Optically active amines. XI. Optical rotatory dispersion and circular dichroism observations on .alpha.- and .beta.-phenylalkylamine hydrochlorides

The prediction of the circular dichroism of the benzene chromophore: TDDFT calculations and sector rules

“…This spectral shape is due to two distinct vibrational progressions with opposite signs, both associated with a totally symmetric vibration (ring breathing) with frequency % 920-1000 cm -1 : an allowed one, starting in correspondence with the 0-0 absorption band at 267-268 nm; and a ''forbidden'' one, starting from a 0-v band, where v % 420 cm -1 is associated with a nontotally symmetric vibration. 31,32 The overall 1 L b -band integral has the same sign of the allowed progression, which is distinctly negative for 3 and 4 and only weakly positive for 1 and 2. The situation changes dramatically at low temperature, where the dominant sign becomes clearly positive (the same of the allowed progression) for 1-3, while the CD of 4 is unchanged.…”

How and How Much Molecular Conformation Affects Electronic Circular Dichroism: The Case of 1,1-Diarylcarbinols

“…The vibrational progression seen in the experimental UV and ECD spectra of compounds 1 and 2 ( Figure 1 ) is typical for the electric-dipole forbidden 1 L b transition of simple aromatic molecules containing substituted phenyl rings [ 47 , 49 , 50 ]. We studied previously this aspect for a few benzene derivatives, including the present compound 2 [ 35 , 47 ].…”

Synthesis and characterization of fluorous (S)- and (R)-1-phenylethylamines that effect heat facilitated resolution of (±)-2-(8-carboxy-1-naphthylsulfinyl)benzoic acid via diastereomeric salt formation and study of their circular dichroism

“…The quadrant sector rule as applied to a-substituted phenylethane may be depicted as shown in Scheme 3a [22]. In Scheme 3a, the signs refer to the rotatory contributions of groups lying above the phenyl ring plane.…”

“…In Scheme 3a, the signs refer to the rotatory contributions of groups lying above the phenyl ring plane. The sign of the rotational perturbation of a group lying in a particular sector was deduced empirically [22]. It was concluded that an alkyl group is not capable of a rotationally significant interaction with the phenyl chromophore.…”

“…The sign of the Cotton effects in the region 240-275 nm can be predicted based on a quadrant sector rule [22] (Scheme 3). The 1 L b band region of 4*HCl with the typical vibrational fine structure shows an expressed solvent sensitivity.…”