(b. Buffalo, New York, 7 August 1853; d. Orlando, Florida, 8 February 1942)
Michael studied chemistry under Hofmann at Berlin (1871, 1875–1878), under Bunsen at Heidelberg (1872–1874), and under Wurtz at Paris (1879). He was professor of chemistry at Tufts College (1881–1889, 1894–1907) and Harvard University (1912–1936). A severe critic of mechanical interpretations of chemical phenomena, he introduced thermodynamic conceptions into organic chemical theory.
Michael’s earliest studies included the discovery of several synthetic reactions. He was the first to synthesize a natural glucoside (helicin, 1879), and the method that he introduced became the standard synthetic route to this class of organic substances. His best-known synthetic method is the direct addition of the sodium derivatives of malonic, acetoacetic, or cyanoacetic esters to α, ²-unsaturated esters, ketones, nitriles, amides, and sulfones (the Michael reaction, 1887). There had been no general method available for the conversion of unsaturated compounds into saturated compounds of a higher carbon series until Michael described his method of additive condensation in his article “Über die Addition von Natriumacetessig- und Natriummalon- säureäthern zu den Aethern ungesättigter Säuren.”
Michael’s primary concern was organic theory. From 1888 he developed a novel theory of organic reactions based on the thermodynamic concepts of free energy and entropy. He maintained that organic structural theory was too qualitative, pictorial, and mechanical; and he hoped to overcome these deficiencies with energetic conceptions, Michael made the second law of thermodynamics the fundamental principle governing organic reactions. He related the course of reactions to energy conversions, including addition and substitution reactions, molecular rearrangements, tautomerism, and stereochemistry within his theory. He concentrated much of his research on the theoretical aspects of addition to the double bond and the behavior of active methylene compounds.
In his role as critic of accepted views, Michael refused to accept Wislicenus’ assumption that addition to unsaturated compounds always proceeded in the cis manner and that elimination reactions occurred more easily with cis isomers than with trans isomers. By carefully planned experiments he proved that trans additions and eliminations did occur and that all of the then accepted configurations of geometric isomers were erroneous (1895–1918).
Michael was a critic of all purely mechanical interpretations of organic reactions, such as steric hindrance and the strain hypothesis. He attempted over many years to show experimentally that these conceptions were extremely limited and inadequate as explanations of chemical phenomena and that they needed to be modified by considerations of chemical affinity and energy.
I. Original Works. Important papers by Michael include “On the Synthesis of Helicin and Phenolglucoside,” in American Chemical Journal, 1 (1879), 305–312; “Über die Addition von Natriumacetessig- und Natriummalonsäureäthern zu den Aethern ungesättigter Säuren,” in Journal für praktische Chemie, 35 (1887), 349–356; 43 (1891), 390–395; 45 (1892), 55–63; and 49 (1894), 20–25; “Untersuchungen Über Alloisomerie,” ibid., 52 (1895), 289–325; “Über die Gesetze der Alloisomerie und Anwendung derselben zur Classificirung ungesättigter organischer Verbindungen,” ibid., 344–372; “Über einige Gesetze und deren Anwendung in der organischen Chemie,” ibid., 60 (1899), 286–384, 409–486; “Valenzhypothesen und der Verlauf chemischer Vorgänge,” ibid., 68 (1903), 487–520; “Stereoisomerism and the Law of Entropy,” in American Chemical Journal, 39 (1908), 1–16; “Outline of a Theory or Organic Chemistry Founded on the Law of Entropy,” in Journal of the American Chemical Society, 32 (1910), 990–1007; and “The Configurations of Organic Compounds and Their Relation to Chemical and Physical Properties,” ibid., 40 (1918), 704–723, 1674–1707.
II. Secondary Literature. Brief accounts of Michael’s life and work are Louis F. Fieser, Edward W. Forbes, and Arthur B. Lamb, in Harvard University Gazette (22 May 1943), 246–248; Dictionary of American Biography, supp. 3 (New York, 1973), 520–521; National Cyclopaedia of American Biography, XV (New York, 1916), 172; and W. T. Read, in Industrial and Engineering Chemistry, 22 (1930), 1137–1138. His thermodynamic conceptions are discussed by Ferdinand Henrich, in Theories of Organic Chemistry, T. B. Johnson and D. A. Hahn, trans. (New York, 1922), 569–584, and Albert B. Costa, “Arthur Michael (1853–1942): The Meeting of Thermodynamics and Organic Chemistry,” in Journal of Chemical Education, 48 (1971), 243–246.
Albert B. Costa