Aromatic six-membered rings

The normal pattern of coupling constants for aromatic six-membered rings is found in the heterocyclic aza systems, except that the ortho coupling to a proton a to a heterocyclic nitrogen is reduced from 7-8 Hz to 4.5-6 Hz. The J2.3 of pyrylium salts is still lower... 

When two carbon atoms of an aromatic six-membered ring are replaced by an amide group (—CONH—) as in 2-pyridone, the aromatic character of the ring is not lost, owing to the importance of... 

Structure of Cgo and a carbon nanotube. Each carbon in Cgo is a bridgehead carbon for a five-membered ring and two six-membered rings. A nanotube is a cylinder composed of aromatic six-membered rings similar to graphite. The end of the tube is half of a C60 sphere. Notice how the five-membered rings cause the structure to curve at the end of the tube. 

Norrestam, R., and Schepper, L. Prediction of molecular geometries of aromatic six-membered rings. Acta Chem. Scand. A35, 91-103 (1981). 

Alicyclic and aromatic six-membered ring containing natural products... 

The 1,3-azarsinines (104) are so far the only known 6n Hiickel aromatic six-membered ring system with two or more heteroatoms containing at least one arsenic atom. 

Endopeptidases Trypsin Chymotrypsin hydrolyzes on the C-side of Arg and Lys hydrolyzes on the C-side of amino acids that contain aromatic six-membered rings (Phe, Tyr, Trp)... 

Again one might expect that the benzoderivatives of aromatic six-membered ring imidoyl halides have reactive halo groups. Recently, an interesting route to six-membered ring benzimidoyl chlorides has been reported ( ). Reaction of o-cyanomethylbenzoic acid (LV) with 2 moles of phosphorus pentachloride produces 1,3-dichloroisoquinoline (LVI). 

The aromatic six-membered ring compound that contains one nitrogen atom is known as pyridine (10) and was first isolated in 1846 from coal tar. Pyridine has been used as a base from time to time in preceding chapters. Because it is aromatic (see Chapter 21, Section 21.7), pyridine is a planar compound with an aromatic n-cloud above and below the plane of the ring. The nitrogen atom is sp2 hybridized, but the lone electron pair on nitrogen is not part of the aromatic... 

Cumpson recently proposed another equation (QSPR) applicable to polymers and other organic materials, and provided IMFP values computed accordingly. IMFP at a kinetic energy of 1,000 eV is computed on the basis on the structural formula alone (number of aromatic six-membered rings and atoms other than hydrogen in the molecule or polymer repeating unit, molecular indices). The IMFP is... 

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