Dan Trombly doubts it:
While chemical weapons are horrific in effect, their lack of clear military efficacy against an opponent willing to absorb the casualties and capable of adapting their tactics does a significant part of explaining their relatively infrequent use. Against a casualty-averse opponent, such as a potential foreign intervening actor, they may be of great use, particularly if that foreign intervening state lacks the capability to escalate in response to CW use. Against a determined popular insurgency, CW use is not particularly efficacious outside specific tactical situations (such as clearing confined areas). That lack of efficacy has compounding effects. Not only does it make states less likely to employ CW, those ordered to employ CW who still fear losing are more likely to defect (particularly when combined with the issue of escalation), or else suffer at the hands of the victors.
Earlier Dish on Syria's chemical weapons here, here and here.
The Dish 