William N. Lipscomb Jr., a Harvard chemistry professor who won a Nobel Prize in 1976 for his research on the structure of molecules and on chemical bonding, died on Thursday in Cambridge, Mass. He was 91.

His death was announced by his son, James. Dr. Lipscomb was a Cambridge resident.

A protégé of the two-time Nobel laureate Linus C. Pauling, Dr. Lipscomb was a pioneering researcher whose work on the chemical structure of boranes — compounds of boron and hydrogen — continued Dr. Pauling’s work at the California Institute of Technology in the 1940s.

In terms of practical applications, boron compounds have shown some promise in radiation therapy for treating brain tumors. But mainly the work significantly advanced basic knowledge of the way atoms bond together.

As Dr. Lipscomb said: “For me, the creative process, first of all, requires a good nine hours of sleep a night. Second, it must not be pushed by the need to produce practical applications.”

Dr. Lipscomb’s research involved developing X-ray diffraction techniques, usually used as a tool in physics, that allowed him to map the connection of the atoms in an important but puzzling group of compounds called boron hydrides. The electronic structure turned out to be not simple linear molecules but rather complex three-dimensional objects. Dr. Lipscomb was able to explain these structures for the first time.

Like Dr. Pauling, who won the Nobel in chemistry in 1954 and the Nobel Peace Prize in 1962, Dr. Lipscomb was an admired teacher at Harvard, where he was a faculty member from 1959 until his retirement in 1990. Three of his doctoral students went on to win Nobel Prizes in chemistry.

“He was always accessible; the door to his office was always open,” said Roald Hoffmann, professor emeritus of chemistry at Cornell University and one of Dr. Lipscomb’s Nobel protégés in 1981. He added, “He created a beautiful and coherent body of work on an important group of molecules that had eluded simple description.”

A man of multiple talents known for his wry sense of humor and his signature string tie, Dr. Lipscomb was a classical clarinetist who performed in chamber groups and had been principal clarinetist with the Pasadena Civic Orchestra and the Minneapolis Civic Orchestra.

He was not above dropping comical elements into his scientific publications. In one 1972 paper, he noted: “We admittedly made this observation with the benefit of hindsight. This science is known as retrospectroscopy.”

William Nunn Lipscomb Jr. was born on Dec. 9, 1919, in Cleveland. When he was a year old, his family moved to Lexington, Ky. One of his early doctoral students gave him his nickname, Colonel, for his Kentucky roots. In 1973, the Honorable Order of Kentucky Colonels made him a member.

Receiving the proverbial chemistry set as a birthday gift at age 11, Dr. Lipscomb became obsessed with science. He later recalled creating “evil smells” using hydrogen sulfide to drive his two sisters out of his room and nearly blowing up the house while concocting gunpowder for homemade fireworks.

Despite his prowess, Dr. Lipscomb told his son, James, that he received a C in high school chemistry. His grade, based on just the final exam, demanded that he memorize the first 10 elements of the periodic table, but Dr. Lipscomb could not be bothered by such mundane tasks. “I could just look it up,” he said. “So I didn’t do it.”

Dr. Lipscomb attended the University of Kentucky on a music scholarship but graduated with a degree in chemistry in 1941. He went on to work with Dr. Pauling and earned his doctorate in chemistry at Caltech in 1946. He joined Harvard after 13 years at the University of Minnesota. From 1982 to 1990 he was on the board of directors of Dow Chemical.

Besides his son, James, and a daughter, Dorothy, from his marriage to the former Mary Adele Sargent, Dr. Lipscomb is survived by his second wife, Jean Evans; their daughter, Jenna; three grandchildren; and four great-grandchildren.

In his later years, Dr. Lipscomb was a regular participant in the annual Ig Nobel Prize awards in Cambridge, sponsored by the Annals of Improbable Research. “We have a bunch of Nobel Prize winners who hand out our prizes,” said Marc Abrahams, the founder of the Ig Nobels. “Bill ended up as our grand star. He played clarinet at the beginning and end of each show, and he narrated funny videos we post on our Web site. He just had great timing.”

Dr. Lipscomb may also be the only Nobel laureate featured in a YouTube video offering instructions on how to tie a string tie.