Discussion
Resol is produced by reaction of ___.
Answer: A
Resol is made from phenol with an excess of formaldehyde in presence of a base catalyst.
Under basic conditions with excess formaldehyde (typically a formaldehyde to phenol ratio above 1), phenol is methylolated at several positions, giving a low-molecular-weight resin rich in reactive methylol groups. Resols are 'one-stage' resins: on heating they cure by themselves without any added crosslinker.
Excess phenol with an acid catalyst gives novolac, a 'two-stage' resin that needs hexamethylenetetramine to cure. Excess phenol with base, or excess formaldehyde with acid, are not the standard routes to either, and an equimolar mixture at neutral pH reacts only slowly.
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