What is the Cannizzaro reaction 6

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Cannizzaro Reaction: Industrial Importance

In industry, too, the crossed Cannizzaro reaction is used in combination with the Aldol reaction to produce polyhydric alcohols. This makes use of the fact that initially all hydrogen atoms in the aldehyde in the α position are replaced by aldol reactions with formaldehyde. The aldehyde function is then reduced to alcohol by an excess of formaldehyde in a cross Cannizzaro reaction.

One example is the synthesis of neopentyl glycol (2,2-dimethyl-1,3-propanediol) from isobutyraldehyde (isobutanal) and formaldehyde. In the first step, the hydrogen in the α position is split off by a base, and a formaldehyde molecule is deposited in an aldol addition.

You work with an excess of formaldehyde and then from a crossed Cannizzaro reaction you get neopentyl glycol, which is used in polyesters (for resins in aircraft or boat construction), synthetic resin paints, synthetic lubricating oils and plasticizers. The neopentyl structure provides a special light, thermal and hydrolysis stability.

The polyols pentaerythritol (2,2-bis- (hydroxymethyl) -propane-1,3-diol) and trimethylolpropane (2,2-bis (hydroxymethyl) -butan-1-ol) are produced in the same way. Of the three, pentaerythritol is the most widely produced formaldehyde derivative. It is mainly used as a raw material for the paint industry. The tetranitrate is an explosive. Some esters of pentaerythritol with higher fatty acids are used as oil additives, plasticizers and emulsifiers. Due to its inexpensive production, trimethylolpropane has led to the replacement of glycerol in many areas (e.g. in alkyd resins). Like other polyols, it is also used to make polyesters and polyurethanes.