fire. The suffix idine was added in compliance with the chemical nomenclature, as in toluidine, to indicate a cyclic compound containing a nitrogen atom. The chemical structure of pyridine was determined decades after its discovery. Wilhelm Körner (1869) and James Dewar (1871) suggested that, in analogy between quinoline and naphthalene, the structure of pyridine is derived from benzene by substituting one C–H unit with a nitrogen atom.<ref>{{cite book|author-link=Albert Ladenburg |last=Ladenburg |first=Albert |url=http://www.sciencemadness.org/library/books/lectures_on_the_history_of_the_development_of_chemistry.pdf |title=Lectures on the history of the development of chemistry since the time of Lavoisier. |pages=283–287}} </ref> The suggestion by Körner and Dewar was later confirmed in an experiment where pyridine was reduced to piperidine with sodium in ethanol. In 1876, William Ramsay combined acetylene and hydrogen cyanide into pyridine in a red-hot iron-tube furnace. This was the first synthesis of a heteroaromatic compound. The first major synthesis of pyridine derivatives was described in 1881 by Arthur Rudolf Hantzsch. The Hantzsch pyridine synthesis typically uses a 2:1:1 mixture of a β-keto acid (often acetoacetate), an aldehyde (often formaldehyde), and ammonia or its salt as the nitrogen donor. First, a double hydrogenated pyridine is obtained, which is then oxidized to the corresponding pyridine derivative. Emil Knoevenagel showed that asymmetrically substituted pyridine derivatives can be produced with this process. The contemporary methods of pyridine production had a low yield, and the increasing demand for the new compound urged to search for more efficient routes. A breakthrough came in 1924 when the Russian chemist Aleksei Chichibabin invented a pyridine synthesis reaction, which was based on inexpensive reagents. This method is still used for the industrial production of pyridine. Occurrence Pyridine is not abundant in nature, except for the leaves and roots of belladonna (Atropa belladonna) and in marshmallow (Althaea officinalis). Pyridine derivatives, however, are often part of biomolecules such as alkaloids. In daily life, trace amounts of pyridine are components of the volatile organic compounds that are produced in roasting and canning processes, e.g. in fried chicken, sukiyaki, roasted coffee, potato chips, and fried bacon. Traces of pyridine can be found in Beaufort cheese, vaginal secretions, black tea, saliva of those suffering from gingivitis, and sunflower honey. Production Historically, pyridine was extracted from coal tar or obtained as a byproduct of coal gasification. The process is labor-consuming and inefficient: coal tar contains only about 0.1% pyridine, and therefore a multi-stage purification was required, which further reduced the output. Nowadays, most pyridines are