Valence electrons Lewis’ research

The utilization of copper(I) catalysis in asymmetric transformations is universal due to the special valence electron, Lewis acidity, and coordination characteristic of the metal. Copper salts are easily available, cost-efficient, and nontoxic. Copper(l)-catalyzed asymmetric cycloaddition and cascade addition-cyclization reactions are straightforward methodologies for the stereoselective construction of various biologically and medicinally important heterocyclic compounds. In the past 5 years, main endeavors have been paid into catalytic asymmetric [3+2] cycloadditions other types of cycloaddition protocols are relatively less developed. The examples described in this chapter clearly demonstrate the potential of chiral Cu(I) complexes in the synthesis of enantioenriched heterocycles. Further studies may lie in the diversification of catalytic system, reaction type, and catalysis mode. Research in this field is still challenging and highly desirable, and it would be expected that more discoveries will come in the near future. 

The NO molecule controls several important human physiological functions. Our bodies use it, for example, to relax muscles, kill foreign cells, and reinforce memory. The 1998 Nobel Prize in Physiology or Medicine was awarded to three scientists for their research that uncovered the importance of NO as a signaling molecule in the cardiovascular system. NO also functions as a neurotransmitter and is implicated in many other biological pathways. That NO plays such an important role in human metabolism was unsuspected before 1987 because NO has an odd number of electrons and is highly reactive. The molecule has 11 valence electrons, and two possible Lewis structures can be drawn. The Lewis structure with the lower formal charges places the odd electron on the N atom ... 

G. N. Lewis was born in Massachusetts but raised in Nebraska. After earning his B.A. and Ph.D. degrees at Harvard University, he began his academic career. In 1912, he was appointed chairman of the Ghemistry Department at the University of Galifor-nia at Berkeley, and he remained there for the rest of his life. Lewis felt that a chemistry department should both teach and advance fundamental chemistry, and he was not only a productive researcher but also a teacher who profoundly affected his students. He developed his concepts about valence electrons and the stability of the noble gas electron... 

Lewis published these ideas in his 1923 book Valence and the Structure of Atoms and Molecules, and they were widely taken up and developed in the U.S.A. and Europe, for example, by N. V. Sidgwick at Oxford, whose Electronic Theory of Valency appeared in 1927. The Nobel Prize in Chemistry was left unfilled in 1919, 1924 and 1933 for lack of candidates of suitable stature, and Lewis would have been an appropriate candidate for any of these years. In fact, he was nominated for a Nobel Prize by the inorganic chemist and historian of chemistry, J. R. Partington (1886-1965) at the University of London. For the first half-century after the award of the first Nobel Prize in Chemistry to van t Hoff in 1901, the chemistry prize went to those who had discovered or characterised new chemical elements, new physico-chemical principles, new chemical reactions, or had elucidated the structure and accomplished the synthesis of natural products. The first award for research into the nature of the chemical bond and its application to the elucidation of the structure of complex substances went in 1954 to Linus Pauling at Caltech. 

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