List of Nobel laureates in Chemistry

The Nobel Prize in Chemistry (Swedish: Nobelpriset i kemi) is awarded annually by the Royal Swedish Academy of Sciences to scientists in the various fields of chemistry. It is one of the five Nobel Prizes established by the 1895 will of Alfred Nobel, who died in 1896. These prizes are awarded for outstanding contributions in chemistry, physics, literature, peace, and physiology or medicine.^[1] As dictated by Nobel's will, the award is administered by the Nobel Foundation and awarded by the Royal Swedish Academy of Sciences.^[2] The first Nobel Prize in Chemistry was awarded in 1901 to Jacobus Henricus van 't Hoff, of the Netherlands. Each recipient receives a medal, a diploma and a monetary award prize that has varied throughout the years.^[3] In 1901, van 't Hoff received 150,782 SEK, which is equal to 7,731,004 SEK in December 2007. The award is presented in Stockholm at an annual ceremony on 10 December, the anniversary of Nobel's death.^[4]

The Nobel Prize in Chemistry was established in the 1895 will of Swedish chemist Alfred Bernhard Nobel.

At least 25 laureates have received the Nobel Prize for contributions in the field of organic chemistry, more than any other field of chemistry.^[5] Two Nobel Prize laureates in Chemistry, Germans Richard Kuhn (1938) and Adolf Butenandt (1939), were not allowed by their government to accept the prize. They would later receive a medal and diploma, but not the money. Frederick Sanger is one out of three laureates to be awarded the Nobel Prize twice in the same subject, in 1958 and 1980. John Bardeen, who was awarded the Nobel Prize in Physics in 1956 and 1972, and Karl Barry Sharpless, who won the Nobel Prize for Chemistry in 2001 and 2022, are the others. Two others have won Nobel Prizes twice, one in chemistry and one in another subject: Maria Skłodowska-Curie (physics in 1903, chemistry in 1911) and Linus Pauling (chemistry in 1954, peace in 1962).^[6] As of 2023, the prize has been awarded to 192 individuals, including eight women (Maria Skłodowska-Curie being the first to be awarded in 1911).^[7]

There have been eight years for which the Nobel Prize in Chemistry was not awarded (1916, 1917, 1919, 1924, 1933, 1940–42). There were also nine years for which the Nobel Prize in Chemistry was delayed for one year. The Prize was not awarded in 1914, as the Nobel Committee for Chemistry decided that none of that year's nominations met the necessary criteria, but was awarded to Theodore William Richards in 1915 and counted as the 1914 prize.^[8] This precedent was followed for the 1918 prize awarded to Fritz Haber in 1919,^[9] the 1920 prize awarded to Walther Nernst in 1921,^[10] the 1921 prize awarded to Frederick Soddy in 1922,^[11] the 1925 prize awarded to Richard Zsigmondy in 1926,^[12] the 1927 prize awarded to Heinrich Otto Wieland in 1928,^[13] the 1938 prize awarded to Richard Kuhn in 1939,^[14] the 1943 prize awarded to George de Hevesy in 1944,^[15] and the 1944 prize awarded to Otto Hahn in 1945.^[16]

In 2020, Ioannidis et al. reported that half of the Nobel Prizes for science awarded between 1995 and 2017 were clustered in just a few disciplines within their broader fields. Atomic physics, particle physics, cell biology, and neuroscience dominated the two subjects outside chemistry, while molecular chemistry was the chief prize-winning discipline in its domain. Molecular chemists won 5.3% of all science Nobel Prizes during this period.^[17]

Laureates

• 1901
• 1910
• 1920
• 1930
• 1940
• 1950
• 1960
• 1970
• 1980
• 1990
• 2000
• 2010
• 2020

Year	Image	Laureate[A]	Nationality[B]	Rationale[C]	Ref
1901		Jacobus Henricus van 't Hoff (1852–1911)	Dutch	"[for his] discovery of the laws of chemical dynamics and osmotic pressure in solutions"	[18]
1902		Hermann Emil Fischer (1852–1919)	German	"[for] his work on sugar and purine syntheses"	[19]
1903		Svante August Arrhenius (1859–1927)	Swedish	"[for] his electrolytic theory of dissociation"	[20]
