Ring number

All you had to do was to find the six-membered ring (numbered) containing the double bond and draw the arrows. 

Ligand, L Complex formula Ring size Number of rings Number of coordinated donor atoms LogV ... 

Once a particular 6-membered ring is selected as a site for applying the Diels-Alder transform, six possible [4 + 2] disconnections can be examined, i.e. there are six possible locations of the Jt-bond of the basic Diels-Alder retron. With ring numbering as shown in 36, and... 

The pyranose rings can adopt either of two different chair conformations called C, and C4. Pyranoses usually adopt a chair conformation that puts the majority of bulky groups in the equatorial position, so that steric interactions are minimized. The Ci(d) conformation and the ring numbering system are shown in formula 1. 

Kato, M. et al.. Accumulation of carotenoids and expression of carotenoid biosynthetic genes during maturation in citrus fruit. Plant Physiol. 134, 82, 2004. Cunningham, F.X. Jr. and Gantt, E., One ring or two Determination of ring number in carotenoids by lycopene epsilon-cyclases, Ptvc. Natl. Acad. Sci. USA 98, 2905, 2001. 

The known benzologs of the above nitrogen bridgehead bicyclic systems are indicated with Chemical Abstracts names and ring numbering on Figures 2-5. 

Extension of the ring numbers, bioisosteric replacement of the benzene ring, and conversion of the quinolone system to the corresponding quinalizinone system has been a subject of research interest during the past decade. For example, Jordis et al. [38] recently reported the syntheses of a series of linear benzo- or pyrido-ciprofloxacin (lin-benzo- and lin-pyrido-ciprofloxacin)... 

In addition to the name and structure of each parent system, the ring numbering of the system has also been given in every case. 

Figure 2 Representative examples of the three classes of lantibiotics. The same color-coding and shorthand notation is used as defined in Figure 1. For Lan and MeLan structures, the segments derived from Ser/Thr are in red whereas those derived from Cys are in blue. The ring numbering is shown for some members and is typically alphabetical from the N- to C-terminus.

Metal Ref. Number of C5H5 Rings Number of JjS-CsHg Rings Average 71—C5H5 M—C Distance (A) Average a M—C Distance Metal Ionic Radius )... 

Fraction 13 contains aromatics with slight alkylation and the ring numbers increase as shown in Figure 5-10. Both fractions 1 4 and 15 (Figure 5 11, 12) contain only aromatics with few alkyl side chains. 

Most partially saturated ring systems, 2,3-dihydro-l,4-dioxin 10 (sometimes named as 1,4-dioxene), 2,3-dihydro-1,4-dithiin 11, 2,3-dihydro-l,4-oxathiin 12, 2,3-dihydro-l,4-benzodioxin or 1,4-benzodioxane 13, 2,3-dihydro-l,4-benzodithiin 14, and 2,3-dihydro-l,4-benzoxathiin 15 are well investigated. Ring numbering for compounds 10-12 is followed as shown, independently of the presence of substituents. 

The purine ring-numbering scheme, 1, and structures of some simple purines, viz. adenine 2, guanine 3, caffeine 4, theophylline 5, adenosine 6, 2 -deoxyadenosine 7, guanosine 8, 2 -deoxyguanosine 9, xanthine 10, and hypoxanthine 11, are shown. 

The same molecule may appear with different orientations. For example, in the current literature, the structure for the 3-ring PAH phenanthrene is drawn as (IVa), (IVb), or (IVc). While one or more IUPAC rules may be broken, their ring numberings are internally consistent. 

However, if two or more substituents are present on the ring, numbering starts from the carbon that has the group of alphabetical priority, and proceeds around the ring so as to give the second substituent the lowest number. 

There is a very important feature of this situation, which we can turn to advantage. It will be observed that the set of four methylene carbon atoms, numbers 1, 4, 5, and 8, possess D4h symmetry by themselves and that the set of four carbon atoms in the ring, numbers 2, 3, 6, and 7, also by themselves constitute a set having D4ll symmetry. Furthermore, the atoms in one set are not equivalent symmetrically to any of those in the other. None of the outer atoms is ever interchanged with any of the inner atoms by any symmetry operation. Thus each of these sets can be used separately as the basis for a representation of the group, and if this is done we obtain from each set a representation, r x, which reduces as follows ... 

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