C 6 H 7 0, is obtained by condensing sodium aceto-acetate with methylene iodide, the ester so formed being then hydrolysed.
This tetrahedral configuration is based on the existence of only one methylene dichloride, two being necessary if the carbon valencies were directed from the centre of a plane square to its corners, and on the existence of two optical isomers of the formula C. A.
These results show that piperonylic acid is the methylene ether of protocatechuic acid.
A larger and more important series of condensations may be grouped together as resulting from the elimination of the elements of water between carbonyl (CO) and methylene (CH 2) groups.
There are polymers which have hardly any inter-relations other than identity in composition; on the other hand, there are others which are related by the possibility of mutual transformation; examples of this kind are cyanic acid (Cnoh) and cyanuric acid (Cnoh) 3, the latter being a solid which readily transforms into the former on heating as an easily condensable vapour; the reverse transformation may also be realized; and the polymers methylene oxide (CH 2 O) and trioxymethylene (CH20)3.
Conversely, by heating protocatechuic acid with potash and methylene iodide, piperonylic acid was regained.
The true nitrile of malonic acid is methylene cyanide, CH 2 (CN) 2, which is obtained by distilling a mixture of cyanacetamide and phosphorus pentoxide.
Pyrrol is readily converted into pyridine derivatives by acting with bromoform, chloroform, or methylene iodide on its potassium salt, t3-brom-and O-chlorpyridine being obtained with the first two compounds, and pyridine itself with the last.