1904		Sir William Ramsay (1852–1916)	British	"[for his] discovery of the inert gaseous elements in air, and his determination of their place in the periodic system"	[21]
1905		Adolf von Baeyer (1835–1917)	German	"[for] the advancement of organic chemistry and the chemical industry, through his work on organic dyes and hydroaromatic compounds"	[22]
1906		Henri Moissan (1852–1907)	French	"[for his] investigation and isolation of the element fluorine, and for [the] electric furnace called after him"	[23]
1907		Eduard Buchner (1860–1917)	German	"for his biochemical researches and his discovery of cell-free fermentation"	[24]
1908		Ernest Rutherford (1871–1937)	New Zealander	"for his investigations into the disintegration of the elements, and the chemistry of radioactive substances"	[25]
1909		Wilhelm Ostwald (1853–1932)	German	"[for] his work on catalysis and for his investigations into the fundamental principles governing chemical equilibria and rates of reaction"	[26]
1910		Otto Wallach (1847–1931)	German	"[for] his services to organic chemistry and the chemical industry by his pioneer work in the field of alicyclic compounds"	[27]
1911		Marie Curie, née Skłodowska (1867–1934)	Polish French	"[for] the discovery of the elements radium and polonium, by the isolation of radium and the study of the nature and compounds of this remarkable element"	[28]
1912		Victor Grignard (1871–1935)	French	"for the discovery of the [...] Grignard reagent"	[29]
		Paul Sabatier (1854–1941)		"for his method of hydrogenating organic compounds in the presence of finely disintegrated metals"	[29]
1913		Alfred Werner (1866–1919)	Swiss	"[for] his work on the linkage of atoms in molecules [...] especially in inorganic chemistry"	[30]
1914		Theodore William Richards (1868–1928)	American	"[for] his accurate determinations of the atomic weight of a large number of chemical elements"	[8]
1915		Richard Martin Willstätter (1872–1942)	German	"for his researches on plant pigments, especially chlorophyll"	[31]
1916	Not awarded
1917
1918		Fritz Haber (1868–1934)	German	"for the synthesis of ammonia from its elements"	[9]
1919	Not awarded
1920		Walther Hermann Nernst (1864–1941)	German	"[for] his work in thermochemistry"	[10]
1921		Frederick Soddy (1877–1956)	British	"for his contributions to our knowledge of the chemistry of radioactive substances, and his investigations into the origin and nature of isotopes"	[11]
1922		Francis William Aston (1877–1945)	British	"for his discovery, by means of his mass spectrograph, of isotopes, in a large number of non-radioactive elements, and for his enunciation of the whole-number rule"	[32]
1923		Fritz Pregl (1869–1930)	Yugoslavian Austrian	"for his invention of the method of micro-analysis of organic substances"	[33]
1924	Not awarded
1925		Richard Adolf Zsigmondy (1865–1929)	Austrian	"for his demonstration of the heterogeneous nature of colloid solutions and for the methods he used"	[12]
1926		The (Theodor) Svedberg (1884–1971)	Swedish	"for his work on disperse systems"	[34]
1927		Heinrich Otto Wieland (1877–1957)	German	"for his investigations of the constitution of the bile acids and related substances"	[13]
1928		Adolf Otto Reinhold Windaus (1876–1959)	German	"[for] his research into the constitution of the sterols and their connection with the vitamins"	[35]
1929		Arthur Harden (1865–1940)	British	"for their investigations on the fermentation of sugar and fermentative enzymes"	[36]
		Hans Karl August Simon von Euler-Chelpin (1873–1964)	German Swedish
1930		Hans Fischer (1881–1945)	German	"for his researches into the constitution of haemin and chlorophyll and especially for his synthesis of haemin"	[37]
1931		Carl Bosch (1874–1940)	German	"[for] their contributions to the invention and development of chemical high pressure methods"	[38]
		Friedrich Bergius (1884–1949)
1932		Irving Langmuir (1881–1957)	American	"for his discoveries and investigations in surface chemistry"	[39]
1933	Not awarded
1934		Harold Clayton Urey (1893–1981)	American	"for his discovery of heavy hydrogen"	[40]
1935		Frédéric Joliot (1900–1958)	French	"[for] their synthesis of new radioactive elements"	[41]
