Assertion: acetaldehyde | /r/CapableOf | serve as precursor
Facets:
value: mainly
type: DEGREE
value: to acetic acid
type: TRANSITIVE-OBJECT
Source sentences:
text: Acetaldehyde once was a dominating product, but production levels have declined to less than 1000000 tons per year because it mainly served as a precursor to acetic acid, which is now prepared by carbonylation of methanol.