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Nanosecond transient resonance Raman spectra of the T1 states and Raman spectra of the S0 states of nine halogenated biphenyl compounds were obtained and ab initio computations were performed to determine the optimized geometry and vibrational wavenumbers of the T1 and S0 states of 10 halogenated biphenyl compounds. Substitution of halogen atoms at meta or para positions relative to the interring C—C bond leads to little change in the structure of the halogenated biphenyl compounds relative to the corresponding S0 and T1 states of biphenyl. Substitution of halogen atoms at ortho positions results in significant increases in the twisting between the two phenyl rings of the S0 and T1 states of the halogenated biphenyl compounds relative to the S0 and T1 states of biphenyl. The degree of twisting between the two phenyl rings in ortho-substituted halogenated biphenyls appears to depend on the steric, electronegativity and/or polarizability properties of the halogen atom. Copyright © 2001 John Wiley & Sons, Ltd.

Nanosecond time-resolved resonance Raman spectra of the T1 states and Raman spectra of the S0 states of 1-bromonaphthalene and 1,4-dibromonaphthalene were measured. Ab initio calculations were also performed to determine the optimized geometries and vibrational spectra for the S0 and T1 states of 1-bromonaphthalene and 1,4-dibromonaphthalene were predicted. The results were compared with those previously found for 2-bromonaphthalene and it was found that the Br atom substitution position and number both affect the changes in the C— Br bond in the T1 and Tn states. The intensities of the time-resolved resonance Raman spectra indicate that the C— Br bond changes its structure much more in the Tn state relative to the T1 state of 2-bromonaphthalene than 1-bromonaphthalene or 1,4-dibromonaphthalene. Possible implications of these substitution position effects on the ‘reluctant’ bond cleavage processes occurring from the Tn states of bromonaphthalenes are discussed. Copyright © 2000 John Wiley & Sons, Ltd.

A method using Raman spectroscopy was recently developed for the determination of the degree of acetylation in modified wheat starch. In this article, we show that the method can be generalized to a wide range of starches of different botanical origin and amylose content. Calibration sets were used to develop regression equations for 11 types of acetylated starches, including cereal (rice, maize, wheat) and noncereal (potato and sweetpotato) sources. The calibration lines were then used to predict the level of acetylation of starch samples with unknown level of acetylation using their Raman spectra. In each case, R2 > 0.98 for linear regression of Raman vs. titrimetric determination of acetylation. The Raman-based calibration curves allow fast and nondestructive determination of the degree of acetylation for different types of starches.

An analytical method using Raman spectroscopy was developed for the determination of amylose concentration in maize starches. FT-Raman spectra of four maize starches with amylose content varying from 3.3 to 66% were obtained. A Raman band at ≈1657 cm-1 correlated linearly with amylose concentration in the four maize starches, and a calibration curve for Raman band intensity versus amylose content was developed. The linear correlation of the I1657/I900 integrated areas with amylose content was r = 0.997. The Raman-based calibration curve allows fast and nondestructive determination of the amylose content in maize starches with minimal sample preparation.