		Irène Joliot-Curie (1897–1956)
1936		Peter Debye (1884–1966)	Dutch	"[for his work on] molecular structure through his investigations on dipole moments and the diffraction of X-rays and electrons in gases"	[42]
1937		Walter Norman Haworth (1883–1950)	British	"for his investigations on carbohydrates and vitamin C"	[43]
		Paul Karrer (1889–1971)	Swiss	"for his investigations on carotenoids, flavins and vitamins A and B2"
1938		Richard Kuhn (1900–1967)	German	"for his work on carotenoids and vitamins"	[14]
1939		Adolf Friedrich Johann Butenandt (1903–1995)	German	"for his work on sex hormones"	[44]
		Leopold Ružička (1887–1976)	Yugoslavian Swiss	"for his work on polymethylenes and higher terpenes"	[44]
1940	Not awarded
1941
1942
1943		George de Hevesy (1885–1966)	Hungarian	"for his work on the use of isotopes as tracers in the study of chemical processes"	[15]
1944		Otto Hahn (1879–1968)	German	"for his discovery of the fission of heavy nuclei"	[16]
1945		Artturi Ilmari Virtanen (1895–1973)	Finnish	"for his research and inventions in agricultural and nutrition chemistry, especially for his fodder preservation method"	[45]
1946		James Batcheller Sumner (1887–1955)	American	"for his discovery that enzymes can be crystallized"	[46]
		John Howard Northrop (1891–1987)		"for their preparation of enzymes and virus proteins in a pure form"	[46]
		Wendell Meredith Stanley (1904–1971)
1947		Sir Robert Robinson (1886–1975)	British	"for his investigations on plant products of biological importance, especially the alkaloids"	[47]
1948		Arne Wilhelm Kaurin Tiselius (1902–1971)	Swedish	"for his research on electrophoresis and adsorption analysis, especially for his discoveries concerning the complex nature of the serum proteins"	[48]
1949		William Francis Giauque (1895–1982)	Canadian American	"for his contributions in the field of chemical thermodynamics, particularly concerning the behaviour of substances at extremely low temperatures"	[49]
1950		Otto Paul Hermann Diels (1876–1954)	West German	"for their discovery and development of the diene synthesis"	[50]
		Kurt Alder (1902–1958)
1951		Edwin Mattison McMillan (1907–1991)	American	"for their discoveries in the chemistry of transuranium elements"	[51]
		Glenn Theodore Seaborg (1912–1999)
1952		Archer John Porter Martin (1910–2002)	British	"for their invention of partition chromatography"	[52]
		Richard Laurence Millington Synge (1914–1994)
1953		Hermann Staudinger (1881–1965)	West German	"for his discoveries in the field of macromolecular chemistry"	[53]
1954		Linus Pauling (1901–1994)	American	"for his research into the nature of the chemical bond and its application to the elucidation of the structure of complex substances"	[54]
1955		Vincent du Vigneaud (1901–1978)	American	"for his work on biochemically important sulphur compounds, especially for the first synthesis of a polypeptide hormone"	[55]
1956		Sir Cyril Norman Hinshelwood (1897–1967)	British	"for their researches into the mechanism of chemical reactions"	[56]
		Nikolay Nikolaevich Semenov (1896–1986)	Soviet
1957		Lord (Alexander R.) Todd (1907–1997)	British	"for his work on nucleotides and nucleotide co-enzymes"	[57]
1958		Frederick Sanger (1918–2013)	British	"for his work on the structure of proteins, especially that of insulin"	[58]
1959		Jaroslav Heyrovský (1890–1967)	Czechoslovakian	"for his discovery and development of the polarographic methods of analysis"	[59]
1960		Willard Frank Libby (1908–1980)	American	"for his method to use carbon-14 for age determination in archaeology, geology, geophysics, and other branches of science"	[60]
1961		Melvin Calvin (1911–1997)	American	"for his research on the carbon dioxide assimilation in plants"	[61]
1962		Max Ferdinand Perutz (1914–2002)	Austrian British	"for their studies of the structures of globular proteins"	[62]
		John Cowdery Kendrew (1917–1997)	British
1963		Karl Ziegler (1898–1973)	West German	"for their discoveries in the field of the chemistry and technology of high polymers"	[63]
