Organic Chemistry I For Dummies, 2nd Edition (2014)

IN THIS PART …

Get acquainted with ten great organic chemists.

Find out about ten cool organic discoveries and the role of serendipity in the discovery process.

See ten interesting organic molecules.

IN THIS CHAPTER

Introducing pioneers in the field of organic chemistry

Finding out about discoveries that transformed organic chemistry

This chapter presents the work of ten (or so) of the great organic chemists from the past. The work of these chemists reflects the diversity of organic chemistry. Some of these folks pioneered the ideas that laid the foundation of organic chemistry as a modern science, while others made more recent contributions. In all cases, the work of these great chemists made a significant, lasting impact on the field and is worthy of admiration.

August Kekulé

By some accounts, August Kekulé (1829–1866) was a bore as a lecturer and a klutz in the lab, but his ideas on the nature of organic compounds were extremely influential (and, more important, correct). He proposed, correctly, that carbon could make four bonds to other atoms, and could form complicated structures by combining with other carbon atoms to make chains and rings. Kekulé also proposed the correct structure for benzene, C₆H₆, and notoriously bragged years after the fact that his inspiration for the cyclic structure of benzene came from a dream he had of a snake biting its tail, a claim as suspect as it is entertaining.

Friedrich Wöhler

Friedrich Wöhler (1800–1882) helped lay the foundation for modern organic chemistry by unseating the established theory of vitalism, the theory that organic molecules contained a vital life force not present in inorganic compounds. By synthesizing the organic molecule urea from inorganic ammonium cyanate, Wöhler helped deal a blow to this notion.

Archibald Scott Couper

Couper (1831–1892) was a pioneer in proposing the structure of organic molecules and in showing how bonding worked. He suggested the tetravalency of carbon before Kekulé did, but his PhD advisor (Wurtz) held back this paper due to how forcefully the paper rejected the current theories, and Kekulé published his paper first. Couper, outraged that his advisor had sat on his paper and led to his ideas being scooped, confronted him angrily. Wurtz did not take this well and kicked him out of his lab. After this event, Couper suffered a nervous breakdown, became mentally ill, and spent the remainder of his life living in his mother’s attic.

Johan Josef Loschmidt

Loschmidt (1821–1895) is one of those often-forgotten pioneers of chemistry. In 1861, he published a pamphlet, Chemische Studien, that provided the two-dimensional structural representations of hundreds of organic molecules. His accomplishment was remarkable because this was done at a time when the idea of a molecular structure (rather than simply a molecular formula) was still a novel idea. Looking back at his pamphlet with the knowledge of today shows how truly remarkable his ideas were, since so many of his structural guesses were accurate. Some people even give him credit for coming up with the cyclical structure of benzene before Kekulé did, because he used a circle to represent the benzene.

Louis Pasteur

Louis Pasteur (1822–1895) discovered the handedness of organic molecules — the fact that molecules can have the same atomic connectivity but different orientations of those atoms in space. Pasteur made this discovery by observing that tartaric acid formed into two distinct types of crystals. He then separated the two types of crystals with tweezers under a microscope and noticed that plane-polarized light (light that oscillates in a single direction) rotated in one direction when it passed through one type of crystal, and in the opposite direction when it passed through the other type of crystal. With these observations, he speculated that this difference in crystal shape and light rotation must relate to different orientations of the atoms in the two crystals. He was right, and the foundation for our current understanding of stereochemistry was laid.

Emil Fischer

Fischer (1852–1919) was one of the pioneers in organic chemistry. After being told by his father that he was too stupid to be a businessman, he attended the University of Bonn and studied science. After receiving his doctorate, he worked at the University of Munich. Fischer worked on synthesizing and determining the structures of sugars, and discovered the d/l stereochemistry of sugars. He then made significant advances in the understanding of purine nucleotides (adenine and guanine, two of the DNA bases, are purine nucleotides). Although the beginning of his career was marked by creative genius, his life ended in tragedy. He suffered from the side effects of the toxic mercury compounds he worked with in the laboratory, and when his wife died, and shortly thereafter two of his three sons were killed in World War I, he committed suicide. Though his life ended in tragedy, his accomplishments in organic chemistry are considered some of the finest by an organic chemist.

Percy Julian

Percy Julian (1899–1975) was a pioneer in the chemistry of steroids, which are complicated ring-containing molecules that make up the backbone of important biomolecules like cholesterol and sex hormones (testosterone, estrogen, and so on). He figured out ways to synthesize these complicated organic molecules on a large enough scale to make possible the treatment of hormone deficiencies, and started a company for the production of these steroids. He was one of the first African Americans to be awarded a doctorate degree and, in 1973, became the first African-American chemist to be admitted into the National Academy of Sciences.

Robert Burns Woodward

Many claim that Woodward (1917–1979) was the greatest of all organic chemists — and certainly, a case can be made for that claim. Prominent among his many accomplishments were his syntheses of astoundingly complex organic molecules such as vitamin B₁₂ (in collaboration with Albert Eschenmoser), strychnine, and quinine. These syntheses are particularly magnificent considering that they were performed at a time when spectroscopy and structure determination were a shadow of what they are today. (In fact, Woodward pioneered several spectroscopic techniques for structure elucidation.) Along with Roald Hoffman, Woodward solved the puzzle of why pericyclic reactions (like the Diels–Alder reaction; see Chapter 14) occur in the manner they do; he did so by using arguments about orbital symmetry, a formulation now called the Woodward–Hoffman rules (which you may learn about if you take the second semester of organic chemistry). He won the Nobel Prize in chemistry in 1965 “for his outstanding achievements in the art of organic synthesis” and would have undoubtedly won the prize again along with Roald Hoffman for the Woodward–Hoffman rules had he not died two years earlier. (Nobel Prizes are not awarded posthumously.)

Linus Pauling

Linus Pauling (1901–1994) used quantum mechanics to describe the nature of chemical bonds and how atoms come together to form molecules. His book, The Nature of the Chemical Bond, is considered a classic in the field. After his theoretical work on chemical bonding, Pauling pioneered the field of chemical biology and elucidated the structures of proteins.

Pauling was an unusual person. He advocated taking massive daily doses of vitamin C, and he was so vocal against government policies that he was denied visas to attend major international science conferences. Some people have suggested that had he attended a conference in which Rosalind Franklin presented her X-ray structures of DNA, with his understanding of helices from his work on proteins, he may have elucidated the structure of DNA before Watson and Crick (who attended the conference). Pauling is the only person to win two unshared Nobel Prizes — one in chemistry, for his insights into the nature of the chemical bond, and the other in peace, for his uncompromising stand against nuclear testing and proliferation. Pauling died in 1994 at the age of 93.

Dorothy Hodgkin

Dorothy Hodgkin (1910–1994) became involved in structure determination using a technique called X-ray crystallography. Although she suffered from severe health problems, including crippling arthritis, she was extremely persistent and hard working, and determined the structures of many important molecules using X-ray crystallography, including the structure of penicillin and, later, the structure of vitamin B₁₂. She won the Nobel Prize in chemistry in 1964 for her work.

John Pople

John Pople (1925–2004) made practical the use of computational techniques. He took theoretical chemistry out of the ivory tower and placed it into the hands of practical wet chemists. He made theoretical calculations available to even the novice chemists, whereas before they had only been available to the hard-core theoreticians with degrees in mathematics. He was the pioneer of the computational program Gaussian, a user-friendly computer software program designed to carry out these molecular calculations. He shared the Nobel Prize in chemistry for his development of computational methods. He died in 2004, after a career that spanned almost an entire century.