Nitrile temperature dependence

A number of cis/trans 4,6-dialkyl-2,2-dimethyl-l,3-dioxanes were studied by C NMR spectroscopy (93JOC5251). The C NMR shifts of C -Me groups (Scheme 8) were found to be very sensitive to the 1,3-dioxane conformation [chair form Me(ax) ca. 19 ppm and Me(eq) ca. 30 ppm— pure 30.89 ppm in the twist-boat form both methyl carbons resonate at ca. 25 ppm (pure 24.70 ppm)]. With these values, AG° of the chair to twist-boat equilibrium was calculated (Table IV). For 13a (nitrile), 13b (alkyne), and 13e (methyl ester) (Scheme 8) in CH2CI2, the temperature dependence of the AG° values was determined. Depending on the substituent, small negative or positive entropy terms were found generally the enthalpy term dominates the -AG° value. In the tram isomers 13, the cyano and alkyne substituents favor the chair conformation, but CHO, ester, alkene, and alkyl substituents, respectively, clearly favor the twist-boat conforma-... 

Fig. 33. Summary of temperature-dependent l3C isotropic chemical shifts for the nitrile carbon of acetonitrile on various zeolites. Loadings were in the range of 0.3-0.9 equiv. (Reprinted with permission from Haw el al. (80). Copyright 1995 American Chemical Society.)...

Fig. 5. 11. Temperature dependence of the ratio of the dual-fluorescence quantum yields for the nitriles DMABN and DMPYRBN (left) and the esters DMABEE and DMPYRBEE (right) in n-butyl chloride.33...

Temperature Dependence of the Nitrile Hydratase-Amidase Cascade System 275... 

The geminal proton-proton coupling constant in a-chloroacrylo-nitrile is both solvent and temperature dependent.Hetero-nuclear spin tickling experiments were used to show that the sign of the geminal coupling constant is of opposite sign to that of... 

The synthesis of a series of isoxazoles 15 and isoxazolines 15a on the solid phase has been reported by Pei and Moos [50] via [3 + 2] cycloaddition of alkenes and alkynes with highly reactive nitrile oxides. The cycloaddition reactions of resin-bound peptoids were carried out in toluene at 100°C or in DCM-H2O at room temperature, depending on the precursors of the nitrile oxides. Benzaldehyde oxime and various nitroalkyl compounds were selected as nitrile oxide precursors. The nitrile oxides were generated in situ by reacting the nitroalkyl compounds with phenyl isocyanate and triethylam-ine or by oxidizing the oximes with sodium hypochlorite in the presence of triethylamine (Fig. 7). 

For injection molding of nitrile rubber/PVC or chlorinated PE or PU or PA or their combination Chemigum TPE), processing temperature depends on the grade the harder the material, the higher the temperature. For Chemigum TPE, recommended melt temperamre is 135-185°C and mold temperamre 10-40°C. 

For polar molecules, the temperature dependence of B T) is different. One way to account for this [74-tso] is to add another term, a/r/ - blT, where a is related to the reduced dipole moment, b is zero for molecules such as aldehydes, ethers, ketones and nitriles which do not hydrogen-bond. Values for a and b have been given [74-tso, 75-tso] for a number of polar substances, but where these parameters are not available it is not possible to predict the second virial coefficient. 

Huang CY, Wang T, Gai E (2003) Temperature dependence of the CN stretching vibration of a nitrile-derivatized phenylalanine in water. Chem. Phys. Lett. 371 731-738... 

Figure 8.10 Temperature dependence of storage and loss moduli for a polyvinyl chloride-nitrile bidadiere rubber film bonded in parallel to a polyvinyl chloride film. Takayanagi model type (a) gives better fit to experiment. (Reproduced with permission fi om Takayanagi, Mem. Fac. Eng. Kyushu Univ., 23, 41 (1963))...

Platinum and manganese catalysts are more active than palladium- and chromium-hased catalysts when oxidizing nitrile compounds. A Pt (HS) catalyst is more active than a manganese catalyst and Pt (LS) catalyst. The Pt high surface area catalyst reaches complete conversion at 225°C while the manganese catalyst does not reach complete conversion until 300°C. Because NOx formation is temperature dependent, the Pt high surface area catalyst can present an advantage. With this catalyst, NOx formation can be minimized because it can be operated at low temperature. 

---