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Sigma-Aldrich (formally MilliporeSigma) [5] [6] is an American chemical, life science, and biotechnology company owned by the multinational chemical conglomerate Merck Group Sigma-Aldrich was created in 1975 by the merger of Sigma Chemical Company and Aldrich Chemical Company.
Merck is a supplier to the life science industry. The Millipore Corporation was founded in 1954, and listed among the S&P 500 since the early 1990s, as an international biosciences company which makes micrometer pore-size filters and tests. In 2015, Merck acquired Sigma-Aldrich and merged it with Merck Millipore.
The life science business of Merck, formerly known as Merck Millipore, was created in July 2010 following the completed acquisition of the US company Millipore. It employs around 19,000 people in 66 countries and runs 65 manufacturing sites and uses the brands Sigma-Aldrich, Milli-Q and Millipore. [ 64 ]
Millipore may refer to: Millipore Corporation, a biosciences company acquired by Merck Group in 2010; MilliporeSigma, former name of Sigma-Aldrich; Merck Millipore, deprecated brand name used by Merck Group after Millipore acquisition
Two pi bonds are the maximum that can exist between a given pair of atoms. Quadruple bonds are extremely rare and can be formed only between transition metal atoms, and consist of one sigma bond, two pi bonds and one delta bond. A pi bond is weaker than a sigma bond, but the combination of pi and sigma bond is stronger than either bond by itself.
In chemistry, π-effects or π-interactions are a type of non-covalent interaction that involves π systems.Just like in an electrostatic interaction where a region of negative charge interacts with a positive charge, the electron-rich π system can interact with a metal (cationic or neutral), an anion, another molecule and even another π system. [1]
Erich Hückel proposed a representation of the double bond as a combination of a sigma bond plus a pi bond. [7] [8] [9] The σ-π representation is the better-known one, and it is the one found in most textbooks since the late-20th century.
Sigma: 1855–1861, 1928 University of North Carolina at Chapel Hill: Chapel Hill, North Carolina: Active [d] Kappa: 1857–1873 College of the City of New York: New York City, New York: Inactive [1] Beta: 1858–1861, 1867–1875, 1883–1897, 1957 University of South Carolina: Columbia, South Carolina: Active [1] Gamma: 1858–1861, 1869 ...