Nonaromatic ring

Such an easy isomerization of acetylenylbenzoic acid amides implies the formation of a five-membered nonaromatic ring condensed with the pyrazole ring. However, the pyrazole analog of o-iodobenzamide (amide of 4-iodo-l-methylpyrazole-3-carboxylic acid) formed under heating with CuC=CPh in pyridine for 9 h only the disubstituted acetylene in 71 % yield is identical in all respects to the compound obtained from the corresponding acid by successive action of SOCI2 and NH3 (90IZV2089) (Scheme 126). 

The required rigidity of a nonaromatic ring carrying two aryl groups was... 

Three common isomers, eight possible, differ in whether each of the six chlorine atoms are in the up or down positions on the nonaromatic ring... 

The atom X, still in an sp hybridization state of a heterocyclic system, is at one end of one unsaturated Y=X bond in a nonaromatic ring. The same conformational profile as in case 1 is expected if reference is made to vinyl ketones or a-diketones, which are corresponding acyclic derivatives. 

Vcyc is the contribution from nonaromatic rings containing no double bonds. 

The ir spectrum, mentioned above, indicates that A contributes more than B. Not only benzene rings but other aromatic rings36 and even nonaromatic rings (p. 338) can react through this kind of intermediate. Of course, the nonaromatic rings do have a formal triple bond. 

A further comparative study will now be made on the number of nonaromatic rings per structural unit (Roar). If it can be assumed that H/C and... 

Each true / value which is smaller than / [Pg.338]

The values in Table VII show that 12 nonaromatic rings should be present for nine mean structural units in the case of exinite, 10 in the case of vitrinite, and 16 in the case of micrinite. Since all faiIt -Rnnr) values are higher than the highest ones obtained from the aliphatic group distribution (see Table IV), all samples must contain nonaromatic rings even if the most probable / values... 

Table VII. Mean Number of Nonaromatic Rings, Rn r per Structural Unit and f

From aromaticity and elementary analysis the total number of rings per mean unit (R) can be derived. The number of nonaromatic rings is then given by R r = R — R.r and includes alicyclic and heterocyclic rings. If all hetero atoms were to form a ring, there could be a maximum of — 0.8 such rings per unit in all three macerals. Limits for the number of alicyclic rings per unit... 

Martin D. Neuworth The author did not make any distinction between sulfur in completely aromatic rings and sulfur in hydroaromatic or nonaromatic ring structures. Since the stability of sulfur in completely aromatic structure is higher than in other configurations, the dyes might be separated on this basis independently of available hydrogen or volatile matter. 

In Section 11.2 peptides based on a variety of aromatic heterocycles are discussed.1 2-21 Some of them are natural products with bioactivities ranging from antibiotics to double stranded DNA intercalators. Heterocyclic systems with five or six atoms, characterized by a single or a combination of N, O, and S heteroatoms, are described. In selected cases reduced, nonaromatic rings are also covered. 

It was demonstrated that this reaction is an efficient method to prepare fused 1,2,3,5-thiatriazoles of type 26 bearing various substituents at the 2-, 4-, 5-positions. The same reaction has also been described for masked or fused amidrazones 27, where the N-l atoms of the amidrazones are involved in aromatic or nonaromatic rings. Indeed this method was used to prepare 1,2,3,5-thiatriazoles 28-32 fused to pyridine, isoquinoline, benzodiazepine, and benzox-... 

As seen from the structural formulas in Figure 16.4, the organochlorine insecticides are of intermediate molecular mass and contain at least one aromatic or nonaromatic ring. They can be placed in four major chemical classes. The first of these consists of the chloroethylene derivatives, of which DDT and methoxychlor are the prime examples. The second major class is composed of chlorinated cyclodiene compounds, including aldrin, dieldrin, and heptachlor. The most highly chlorinated members of this class, such as chloredecone, are manufactured from hexachlorocyclo-pentadiene (see Section 16.3). The benzene hexachloride stereoisomers make up a third class of organochlorine insecticides, and the third group, known collectively as toxaphene, constitutes a fourth. 

Exposure of the diastereomeric mixture of alcohols 497 to TFA leads to the construction two nonaromatic rings via a cation-alkene cyclization process. The chroman 498 is isolated as a 1 1 mixture of epimeric alcohols and is a key intermediate during cannabinoid synthesis (Equation 203) <2000JOC6576>. 

The accuracy to which covalent states of benzene can be described with 7t-only correlation is a further justification for invoking a-n separation for the various aromatic, antiaromatic and nonaromatic ring systems that we consider here. We have not addressed the question of whether it is primarily the a electrons or the n electrons of benzene that drive the preference for a high symmetry structure [45]. Similarly, we do not investigate here any bent bond solutions, based on mixing a and n orbitals [46]. 

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