Optical rotatory power of the flexible aromatic compounds (S)-(-)-1-phenylethanol and (S)-(-)-1-(2-methylphenyl)ethanol

Optically active amines. 25. Circular dichroism of 1-substituted indans

“…It thus follows that the coupled oscillator contribution to the 'Lb Cotton effects of (S')-! and those of the other 1-substituted indans not containing an additional chromophoric group (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) in CHART I is positive. The observed negative 'Lb Cotton effects for these 1-substituted indans may then be due to the dominance of a negative one-electron contribution to the rotational strength.…”

Chiroptical Properties of the Benzene Chromophore. A Method for the Determination of the Absolute Configurations of Benzene Compounds by Application of the Benzene Sector and Benzene Chirality Rules

“…As was also discussed above, when the vibronic and induced contributions to the 1 L b CEs are of opposite sign, a prediction as to the sign of the 1 L b CEs shown by a particular enantiomer is somewhat ambiguous. However, all of the phenylalkylcarbinamines and phenylalkylcarbinols so far reported that are ortho or para-substituted with an atom or group with a positive spectroscopic moment show 1 L b CEs of opposite sign to that of their unsubstituted parents, ,,,,,,,,− including ortho- and para-substituted ( R )-β-hydroxy-β-phenylpropionic acid [( R )- 22 , R = F, Cl, or Br]…”

“…On this basis the sign of the 1 L b CEs are predicted to be positive as is observed (Table ). On substitution of the benzene ring of ( S )- 26a and b with a methyl group at the ortho position, it can be safely assumed that the preferred conformation is such that the hydrogen atom at the chiral center still eclipses the benzene ring plane. , On this basis, the sign of the 1 L b CEs for both ( S )- N -methyl-2-( o -methylphenyl)pyrrolidine [( S )- 26c ] and ( S )- N -methyl-2-( o -methyl-phenyl)piperidine [( S )- 26d ] are predicted and are observed to be negative (Table ), the methyl group causing a negative induced contribution to the 1 L b CEs which overshadows the positive vibronic contribution.…”

“…For benzene compounds with a contiguous chiral center incorporating a hydrogen atom, empirical potential function 65 and molecular orbital calculations [66][67][68] as well as X-ray, 66,69 proton nuclear magnetic resonance, 67,[70][71][72] gas electron diffraction, 73 and jet laser 74 spectroscopy indicate that the preferred conformation ( 5) is such that the hydrogen atom at the carbon center eclipses or almost eclipses the phenyl ring plane (Table 2). Thus the CD data in Table 2 suggest the quadrant projections in Figure 8A which show the sign of the vibronic contribution to the 1 L b CEs of a monosubstituted benzene chromophore by atoms or groups attached to a chiral center and lying in sectors in front of the benzene ring plane (near sectors).…”

Optically Active Amines. 41.1 Application of the Benzene Chirality Rule to Chiral Ring-Substituted Benzylcarbinamines and Benzylcarbinamine Salts

“…When the vibronic and induced contributions to the 1 L b CEs are of opposite sign, a prediction to the sign of the 1 L b CEs shown by a particular enantiomer is somewhat ambiguous. However, all of the phenylalkylcarbinamines and -carbinols so far reported that are ortho- and para-substituted with an atom or group having a positive spectroscopic moment (CH 3 , Cl, Br, OH, OCH 3 ) show 1 L b CEs of opposite sign to that of their unsubstituted parent. − ,,− For phenylalkylcarbinamines and -carbinols having a group with a negative spectroscopic moment (CN, CF 3 ) in the meta position, the sign of the 1 L b CEs is not changed from that of the unsubstituted parent …”