Substituents numbering

Figure 2 40. To illustrate the isomorphism problem, phenylalanine is simplified to a core without representing the substituents. Then every core atom is numbered arbitrarily (first line). On this basis, the substituents of the molecule can be permuted without changing the constitution (second line). Each permutation can be represented through a permutation group (third line). Thus the first line of the mapping characterizes the numbering of the atoms before changing the numbering, and the second line characterizes the numbering afterwards. In the initial structure (/) the two lines are identical. Then, for example, the substituent number 6 takes the place of substituent number 4 in the second permutation (P2), when compared with the reference molecule.

A detailed analysis of Ni11 complexes with mew-substituted porphyrins bearing zero, one, two, or four /-butyl groups revealed that both the out-of-plane and in-plane distortion depend on the perturbation symmetry of the peripheral substituents (number and position of substitutents), and their orientation.1775 These results have implications for understanding the role of nonplanar distortions in the function of metalloproteins containing nonplanar porphyrins.1776... 

Thus, r° for an X—Y bond is shortened or elongated when electronegative or electropositive atoms (a, b, c, d,...) are connected to either X or Y, respectively. The amount of change in r° decreases with the substituent number (i.e. the first substituent has the largest effect, the second a smaller one and so on substituents are ordered according to their Ar values). A secondary electronegativity effect which changes r° of X—Y in X—Y—Z based on the substituent on Z, and which amounts to 0.4 times the primary effect, is also used in MM3. 

The order of seniority of subunits is of primary importance in the generation of polymer names. Further classification according to seniority is based on the nature of the subunits (kind or size or both) and, among identical subunits, (a) on their degree of unsaturation and (b) on their substituents (number, kind and locants). The following criteria are applied consecutively until a decision is reached. 

The side chain atom concerned is underlined. Note that substituent numbering may vary from the normal system to preserve the correct coupling relations through the table. Signs are given where they have been determined. bFu = furyl. 

The molecule has a chain of eight carbons (octane) with two methyl substituents. Numbering from the end nearer the first methyl substituent indicates that the methyls are at C2 and C6, giving the name 2,6-dimethyloctane. The numbers are separated by a comma and are set off from the rest of the name by a hyphen. 

The ring was numbered the wrong way to give the lowest substituent numbers. The correct name is 1,2-dimethylcyclopropane. 

Aromatic acids of the form Ar—COOH are named as derivatives of benzoic acid, Ph—COOH. As with other aromatic compounds, the prefixes ortho-, meta-, and para-may be used to give the positions of additional substituents. Numbers are used if there are more than two substituents on the aromatic ring. Many aromatic acids have historical names that are unrelated to their structures. 

The nomenclature for cycloalkanes follows the same rules as for the other alkanes except that the root name is preceded by the prefix cyclo-. The ring is numbered to yield the smallest substituent numbers possible. 

Alcohols are characterized by the presence of the hydroxyl group (—OH). Some common alcohols are shown in Table 22.5. The systematic name for an alcohol is obtained by replacing the final -e of the parent hydrocarbon with -o/. The position of the —OH group is specified by a number (where necessary) chosen so that it is the smallest of the substituent numbers. Alcohols are classified according to the number of hydrocarbon fragments bonded to the carbon where the —OH group is attached,... 

With two different substituents, number the ring to assign the lower number to the substituents alphabetically. 

Isomerism.— An examination of the formula for anthracene will show that the number of isomeric substitution products may be greater in number than in the case of naphthalene. The facts in regard to the mono- and di-substitution products are that there are three mono-substitution products and fifteen di-substitution products with like substituents. Numbering the positions in the anthracene formula we have ... 

View the lowest priority substituent, number 4, looking through the stereogenic carbon, If the substituent priority sequence 1 — 2 — 3 is clockwise, then the configuration is R. If anticlockwise, the configuration is S. 

Numbering the longest chain so that the double bond has the lowest number takes precedence over keeping the substituent numbers low. 

The bathochromic shift, according to acidic and basic conditions, is observed for alkylphenols and chlorophenols around 19 nm (Table 4). For nitrophenols, the shift depends on the substituents number and position. 

Figure 9.24 Gel permeation chromatograms of aminopropyl-termin-ated poly(dimethyl)-co-(diphenyl)si-loxane composed of 50wt% dimethyl and 50wt% diphenyl substituents number average molecular weight is 5,000 (Elsbernd et al., 1990b).

Formula R Structure Other Substituents (Numbers indicate position on macrocycle) Yield (X) References... 

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