		Giulio Natta (1903–1979)	Italian
1964		Dorothy Crowfoot Hodgkin (1910–1994)	British	"for her determinations by X-ray techniques of the structures of important biochemical substances"	[64]
1965		Robert Burns Woodward (1917–1979)	American	"for his outstanding achievements in the art of organic synthesis"	[65]
1966		Robert S. Mulliken (1896–1986)	American	"for his fundamental work concerning chemical bonds and the electronic structure of molecules by the molecular orbital method"	[66]
1967		Manfred Eigen (1927–2019)	West German	"for their studies of extremely fast chemical reactions, effected by disturbing the equilibrium by means of very short pulses of energy"	[67]
		Ronald George Wreyford Norrish (1897–1978)	British
		George Porter (1920–2002)
1968		Lars Onsager (1903–1976)	Norwegian American	"for the discovery of the reciprocal relations bearing his name, which are fundamental for the thermodynamics of irreversible processes"	[68]
1969		Derek H. R. Barton (1918–1998)	British	"for their contributions to the development of the concept of conformation and its application in chemistry"	[69]
		Odd Hassel (1897–1981)	Norwegian
1970		Luis F. Leloir (1906–1987)	Argentine	"for his discovery of sugar nucleotides and their role in the biosynthesis of carbohydrates"	[70]
1971		Gerhard Herzberg (1904–1999)	West German Canadian	"for his contributions to the knowledge of electronic structure and geometry of molecules, particularly free radicals"	[71]
1972		Christian B. Anfinsen (1916–1995)	American	"for his work on ribonuclease, especially concerning the connection between the amino acid sequence and the biologically active conformation"	[72]
		Stanford Moore (1913–1982)		"for their contribution to the understanding of the connection between chemical structure and catalytic activity of the active centre of the ribonuclease molecule"	[72]
		William H. Stein (1911–1980)
1973		Ernst Otto Fischer (1918–2007)	West German	"for their pioneering work, performed independently, on the chemistry of the organometallic, so called sandwich compounds"	[73]
		Geoffrey Wilkinson (1921–1996)	British
1974		Paul J. Flory (1910–1985)	American	"for his fundamental work, both theoretical and experimental, in the physical chemistry of macromolecules"	[74]
1975		John Warcup Cornforth (1917–2013)	Australian British	"for his work on the stereochemistry of enzyme-catalyzed reactions"	[75]
		Vladimir Prelog (1906–1998)	Yugoslavian Swiss	"for his research into the stereochemistry of organic molecules and reactions"	[75]
1976		William N. Lipscomb (1919–2011)	American	"for his studies on the structure of boranes illuminating problems of chemical bonding"	[76]
1977		Ilya Prigogine (1917–2003)	Belgian	"for his contributions to non-equilibrium thermodynamics, particularly the theory of dissipative structures"	[77]
1978		Peter D. Mitchell (1920–1992)	British	"for his contribution to the understanding of biological energy transfer through the formulation of the chemiosmotic theory"	[78]
1979		Herbert C. Brown (1912–2004)	American	"for their development of the use of boron- and phosphorus-containing compounds, respectively, into important reagents in organic synthesis"	[79]
		Georg Wittig (1897–1987)	West German
1980		Paul Berg (1926–2023)	American	"for his fundamental studies of the biochemistry of nucleic acids, with particular regard to recombinant-DNA"	[80]
		Walter Gilbert (b. 1932)		"for their contributions concerning the determination of base sequences in nucleic acids"	[80]
		Frederick Sanger (1918–2013)	British
1981		Kenichi Fukui (1918–1998)	Japanese	"for their theories, developed independently, concerning the course of chemical reactions"	[81]
		Roald Hoffmann (b. 1937)	Polish American
1982		Aaron Klug (1926–2018)	British	"for his development of crystallographic electron microscopy and his structural elucidation of biologically important nucleic acid-protein complexes"	[82]
1983		Henry Taube (1915–2005)	Canadian American	"for his work on the mechanisms of electron transfer reactions, especially in metal complexes"	[83]
