"Lavoisier and his Wife," a neoclassical portrait by 18th-century French master Jacques-Louis David, has been given "anonymously" to the Metropolitan Museum of Art. Sources, who yesterday identified the donors as Charles and Jayne Wrightsman, said the couple paid approximately $6 million when they bought the picture recently from New York's Rockefeller University.

The auction record for a painting was set by a Velazquez portrait which was purchased, for $5,544,000, by the Metropolitan in November 1970.

Spokesmen for both the museum and the research university yesterday acknowledged the transaction but they would not name the buyers, nor would they discuss the price.

"I'd rather not talk about the painting," said Charles Wrightsman yesterday from Palm Beach, Fla. "The museum will make an announcement soon."

The Wrightsmans, whose money comes from Texas oil, are Metropolitan trustees. "If one excludes the Norton Simon collection, which is no longer privately owned, and the Paul Mellon collection, which is unique," observes John Walker, former director of the National Gallery of Art, "then Charles and Jayne Wrightsman possess the most important provate collection left in this county."

The man in the David portrait is Antoine-Laurent Lavoisier, "the father of modern chemistry," who named oxygen, discovered the composition of water, and was guillotined in 1794. The woman, "depicted as a kind of muse inspiring her husband," is Anne-Pierrette Paulze (1756-1836), who once painted Benjamin Franklin's portrait. The armchair at the left supports a portfolio of her [TEXT ILLEGIBLE] acquired it about 1922," said university vice president Rodney Nichols. "Mr. Rockefeller bought the picture two or three years earlier. He thought we'd like it. It is one of the few major pictures by a major artist with a major scientist as its subject."

Sources say the David has been on the market for some time. "A few years ago they were asking $4 million," says one source. "The price has since inflated as, of course, prices will."