Infrared characterization

Wavenumbers are frequently used to characterize infrared radiation, with the units given in reciprocal centimeter (cm ). 

Characterization. Infrared Spectroscopic Analysis - The infrared spectra of all the chemically modified polybutadienes were obtained using a P.E. 1330 Infrared Spectrophotometer. The samples were prepared by casting polymer films on NaCl plates. 

While the broad mission of the National Bureau of Standards was concerned with standard reference materials, Dr. Isbell centered the work of his laboratory on his long interest in the carbohydrates and on the use of physical methods in their characterization. Infrared spectroscopy had shown promise in providing structural and conformational information on carbohydrates and their derivatives, and Isbell invited Tipson to conduct detailed infrared studies on the extensive collection of carbohydrate samples maintained by Isbell. The series of publications that rapidly resulted furnished a basis for assigning conformations to pyranoid sugars and their derivatives. Although this work was later to be overshadowed by application of the much more powerful technique of nuclear magnetic resonance spectroscopy, the Isbell— Tipson work helped to define the molecular shapes involved and the terminology required for their description. 

Sample Characterization. Infrared spectra of the adsorbed films were obtained with a Perkin-Elmer 1710 FTIR Spectrometer, equipped with a DTGS detector and a nitrogen-purged sample chamber. The transmission IR spectra (high frequency range >2000 cm 1) of the adsorbed species were directly measured on the glass slides. The... 

Characterization. Infrared spectra of bisdichloromaleimide monomers and polymers in KBr pellets were recorded, using a Perkin-Elmer 180 spectrophotometer. Elemental analyses were provided by Huffman Laboratories. Mass spectra were recorded at 70 eV on a Hewlett-Packard MS 5980 instrument by the direct inlet procedure. A DuPont 990 thermal analyzer was used to evaluate thermal behavior of bisdichloromaleimide monomers and polymers. Reduced viscosity of the polymers was determined in DMF at 30°C with a Cannon viscometer. Thermal polymerization was studied by heating a known weight of the material from room temperature to the desired temperature in a glass tube. The extent of curing was evaluated by extraction with DMF at room temperature. 

Ori ally ai lied jH edominantly as an analytical tool in the field of polymer characterization infrared spectroscopy has bem increasingly utilized in the last decades for the ducidation of the diysical structure of polymers. However, with the advent of rapid-scanning FTIR instruments and the development of the iheo-optical FTIR technique infrared spectro py has been launched into a completely new ex of polymer ph ical applications. 

Fourier transform infrared (FTIR) analysis (characterization) Infrared spectroscopy using the adsorption of IR radiation by the molecular bonds to identify the bond types that can absorb energy by vibrating and rotating. In Fourier transform infrared spectrometry (FTIR), the need for a mechanical slit is eliminated by frequency modulating one beam and using interferometry to choose the IR band. 

Using Infrared Spectrometry to Characterize Petroleum Fractions according to the Nature of the Carbon Atoms... 

Nevertheless, a molecule possesses sufficient vibrations so that all its frequencies taken together can be used to characterize it. In this sense the infrared spectrum is generally considered to be a molecule s fingerprint."... 

The external reflection of infrared radiation can be used to characterize the thickness and orientation of adsorbates on metal surfaces. Buontempo and Rice [153-155] have recently extended this technique to molecules at dielectric surfaces, including Langmuir monolayers at the air-water interface. Analysis of the dichroic ratio, the ratio of reflectivity parallel to the plane of incidence (p-polarization) to that perpendicular to it (.r-polarization) allows evaluation of the molecular orientation in terms of a tilt angle and rotation around the backbone [153]. An example of the p-polarized reflection spectrum for stearyl alcohol is shown in Fig. IV-13. Unfortunately, quantitative analysis of the experimental measurements of the antisymmetric CH2 stretch for heneicosanol [153,155] stearly alcohol [154] and tetracosanoic [156] monolayers is made difflcult by the scatter in the IR peak heights. 

