IR Infrared

Originally quite an important tool in the structure elucidation of natural compounds, nowadays its use is limited. Because of its highly characteristic pattern of absorptions, IR is particularly useful for the confirmation of the 

MS — molecular weight, known fragments, simple derivative of known alkaloid (fragments +14, +16, +30, etc.) 

The structural elements found are, based on biosynthetic reasoning, combined into possible structures. These structures are compared with all spectral data. This will lead to a final proposal for a structure. 

Chiroptical methods have developed as major tools for solving the absolute stereochemistry in natural products (Scopes 1975). For example, in the case of indole alkaloids the configuration at C-2 and C-3 can be determined by 

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Ref. 277 unless otherwise noted gc = gas chromatography hplc = high pressure Hquid chromatography ir = infrared spectroscopy uv = ultraviolet spectroscopy glc = ga sliquid chromatography eia = enzyme immunoassay vis = visible spectroscopy. 

Infrared Spectroscopy (ir). Infrared curves are used to identify the chemical functionality of waxes. Petroleum waxes with only hydrocarbon functionality show slight differences based on crystallinity, while vegetable and insect waxes contain hydrocarbons, carboxyflc acids, alcohols, and esters. The ir curves are typically used in combination with other analytical methods such as dsc or gc/gpc to characterize waxes. 

HEED = high energy electron diffraction IILE = ion-induced light emission INS = ion-neutralization spectroscopy IRS = infrared spectroscopy ISS = ion-scattering spectroscopy LEED = low energy electron diffraction LEIS = low energy ion scattering ... 

Activity R = Raman-active, ir = infrared-active, S = optically silent, observed in neutron scattering. tCarbon atom displacement il or J. to C. 

Met. = Method. C = chronocoulometry, CC = corrosion current method, EC = Electrocapillary method, EL = Ellipsometric method, IR = Infrared spectroscopic method, CV = cychc voltammetry, RT = Radiotracer method, T = Tensammetry, TF = Thin film resistance, WL = weight loss method. When a combination of methods was used aU methods are listed separated by slashes. See also list of symbols. 

Ra = Raman active, IR = infrared active, ia = inactive molecular vibration. R and T denote rotations and translations, respectively... 

Wavenumbers scaled by optimized factors. Intensities for Raman active modes classified by the present authors on the basis of the calculated values. The intensities of two IR active vibrations were calculated to be equal (Ra) = Raman active, (IR) = infrared active [181]... 

IR = infrared spectrometry GC = gas chromatography FID = flame ionization detector NPD = nitrogen-phosphorous detector IDMS = isotope dilution mass spectrometry MS = mass spectrometry. 

Reference 60. In an Ar matrix. R, Raman IR, infrared vs, very strong s, strong m, medium w, weak vw, very... 

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