Diazo

Diazo refers to a type of organic compound called diazo compound that has two linked nitrogen atoms (azo) as a terminal functional group. The general formula is R₂C=N₂. The simplest example of a diazo compound is diazomethane. The electronic structure of diazo compounds involves a positive charge on the central nitrogen and negative charge distributed between the terminal nitrogen and the carbon. Some of the most stable diazo compounds are α-diazo-ß-diketones and α-diazo-ß-diesters since the negative charge is delocalized into the carbonyls. In contrast, most alkyldiazo compounds are explosive. A commercially relevant diazo compound is ethyl diazoacetate (N₂CHCOOEt). A group of isomeric compounds with only few similar properties are the diazirines, where the carbon and two nitrogens are linked as a ring.

Four resonance structures can be drawn:

Diazo compounds should not be confused with azo compounds of the type R-N=N-R or with diazonium compounds of the type R-N₂⁺.

History

Diazo compounds were first produced by Peter Griess who had discovered a versatile new chemical reaction, as detailed in his "preliminary notice on the influence of nitrous acid on aminonitro- and aminodinitrophenol."

Diazo (software)

Diazo, previously named xdv, is a general-purpose, open source website theming tool. It is written in Python and generates XSLT. Diazo creates a separation between theme pages (static HTML) and transformation rules (Diazo's own domain specific language based in XML), allowing web designers to work on templates in plain HTML, without knowledge of XSLT or special template-related codes.

Diazo creates a themed site by using user-defined rules to combine vanilla content from a dynamic website together with a static HTML theme. The rules file (conventionally named rules.xml) has directives which, for example, may replace the contents of an HTML node in the theme with the contents of one in the content.

Web server support

The Diazo compiler generates XSLT, which can be deployed on any proxying web server with an XSLT processor such as Apache (using mod_transform), Varnish, or WSGI.

WSGI also has more direct Diazo support: the DiazoMiddleware filter will compile and cache Diazo themes on the fly.