Ring of atoms

Atom-kem, m. atomic nucleus, -kette,/. chain of atoms, atomic chain, -lage, /. atomic layer atomic position, -lehre, /, doctrine of atoms, atomic theory, -mechanik, /. mechanics of the atom, -modell, n, atomic model, -nummer, /, atomic number, -ord-nung, /. atomic arrangement, -refraktion, /. atomic refraction, -rest, m. atomic residue (= Atomrumpf). -ring, m. ring of atoms, -rumpf, m. atomic residue or core (remainder of an atom, as after removal of some electrons), -schale, /, atomic shell, -strabl, m. atomic ray, -tafel, /, atomic table, atomtbeoretisch, a. of or according to the atomic theory,... 

Shortly after the tetravalent nature of carbon was proposed, extensions to the Kekule-Couper theory were made w7hen the possibility of multiple bonding between atoms was suggested. Emil Erlenmeyer proposed a carbon-carbon triple bond for acetylene, and Alexander Crum Brown proposed a carbon-carbon double bond for ethylene. In 1865, Kekule provided another major advance when he suggested that carbon chains can double back on themselves to form rings of atoms. 

How can there be so many compounds containing this one element The answer lies in the molecular structures. We shall find that carbon atoms have an exceptional tendency to form covalent bonds to other carbon atoms, forming long chains, branched chains, and rings of atoms. Each different atomic arrangement gives a mole-... 

Charles s law The volume of a given sample of gas at constant pressure is directly proportional to its absolute temperature V T. chelate A complex containing at least one polydentate ligand that forms a ring of atoms including the central metal atom. Example [Co(en)3]3+. chemical analysis The determination of the chemical composition of a sample. See also qualitative, quantitative. 

A cycloaddition reaction produces a ring of atoms by forming two new G-bonds, for example the formation of a cyclobutane dimer from two alkene molecules. The direct photoreaction involves the concerted reaction of the singlet Jtpt ) excited state of one alkene with the ground state of the other. Stereospecific reactions in which the dimers preserve the ground-state geometry occur when liquid cis- or trans-but-2-ene are irradiated at low temperature ... 

The products have structures (35) related to the icosahedron but with 6 atoms instead of 5 in the tropical (ortho or meta) rings of atoms (Fig. 18). 

In a cycloaddition reaction, two sigma bonds are formed to give a new ring of atoms, and one classification of these reactions is based on the number of ring atoms thal derive from each of the reacting units. One of the simplest classes are (2 + 2 cycloadditions, such as... 

Chelate (cyclic complex) An inorganic metal complex having a close ring of atoms formed by attachment of ligands to a metal atom at two points, e.g.,... 

Heterocyclic compound Compound in which the structure contains one or more rings of atoms with at least one atom being an element other than carbon... 

As seen, both of these complex ions have five-membered rings of atoms they are called chelates (Chap. 22). The four oxygen atoms bound to the beryllium are actually not in the same plane rather, they are at the corners of a regular tetrahedron with the beryllium ion at the center. 

Many organic compounds are cyclic They contain rings of atoms. The carbohydrates we eat are cyclic, the nucleotides that make up our DNA and RNA are cyclic, and the antibiotics we use to treat diseases are cyclic. In this chapter, we use the cycloalkanes to illustrate the properties and stability of cyclic compounds. 

How single bonds are free to rotate, but spend most of their time in just two or three well-defined arrangements How rings of atoms are usually not planar, but puckered ... 

After receiving his doctorate at the University of Giessen, he became a lecturer at Heidelberg in 1855 and a professor of chemistry at Ghent (1858) and Bonn (1867). His real-, ization that carbon can form rings of atoms was said to have come to him in a dream in which he saw a snake biting its tail. 

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