1984		Robert Bruce Merrifield (1921–2006)	American	"for his development of methodology for chemical synthesis on a solid matrix"	[84]
1985		Herbert A. Hauptman (1917–2011)	American	"for their outstanding achievements in developing direct methods for the determination of crystal structures"	[85]
		Jerome Karle (1918–2013)
1986		Dudley R. Herschbach (b. 1932)	American	"for their contributions concerning the dynamics of chemical elementary processes"	[86]
		Yuan T. Lee (b. 1936)	Taiwanese
		John C. Polanyi (b. 1929)	Canadian
1987		Donald J. Cram (1919–2001)	American	"for their development and use of molecules with structure-specific interactions of high selectivity"	[87]
		Jean-Marie Lehn (b. 1939)	French
		Charles J. Pedersen (1904–1989)	American
1988		Johann Deisenhofer (b. 1943)	West German	"for their determination of the three-dimensional structure of a photosynthetic reaction centre"	[88]
		Robert Huber (b. 1937)
		Hartmut Michel (b. 1948)
1989		Sidney Altman (1939–2022)	Canadian American	"for their discovery of catalytic properties of RNA"	[89]
		Thomas Cech (b. 1947)	American
1990		Elias James Corey (b. 1928)	American	"for his development of the theory and methodology of organic synthesis"	[90]
1991		Richard R. Ernst (1933–2021)	Swiss	"for his contributions to the development of the methodology of high resolution nuclear magnetic resonance (NMR) spectroscopy"	[91]
1992		Rudolph A. Marcus (b. 1923)	Canadian American	"for his contributions to the theory of electron transfer reactions in chemical systems"	[92]
1993		Kary B. Mullis (1944–2019)	American	"for contributions to the developments of methods within DNA-based chemistry [...] for his invention of the polymerase chain reaction (PCR) method"	[93]
		Michael Smith (1932–2000)	British Canadian	"for contributions to the developments of methods within DNA-based chemistry [...] for his fundamental contributions to the establishment of oligonucleotide-based, site-directed mutagenesis and its development for protein studies"	[93]
1994		George A. Olah (1927–2017)	Hungarian American	"for his contribution to carbocation chemistry"	[94]
1995		Paul J. Crutzen (1933–2021)	Dutch	"for their work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone"	[95]
		Mario J. Molina (1943–2020)	Mexican
		Frank Sherwood Rowland (1927–2012)	American
1996		Robert F. Curl Jr. (1933–2022)	American	"for their discovery of fullerenes"	[96]
		Sir Harold W. Kroto (1939–2016)	British
		Richard E. Smalley (1943–2005)	American
1997		Paul D. Boyer (1918–2018)	American	"for their elucidation of the enzymatic mechanism underlying the synthesis of adenosine triphosphate (ATP)"	[97]
		John E. Walker (b. 1941)	British
		Jens C. Skou (1918–2018)	Danish	"for the first discovery of an ion-transporting enzyme, Na+, K+ -ATPase"	[97]
1998		Walter Kohn (1923–2016)	Austrian American	"for his development of the density-functional theory"	[98]
		John A. Pople (1925–2004)	British	"for his development of computational methods in quantum chemistry"	[98]
1999		Ahmed Zewail (1946–2016)	Egyptian American	"for his studies of the transition states of chemical reactions using femtosecond spectroscopy"	[99]
2000		Alan J. Heeger (b. 1936)	American	"for their discovery and development of conductive polymers"	[100]
		Alan G. MacDiarmid (1927–2007)	New Zealander American
		Hideki Shirakawa (b. 1936)	Japanese
2001		William S. Knowles (1917–2012)	American	"for their work on chirally catalysed hydrogenation reactions"	[101]
		Ryōji Noyori (b. 1938)	Japanese
		K. Barry Sharpless (b. 1941)	American	"for his work on chirally catalysed oxidation reactions"	[101]
2002		John B. Fenn (1917–2010)	American	"for the development of methods for identification and structure analyses of biological macromolecules [...] for their development of soft desorption ionisation methods for mass spectrometric analyses of biological macromolecules"	[102]
		Koichi Tanaka (b. 1959)	Japanese
		Kurt Wüthrich (b. 1938)	Swiss	"for the development of methods for identification and structure analyses of biological macromolecules [...] for his development of nuclear magnetic resonance spectroscopy for determining the three-dimensional structure of biological macromolecules in solution"	[102]
