Cyclic arrangement

Carbon atoms can also form cyclic compounds. Aromatic hydrocarbons (arenes), of which benzene is the parent, consist of a cyclic arrangement of formally unsaturated carbons, which, however, give a stabilized (in contrast to their hypothetical cyclopolyenes), delocalized system. 

It is obvious that these compounds have in common an uninterrupted cyclic arrangement of cross-conjugated jr-systems. Compound 5 likewise contains the maximum number of exocyclic double bonds at a perimeter consisting only of sp2-hybridized carbon atoms. Thus, our definition allows one to call it a radialene, i.e. naphtharadialene on the other hand, it excludes hydrocarbons such as 6 [3,4,5,6-tetrakis(methylene)cyclohexene]. Although in the latter molecule all carbon atoms are indeed sp2-hybridized, the number of exocyclic double bonds has not reached its maximum. In 5, however, the number of double bonds cannot be increased further. 

Figure 1.10 Schematic of the more common types of primary cyclic arrangements of the structural units, Si04, in xerogels (A) four-membered siloxane ring (SiO)4 and (B) six-membered siloxane ring (SiO)6. (Reproduced from ref. 15, with permission.)...

Curie measure of radiation activity equal to 3.7 X 10 ° disintegrations per second Cyclic arrangement of molecule in which carbons are bonded together in a ring-pattern... 

Mercury(II) forms a series of compounds in which it is bonded to a transition metal to form heteronuclear Hg—M bonds.540,541 The most widely used synthetic routes have been reviewed elsewhere.542-549 Besides heteronuclear bonds M—Hg there are structural elements M—Hg— M, 550 e.g. (31), or cyclic arrangements as in Os3(CO)uHg 3415 or (1/5-MeC5H4)Mn(CO)2Hg 4.416 A trigonal prismatic coordination of mercury has been reported in the green zerovalent mixed metal cluster [Hg Pt(2,6-Me2C6H3NC)fi ]. a... 

General formula intended to indicate linear arrangement of CNN. 6 General formula intended to indicate cyclic arrangement of CNN. 

The base-stabilized germylene 15 and the corresponding germanethione, selenone, and tellurone 16 are not covalently bonded cyclobutane derivatives however, strong intramolecular coordination with nitrogen leads to the four-membered cyclic arrangement, which has been supported by X-ray studies <19970M2116>. 

Figure 2.2.3 nicely illustrates that 3 simultaneously interacts with the anion and the cation. As expected, the cation is included in the shallow dish-shaped cavity formed by the aromatic peptide subunits. The cyclic arrangement of peptide NH... 

Equimolar amounts of achiral urea 1 and the optically active calix[4]urea 5 give rise to the formation of a heterodimeric capsule with only one cyclic arrangement of the urea hydrogen bonds (Fig. 11), and in the presence of a chiral racemic substrate like norcamphor two diastereoisomeric complexes were present in a 1.3 to 1 ratio. 

One of the most versatile applications of [Os]-anisole chemistry is the efficient generation of complex polycyclic systems. Through the application of a variety of methodologies, anisole complexes have been used to generate a number of cyclic arrangements, including a bi-cyclo[2.2.2]octadiene, decalins, tetralins, and tricyclic arrays. 

Cyclic. Arranged in a closed ring rather than an open chain. 

The -D chair conformation is also stabilized in the crystalline state by the formation of an intramolecular hydrogen bond in both methyl-1,5-dithio-a-ribopyranoside quarterhydrate [MDTRPY20] and methyl-1-thio-a-ribopyranoside [MTRIBP 10]. In the former structure there are two symmetry-independent molecules with different directions for the 0(2)H to 0(4)H bond, as shown in Fig. 13.8. In the methyl-1 -thio-a derivative the direction is 0(2)H 0(4) and the bond forms part of an infinite chain, as shown in Fig. 13.9. In the methyl-1,5-dithio-a-ribopyranoside quarterhydrate, the hydrogen-bond direction is 0(4)H 0(2) in one molecule and 0(2)H 0(4) in the second crystallograph-ically independent molecule in the same crystal structure. As shown in Fig. 13.10, the intramolecular hydrogen bond is part of a cyclic arrangement of eight bonds,... 

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