Spectra, halogens

Keywords Anion-n interaction Charge transfer Electronic spectra Halogen n-bonding X-ray crystallography... 

Lamps are continuous-spectrum, halogen, or tungsten for visible spectrum, and deuterium or xenon for UV. 

Fig. Vni-12. Energy spectrum of Ne" ions that are scattered over 90° by a halogenated nickel surface. The incident energy of the ions is 300 V. (From Ref. 92.)...

Usually, the ultraviolet and visible regions of the spectrum are recorded. Many of the most intense emission lines lie between 200 nm and 400 nm. Some elements (the halogens, B, C, P, S, Se, As, Sn, N, and O) emit strong lines in the vacuum ultraviolet region (170-200 nm), requiring vacuum or purged spectrometers for optimum detection. 

Thiophenes substituted with groups such as alkyl, halogens, OCH3, and SCH3 show small but characteristic differences between 2- and 3-substituted compounds. In these cases, however, it is the 2-isomer which shows the less complex spectrum. Thus, 2-substituted alkylthio-phenes and halothiophenes show a single band with greater extinction than the 3-isomers whose spectra exhibit two peaks in a broadened absorption band. These differences are also present in the spectra of 2,5- and 3,4-dihalosubstituted compounds. In 2-substituted thiophenes, the intensity of the band varies inversely as the electronega-... 

B. Sample Mass Spectrum of an Aliphatic Halogenated Compound... 

A. Preparation.—Halogen displacement reactions have been used to prepare a number of new aminofluorophosphines. Aminodifluorophos-phine (1) has been prepared for the first time, from either bromodifluoro-phosphine or chlorodifluorophosphine, and ammonia. Studies of its n.m.r. spectrum have been made (see Chapter 11). The related NN-difluoroaminodifluorophosphine (2) has been prepared, from difluoroiodo-phosphine, and found to be explosive. Two syntheses of A-alkyl-amino-difluorophosphines have been reported, one of which was complicated by the subsequent formation of the phosphorane (3) and the bis-(A-alkylamino)fluorophosphine (4). 

DIBF has the absorbance spectrum shown in Figure 4. Coating mixtures containing this photoinitiator can be cured with an intense tungsten halogen lamp, such as a projector bulb. When DIBF is irradiated it forms an excited state which has a very low absorbance, i.e., it photobleaches (1). This allows light to penetrate deeply into the coating. 

The third member, trimethylenemethane (3), had some relevance to our studies on carbenes, since besides methylene and its simply substituted derivatives trimethylenemethane 3 is one of the few molecules having a triplet ground state.22 Also the experience with 3 could be of help in order to deal with the singlet/triplet differentiation in matrix-isolated carbenes. We learned that, if the calculated IR spectra of the singlet and triplet molecule are sufficiently different, it might be possible to determine the multiplicity of the matrix-isolated species by comparison with the experimental IR spectrum. In this context it is also worth mentioning that we were able to measure the matrix IR spectrum of 3, but a special technique (irradiation in halogen-doped xenon matrices) had to be developed in order to achieve a concentration of 3 sufficient for its IR detection.23... 

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