Infrared Peak Research Articles

Infrared spectroscopy-based property-reactivity correlations for predicting environmental fate of organic chemicals

A conventional structure-activity relationship (SAR) has been established between the alkaline hydrolysis rate constants (koh) of 12 alkyl and aryl formates and acetates and the linear combination of the frequencies of the C=o and C—o infrared (IR) absorbance peaks. The inability of this relationship to predict koh values for more structurally diverse carboxylic acid esters led to the development of a prototype of a prediction system that employs multiple linear regression analysis, using points from the Fourier transforms (FTs) of IR spectra. Conventional SARs have also been observed between single IR peak parameters and the microbial degradation rate constants of amides (C=O peak frequencies), 2,4-dichlorophenoxyacetate esters (CH peak intensities), phenols (OH peak frequencies), and anilines (NH stretching peak intensities). These observations indicate the feasibility of extending the FT-based prediction system to microbial degradation when reliable rates are available for additional compounds.

Effect of annealing on carbon concentration in edge-defined film-fed grown polycrystalline silicon

Carbon complex formation during annealing in the temperature range from 450 to 1150 °C is studied in a carbon-rich polycrystalline edge-defined film-fed grown (EFG) silicon sheet. The result is compared with that obtained in Czochralski (CZ) single-crystal silicon. Infrared (IR) spectroscopy reveals that carbon removal from substitutional sites above 600 °C is greatly inhibited in EFG silicon with respect to that seen in the CZ material. A broad IR peak attributed to C-O complexes appears only after annealing at highest temperatures, while there is no evidence for appearance of the sharp band at 794 cm−1 usually assigned to SiC precipitation. The suppression of carbon complex formation in EFG material is attributed to decreased availability of silicon self-interstitials necessary to promote removal of carbon from substitutional sites and to enhance its diffusivity.

Thermodynamic properties of MgSiO3 ilmenite from vibrational spectra

Unpolarized infrared (IR) reflectance spectra for MgSiO3 ilmenite taken from a single-crystal and from a densly packed polycrystalline sample possessed all eight peaks mandated by symmetry between 337 and 850 cm−1. Polarizations were inferred from intensity differences between the two samples. IR peak positions differ by up to 250 cm−1 from recent calculations, but on average are within 11%. Heat capacity C p calculated from these data by using a Kieffer-type model are within the experimental uncertainty of calorimetric measurements from 170 to 700 K. Outside this range, calculated C p is probably accurate within a few percent, based on recent results for garnets. Calculated entropy is only slightly less accurate, giving S 0 (298.15 K) as 54.1 ±0.5 J/ mol-K, which is 10% lower than recent estimates based on phase equilibria. The slope of the phase boundary between ilmenite and perovskite is used to predict S 0 (298.15 K) of perovskite as 58.7 ±1.4 J/mol-K, which is 10% lower than previous values.

INFRARED SPECTROSCOPY-BASED PROPERTY-REACTIVITY CORRELATIONS FOR PREDICTING ENVIRONMENTAL FATE OF ORGANIC CHEMICALS

A conventional structure-activity relationship (SAR) has been established between the alkaline hydrolysis rate constants (koh) of 12 alkyl and aryl formates and acetates and the linear combination of the frequencies of the C=o and C—o infrared (IR) absorbance peaks. The inability of this relationship to predict koh values for more structurally diverse carboxylic acid esters led to the development of a prototype of a prediction system that employs multiple linear regression analysis, using points from the Fourier transforms (FTs) of IR spectra. Conventional SARs have also been observed between single IR peak parameters and the microbial degradation rate constants of amides (C=O peak frequencies), 2,4-dichlorophenoxyacetate esters (CH peak intensities), phenols (OH peak frequencies), and anilines (NH stretching peak intensities). These observations indicate the feasibility of extending the FT-based prediction system to microbial degradation when reliable rates are available for additional compounds.

The nature of several intense Si-H infrared stretching peaks in the neutron-transmutation-doped Si-H system

The authors experiments show that there are four, three, two and one hydrogen atoms involved in the defect complexes corresponding to the 2210 cm-1, 2066 cm-1, 1980 cm-1 and 1832 cm-1 infrared (IR) peaks, respectively, in the neutron-transmutation-doped floating-zone silicon (NTD FZ-Si) system. On the basis of the correlation of the thermostability and the oscillator frequency with the number of hydrogen atoms involved in these IR peaks, they attribute the 2210 cm-1, 2066 cm-1, 1980 cm-1 and 1832 cm-1 IR peaks to the vacancy+4H, vacancy+3H, vacancy+2H and vacancy+1H defect complexes, respectively. The mechanism of the formation of the vacancy+nH defect complexes in the NTD FZ-Si:H system has been discussed.

A Multivariate Analysis of the Infrared Spectra of Drugs of Abuse

The infrared (IR) spectra of 15 drugs of abuse were analyzed for similarity by using techniques of numerical taxonomy. The study included six barbiturates (amobarbital, barbital, butabarbital, phentobarbital, phenobarbital, and secobarbital), four amphetamine-related compounds (amphetamine, ephedrine, methamphetamine, and phentermine), and five other drugs (cocaine, heroin, phencyclidine, phendimetrazine, and diazepam). Three character sets were based on increasing numbers (10, 24, and 36) of IR peaks. The cluster analysis, principal component analysis, and nonmetric multidimensional scaling elements of the program system NT-SYS were used to structure taxonomic distances between drugs. Best results were obtained from the 36-peak data set; ordination diagrams proved to be more visually informative than phenograms. Preliminary results from our analysis of this set of drugs indicate that an expanded multivariate approach to drug classification may be useful.