1900	Grignard begins to use RMgX compounds to add carbons in synthesis	organic chemistry
1901	Hopkins discovers first essential amino acid: tryptophan	bio/medicinal chemistry
1902	Fischer, Hofmeister: polypeptides and proteins consist of amino acids	bio/medicinal chemistry
1903	Nernst discovers buffers	solution chemistry
1904	Abegg: rule of 8	atomic/molecular structure
1905	Hahn discovers Pb to be the ultimate product of uranium decay	nuclear chemistry
1906	Harden: enzymes catalyze fermentation	bio/medicinal chemistry
1907	Fischer synthesizes peptides& compares them to digestive products	bio/medicinal chemistry
1907	Boltwood uses U/Pb (see 1905) to date billion year rocks	nuclear chemistry
1908	Haber process of producing ammonia from air and hydrogen	industrial inorganic chemistry
1908	Baekeland invents Bakelite: first plastic	polymer chemistry
1908	Brandenburger invents cellophane	polymer chemistry
1908	Perrin calculates Avogadro's number based on Einstein's paper on Brownian motion; molecular theory becomes stronger	solution chemistry
1909	Benedictus invents safety glass	polymer chemistry
1909	Hoffamn produces synthetic rubber from butadiene	polymer chemistry
1909	Sorenson develops pH scale	solution chemistry
1910	Staudinger synthesizes isoprene	organic chemistry
1911	Rutherford proposes nuclear model of the atom	atomic/molecular structure
1911	Levene discovers ribose and RNA	bio/medicinal chemistry
1912	Von Laue begins x ray crystallography	atomic/molecular structure
1912	Hopkins discovers that vitamins are essential for health	bio/medicinal chemistry
1912	Panet and Hevesy develop radioactive tracers for molecular reactions	nuclear chemistry
1913	Bohr proposes energy levels for electrons	atomic/molecular structure
1913	William and Lawrence Bragg: Bragg's law later helps in determining molecular structure with x rays	atomic/molecular structure
1913	McCollum and Funk discover vitamins A and B (1912), respectively	bio/medicinal chemistry
1913	Soddy proposes isotope theory	nuclear chemistry
1913	Moseley shows relationship between x ray wavelength and atomic number	nuclear chemistry
1913	Bergius uses pressure and H2 to convert coal into petrol and kerosene	petrochemistry
1913	Burton: thermal cracking methods double amount of petrol from crude oil	petrochemistry
1916	Lewis: valence theory of bonding	atomic/molecular structure
1918	mass spectrometer invented by Aston: allows isotopic ions to be separated	nuclear chemistry
1919	Aston discovers that mass number is whole number sum of protons and neutrons	nuclear chemistry
1919	Using a mass spectrometer (which was a spinoff of his classic expt. that led to electron's m/e, Thomson shows that stable elements also have isotopes	nuclear chemistry
1920	McCullum discovers vitaminD; other team discovers vitamin D-sunlight connection	bio/medicinal chemistry
1921	Midgley: uses tetraethyl lead as antiknocking agent; compound is later banned fifty years later	petrochemistry
1922	Staudinger: rubber discovered to be natural polymer, a macromolecule	organic chemistry
1923	Bronsted  and Lowry independently propose acid base theory based on protons	solution chemistry
1925	Pauli: no two electrons can have identical sets of quantum numbers	atomic/molecular structure
1925	Mb and Rh are discovered by a German team	new elements
1926	First enzyme is crystallized: urease	bio/medicinal chemistry
1927	Sidgwick: modern valence theory relates valence to outershell number of electrons	atomic/molecular structure
1928	Gyorgyi isolates Vitamin C	bio/medicinal chemistry
1928	Diels and Alder introduce way of synthesizing cyclic carbon compounds from dienes	organic chemistry
1928	German and American companies invent PVC = polyvinyl chloride	polymer chemistry
1929	Fleming discovers penicillin	bio/medicinal chemistry
1929	Levene discovers deoxyribose and DNA	bio/medicinal chemistry
1929	Houdry develops catalytic method of cracking crude oil; important to plastics industry	petrochemistry
1930	Debye uses x rays to obtain interatomic distances and molecular structure	atomic/molecular structure
1930	Midgley: synthesizes the first Freon, which soon became the universal coolant in appliances but which in the 1970's was linked to ozone destruction	industrial organic chemistry
1930	Chalmers invents acrylic plastic(plexiglas)	polymer chemistry
1930	Tiselius discovers electrophoresis	solution chemistry
1931	Urey and Washburne discover deuterium from noting higher density of electrolyzed water	nuclear chemistry
1932	Krebs discovers urea cycle	bio/medicinal chemistry
1932	Domagk synthesizes the first sulfa drug	bio/medicinal chemistry
1932	Chadwick discovers the neutron	nuclear chemistry
1932	Dupont produces neoprene(polychloropene): first commercial synthetic rubber	polymer chemistry
1933	Huckel and Coulson  independently develop molecular orbital theory	atomic/molecular structure
1933	Richard Kuhnis isolates and determines  structure of ribovlavin(vitamin B2)	bio/medicinal chemistry
1933	King determines structure of vitamin C; names it ascorbic acid; Hawaorth ad Reichstein independently synthesize it	bio/medicinal chemistry
