Schmidt mechanical requirements

The examples of ex situ steady-state X-ray photodiffraction utihzed to follow the photodimerizations of olefin bonds in a single-crystal-to-single-crystal (or nearly so) manner are ubiquitous in the chemical literature. The interest of sohd-state chemists in this reaction dates back to the work of Cohen and Schmidt [30, 31], and it has become much of a guinea pig in organic solid-state photochemistry. In 1993, Enkelmann and collaborators published two seminal papers in the Journal of the American Chemical Society [32] and in Angewandte Chemie [33], where they presented a series of structures of a-tra s-cinnamic acid crystals reacted to various extents. These reports laid the way for a plethora of later studies on the olefin photodimerization reaction. The convenience of the high conversion and the simple mechanism, combined with the relatively small structural perturbation that it requires, has turned this reaction into a very useful tool to probe intermolecular... 

In the troposphere and in the lower stratosphere, the chemical production of H2 is due to the photolysis of formaldehyde produced by methane oxidation. About 13 Tg H2/yr are produced by this mechanism (Schmidt et al., 1980). Oxidation of isoprene and other terpenes in the lower troposphere leads to an additional production of about 10-35 Tg H2/yr. A precise determination of these quantities requires a... 

The second balloon-expandable stent type has been made from a single tantalum filament, which was woven into a cylindrical wire mesh. Again, the choice of thickness of the tantalum wire and the knitting technique determines the mechanical properties of this stent type. This particular stent type has been known as the Strecker stent (Boston Scientific, Natick, MA) (Strecker et al. 1990). This stent requires balloon dilatation for deployment like the Palmaz type stents. Generally, it is more flexible but also less resistant to compressive forces than the stainless steel balloon-expandable stents. Stents for use in the respiratory system came in lengths between 20 and 40 mm, and were expandable to diameters between 5 and 11 mm. Due to its relatively low radial forces, this particular stent had the unique feature of possible stent removal, thus it can be used for temporary stenting (Schmidt et al. 1999 Witt et al. 1997). 

The highly ring strained cyclopropanone (which is conveniently stored and used as a mixed ketal) also undergoes Schmidt chemistry to afford M-substituted jS-lactams along with ethyl carbamates in about a 1 1 ratio (Scheme 7.9). Presumably, the p-laclam is formed via the typical ring expansion mechanism described above. Ethyl carbamates are more mechanistically intriguing, requiring the formal loss of ethylene and N2 followed by recombination of a silylated isocyanate with ethanol. 

The Schmidt reaction of aldehydes has some features as follows. (1) Aldehydes react with hydrazoic acid faster than carboxylic acids. (2) The formation of for-mamides is often observed as side reaction. The factors that affect the distribution of nitriles and formamides in products have been figured out nowadays because the mechanism has been finally established [34]. (3) Since the reaction requires acidic conditions to achieve high yields, the using of aldehydes is usually limited to aromatic aldehydes due to stability reasons. For aliphatic aldehydes, only acetaldehyde could work to give acetonitrile in the presence of aqueous sulfuric acid. (4) Hydrazoic acid, handled either as a solution or generated in situ, is publicly acknowledged to be toxic and explosive especially on large scale. 

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