Membered rings

O in higher esters 11.0 Ring, 3-membered as in ethylene oxide -6... 

Membered ring 5-Membered ring 4-Membered ring 3-Membered ring (2-Membered ring)... 

Number of ring members Rings containing nitrogen Rings containing no nitrogen ... 

Prefixes and Affixes. Prefixes are arranged alphabetically and placed before the parent name multiplying affixes, if necessary, are inserted and do not alter the alphabetical order already attained. The parent name includes any syllables denoting a change of ring member or relating to the structure of a carbon chain. Nondetachable parts of parent names include... 

Heterocyclics with seven and more ring members display an enormous variety of shapes. Bond lengths are often close to those of open chain counterparts, but bond angles can be greatly different. Aromaticity is possible where the conditions of planarity and Hiickel s rule are met, but the majority of fully unsaturated large heterocycles are not aromatic (see below). 

The NMR spectra of heterocyclic compounds with seven or more ring members are as diverse as the shape, size and degree of unsaturation of the compounds. NMR is perhaps the most important physical method to ascertain the structure, especially the conformational statics and dynamics, of large heterocycles. Proton-proton coupling constants provide a wealth of data on the shape of the molecules, while chemical shift data, heteroatom-proton coupling constants and heteronuclear spectra give information of the electronic structure. Details are found in Chapters 5.16-5.22. Some data on seven-membered rings are included in Table 10. 

Large systems contain ring atoms enough to allow more than one way of bonding between a given sequence of atoms, and a wealth of valence isomerizations becomes possible. Already for seven ring members, two types of bicyclic isomer are observed, namely the [4.1.0] and the [3.2.0] systems, each with positional ring isomers if more than one heteroatom is present. 

The loss of one or two (or sometimes more) ring members from heterocyclics, concerted with or followed by formation of a new ring, is a highly versatile method for heterocyclic synthesis. Loss of N2, CO, CO2, S, SO, SO2, H2C=CH2, etc. is common. Diradical or dipolar intermediates are often encountered, and valence isomerization before the actual fragmentation is characteristic for some systems. 

A number of substances have been discovered in the last thirty years with a macrocyclic structure (i.e. with ten or more ring members), polar ring interior and non-polar exterior. These substances form complexes with univalent (sometimes divalent) cations, especially with alkali metal ions, with a stability that is very dependent on the individual ionic sort. They mediate transport of ions through the lipid membranes of cells and cell organelles, whence the origin of the term ion-carrier (ionophore). They ion-specifically uncouple oxidative phosphorylation in mitochondria, which led to their discovery in the 1950s. This property is also connected with their antibiotic action. Furthermore, they produce a membrane potential on both thin lipid and thick membranes. 

Ring-member substitution, a very characteristic reaction of some 18-e borabenzene complexes (see Section VII,B), can also occur with 1,4-dibora-2,5-cyclohexadiene complexes. The cobalt complex 53 cleanly reacts with MeCOCl/ A1C13 to give the cation 54 (Scheme 7) (75). The Rh complex (C5Me5)Rh[MeB(CHCH)2BMe] reacts analogously (75). 

The comparatively unreactive complex Mn(CO)3(C5H5BMe) (14) with MeCOCl/AlCl3 produces the 2-acetyl derivative 84 and small amounts of [Mn(CO)3(PhMe)]+ (27). The product ratio is rather insensitive to reaction conditions. It is reasonable to assume a common intermediate 85 (of unspecified stereochemistry at C-6) which under kinetic control may either irreversibly deprotonate to 84 or undergo a rearrangement ultimately leading to the ring-member substitution product (27). 

Formation of the Second Ring by Insertion of One-Atom Ring Member between Two Adjacent... 

Formation of the Second Ring by Addition of a Three-Atom Ring Member to Two Ring... 

Formation of the Second Ring by Insertion of One-Atom Ring Member between Two Adjacent Substituents at the First Ring, Each Providing One Atom for the Second Ring (5)1,1+1 — (5,5)... 

Abstract Heterocyclic compounds containing atoms of the elements snch as nitrogen, snUhr and oxygen as ring members are commonly nsed in varions fields of indnstiy as analytical reagents, ligands, dyestuffs, pharmaceutical substances and bioindicators. 

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