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MASSENSPEKTREN HETEROAROMATISCHER NITRILE (1975)

Holzmann, G. ; Rothkopf, H. W. ; Müller, R. ; [et al.]

Chichester : Wiley-Blackwell

Biological Mass Spectrometry 10 (1975), S. 97-115

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ISSN: 0030-493X

Keywords: Chemistry ; Analytical Chemistry and Spectroscopy

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The electron-impact and field ionisation spectra of nineteen di- and tetracyanopyrazines are presented. The use of high resolution mass measurement and metastable analysis allows the proposal of some general fragmentation mechanisms. The 5,6-disubstituted (alkyl or arene) 2,3-dicyanopyrazines examined show, apart from a less important loss of the nitrile and dicyano groups, fragmentation of the heterocyclic system directed by the nitrogen atoms. In contrast, anellation in the 5,6-position, leads only to loss of the nitrile and dicyano groups being observed. These general fragmentation mechanisms are also observed for the tetracyanopyrazines examined. A comparison of di- and tetracyanobenzene with five ring heterocycles containing four cyano groups shows that fragmentation of nitrile groups is greatly dependent upon the aromaticity of the cyclic system.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/oms.1210100204

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CO2 laser welding of polymers (1992)

Duley, W. W. ; Mueller, R. E.

Stamford, Conn. [u.a.] : Wiley-Blackwell

Polymer Engineering and Science 32 (1992), S. 582-585

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ISSN: 0032-3888

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Deep penetration welding of polymers can be carried out at high speed with relatively low laser power. This results from an efficient coupling CO2 laser radiation to polymers that leads to volume heating. A brief review of energy coupling and heat transfer effects in polymers under CO2 laser welding conditions is given. Some examples of low power (10 to 100 watt) CO2 welding of polypropylene and polyethylene at depths of up to 1.5 cm are discussed.

Additional Material: 5 Ill.