Benzene ring s. a. Arenes

Thiepin, as a seven-membered conjugated system with sulfur as heteroatom, is a member of the 8 7t-electron heteroannulenes which are antiaroinatic according to Hiickel s rule. In contrast to oxepin, thiepin is not stable at room temperature and no valence isomerism with an arene sulfide has been observed. Stable thiepins are obtained only when two bulky substituents, e.g. /ert-butyl, are introduced into positions 2 and 7. In benzothiepins the annellation effect of the aromatic rings contributes decisively to the stability of these compounds stability increases with an increasing number of fused benzene rings. 

Phanes are compounds with at least one aromatic nucleus and at least one bridge 28 Such structures can incorporate a great number of arenes — carbophanes contain carbocycles such as benzene or naphthalene, heterophanes heteroaromatic rings including metallocenes — and a wide variety of bridges spanning the ring (s) in different positions from one to several simple alkylidene residues (e.g. hexamethylene or... 

Ikeda, A., Tsuzuki, H., Shinkai, S. 1994. X-ray crystallographic studies of a 1,3-al-temate-calix[4]arene Na+ complex - Is the cation-pi interaction operative between the benzene rings and Na+ Tetrahedron Lett. 35 8417-8420. 

Another synthesis of aryl-substituted methylidynetricobalt nonacar-bonyls was developed by Dolby and Robinson (15) who found that chloro-methylidynetricobalt nonacarbonyl alkylate s aromatic compounds in a Friedel-Crafts-type reaction. High product yields were obtained when equimolar amounts of ClCCo3(CO)9 and aluminum chloride and an excess of the arene were stirred at 60°-70°C for 2 hours. When the arene was a solid, the reaction was carried out in dichloromethanc solution. Both ortho and para substitution was encountered, the size of the substituent (s) already present on the benzene ring appearing to determine the position of substitution (Table IV). Noteworthy is that milder temperature conditions affected the position of substitution thus, reaction of chlorobenzene with chloromethylidynetricobalt nonacarbonyl in dichloromethane at 42° gave... 

Chapter 19 focuses on the reactions of benzene and substituted benzenes. Although benzene, alkenes, and dienes are all nncleophiles (becanse they all have carbon-carbon tt bonds), benzene s aromaticity causes it to react in a way that is qnite different from the way alkenes and dienes react You will see how a substituent can be placed on a benzene ring and some reactions that can change the substiment after it is on the ring. You will also learn how a substituent affects both the reactivity of a benzene ring and the placement of an incoming snbstituent Chapter 19 also describes two additional types of reactions that can be used to synthesize snbstituted benzenes the reactions of arene diazonium salts and nucleophilic aromatic substitution reactions. 

Aromatic compounds are unsaturated cyclic molecules that possess additional stability as a result of the arrangement of 7i-electrons associated with the unsaturation of the ring system. This book will concentrate on the chemistry of benzene (4) and its derivatives and related polynuclear hydrocarbons. Aromatic compounds are also known as arenes they can becarbocydic, indicating that the ring skeleton contains only carbon atoms, or heterocyclic, with at least one atom other than carbon in the ring. These heteroatoms are typically N, O or S. Heterocyclic compounds, which can be aromatic or alicyclic, are covered in another book in this series. 

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