1934	Frederic and Irene Curie use alpha particle sto create first artificial radioactive isotopes	nuclear chemistry
1934	Fermi proposes ß-decay theory, coalescing previous work on neutrino. Later demonstrated that transformation occurs in almost every element subjected to neutron bombardment.	nuclear chemistry
1934	Carothers develop polyamide based nylon	polymer chemistry
1935	Stanley discovers that viruses are not organisms	bio/medicinal chemistry
1935	Kendall isolates cortisone form adrenal cortex	bio/medicinal chemistry
1935	Dempster synthesizes U235-fissionable version of uranium	nuclear chemistry
1935	Polyethylene synthesized by Michael Perrin	polymer chemistry
1936	Vitamin E is isolated by Evans. Oliver and Emerson	bio/medicinal chemistry
1936	Gamow and Teller develop theory of beta decay	nuclear chemistry
1936	Sun Oil Co, introduces catalytic cracking	petrochemistry
1937	Krebs discovers citric acid cycle	bio/medicinal chemistry
1937	Elvehjem discovers niacin (B3), which prevents pellagra	bio/medicinal chemistry
1937	Using deuterium and molybdenum Segre and Perrier create first element in lab: technetium	nuclear chemistry
1937	Dow begins production of polystyrene	polymer chemistry
1938	Plunkett discovers tetrafluoroethylene (Teflon)	polymer chemistry
1939	Pauling applies quantum mechanics to chemical bond	atomic/molecular structure
1939	Doisty find structure of Vitamin K and synthesizes it	bio/medicinal chemistry
1939	Muller synthesizes DDT	industrial organic chemistry
1939	Fluidized bed catalytic cracking of petroleum discovered by Lewis and Gilliand of M.I.T. Still used today	petrochemistry
1940	Kamen discovers carbon 14	nuclear chemistry
1940	Dunning used diffusion to isolate U-235 fluorides of uranium	nuclear chemistry
1941	Lepmann discovers coenzyme A; shows that it is involved in the acetylation of choline, in   synthesis of citrate and acetoacetate, and in pyruvate and fatty acid metabolism.	bio/medicinal chemistry
1943	Silicone rubber is developed	polymer chemistry
1944	Avery, Macleod and McCarthy demonstrate role of DNA in inheritance	bio/medicinal chemistry
1944	Woodward and Doering synthesize quinine	organic chemistry
1946	Carbon 13 is discovered and used to treat metabolic diseases	bio/medicinal chemistry
1946	Purcell and Bloch independently develop nmr, an important analytical tool in organic chemistry	organic chemistry
1947	Todd synthesizes ATP	bio/medicinal chemistry
1947	Libby develops carbon 14 dating	nuclear chemistry
1948	Feynman, Schwinger and Tomonoga independently develop quantum electrodynamics	nuclear chemistry
1948	Aldrich and Nier establish basis for potassium argon dating	nuclear chemistry
1949	Hodgkin uses x ray crystallography to determine structure of penicillin	atomic/molecular structure
1951	Pauling and Corey determine structure of spiral proteins	bio/medicinal chemistry
1951	Woodward synthesizes cortisone	organic chemistry
1952	Franklin discovers  sugar-phosphate backbone of DNA lies on the outside of the molecule. She discovers the helical structure of DNA has two strands.	bio/medicinal chemistry
1953	Watson and Crick elucidate rest of structure of salt of DNA molecule and suggest method of replication	bio/medicinal chemistry
1954	Wittig:used phosphorus ylides to create alkenes from carbonyl containing compounds	organic chemistry
1954	Woodward synthesizes lysergic acid and highly complex strychnine	organic chemistry
1954	Natta: obtains polypropylene using stereospecific catalysts	polymer chemistry
1955	Hodgkin determines structure of vitamin B12 using xray crystallography	bio/medicinal chemistry
1956	Kornberg synthesizes DNA and discovers that bacteria use DNA polymerase	bio/medicinal chemistry
1957	Brown synthesizes organoboranes which are used to create organic acids and ketones	organic chemistry
1959	Peruts determines structure of hemoglobin	bio/medicinal chemistry
1960	Woodward an Strell independently synthesize chlorophyll	organic chemistry
1961	Crick and Brenner realize that DNA base triplets code for amino acids	bio/medicinal chemistry
1961	Jacob and Monot discover messenger RNA, the molecule that transfers genetic information form DNA to the site of protein synthesis	bio/medicinal chemistry
1967	Pederson discovers Crown ethers	organic chemistry
1968	DENDRAl computer system for identifying compounds from mass spectra	organic chemistry
1969	Hodgkin finds the structure of insulin, allowing it to be synthesized in the laboratory	bio/medicinal chemistry
1971	Woodward synthesizes vitamin B12; work led to symmetry theory for pericyclic reactions involving cyclic transition state	organic chemistry
1973	Cohen and Boyer develop recombinant DNA technique and move snippets of DNA across species	bio/medicinal chemistry
1974	Molin, Rowland and Crutzen warn public about dangers of CFC's	environmental chemistry
1977	Sanger sequences entire DNA of virus phiX174 using gel electrophoresis	bio/medicinal chemistry
1981	Michel and Reveau prepare superconducting mixture that works at relatively high temperatures	materials chemistry
1985	Kroto, Curl and Smalley discover fullerenes	organic chemistry