Performance of a Grignard Reagent

Before advancing any mechanistic interpretation, it is necessary to add some further experimental evidence  

Inconsistent results were observed with different batches of magnesium turnings. This fact speaks in favor of other metal impurities present in the magnesium metal employed and inadequate processing of propargyl halide. 

The product ratio, particularly in reference to products III, IV, and V, remained the same regardless of the quenching procedure water, 5% sulfuric acid, saturated ammonium chloride, and so on. This means that products IV and V are not the consequence of allene isomerization during work-up. Further, dienes VI and VII are apparent isomerization products of III, although without the actual control experiment at hand, this assertion cannot be proved. 

XIII with propargylic magnesium derivative XV would be a facile entry into the otherwise unexplainable IV. In addition, dienes VI and VII, which are probably not the consequence of this scheme, may result from the isomerization of in or by means of another rather obscure process not open to this writer s mind. 

this scheme can be easily restructured using free radical intermediates on the grounds that a single electron transfer occurs instead of the more familiar two-electron transfer described here. This option may also be disregarded, however, if one takes into consideration the exclusive formation of alkynes from the free radical chlorination of propyne and allene.4 

---