Seagram Co. announced today that it will send the 28 million shares of Conoco Inc. stock it purchased in an unsuccessful attempt to win control of the oil company to E.I. du Pont de Nemours & Co., the winner of the most expensive corporate takeover battle in history.

Under the terms of the Du Pont takeover offer, Seagram will receive about 47.6 million shares of Du Pont, or about 21 percent of the merged Seagram-Conoco, for its Conoco shares. That will make Seagram the biggest shareholder in the nation's largest chemical company.

Seagram Chairman Edgar Bronfman said that although Seagram, the big Canadian distiller, would have been "delighted" to win the 51 percent of Conoco it sought, he is "pleased at the prospect" of becoming a major shareholder in the merged Conoco-Du Pont.

Wall Street sources speculate that Seagram may exchange its Du Pont stock for assets of the company, but Conoco Chairman Ralph Bailey said last week that it is "utter nonsense" to suggest that Du Pont would give up Conoco's coal company, Consolidation, to the Seagram interests. Seagram itself has given no indication whether it wants to force Du Pont to give up assets or whether Seagram will be content to be a major stockholder in Du Pont.

Mobil Corp., the third major bidder for Conoco, stumbled because investors feared the government would not approve a merger of the nation's second- and ninth-biggest oil companies.