Allan J. Bloostein, president and chief executive officer of Hecht's, yesterday was named vice chairman of the St. Louis-based May Department Store Companies, effective July 1.Bloostein also was nominated to the board of directors of May, parent company of Hecht's and the nation's second-largest department store firm.

No successor here has been selected, Bloostein said in an interview yesterday. With 20 big stores in the combined Washington-Baltimore market (fourth largest in the U.S.), Hecht's is the largest regional department store retailer and second in general merchandise sales only to Sears, Roebuck & Co.

Bloostein will be based in New York and will have responsibilities for six May companies -- Hecht's, The May Co. of Cleveland, M. O'Neil Co. of Akron, Strouss of Youngstown, G. Fox & Co. of Hartford, and May-Cohens of Florida.

May Department Store Cos. president and chief executive officer David Farrell said that creation of the position of vice chairman and Bloostein's appointment "is another step in our continuing effort to strengthen our senior management for the challenge of the 1980s."

During the 1970s, with Bloostein at the helm, Hecht's adopted an aggressive marketing approach to attract the growing market of younger and more affluent Washington area consumers. Stores were redesigned and given a more modern, sophisticated look, and an advertising campaign was launched to emphasize the "excitement" of shopping at Hecht's.

Bloostein also was responsible for bringing together the Washington and Baltimore divisions under a single management.

Bloostein came to Hecht's (then the Hecht Co. ) in 1970 and was appointed a vice president of the May Department Store Co. the same year.He has been in retailing since 1953. In 1965, at the age of 35, he became president of Stern Brothers Department Store in New York City. He was named president and chief executive officer of the Hecht Co., Washington-Baltimore in 1973.

Hecht's is opening a new store in Fairoaks in Fairfax and another one next year in Laurel.

"Being the largest department store group in the Washington-Baltimore market, we think, requires more units and we're doing the research and follow-up to make sure we're adequately represented," Bloostein said.