A former Mobil Oil Corp. consultant was sentenced in federal court here today to six months imprisonment and a $5,000 fine after his conviction in what prosecutors called a scheme to trade insider information on a multimillion-dollar Defense Department computer software contract in exchange for $670,000 in bribes.

A. Walton Hill, 38, of New York, the alleged bagman in the bribery-conspiracy case, was directed by U.S. District Court Judge John R. Hargrove Sr. to spend the six months in a work-release halfway house in New York.

Codefendant Edward D. Thomas, 48, a $50,000-a-year civilian Pentagon official accused of leaking the insider information to Hill, pleaded guilty to bribery last June and was sentenced to 18 months in prison by Hargrove in July.

Hargrove gave Hill a lighter sentence today after hearing arguments from prosecutor Steven A. Allen that Hill was "not as culpable as Thomas," but rejected Allen's recommendation that Hill go to prison for up to 15 months.

During a four-day trial last June, Allen contended Hill, a $46,000-a-year training consultant for Mobil's overseas operations, and Thomas sought up to $670,000 in bribes from the Boston-based Intersystems software firm in exchange for information to help the firm get all or part of a $44.5 million contract for a computerized health care system planned by the Defense Department's Tri-Service Medical Information Systems office (TRIMIS).

Intersystems officials notified the FBI of the alleged bribe attempt. The FBI in turn assigned an undercover agent to pose as an Intersystems representative to complete arrangements for an inital payoff of $50,000 in exchange for preliminary contract information. Hill and Thomas were arrested in Bethesda last February during a rendevous with the agent.