Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Syringaldehyde is a naturally occurring aromatic aldehyde soluble in alcohol. Some species of insects use syringaldehyde in their chemical communication systems. Refractive index of syringaldehyde is 1.53. Syringaldehyde can be found naturally in the wood of Spruce and Maple trees. The Duff reaction or hexamine aromatic formylation is a formylation reaction used in organic chemistry for the synthesis of benzaldehydes with hexamine as the formyl carbon source.