2003		Peter Agre (b. 1949)	American	"for discoveries concerning channels in cell membranes [...] for the discovery of water channels"	[103]
		Roderick MacKinnon (b. 1956)		"for discoveries concerning channels in cell membranes [...] for structural and mechanistic studies of ion channels"	[103]
2004		Aaron Ciechanover (b. 1947)	Israeli	"for the discovery of ubiquitin-mediated protein degradation"	[104]
		Avram Hershko (b. 1937)
		Irwin Rose (1926–2015)	American
2005		Yves Chauvin (1930–2015)	French	"for the development of the metathesis method in organic synthesis"	[105]
		Robert H. Grubbs (1942–2021)	American
		Richard R. Schrock (b. 1945)
2006		Roger D. Kornberg (b. 1947)	American	"for his studies of the molecular basis of eukaryotic transcription"	[106]
2007		Gerhard Ertl (b. 1936)	German	"for his studies of chemical processes on solid surfaces"	[107]
2008		Osamu Shimomura (1928–2018)	Japanese[108]	"for the discovery and development of the green fluorescent protein, GFP"	[109]
		Martin Chalfie (b. 1947)	American
		Roger Y. Tsien (1952–2016)
2009		Venkatraman Ramakrishnan (b. 1952)	British American	"for studies of the structure and function of the ribosome"	[110]
		Thomas A. Steitz (1940–2018)	American
		Ada E. Yonath (b. 1939)	Israeli
2010		Richard F. Heck (1931–2015)	American	"for palladium-catalyzed cross couplings in organic synthesis"	[111]
		Ei-ichi Negishi (1935–2021)	Japanese
		Akira Suzuki (b. 1930)
2011		Dan Shechtman (b. 1941)	Israeli American	"for the discovery of quasicrystals"	[112]
2012		Robert Lefkowitz (b. 1943)	American	"for studies of G-protein-coupled receptors"	[113]
		Brian Kobilka (b. 1955)
2013		Martin Karplus (1930–2024)	Austrian American	"for the development of multiscale models for complex chemical systems"	[114]
		Michael Levitt (b. 1947)	South African American British Israeli[115]
		Arieh Warshel (b. 1940)	Israeli American
2014		Eric Betzig (b. 1960)	American	"for the development of super-resolved fluorescence microscopy"	[116]
		Stefan W. Hell (b. 1962)	Romanian[117] German
		William E. Moerner (b. 1953)	American
2015		Tomas Lindahl (b. 1938)	Swedish British	"for mechanistic studies of DNA repair"	[118]
		Paul L. Modrich (b. 1946)	American
		Aziz Sancar (b. 1946)	Turkish
2016		Jean-Pierre Sauvage (b. 1944)	French	"for the design and synthesis of molecular machines"	[119]
		Fraser Stoddart (1942–2024)	British American
		Ben Feringa (b. 1951)	Dutch
2017		Jacques Dubochet (b. 1942)	Swiss	"for developing cryo-electron microscopy for the high-resolution structure determination of biomolecules in solution"	[120]
		Joachim Frank (b. 1940)	German American[121]
		Richard Henderson (b. 1945)	British
2018		Frances Arnold (b. 1956)	American	"for the directed evolution of enzymes"	[122]
		George Smith (b. 1941)		"for the phage display of peptides and antibodies"
		Sir Gregory Winter (b. 1951)	British
2019		John B. Goodenough (1922–2023)	American	"for the development of lithium ion batteries"	[123]
		M. Stanley Whittingham (b. 1941)	British American
		Akira Yoshino (b. 1948)	Japanese
2020		Emmanuelle Charpentier (b. 1968)	French	"for the development of a method for genome editing"	[124]
		Jennifer Doudna (b. 1964)	American
2021		Benjamin List (b. 1968)	German	"for the development of asymmetric organocatalysis"	[125]
		David W.C. MacMillan (b. 1968)	British
2022		Carolyn Bertozzi (b. 1966)	American	"for the development of click chemistry and bioorthogonal chemistry"	[126]
		Morten Meldal (b. 1954)	Danish
		K. Barry Sharpless (b. 1941)	American
2023		Moungi G. Bawendi (b. 1961)	French Tunisian American	"for the discovery and synthesis of quantum dots"	[127]
		Louis E. Brus (b. 1943)	American
		Alexey Ekimov (b. 1945)	Russian
2024		David Baker (b. 1962)	American	"for computational protein design"	[128]
		Demis Hassabis (b. 1976)	British	“for protein structure prediction”
		John M. Jumper (b. 1985)	American

See also

• Timeline of chemistry