I know some journals require authors to declare conflicts of interests as a matter of policy; even if there is no CoI, a section title Conflict of Interests is still included which declares that there were no conflicts.
However, I notice that for some journals this is not the case. For example, this paper in the Journal of Organic Chemistry does not appear to have a CoI section.
Is declaration of conflicts of interest considered optional for scholarly publications? Is it possible to ascertain whether CoIs exist for a paper like this, where nothing is indicated?