Calculations Predict That Carbon Tunneling Allows the Degenerate Cope Rearrangement of Semibullvalene to Occur Rapidly at Cryogenic Temperatures

Calculations predict that carbon tunneling allows the degenerate cope rearrangement of semibullvalene to occur rapidly at cryogenic temperatures.

Calculations on the role of tunneling in the degenerate Cope rearrangements of semibullvalene (1) and barbaralane (3) predict that, at temperatures below 40 K, tunneling from the lowest vibrational level should make the temperature-independent rate constants k = 1.43 x 10(-3) s(-1) and k = 7.28 x 10(-9) s(-1), respectively. An experiment, using semibullvalene-2(4)-d(1), is proposed to test the ...

Refractive Index of ZnSe at Cryogenic Temperatures†

This report describes an extensive data set on the refractive index of ZnSe that provides full high resolution coverage of the CRIRES operating range in both wavelength and temperature. By combining our prototype instrument model of CRIRES with these data our project to provide wavelength calibration for IR Echelle spectrographs (WIRE) has reached an important milestone and is ready to support ...

Antarafacial-Antarafacial Cope Rearrangement

Thermal rearrangement of 2-thiabicyclo[ 3.2.0]hepta-3,6-diene-6,7-dicarbonitriles 1-3 to their 4,5-dicarbonitrile isomers 4-6 takes place at 110-140 "C in yields of 82-84%. The reactions are first order with rates almost independent of the polarity of the solvent. Activation parameters (m = 120-140 kJ mol-' and AS* = 0 J K-l mol-') are in agreement with a concerted symmetry-allowed antarafacial...

Characterization of the Opa350 Operational Amplifier at Cryogenic Temperatures

As part of the development of EMIR, an infrared multiobject spectrograph for the Gran Telescopio de Canarias (GTC), the OPA350 operational amplifier is being successfully used at cryogenic temperatures (77K). The use of off-theshelf electronics (not specifically designed for cryogenics) is advantageous since it allows us to get signal amplification very close to the detector without the need of...

Investigation of the Tribological Behavior of Polytetrafluoroethylene at Cryogenic Temperatures