observed trends

Influence of Substituents on the Through-Space Shielding of Aromatic Rings

A series of naphthalene derivatives, bearing a methyl group and a substituted phenyl ring in a 1,8-relationship, have been synthesized. The chemical shifts of the protons of the methyl group, which are pointed toward the shielding zone of the phenyl ring, were monitored as the phenyl substituents were varied. This work indicates that the shielding effect of the phenyl ring is not so severely altered by the substituents as to significantly influence the chemical shift of the methyl group. Nonetheless, within the small changes observed experimentally, there appears to be a tendency for electron-withdrawing X to shift the methyl signal downfield, whereas electron-donating X-groups cause a more upfield shift. Polarization and field effects are discussed as possible causes for this phenomenon. Chemical shifts computed for selected members of the series, using the recently published procedures of Rablen and Bally, are in agreement with the experimentally observed trends

Influence of Substituents on the Through-Space Shielding of Aromatic Rings

A series of naphthalene derivatives, bearing a methyl group and a substituted phenyl ring in a 1,8-relationship, have been synthesized. The chemical shifts of the protons of the methyl group, which are pointed toward the shielding zone of the phenyl ring, were monitored as the phenyl substituents were varied. This work indicates that the shielding effect of the phenyl ring is not so severely altered by the substituents as to significantly influence the chemical shift of the methyl group. Nonetheless, within the small changes observed experimentally, there appears to be a tendency for electron-withdrawing X to shift the methyl signal downfield, whereas electron-donating X-groups cause a more upfield shift. Polarization and field effects are discussed as possible causes for this phenomenon. Chemical shifts computed for selected members of the series, using the recently published procedures of Rablen and Bally, are in agreement with the experimentally observed trends

Influence of Substituents on the Through-Space Shielding of Aromatic Rings

A series of naphthalene derivatives, bearing a methyl group and a substituted phenyl ring in a 1,8-relationship, have been synthesized. The chemical shifts of the protons of the methyl group, which are pointed toward the shielding zone of the phenyl ring, were monitored as the phenyl substituents were varied. This work indicates that the shielding effect of the phenyl ring is not so severely altered by the substituents as to significantly influence the chemical shift of the methyl group. Nonetheless, within the small changes observed experimentally, there appears to be a tendency for electron-withdrawing X to shift the methyl signal downfield, whereas electron-donating X-groups cause a more upfield shift. Polarization and field effects are discussed as possible causes for this phenomenon. Chemical shifts computed for selected members of the series, using the recently published procedures of Rablen and Bally, are in agreement with the experimentally observed trends