Salicylaldehyde is a derivative of benzene used in chelation chemistry to create metal chelates, which are used in fertilizers. It can also be chemically modified for specific purposes, such as reducing heart disease. Salicylaldehyde is also used in condensation reactions to create more complex species.
Salicylaldehyde (HO-C6H4-CHO) is the common name of 2-hydroxybenzaldehyde, an oily organic liquid that smells like buckwheat. It is a simple derivative of the hexagonal ring compound benzene (C6H6). One of the hydrogen atoms of benzene is replaced by an aldehyde group (-CHO). A hydroxyl group (-OH) replaces another hydrogen atom attached to an adjacent carbon. Thanks in part to these reactive side groups and their “one-two” position on the benzene ring, salicylaldehyde is a powerful tool in chelation chemistry and ring-generating condensation chemistry.
Salicylaldehyde’s most important use involves chelates, molecules that act, as the name suggests, like crab claws. One or more aldehyde molecules or derivatives attach to a target metal atom through coordination bonding, which occurs when both electrons are provided by only one atom. For salicylaldehyde copper chelate, the four oxygen atoms of the two aldehyde molecules symmetrically surround, then attach to, a lone copper atom. Metal chelates, partly due to their stability in adverse environments, are used in fertilizers.
In some cases, the chelate itself is not what is desired commercially. Rather, it is the ability to form chelates at the point of use that is valuable. When this is the situation, salicylaldehyde is almost always chemically modified before use. It forms a particular derivative and is designed to be applicable in a very specific situation. One example is salicylaldehyde isonicotinoyl hydrazone, which has been shown to reduce dangerous levels in a non-rare heart disease called catecholamine cardiotoxicity.
Another chelating use of aldehyde involves reacting it first with hydroxylamine to form salicyladoxime. This aldehyde oxime is practical to the analytical chemist because it generates bright and distinct colors in the presence of transition metal ions. Transition metals are those metals whose d-subshell electron orbital is incomplete and include metals such as nickel, iron, chromium, copper and cobalt. Insoluble transition metal complexes are formed which are then collected, dried and quantified using appropriate laboratory procedures. A similar titration procedure uses phenylhydrazone to quantify organometallic reagents.
Other important organic syntheses unrelated to chelates using salicylaldehyde include condensation reactions. Condensation reactions combine two or more molecules to form larger, more complex species. An example is the reaction of aldehyde with ethyl malonate in the presence of other minor reactants to form the aldol condensation product 3-carbethoxycoumarin, a two ring structure. Not all reactions using salicylaldehyde create more complex species; some, such as the oxidation to catechol, are simple conversion reactions.
Protect your devices with Threat Protection by NordVPN
