a
The pentaerythritol is typically produced cia a base - catalyed reaction of acetaldehyde with excess formaldehyde. the aldol condenstion of three moles of formaldehyde with one mole of acetaldehyde is folloed by a crossed cannizzaro reaction between pentaerythritol product and sodium formate as a byproduct. These reaction are shown below

\(\mathop {C{H_3}CHO\, + \,3HCHO\, \to \,}\limits_{(three\,aldol\,condensation)} C{(C{H_2}OH)_3}CHO\)

\(C{(C{H_2}OH)_3}CHO\, + \,HCHO\, + \,NaOH\) \(\mathop { \to \,C{{(C{H_2}OH)}_4}\, + \,HCOONa}\limits_{(Cannizaro's\,\,reaction)} \)