Other important characterization techniques include electrophoresis measurements of droplets [11, 12] (see Section XIV-3C), infrared absorption of the constituent species [13], and light or x-ray scattering. NMR self-diffusion measurements can be used to determine droplet sizes in W/0 emulsions [14]. 

Ayotte P, Bailey C G, Weddle G FI and Johnson M A 1998 Vibrational spectroscopy of small Br (Fl20) and I Fl20) clusters infrared characterization of the ionic hydrogen bond J. Phys. Chem. A 102 3067-71... 

Marshaii M D, Charo A, Leung H O and Kiemperer W 1985 Characterization of the iowest-iying n bending state of Ar-HCi by far infrared iaser-Stark spectroscopy and moieouiar beam eiectric resonance J. Chem. Phys. 83 4924-33... 

Monolayers of alkanetliiols adsorbed on gold, prepared by immersing tire substrate into solution, have been characterized by a large number of different surface analytical teclmiques. The lateral order in such layers has been investigated using electron [1431, helium [144, 1451 and x-ray [146, 1471 diffraction, as well as witli scanning probe microscopies [122, 1481. Infonnation about tire orientation of tire alkyl chains has been obtained by ellipsometry [149], infrared (IR) spectroscopy [150, 151] and NEXAFS [152]. 

Porter M D, Bright T B, Allara D L and Chidsey C E D 1987 Spontaneously organized molecular assemblies. 4. Structural characterization of normal-alkyl thiol monolayers on gold by optical ellipsometry, infrared-spectroscopy, and electrochemistry J. Am. Chem. Soc. 109 3559-68... 

Karge FI G, Flunger M and Beyer FI K 1999 Characterization of zeolites—infrared and nuclear magnetic resonance spectroscopy and x-ray diffraction Catalysis and Zeolites, Fundamentals and Applications ed J Weitkamp and L... 

The infrared spectra of a set of 2-thiazolylthioureas are reported in Ref. 486. The ultraviolet spectra of l-aryl-3-(2-thiazolyl)thioureas are characterized by two bands of approximate equal intensity around 282 and 332 nm (492). For l-alkyl-3-(2-thiazolyl)thioureas these bands are shifted to 255 and 291 nm, respectively (492). The shape of the spectrum is modified further when l.l -dialkyl-3-(2-thiazolyl)thioureas are considered (491). Fragmentation patterns of various 2-thiazolylthioureas have been investigated (100, 493), some of which are shown in Scheme 158. Paper and thin-layer chromatography provide an effective tool for the analysis of these heterocyclic thioureas (494. 495). 

The infrared spectra of A-4-thiazoline-2-ones are characterized by a strong absorption around 1650 cm (55, 86, 103, 107. 870). For the N-H derivatives, the whole range 2700 to 3200 cm is covered by a strong absorption related to the dimeric and oligomeric states of the hydrogen-bonded structures (85, 86). 

The 4-Hydroxy-thiazoles are characterized by infrared absorption near 1610 cm (KBr) (3) or 1620 to 16.S0cm (CCI4) (8), indicating a strongly polarized carbonyl group. H-5 resonates near 5.6 ppm in the NMR spectrum like similar protons in other mesoionic compounds (3). Two fragmentations of the molecular ion are observed in the mass spectra. The first involves rupture of the 1,2 and 3,4 bonds with loss of C2R 0S . In the second, the 1,5 and 3,4 bonds are cleaved with elimination of C2R 0. ... 

Infrared The infrared spectra of ethers are characterized by a strong rather broad band due to antisymmetric C—O—C stretching between 1070 and 1150 cm Dialkyl ethers exhibit this band consistently at 1120 cm as shown m the IR spectrum of dipropyl ether... 

Section 20 21 Acyl chlorides anhydrides esters and amides all show a strong band for C=0 stretching m the infrared The range extends from about 1820 cm (acyl chlorides) to 1690 cm (amides) Their NMR spectra are characterized by a peak near 8 180 for the carbonyl carbon H NMR spectroscopy is useful for distinguishing between the groups R and R m esters (RCO2R ) The protons on the carbon bonded to O m R appear at lower field (less shielded) than those on the carbon bonded to C=0... 

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