Fingerprinting

of course, possible to use rotation spectra or rotational fine structure in other spectra simply as a method of recognizing or identifying samples, and extensive lists of microwave line positions have been published to facilitate these processes. The method is particularly applicable in the microwave region, where the narrow instrumental and spectral line widths mean that lines even less than 1 MHz apart can easily be distinguished. 

CHsCsCH, CH3CN, NH2CHO, CH2=NH, HCOOCH3, CH3CH2OH, H(CsC) CN (n = 1-5) 

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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."... 

Rowell and co-workers [62-64] have developed an electrophoretic fingerprint to uniquely characterize the properties of charged colloidal particles. They present contour diagrams of the electrophoretic mobility as a function of the suspension pH and specific conductance, pX. These fingerprints illustrate anomalies and specific characteristics of the charged colloidal surface. A more sophisticated electroacoustic measurement provides the particle size distribution and potential in a polydisperse suspension. Not limited to dilute suspensions, in this experiment, one characterizes the sonic waves generated by the motion of particles in an alternating electric field. O Brien and co-workers have an excellent review of this technique [65]. 

The diffraction pattern observed in LEED is one of the most connnonly used fingerprints of a surface structure. Witii XRD or other non-electron diffraction methods, there is no convenient detector tliat images in real time the corresponding diffraction pattern. Point-source methods, like PD, do not produce a convenient spot pattern, but a diffrise diffraction pattern that does not simply reflect the long-range ordermg. 

A fingerprint ofa chemical structure tries to identify a molecule with some special characteristics, much in the same way as a human fingerprint identifies a person. The characteristic property can, for example, be described by the structure or struc-... 

Figure 2-65. This fingerprint was received by hashing, whereas only one part of all the substructures is specified in the illustration. The asterisk indicates the address of a collision in the bit string, generated by the algorithm.

Fingerprints structural keys identify a molecule - code is highly compact represented in bits ambiguous not convertible to other representations dependent on the fragment library... 

Methods of analyzing the diversity of the selected subset ensure that an appropriate chemical space is covered. Descriptors such as fingerprints, and 2D, and 3D descriptors, as well as molecular surface properties, which can be... 

Hashed fingerprints, structural keys 2D structure See Section 12.2... 

Dowms G M and J M Barnard 1997. Techniques for Generating Descriptive Fingerprints in Combina torial Libraries. Journal of Chemical Information and Computer Science 37 59-61. 

The tetroxide has been used to detect fingerprints and to stain fatty tissue for miscroscope slides. The metal is almost entirely used to produce very hard alloys, with other metals of the platinum group, for fountain pen tips, instrument pivots, phonograph needles, and electrical contacts. 

He therefore wanted to synthesise TM 29 to check. Even with modem spectroscopic methods the quickest way to check the identity of a compound will often be to synthesise it by an unambiguous route and compare the n.m.r. and fingerprint i.r. spectra. How then would you make TM 29 ... 

Fingerprint region (Section 13 20) The region 1400-625 cm of an infrared spectrum This region is less character istic of functional groups than others but varies so much from one molecule to another that it can be used to deter mine whether two substances are identical or not Fischer esterification (Sections 15 8 and 19 14) Acid cat alyzed ester formation between an alcohol and a carboxylic acid... 

The mass spectrum is a fingerprint for each compound because no two molecules are fragmented and ionized in exactly the same manner on electron-impact ionization. In reporting mass spectra the data are normalized by assigning the most intense peak (denoted as base peak) a value of 100. Other peaks are reported as percentages of the base peak. 

This fragmentation is characteristic for a given substance, similar to a fingerprint, and is referred to as a mass spectrum. 

The mass spectrum is characteristic for different substances and can be used like a fingerprint to identify a substance, either by comparison with an already known spectrum or through skilled interpretation of the spectrum itself (Figure 3.2). 

Many elements have two or more isotopes, and the presence of these correspondingly gives a spectrum having many peaks. On the other hand, the patterns of these isotopes in a mass spectrum often prove invaluable in identifying which elements are present, with the patterns serving as fingerprints for certain elements. 

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