Low temperature infrared spectroscopy

Sordo et al. [144] explained the stereoselectivity on the basis of torquoelectronic effects. Low-temperature infrared spectroscopy was also used to identify the reactive intermediates [145]. Two mechanisms were proposed to explain the product distribution in the (3-lactam formation reaction. The ketene mechanism was observed in a low temperature infrared spectroscopy study [145], while the acylation of imine mechanism was believed to be involved in some [122]. Both mechanisms were supported by evidences. It had been hypothesized that cycloaddition of the imine occurs from the least hindered side of the ketene, and this process generates zwitterionic intermediates conrotatory cyclization of these intermediates then produce cis- and //Y/ .v-[S-lactanis. Acylation of the imine by the acid chloride to form /V-acyliminium chloride also produced zwitterionic intermediates (Scheme 10). 

The present chapter is therefore dedicated to review the low temperature infrared spectroscopy of C60 and C70 fullerenes, C60H18 fullerane (one of the most stable hydrogenated derivative of fullerenes) and a mixture of hydrogenated fullerenes referred collectively as C60H/C70Hy. Additionally, also the gas phase spectra of C60 and C70 fullerenes will be shortly reviewed. 

Low Temperature Infrared Spectroscopy of and C70 Fullerenes and Fullerane C60H18 205... 

A major advance was made by Brown and Pimentel (1958), who found CHjO and HNO as the initial photoproducts in a solid Ar matrix at 20 K with photolysis of CH3ONO between 240 and 360 nm from a mercury arc. They identified these products by low-temperature infrared spectroscopy. Confirmation that HNO was produced was given by Dalby (1958), who observed its absorption spectrum in the wavelength region 650-770 nm in the flash photolysis of iso-amyl nitrite. McGraw and Johnston (1969) also observed HNO by its infrared absorption at 3300 cm . 

Most low-temperature infrared spectroscopy has been performed using thin films. Some membrane proteins, such as bacteriorhodopsin, lend themselves easily to thin film use. The use of thin films affords some advantages, such as small volumes (tens of microliters), good compatibility with vacuum cryostat mounting, and excellent thermal contact with the cold stage. 

N. Sheppard, Low-Temperature Infrared Spectroscopy, Molecular Spectroscopy, Rept. Conf., Inst. Petroleum, London, 1954, 136-149, 1955. Review with 70 references. 

C. E. Weir, and E. R. Lippincott, 1962. Lattice frequencies and rotational barriers for inorganic carbonates and nitrates from low-temperature infrared spectroscopy. J. Res. Natl. Bur. Std. 66A 407. 

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